CERAMIC
BURNERS

FOR MODEL STEAM BOILERS

CERAMIC
BURNERS

FOR MODEL STEAM BOILERS

Alex Weiss

With technical assistance from Kevin Walton

First published in 2020 by
The Crowood Press Ltd
Ramsbury, Marlborough
Wiltshire SN8 2HR

enquiries@crowood.com

www.crowood.com

This e-book first published in 2020

© Alex Weiss 2020

All rights reserved. This e-book is copyright material and must not be copied, reproduced, transferred, distributed, leased, licensed or publicly performed or used in any way except as specifically permitted in writing by the publishers, as allowed under the terms and conditions under which it was purchased or as strictly permitted by applicable copyright law. Any unauthorised distribution or use of this text may be a direct infringement of the author’s and publisher’s rights, and those responsible may be liable in law accordingly.

British Library Cataloguing-in-Publication Data

A catalogue record for this book is available from the British Library.

ISBN 978 1 78500 766 8

DISCLAIMER

Safety is of the utmost importance in every aspect of metalworking. When using tools, always follow closely the manufacturer’s recommended procedures. However, the author and publisher cannot accept responsibility for any accident or injury caused by following the advice given in this book.

Acknowledgements

WHEN I WROTE THE book Building Small Boilers for Gas Firing in 2013, each of the four larger boilers, the three vertical fire-tube ones, and the horizontal water-tube one, was fitted with a commercially available ceramic burner. These burners were either round or rectangular and worked extremely well. They were also quite expensive to purchase.

This led me to wonder whether I could make my own burners with similar dimensions. I discovered that the jewellery trade uses ceramic honeycomb for manufacturing decorative items. This honeycomb material is hard, resists crumbling, and has proved to be ideal for making ceramic burners. Furthermore, the plumbing trade provides a large variety of end caps that are suitable for use as housings for all the circular burners, together with the occasional length of copper tube. All the burners need short lengths of brass rod for the gas-jet holders and housings, and the rectangular burners require small flat sheets of copper or brass, widely available from the suppliers to model engineers. The success of these designs led to the production of some even smaller burners, suitable for Mamod, Wilesco and similar-size small boilers.

I must thank my friend Kevin Walton, who has provided much of the technical input and detailed recommendations that have made possible the building of the burners described in this book. He has also helped with the construction of all the burners, and has solved some significant problems relating to how they were built and in their operation.

Finally, I must mention my appreciation of my wife Lynda, who has had to put up with all the work involved in making the burners, testing and photographing them, as well as the many months writing up and organizing the results on my computer.

Introduction

HEAT HAS ALWAYS BEEN an essential for humans. Its earliest use was in the form of wood fires used to keep warm and to cook food. For some people, oil or tar emerged from the surface of the ground and was also found to burn well. It was particularly useful for providing torchlight at night. The first steam-powered device dates back to ancient Greek times, but it wasn’t until the start of the industrial revolution that useful work was obtained from steam engines.

There is something incredibly appealing about operating model steam engines. They may require a heat source and a boiler to generate the steam, but they produce almost silent power, normally without the need for gear changes to drive their load. And they are a glorious reminder of the golden age of the industrial revolution.

Steam engines, as originally envisaged by Newcomen, Trevithick, Watt and others, have become the life blood of many preservation organizations, but the steam turbine, invented by Charles Parsons, is still happily turning the generators in power stations that produce electricity, as well as propellers in some ships. The steam generators for these turbines may be heated by coal, gas, oil or a controlled nuclear chain reaction.

FIG. 1
A Stuart beam engine powered by a 108mm (4¹⁄₄in) vertical fire-tube boiler heated by a 67mm round ceramic burner.

FIG. 2
A 76mm (3in) horizontal water-tube boiler fitted with a 70 × 50mm rectangular burner steaming a single-cylinder mill engine.

Running a model steam engine on compressed air is neither good for the engine nor in any sense realistic. Running on steam from the right size of model boiler is exhilarating, and with a displacement lubricator, feeds small amounts of oil through the valves into the cylinder to minimize wear to the valve gear and on the cylinder/piston combination.

There are many ways of heating the water in a model steam boiler. They include using coal, liquefied petroleum gas (LPG), paraffin, methylated spirits, impregnated pellets and historically petrol, although petrol is not considered a safe option in the twenty-first century. This is because petrol vapour is explosive, and as a result, using a petrolfuelled blowlamp to heat a boiler has, fortunately, all but disappeared.

Each source of heat comes with its own set of problems. With coal, the fire requires a stoker, normally human, to add coal regularly to the firebox. Starting the fire with kindling can also be a time-consuming task. On the other hand, LPG gives a virtually instantaneous heat and can provide a high heat output. However, it does require a safe gas tank and care in handling the gas. Paraffin or kerosene is not a very volatile liquid and is difficult to vaporize ready for burning. Methylated spirits will produce relatively small amounts of heat, and again will require a safe spirit container. The flame is virtually invisible and the storage tank must be protected from the heat.

However, neither methylated spirits nor LPG need an operator in attendance. They are thus suitable for installation in model vehicles and steam boats – but take care to ensure the heat source is exhausted before the boiler water has run out. The same warning applies to stationary installations. A boiler that has run out of water is readily destroyed if the heating is not turned off.

Over the past ten years, the author and Kevin Walton have designed and built nine different boilers of a variety of shapes, sizes and configurations, but all within the 3-bar litre limit detailed in the UK Boiler Test Code 2018 Volume 2. Some years ago Building Small Boilers for Gas Firing was published by Camden Miniature Steam Services, giving detailed instructions on how to build these boilers. The majority of the boilers were heated by commercial ceramic burners, but some subsequent experiments led to fitting new home-made burners to most of these boilers, and writing about how to make the burners in a typical model engineer’s workshop, and also how to operate these burners.

As a result, this book describes a range of easy-tomake ceramic burners for the home builder. They all burn a propane/butane gas mixture, two of a range of LPGs that are widely available. These burners provide high heat outputs from burners of relatively small size, are clean to operate, and that may be powered from small disposable gas cylinders or from easy-to-purchase refillable ones. However, do take care when using these gases. They are heavier (denser) than air and will therefore pool in any enclosed area – the floor of a workshop, the hull of a model boat or even the interior of a car. With air they form a volatile mixture that can readily be ignited by either a spark or a naked flame. While this sounds a very severe area for concern, provided you are careful, their use as a fuel presents no problems, and it is worth remembering that they are widely used for camping stoves.

There are several different commercially available designs of small burner for model steam boilers currently on the market. Some use a ceramic element, and there are several different types of ceramic element, while some use a metal disc with holes drilled in it. Of burners that plug into a horizontal flue, some have secondary air holes, some do not. The same is true of the similarly configured burners described in this book. All the burners described in this volume use a hard ceramic element of the type used by the jewellery trade, rather than the softer type that is more prone to damage.

FIG. 3
An 89mm (3¹⁄₂in) vertical fire-tube boiler heated by a 54mm round burner.

FIG. 4
Construction details are given for all eleven of these ceramic burners.

Three different configurations and nine different sizes of burner are described in detail in this book, together with two minor variants. They are shown in Figure 4. They are all suitable for use in boilers that are below the 3-bar litre limit covered in the UK Boiler Test Code 2018. Such boilers face a less stringent testing regime than larger boilers. Three different-size burners are suitable for fitting in the centre flues of boilers, and there is one variant for any boiler where the end of the flue is flush with the boiler end plate. The other six burners fit in a firebox and are suited to heating vertical fire-tube or horizontal water-tube boilers, or even just pot boilers. There are three different sizes of round burner, and likewise three rectangular ones, again with a variant made from brass sheet instead of copper.

The nine larger designs work well, are quick to build, and maintain steam pressure in suitably sized boilers, typically vertical ones varying in size from 51mm (2in) to 108mm (4¹⁄₄in) diameter. Horizontal boilers with 28mm, 35mm or 42mm flues should not exceed 108mm (4¹⁄₄in) diameter or 250mm (10in) long. The same size limitations apply to horizontal boilers with a firebox below.

FIG. 5
This Mamod traction engine will run well with a small round burner fitted in the firebox.

FIG. 6
A squat 108mm (4¹⁄₄in) boat boiler with a 67mm round ceramic burner on a test rig steaming a twin-cylinder Marcher engine.

FIG. 7
The Stuart 4000 boiler running at 30psi (2 bar) with a 42mm burner and brass adapter ring, driving a Stuart Double 10 engine turning a small generator powering the overhead light.

The two smallest burners, one round and one rectangular, also perform extremely well and have been specially designed to heat the boilers of Mamod, Wilesco and similar static steam plants, as well as their steam rollers and traction engines such as the one in Figure 5.

All burners require both primary and secondary sources of air if the gas is to burn efficiently. Primary air passes through holes drilled in the gas-jet housings of all the burners, and the jet can be moved by undoing the locking bolt in its holder and moving the jet further in or out of the housing. For the two larger burners that fit in flues, the secondary air comes with the primary air, while the holes in the outer shell of the two smallest burners provide secondary air. All the vertically mounted burners draw their air through holes in the boiler firebox.

FIG. 8
The 67mm round burner is well alight and showing blue cones.

FIG. 9
The large rectangular burner provides plenty of heat and is burning well.

FIG. 10
The smallest rectangular burner provides excellent heat for its size, and has blue cones visible on the top of its ceramic element.

FIG. 11
The 42mm burner well alight with the jet correctly adjusted to provide a good hot flame.

To make any of these burners some fairly basic skills in drilling, tapping and turning will be required. The small number of parts that will be needed can be made using a lathe, but for the smallest 28mm burner you will really need access to a milling machine and a rotary table. For all the burners, you will also need to gain the ability to carry out simple silver soldering, a skill that many model engineers have already learned. This can be done with a relatively small, self-contained MAP (methylacetylenepropadiene) torch or a larger propane gas torch with a modest-size head. Some firebricks, heat-resisting blocks or Vermiculite board will also be needed to support the work being soldered.

The seven round burners are made using copper plumbing end caps of the appropriate dimensions. The rectangular ones use folded copper or brass boxes. The right size gas jet for each particular burner will be required, and a jet holder with pipe that can be connected to the valve of a small gas container. These are available from a number of model engineering suppliers, listed at the end of this book, or you can turn a holder yourself from brass rod. All the burners then need a short length of tube turned from brass rod to provide primary air and to act as a housing for the gas-jet holder.

The two large round burners and the three larger rectangular ones need two gas-diffusing components: a short length of stainless-steel spring of ¹⁄₂in or 12mm diameter in their bodies from the primary air tube to the other end of the burner body, and a small strip of stainless-steel mesh of twenty holes per inch. You will also need a small block of ceramic material that can be easily cut and filed to size and shape. The spring, the mesh and the ceramic material can be glued in place with high-temperature adhesive filler such as Ceramix, Vitcas or Mapeflex. The smallest rectangular burner needs a ³⁄₈in or 10mm spring and the same mesh.

FIG. 12
A 35mm burner provides plenty of heat for this 108mm (4¹⁄₄in) horizontal boiler to drive a Stuart mill engine.

You may choose to finish copper burners with high-temperature paint, but this will not work for brass as there are no high-temperature etch primers. Therefore as an alternative, the burner jet housings and the brass bodies can be polished.

FIG. 13
The author’s workshop is well equipped with a lathe, milling machine and pillar drill with X/Y table. The lathe is the only machine tool necessary for making all but one of the ceramic burners.

FIG. 14
Kevin Walton’s workshop also has three similar machine tools, but making the ceramic burners has largely been completed on the Chester lathe.

You may already have a well-equipped workshop such as those shown in Figures 13 and 14, but as long as you have access to a lathe, you can make all but one of the burners without any other workshop machinery.

ABOUT THIS BOOK

Since the main components used to make the burners are metric sizes, metric dimensions are used but with equivalent imperial measurements where these are practicable. In some cases, there is no imperial equivalent. For example, gas pipe connectors require ¹⁄₈in copper pipe and 3mm pipe would not be suitable. Likewise, gas jets are threaded 1BA and therefore this imperial thread has to be used in any gas-jet holder.

Each chapter commences with a short summary of its contents. The first chapter starts with an explanation of the various material and tools, including some basic machine tools that you will need. It is followed by details of how to silver solder the relatively small burner bodies and gas pipes. This chapter also includes information on the types of gas torch you will need for this task, and the LPG they use. There is then a description of three burners, with one variant, for boilers with horizontal flues. These burners fit 42mm, 35mm and 28mm flues, but details are given of how to make an adaptor to fit slightly different-size flues.

Construction details follow for two round burners, one larger than the other, for vertical boilers with fireboxes. There are also instructions on how you can build two different sizes of rectangular burner for use in horizontal water-tube or pot boilers, with a variant for the larger one. This is followed by an account of building a small round and a diminutive oblong burner for use in Mamod and Wilesco and similar boilers. The next chapter deals with the provision of LPG for the ceramic burners and the tanks to hold it, as well as the connecting pipework and necessary valves and connecters.

Then there is advice on how to set up, install and operate the burners in your boiler to ensure optimal heating, and for burners that fit in a firebox, advice on how to avoid blowback and how to repair a burner if blowback occurs. The following chapter looks at a number of electronic and mechanical automatic gas-control systems that monitor the boiler pressure you have set, and adjust the gas flow to try and maintain the desired pressure. They will help to reduce gas consumption and simplify the operation of gas-fired boilers in model boats and land vehicles. This is followed by some conclusions.

Finally, the Appendix provides a concise summary of the UK Boiler Test Code 2018 Volume 3 that deals with making LPG tanks under 250ml capacity. A list of the addresses of useful suppliers detailing the relevant items they can supply is provided at the end of this book. There is also a comprehensive index.

WARNING

Please ensure that you read and understand the advice on using liquefied petroleum gas (LPG) given in Chapters 2 and 6 before silver soldering any of the gas burners described in this book, and before operating them.

1
Materials and Tools

THIS CHAPTER DESCRIBES ALL the tools and basic ready-made items that can be purchased, as well as the raw materials that will also be required to build the burners described in this book. It also covers the workshop facilities, including machine tools, that are likely to be needed. It does not include what is needed for silver soldering, which is covered in Chapter 2.

Building ceramic burners is not a difficult task, but does require a few items not normally found in many modellers’ workshops. One unusual tool is required, a ceramic saw, as well as high-temperature adhesive/ filler and high-temperature paint. These are easily obtained either from DIY or specialist suppliers, or on eBay. Building burners also requires a range of machine tools, some of which are fairly normal such as a lathe, and a few that are slightly less common, but that you may need depending on which burner you decide to build, such as a vertical milling machine and a rotary table. Likely to be found in the scrap box are short lengths of brass rod and possibly some pieces of copper tube.

COPPER AND BRASS

Two metals are predominantly used in the construction of all the burners in this book: copper and brass. Copper is not simple to machine or drill but is very malleable and easy to bend into shape. Drilling is best done with a special copper-drilling bit that looks similar to a wood drill. Brass, on the other hand, is straightforward to machine, though drilling can be awkward at the point of breakthrough. Brass is readily bent but not as easily as copper. Annealing either metal makes bending relatively simple. Brass needs an etch primer if you wish to paint it, but to date there are no heat-resistant etch primers.

It is important to realize that lengths of copper pipe from plumbing suppliers will be a different size from those purchased from model engineering suppliers, so it is important that where end caps and short lengths of tube are needed, they will fit into each other.

Cutting Lubricant for Copper

A number of lubricants are recommended for use when machining copper: sulphur-free cutting oil, dry soluble oil, lard oil, and paraffin or mineral lard oil. A practical tip I learned from Martin Gearing in his Model Engineer articles on the ME vertical boiler is to use original bright-green Swarfega Classic as a lubricant when drilling copper. A can is illustrated in Figure 15. It cleans off easily and has no negative effect on silver soldering. It is an excellent cutting fluid, or rather a jelly, for copper. It is still widely available both from Screwfix and Amazon. For drilling and milling, the bit can be dipped into some Swarfega, whilst for turning, a brush will prove ideal for applying it. Although it is also ideal for cleaning hands at the end of a session, do keep two separate containers to prevent polluting the hand cleaner with swarf.

FIG. 15
Swarfega Classic, the original hand cleaner, is a fine lubricant when machining copper.

BURNER BODIES

The bodies of the round burners described in Chapter 3 are made from copper plumbing end caps of different sizes, and short lengths of copper plumbing tube. Likewise, all the round burners in Chapters 4 and 5 involve the use of plumbing end caps. A number of different-size end caps can be seen in Figure 16. It is essential that these end caps are not the Yorkshire type, as these contain a ring of soft solder that will make silver soldering impossible. As all copper plumbing materials are only available in metric dimensions, imperial sizes are not normally quoted by suppliers.

FIG. 16
A small selection of copper plumbing end caps, the two left-hand ones for making large circular burners, the right-hand pair for making burners to fit horizontal flues.

All these copper plumbing parts should be to EN 1057 – Type X (previously BS 2871 Table X). They can be bought from plumbers’ merchants or DIY supermarkets, but it is probably easier and cheaper to order them on the Internet. For the 28mm burner a pair of end caps will be needed, one of 22mm and the other of 28mm. The 35mm burner for horizontal flues requires end caps of 28mm and 35mm. Likewise the 42mm burner needs end caps of 35mm and 42mm. In addition, the two larger burners require short lengths of copper tube, of 28mm and 35mm diameter respectively. You might have offcuts yourself, or you may be able to scrounge a short length – 50mm will do – from one of your friends.

It is possible to build the circular burners for boilers with fireboxes from 35mm, 54mm or 67mm end caps, depending on the size of burner required, but the height of the end cap will have to be reduced: this can be easily done in a lathe or using a hacksaw and file.

FIG. 17
The folded copper box that forms the body of the large rectangular burner.

Any of the larger rectangular burner bodies can be made from 1.6mm thick (16 SWG) copper or brass sheet, cut and folded to size as illustrated in Figure 17. The smallest oblong one uses 0.9mm (20 SWG) brass sheet. All the oblong burner housings are then silver soldered at the corners. You will need to drill the bodies, whether round or square, so that the gas-jet housing you have made can be silver soldered into place.

GAS-JET HOUSINGS

It is a relatively straightforward task to make the gas-jet housing. Drill a short length of ¹⁄₂in or 12mm brass rod right through, and then, for the smaller burners, turn down one half to a smaller diameter. Carefully cross-drill the holes for primary air, then drill and tap a small hole for a 6BA or M3 bolt in order to secure the jet holder in place and allow its position to be adjusted. Examples of the two main variants can be seen in Figures 18 and 19.

FIG. 18
The type of brass gas-jet housings needed for burners for horizontal flues.

FIG. 19
The different gas-jet housing required for burners that fit in fireboxes.

GAS-JET HOLDERS

While gas-jet holders are widely available from companies that sell gas jets, they are also very easy to make. All that is needed is a short length of 8mm (⁵⁄₁₆in) round brass rod. The holder is 25mm (1in) long, and is drilled 4.5mm for a depth of 20mm (³⁄₄in), and then tapped 1BA to match the gas jet. Finally, a ¹⁄₈in hole must be drilled for the gas pipe. This can be either cross-drilled near the base of the holder, or through the base depending on how you want the gas pipe to run.

GAS PIPE

The UK standard for gas pipe, suitable for LPG burners that heat model boilers, is ¹⁄₈in. It is normally supplied as bending-grade copper tube in a coil. The pipe can be easily straightened and cut to the required length, and then silver soldered into the gas-jet holder. The other end needs silver soldering into the gas-valve connecter to the gas tank. A small pipe bender, such as the one shown in Figure 20, will help to ensure a neat installation of the gas pipe.

FIG. 20
A coil of ¹⁄₈in copper pipe and an economically priced pipe bender to enable the making of a neat gas-pipe installation.

NUT SPINNERS

Adjusting the position of the gas jet in the housing is an awkward task – holding the housing, moving the gas-jet holder, and loosening and tightening the bolt that fixes the holder in place in the housing. Trying to do this using an open-ended spanner is almost impossible, so the use of a nut spinner makes a difficult task significantly easier. Figure 21 shows examples of a long and a compact nut spinner used for this task.

FIG. 21
Two alternative examples of 6BA nut spinners, either of which will be found useful when setting up your burner.

GAS-DIFFUSER COMPONENTS

Without any diffusing components, the gas will not be evenly distributed in the larger burners, and the ceramic material in some of them will not burn evenly across its surface when lit, seriously reducing heat output. The burners that plug into the flue have gas-jet holders that extend to within 3mm (¹⁄₈in) of the far wall of the burner body, resulting in the gas dispersing across the relatively small surface area of the ceramic.

For the larger round and oblong burners that fit in the firebox, various possible solutions were tested. These included using a tube of mesh fitted across the width of the burner body from the gas/air inlet, a sheet of mesh fitted under the ceramic element, and the use of baffles in the body of the burner. None of these methods worked as well as a strip of mesh to diffuse the gas and a length of spring to give it swirl, which resulted in the gas spreading evenly across the burner body. The two materials that help resolve this issue, springs and mesh, are both made of stainless-steel.

Stainless-Steel Springs

The four largest burners have a length of stainlesssteel spring in their bodies from the gas-jet housing to the other side of the burner body to impart a degree of swirl to the gas/air mixture entering the chamber. This can be easily cut from a short length of ¹⁄₂in or 12mm diameter stainless-steel spring of 1.6mm thick wire (16 SWG). The two smallest burners for Mamod and Wilesco boilers use a thinner ³⁄₈in (9 or 10mm) diameter stainless-steel spring of 0.9mm (20 SWG) or 1.2mm (18 SWG) wire thickness. Figure 22 shows examples of both these springs.

FIG. 22
Lengths of ³⁄₈in (9mm or 10mm) and ¹⁄₂in or 12mm stainless-steel spring; the former is suitable for the smallest oblong burner and the latter for large rectangular and round burners.

Stainless-Steel Mesh

A small amount of stainless-steel mesh will be needed in the burner body. This locates where the gas enters the burner body, for all but one of the burners that fit under the boilers. Twenty holesper-inch mesh is ideal, so look for the following: 20 mesh – 1.02mm aperture – 0.25mm wire diameter – SS316L grade – woven wire mesh. An economic A5 sample sheet is plenty for several burners – a sample is shown in Figure 23. The mesh is easily cut to size with tin snips or even old scissors.

FIG. 23
An A5-size sheet of stainless-steel mesh. Only a small strip is needed for the round or rectangular burners that fit under boilers.

CERAMIC ELEMENTS, AND HOW TO CUT THEM

The ceramic part of each burner must be cut to shape from a small sheet of ceramic material, which is widely used in, and is available from, the jewellery trade. It is a non-asbestos-based material. The standard thickness is usually 12.5mm (¹⁄₂in), and this is preferable for use in burners rather than thicker ceramic honeycomb. It comes in blocks of about 135 × 95mm (5⁵⁄₁₆ × 3in): such a block can be seen in Figure 24. Depending on the source of the ceramic, it may be white or off white, but it always has a pattern on the front with tiny hills and valleys. As the material is rigid, its reverse side can be easily marked with a pencil using the burner body as a template.

FIG. 24
A sheet of the right type of ceramic material for making burners that is used by, and is available from, the jewellery trade.

FIG. 25
A low-cost ceramic saw is ideal for cutting the ceramic elements roughly to size prior to filing the ceramic to fit the burner body.

FIG. 26
Cutting a rectangular piece of ceramic material with a ceramic saw.

FIG. 27
Carefully held in the vice, sawing a round ceramic element to shape from a square piece of sheet. The outline marked in pencil clearly shows where to cut.

Although it is hard, the ceramic material can be readily cut with a ceramic saw, such as the one in Figure 25, although the cut edges can be rather crumbly as they are worked with the saw. Figures 26 and 27 illustrate how to cut rectangular and round pieces of ceramic; then file or sand them. An old medium file will allow you to trim the element to the exact size of the burner body.

Do not over-tighten the vice used to hold the ceramic material. A slight taper will enable the ceramic element to slide part-way into the burner body. The ceramic for both burners described in Chapter 5 needs thinning to 9mm (³⁄₈ in) by rubbing on sandpaper.

FIG. 28
A circular piece of the ceramic material cut out ready for installation in a 42mm burner.

Despite these minor warnings, you should experience no problems in getting the ceramic to the right shape and size, as can be seen in Figure 28, but do make regular trial fits in the burner body.

Ceramic Adhesive

There are several ceramic adhesive fillers available on the market, but all the burners in this book have been made using white FortaFix Ceramix TC (Figure 29), except for the two smallest, where Vitcas Heat Resistant Filler (Figure 30) was used. In addition, Mapei Mapeflex Firestop (Figure 31) has been used successfully on two additional burners, and although grey in colour, it also works well. All three adhesives can withstand temperatures of over 1,000°C, and they can be obtained from fireplace shops, DIY stores, Amazon and the Internet.

FIG. 29
A tube of Ceramix TC high-temperature caulking used to glue the ceramic element, mesh and springs into the metal housing.

FIG. 30
Vitcas heat-resistant filler for gluing ceramic material and other metal parts inside the burner.

FIG. 31
Mapei Mapeflex Firestop high-temperature grout can also be used to glue ceramic and metal parts.

These adhesives set fairly quickly, but need to harden for at least twenty-four hours. Their thickness allows them to fill any small gaps between the ceramic and its casing. When applied, the adhesive fillers are water soluble, allowing them to be smoothed and any excess wiped off. They are also odourless. In addition, they should be used to secure any mesh or spring, used for gas diffusion, in the burner casing.

Ceramix TC is a water-based thixotropic ceramic sealing compound designed for use where heat resistance is an important requirement. Vitcas® Heat Resistant Sealant is a high-temperature sealing and caulking paste. Mapeflex Firestop 1200°C is an asbestos-free, quick-setting, rigid, silicate refractory fire-resistant sealing grout. It is used for joining or sealing ceramics to metal. All three materials provide good adhesion and gap filling to seal and join these materials, and it should not be difficult to obtain a neat finish around the ceramic.

PAINT

Although it is not essential to paint the metal body of completed burners, they do look better with a painted finish, especially the copper parts.

It is important that the selected paint is heat resistant to a reasonably high temperature: those suitable for painting barbecues are ideal. Most will withstand temperatures up to 600°C and come in tins or in aerosols. Two popular brands, Blackfriar High-Heat Resistant Paint and Hammerite Barbecue Paint, are illustrated in Figure 32, but there are many alternatives. They can be painted or sprayed directly on to copper. The most widely available colour is black, usually matt, and a small 125ml or 250ml tin will more than suffice.

FIG. 32
Two quite different approaches to heat-resistant paint: brushing or spraying. Both will survive the high temperatures experienced when the burner is lit and creating steam in a model boiler.

If a suitable heat-resistant paint is not chosen, it will discolour, blister, or even start to melt. Paint will not stick well to brass, and there are no hightemperature etch primers that can go under the paint. It is therefore better to polish any brass parts as paint will rapidly deteriorate and crumble off the brass.

HEAT-RESISTANT GLOVES

There are two reasons why you should invest in a pair of heat-resistant gloves. The first is to protect your hands when silver soldering. The temperature of the metal will quickly reach over 700°C, and it is only too easy to burn yourself. The second reason for using them is when plugging a lit burner into the flue of a boiler: once the burner is lit, its bodywork will heat up fairly quickly, and with flames from the ceramic element, there is again the risk of a burn. A typical example of these gloves can be seen in Figure 33.

FIG. 33
A pair of heat-resistant gloves will protect your hands from flames and hot metal when silver soldering and when handling hot burners.

Silver Soldering Burner Bodies
2

THIS CHAPTER DESCRIBES THE equipment needed to silver solder small ceramic burners successfully, and how to undertake the process. It includes some basic information about liquefied petroleum gases, including safety instructions, and describes suitable torches for heating the metal parts, techniques for silver soldering, suitable hearths, and methods of chemically cleaning the parts of the burner once silver soldering is complete.

GAS FOR SILVER SOLDERING

You will need to use liquefied petroleum gas (LPG) to provide the heat for silver soldering. LPG is a fossil fuel closely linked to oil, and is used in many applications including heating. The gas has a powerful odorant added so that leaks are easily detected from the smell. It is flammable, and heavier (denser) than air, so it settles and accumulates in low spots. Serious leaks can present a fire hazard, or even the risk of an explosion.

FIG. 34
A 13kg bottle of propane carries enough gas to solder the bodies of hundreds of ceramic burners.

LPG under pressure is available in portable cylinders. When compressed, it readily changes to a liquid, so a large amount of gas can be stored in a relatively small space. However, in order to be burned the LPG must be able to boil, expanding significantly to form a gas. Propane is supplied in a range of cylinder sizes of which those suitable for use in home workshops contain either 6kg or 13kg of the liquid gas and will power a torch with a small nozzle for a very long time. Figure 34 shows a typical cylinder. Propane cylinders connect to torches through fittings with left-hand threads.

FIG. 35
A MAP (methylacetylene-propadiene) gas torch screwed on to a MAP gas cylinder.

For silver soldering, propane is the gas normally employed by model engineers, though MAPP gas – methylacetylene-propadiene propane – is a useful alternative where relatively small amounts of heat are required, such as when making ceramic burners. It is also called MAP gas. It burns at just over 2,000ºC, whereas propane burns at a little below that figure. The increased temperature and the design of MAPPgas burners help to simplify silver soldering small items such as the bodies of ceramic burners. Figure 35 is a photo of a MAP-gas torch. The cylinders for MAP gas contain a nominal 400g (14oz) of gas, and although it is at least 50 per cent more expensive than propane, not much gas is used when making a burner.

BASIC SAFETY NOTICE

Most of you will hate ‘health and safety’ warnings, but the best advice for all model engineers is to read any warning and remember to be careful – as careful as you would be when dealing with gas or electricity in your home or petrol in your car. You need to observe some safety precautions when using propane or MAP gas, which are both forms of LPG, for silver soldering.

■LPG is denser than air. Any leaking gases will pool on your workshop floor so it is essential to check that your connecters and pipework are correctly installed and do not leak. You should frequently inspect all of them. In warmer weather, you should consider silver soldering in a shady outdoor place – though be aware this will make it harder to judge when the item you are soldering is coming up to red heat

■Always carefully turn off the gas at the cylinder at the end of each soldering session. If you are using a propane torch, disconnect the pipes from the gas cylinder once you have finished soldering

■Inevitably your gas torch will heat up metal quickly – and your skin if you are not careful. So do wear a pair of protective gloves when silver soldering. Even with the torch off for a couple of minutes, its metal can still burn you painfully if you touch it

■Be careful if you use dilute sulphuric acid as a pickle. Never add water to acid, only ever add acid to water. Wear protective clothes, gloves and a face mask. If you do get acid on your skin or clothes, quickly wash it off with water. And only dispose of the acid after neutralizing it with baking powder

TORCHES FOR SILVER SOLDERING

You will need some facilities for silver soldering to make any of the burners. You may already have some silver solder and flux, as well as a gas torch. The two practical alternatives are a propane gas torch and cylinder with a choice of nozzle sizes, or a MAPP gas torch where the burner head screws on to the top of the small gas cylinder. The head also contains a piezo-electric ignition system.

FIG. 36
A Sievert gas torch; any of the smallest three burners will provide adequate heat when making ceramic burners.

The low mass of the metal used in ceramic burners means that they do not require a huge amount of heat to raise their temperature sufficiently to silver solder them. Thus a propane gas torch (like the one in Figure 36) is, perhaps, overkill for making ceramic burners – but such a torch will have many other uses including building steam boilers to power locomotives, traction engines, lorries or static steam engines. You need to be aware that small DIY butane-powered gas torches used for soft soldering will not provide sufficient heat for silver soldering.

SILVER SOLDERING

It is essential to realize that soft solder is unsuitable for making the burners in this book because it has little or no strength at the temperatures experienced in a burner body. Even worse, a joint failure could cause a gas leak, which is also potentially dangerous. Finally, it is worth remembering that any metal that has been soft soldered cannot then be silver soldered. For those who have already built a boiler, silver soldering a burner should provide no problems. For those who are inexperienced, it is not difficult to become proficient at silver soldering, and making burners is an ideal place to start acquiring the techniques. The following are a few important issues that must be learned:

ISSUE 1: All the parts of the burner that are to be silver soldered must be completely clean. This means removing any oxides, grease (including finger marks), oil and dirt. As a minimum, this involves cleaning well with wire wool until the metal shines. Seriously stained metal can be pickled and then washed in water to clean it.

FIG. 37
Lengths of 1.5 × 500mm Silver-Flo SF55 solder that is cadmium free. It is the ideal silver solder for making any of the burners.

FIG. 38
Easy-flo flux comes in powdered form in various sizes of plastic container, ready for mixing with water.

ISSUE 2: It is essential to use the right silver solder and flux. Silver-Flo 55, lengths of which are shown in Figure 37, is today the preferred, non-cadmium bearing, relatively low-temperature silver solder and Easy-Flo is an ideal flux. Figure 38 shows pots of the flux powder. The solder has a melting range of 630°C–660°C, flows well and provides moderate fillets.

Brush Easy-Flo 2 flux around the edges of every joint. The powdered flux should be mixed with water and one drop of washing-up liquid so the flux spreads easily on the bare metal, stirring until the mixture has the consistency of thick cream. Only a small amount of flux will be needed, and only part of a 600mm length of 1.5mm Silver-Flo 55 to make any one of the eleven different burners.

For soldering copper gas-pipe connections, it is easier not to apply too much solder if a thinner rod or solder wire can be used. Regardless, silver solder is expensive to buy so take care not to waste it.

ISSUE 3: A suitable heat source that provides sufficient but not excessive heat should be used. For building ceramic burners, a relatively low-cost, self-contained MAPP gas torch, if you have access to one, is ideal. However, if you already have a propane torch, you can use a small nozzle on this type of torch and can run it from a large propane gas cylinder. And do wear heat-resistant gloves to avoid burning your fingers.

FIG. 39
If you have the space, you can create a simple hearth from Thermalite blocks on a bench in your workshop or on top of a Black and Decker Workmate.

FIG. 40
An old firebrick 200mm (8in) square is sufficiently large for silver soldering a burner.

FIG. 41
A well-cleaned 35mm burner on a firebrick supported by pieces of Scanalex and ready for soldering.

ISSUE 4: You will need a small hearth made of Thermalite or similar blocks (see Figure 39), or just a firebrick, shown in Figure 40, or even a piece of vermiculite board on which to place the burner parts that are to be soldered together. So paint the flux around the joints that are to be soldered, and place the parts on the hearth, with the burner tube supported on a thin piece of fireproof material. This is demonstrated in Figure 41. Vermiculite board, Scamolex or Skamolex, a vermiculite-based board, is ideal for this and can be sawn and filed to size.

FIG. 42
The 35mm burner metal is red hot and the solder is flowing nicely around the join between the jet-holder housing and the smaller end cap.

FIG. 43
The 42mm burner showing how the silver solder has flashed around the joint between its two end caps.

Now heat the metal parts until they are red hot. You will see the flux sizzle and then go clear, and the metal parts will return to their shiny colours as red heat is reached. (It is advisable to avoid silver soldering in direct sunlight as it is difficult to see when the metal reaches red heat.) A light touch of silver solder rod on each joint, which has first been briefly heated in the flame and then dipped in the powdered flux, should result in the solder melting and flashing around your joint. This can be seen in Figures 42 and 43. Do not overheat the parts to be joined. Overheating can prevent the flux working effectively, and the solder from flowing around the joint.

FIG. 44
Repairing a corner joint on the large rectangular burner to ensure a good seal.

ISSUE 5: After cleaning the burner, carefully inspect it to ensure that all joints are filled with solder and gas tight. Any doubtful joints should be re-fluxed and then re-soldered and finally re-cleaned. Figure 44 shows the corner of a rectangular burner that has been cleaned and is being reheated to improve the seal on a corner joint.

Sifbronze Brazing

Because silver solder is expensive due to its high silver content, experiments were made using Sifbronze, a brass (despite its name) brazing alloy that is much cheaper. It does, however, have a much higher melting temperature of 875°C–895°C than silver solder, and it resulted in brass components in the burner melting. It is therefore not recommended for making ceramic burners. Silver solder is by far the best solution, and you will not use much.

CLEANING AND PICKLING

Some cleaning of the burner will be necessary once you have completed the soldering but before fitting any gas-diffusing components or the ceramic. This is readily done in a pickle of either citric or dilute sulphuric acid. Figure 45 shows a burner body after pickling. However, you must wait until the burner is completely cool before putting in any pickle.

FIG. 45
After cleaning in pickle and washing, carefully check all the joints. This is particularly vital on all rectangular burners.

FIG. 46
Citric acid is a safer but slower-acting pickle; it is widely available in crystal form that readily dissolves in water to produce the acid.

FIG. 47
Sulphuric acid is a highly corrosive liquid, but in its dilute form it is an excellent pickle.

Citric acid is slower to clean the metal, but is safer; it is readily bought from chemists and supermarkets, as the packet shown in Figure 46. It is available in liquid or in powder form ready for you to dissolve it in water. A mix of 25g of citric acid monohydrate to 250ml is sufficient to pickle a burner. Sulphuric acid is most easily found on the Internet or extracted as acid from an old battery. Do not even think about buying concentrated acid. A 10 per cent concentration or thereabouts is quite sufficient for a pickle. Figure 47 shows an old 5ltr (1gal) container of dilute acid.

Please make sure you wear eye protection and gloves when handling sulphuric acid. If for any reason you get acid on your skin, quickly wash with cold water to prevent your skin being affected by the acid. If you get any in your eye, immediately rinse thoroughly with saline solution rather than tap water.

FIG. 48
Pickling a soldered 28mm burner in a plastic box filled with dilute sulphuric acid.

Typically, a burner will clean up nicely in sulphuric acid in half to one hour as shown in Figure 48, while immersion in citric acid requires several hours. Once removed from the pickle, rinse the item several times in fresh water, dry, and then clean off any residual coating with wire wool before polishing any brass parts that will not be painted.

DISPOSING OF UNWANTED SULPHURIC ACID

Before discarding any old or unwanted acid, just add sodium bicarbonate – ordinary baking powder – to neutralize it and render it inert. Thus you will eliminate the possibility of burning yourself or anyone else, and it can safely go down the drain.

Burners for Round Horizontal Flues
3

THIS CHAPTER DESCRIBES HOW to build a range of small burners that will plug into round horizontal flues on different sizes of boiler with varying flue diameters. Details are given of the dimensions of the parts that will have to be made, and the way they are assembled to provide successful burners.

FIG. 49
From left to right: A 42mm burner with a brass flue adapter fitted, a 28mm burner then a 35mm one, a 28mm burner with a copper insert to plug into rather than over a flue, and a 42mm burner.

Burners for model steam boilers with centre flues running along their length need to operate when mounted horizontally, and must fit snugly over the end of the flue. Thus the popular sizes of flue diameter – 42mm, 35mm and 28mm – will need different-sized burners, shown in Figure 49, to produce the optimum heat output. However, for boilers with imperial or other ‘non-standard’ size flues, it is easy to fabricate a suitable adaptor ring, shown fitted to the left-hand burner in Figure 49.

FIG. 50
A 35mm burner fitted to an Ahoy 108mm (4¹⁄₄in) horizontal boiler that has eight Galloway tubes in the flue.

Three of the burners described in this chapter are an easy push fit on to the end of the boiler flue. Figure 50 shows a 108mm diameter horizontal boiler with a 35mm burner fitted over its flue. However, occasionally a flue may need a ‘male’ rather than a ‘female’ burner to fit into, rather than over the flue. The method of doing this is shown for the 28mm burner. A similar modification to both the two larger burners can easily be applied. And for different flue sizes, an adaptor can be made from a short length of brass rod.

Each of these burners can be readily made from two different sizes of copper plumbing stop ends, a length of copper tube or brass rod, a ceramic honeycomb disc and a short length of ¹⁄₂in or 12mm brass rod. Some ceramic adhesive filler will also be needed to fix the ceramic element in place.

The parts of the burners must be silver soldered as soft solder will not be strong enough at the temperatures experienced. The smallest burner should provide sufficient heat for a 75mm (3in) boiler, the 35mm burner for 90mm (3¹⁄₂in) to 100mm (4in) diameter ones, and the largest 42mm burner for 108mm (4¹⁄₄in) and any other similar size boilers.

The metals used to build the burners, unlike those used to build model boilers, are not subjected to any pressures or continuous exposure to steam and hot water. As LPG fuel passes through them, they do need to have their joints sealed, and of course they will be exposed to considerable heat. Finally, the length of the inner tube holding the ceramic element can be altered to suit the flue. It can be made a little longer or shorter if required, depending on how far the flue tube sticks out of the boiler.

FIG. 51
Eight secondary air holes are needed in the end cap for a 28mm burner.

There is debate about whether secondary air holes around the larger end cap are a benefit. Figure 51 shows an end cap for a 28mm burner with secondary air holes drilled around its end. Some manufacturers include these air holes, others do not. Tests with the three sizes of burner in this chapter showed that excluding secondary air holes in the larger two burners improved the heat output to the boiler and also reduced potential whistling in the flue. Figure 52 shows early 35mm and 28mm burners with secondary air holes used in the tests. However, contrary to expectation, the 28mm burner still needs secondary air holes to burn correctly. The larger two burners clearly get sufficient secondary air through the primary air holes, while for the smallest burner, the air flow appears to be insufficient and secondary air holes will need to be included.

FIG. 52
An early prototype 35mm burner with twelve secondary air holes drilled around its perimeter beside a 28mm burner with eight secondary air holes.

Testing was carried out with burners with secondary air holes fitted to horizontal boiler flues to check the temperature of the hot air coming out of the chimney, and the time taken for a cold boiler to reach its working temperature. This was then repeated with the secondary air holes blocked, confirming that both the 42mm and the 35mm burners performed better without secondary air holes.

BRASS GAS-JET HOUSINGS

The gas-jet housings are virtually identical for the 42mm, 35mm and 28mm burners. The housing is the first part to make (see Figure 53). It consists of a length of ¹⁄₂in or 12mm brass rod faced each end to the required length, which varies depending on the size of the burner; turn down about half its length to 8mm (⁵⁄₁₆in) to fit the burner body. Drill it 6mm right through from the narrow end, and then drill the wide end 8mm (⁵⁄₁₆in) to a depth of 20mm (²⁵⁄₃₂in). Finally cross-drill right through 6mm (¹⁄₄in) for primary air at a point 12.5mm (¹⁄₂in) from the wider end, and also drill and tap at a point 6mm (¹⁄₄in) from the wide end for a 6BA or M3 bolt to adjust and hold the gas jet in place. Figure 54 provides the dimensions of the parts.

FIG. 53
A typical gas-jet housing suitable for 42mm, 35mm and 28mm burners. The length of the thin end varies according to the diameter of the burner.

FIG. 54
The essential dimensions needed to construct the gas-jet housing from brass rod.

42MM (1⁵⁄₈IN) BURNER

This relatively large burner, pictured in Figure 55, utilizes two copper stop ends, one 42mm the other 35mm, a length of 35mm copper pipe, a small piece of honeycomb ceramic plate, and a short 6BA or M3 bolt. As already shown in Figure 53, you will need to turn a 58mm (2⁹⁄₃₂in) length of ¹⁄₂in or 12mm brass rod to size, then drill and cross-drill it, to form the housing to mount the gas-jet holder.

FIG. 55
A finished 42mm burner ready to have the gas-jet holder fitted before installation in a boiler.

FIG. 56
The dimensions of the main components (excluding the gas-jet housing) needed to build the 42mm burner.

The outer casing of the burner is then made from the larger 42mm stop end with a 35mm hole bored in its centre to fit the burner tube. This tube fits into the smaller 35mm stop end, and they both have an 8mm (⁵⁄₁₆ in) hole cross-drilled for the gas-jet housing to extend right through one side of them so that the end of the housing is 3mm (¹⁄₈in) from the opposite inside wall of the burner tube. The sizes of the various components are illustrated in Figure 56.

FIG. 57
Boring the centre hole in a 42mm end cap to a diameter of 35mm.

FIG. 58
The set of metal parts that will be needed to make the 42mm burner.

Fit the larger 42mm end cap in the lathe and drill a hole large enough to enable the boring bar to be employed, using standard green Swarfega as a lubricant. Now bore out this centre hole in the lathe so the length of 35mm copper pipe will pass through it with about 0.13mm (0.005in) clearance for silver solder. Figure 57 shows the end cap being bored, while Figure 58 shows a complete set of machined parts.

FIG. 59
Silver soldering together the metal parts of the 42mm burner.

Carefully clean, flux and assemble the parts ready for silver soldering. This excludes the bolt that will hold the gas jet in position. As Figure 59 demonstrates, support the larger end cap, since the copper tube sticks some 4mm (⁵⁄₃₂in) below it, ensuring the larger end cap is up against the smaller end cap. Check that the gap from the end of the jet housing across to the copper tube is 3mm (¹⁄₈in). Flux all the joints as you assemble the items.

Finally, the whole assembly is ready to be soldered with a hand-held MAPP gas torch or a propane torch fitted with a small burner. Run silver solder around the gas-jet housing joint to the smaller end cap, and the joint of the outer casing to the copper tube and smaller end cap. When cool, the complete assembly can be pickled, washed, then any remaining flux cleaned off, and finally any excess solder removed with a file. Do check that good, gas-tight joints have been made.

FIG. 60
The ceramic element is ready to be glued into the cleaned-up burner body.

To make the ceramic element for the burner, place the 35mm copper tube on the reverse, flat side of the piece of ceramic material, and run a pencil round it to make the size of the circle required. Cut round the material with the ceramic saw, and then file the resulting circle to size so that it fits into the end cap for just half the thickness of the ceramic – in effect the round edge should be slightly conical. The piece of ceramic and the completed burner body can be seen in Figure 60.

To glue the ceramic element in the burner, run a thin line of ceramic adhesive filler around both the inside top of the copper tube and the lower outer edge of the ceramic disc, push the disc in place, and clean off any excess adhesive with a damp cloth. If there are any unfilled gaps between the ceramic and the tube, add more heat-resistant filler and smooth in place. A little water helps both to smooth the adhesive and remove it from places where it is not wanted.

FIG. 61
The completed 42mm burner ready to fit a gas-jet holder and gas jet so the correct gas/air mixture can be set.

Paint the outer copper parts of the burner with heat-resistant paint; black is ideal. However, the brass can be left bare or polished, as there are no suitably heat-resistant etch primers. Without such a primer, any paint on the brass will rapidly start to come off. Figure 61 shows the finished burner.

FIG. 62
A 42mm burner alight and already, as it warms up, providing a fair amount of heat.

Finally, fit a No. 8 jet (possibly even a No. 10 jet) in the holder, and the holder in the gas-jet housing so its end is just over half way along the primary air hole. Connect the jet to a tank of a propane/butane mix, check there are no leaks, turn on the gas and light the flame on the ceramic element. Adjust the position of the jet and the rate of gas flow so that blue cones form all over the surface, as demonstrated in Figure 62. Then, wearing heat-resistant gloves, the burner can be carefully inserted in the flue of the boiler to raise steam.

FIG. 63
A simple ring adaptor to fit over the flue of a Stuart 4000 boiler and also to fit a 42mm burner. Two 5BA bolts lock the items in place.

The 42mm burner will heat relatively large boilers, such as the Stuart HB4 boiler or the older Stuart 4000. However, the latter will need a brass or bronze adaptor such as the one shown in Figure 63, with one end bored to fit over the flue and the other to house the burner.

35MM (1³⁄₈IN) BURNER

This burner also employs a pair of copper stop ends, one 35mm the other 28mm, a short length of 28mm copper pipe, a small disc of ceramic, and a short 6BA/ M3 bolt as can be seen in Figure 64. As described on page 36, a brass gas-jet housing will again have to be made from a 51mm (2in) length of brass rod.

FIG. 64
A complete 35mm burner that needs a gas-jet holder so it can be tested.

FIG. 65
Apart from the gas-jet housing, the dimensions of the four other components that are required to complete a 35mm ceramic burner.

Again, the larger 35mm stop end forms the outer casing. The length of burner tube fits into the smaller 28mm stop end. Both have an 8mm (⁵⁄₁₆in) hole drilled for the gas-jet housing to fit right through one side of them, so that the tip of the housing is 3mm (¹⁄₈in) from the opposite side of the burner. The measurements for the various components are given in Figure 65.

FIG. 66
The five metal components of the 35mm burner.

Use the lathe to drill a hole in the centre of the 35mm end cap that forms the outer casing. Then the centre hole can be bored out so the length of 28mm copper pipe will pass through it with about 0.13mm (0.005in) clearance. Figure 66 shows all the metal parts ready for assembly.

FIG. 67
Silver soldering the four metal components of a 35mm burner (excluding the bolt that secures the gas-jet holder in place).

Make sure that all the parts have been cleaned, fluxed and assembled so they are ready to be silver soldered. The larger end cap will have to be supported since the copper tube sticks 9mm (³⁄₈in) below it. Ensure the larger cap is a snug fit with the smaller end cap. Check that the gap between the end of the jet housing and the inside of the copper tube is 3mm (¹⁄₈in). Now silver solder the whole assembly with the gas torch, ensuring that silver solder runs round the gas-jet housing join to the small end cap and the join of the large end cap, the copper tube and the small end cap. Figure 67 shows the original burner being soldered.

Once the assembly is cool, the complete burner can be pickled, carefully washed and dried; then clean off any flux, file or emery off any excess solder, and check for good, gas-tight joints.

FIG. 68
The ceramic element is ready to be glued into the cleaned-up body of a 35mm burner.

To make the size of the ceramic needed, mark its back with a pencil using the 28mm tube as a template, then saw it roughly to size. File the resulting circle of ceramic to a slight taper so it fits into the end cap. About half the thickness of the ceramic should be in the copper tube and half sticking out. Figure 68 shows the ceramic disc and the soldered burner body.

To glue the ceramic into the burner body, place a small amount of ceramic adhesive filler round the inside top of the copper tube and round the ceramic disc, and then press the disc firmly in place. Remove excess adhesive and fill any gaps between the element and the copper tube with a bit more filler. Then smooth in place. Some water and a damp cloth will help to smooth the glue so any excess can be cleaned off.

The look of the burner can be improved by painting its outer copper parts with black heatresistant paint. However, leave the brass part bare and polish it, as no heat-resistant etch primers are available. Without a primer, any paint on the brass is unlikely to last long in good condition.

FIG. 69
The heat of the flame is now starting to show above the blue cones on the 35mm burner.

Fit a No. 8 jet in the holder, and place the holder in the gas-jet housing so the jet fills just over half the primary air hole. Connect the jet to the gas tank, check to ensure there are no leaks, turn on the gas and light the ceramic element. Adjust the jet’s position and the rate of gas flow so blue cones, as those shown in Figure 69, form on the surface: now you are in business!

28MM (1 ⁷⁄₆₄ IN) BURNER

This smallest burner is made in a similar way to the two larger ones, but uses 28mm and 22mm end caps. However, a length of 22mm copper tube is not acceptable as it leaves insufficient space between the flue and the tube. As a result, turn a 43mm (1¹¹⁄₁₆ in) length of 25mm or 1in brass down to a diameter of 22mm (1⁵⁵⁄₆₄ in). Then turn one end down to 20.5mm (1¹³⁄₁₆in) for a length of 25mm (1in). Finally, bore to a diameter of 19mm (³⁄₄in). While turning, check that the broad end fits into the small end cap. The ceramic element will glue into the slimmer end (see Figure 70). The measurements of the various parts can be obtained from Figure 71.

FIG. 70
The completed 28mm burner, clearly showing the secondary air holes.

FIG. 71
The sizes of the components, apart from the gas-jet housing, that are required to make a 28mm ceramic burner.

FIG. 72
Using a 6mm slot drill to form the eight holes in a 28mm end cap.

Drill a hole in the centre of the 28mm end cap using Swarfega as a lubricant, so it can be bolted to the rotary table with a suitably sized spacer. Ensure the centre of the rotary table is under the millingmachine-chuck centre line. Tilt the table to 45 degrees, and move the whole table along the X-axis until a 6mm (¹⁄₄in) mill or copper drill in the chuck is directly over the location of the first hole. The set-up can be seen in Figure 72. Lock the milling machine and rotary table and drill the first hole. Turn the rotary table through 45 degrees, relock it and drill the second hole. Repeat every 45 degrees to form eight holes in the larger end cap, each 6mm (¹⁄₄in) diameter and 45 degrees apart.

FIG. 73
The five metal component parts of the 28mm burner, together with the disc of ceramic.

Next, bore out the central hole to 22mm (⁷⁄₈in) in the lathe, again providing some 0.13mm (0.005in) clearance for silver solder. Locate the larger end of the turned brass tube in the small end cap, and mill or drill an 8mm (⁵⁄₁₆in) hole in the copper end cap and the brass tube 12.5mm (¹⁄₂in) from its bottom for the gas-jet housing. The gas-jet housing is the same as the one for the other burners, but the narrower end is shorter at 19mm (³⁄₄in) to maintain a gap to the edge of the housing at about 3mm (¹⁄₈in). Figure 73 shows a complete set of machined parts.

FIG. 74
The main parts of the 28mm burner being silver soldered.

Now all the parts can be carefully cleaned, fluxed and fitted together. Silver soldering is straightforward as the change in diameter of the inner tube ensures that the parts locate in the correct position. When inverted, the large end cap may need some 3mm (¹⁄₈in) supports to keep it steady. Now heat the whole assembly until the flux flows and the metal starts to glow red. Run silver solder around the gas-jet housing joint to the smaller end cap, as illustrated in Figure 74, and the joint of the outer casing to the brass tube and smaller end cap. When it has cooled, the complete assembly should be pickled, washed, and then any excess flux cleaned off; remove any surplus solder, and check that gas-tight joints have been made.

To make the ceramic element, place the 22mm brass tube on the reverse, flat side of the piece of ceramic, and mark a circle the size needed. Cut the material with the ceramic saw, and then file the edge of the resulting disc to the slightly conical shape that fits into the end cap for just half its thickness.

FIG. 75
The cleaned-up 28mm burner with its ceramic element ready to fit.

At this stage, shown in Figure 75, the ceramic element can be glued into the burner. Run a thin strip of adhesive filler around both the inner top of the brass tube and the ceramic, press the ceramic disc in place, and clean off excess filler with a damp cloth. Check for unfilled gaps between the element and the brass tube. If there are any, add some more filler, smooth it down and clean off any remaining excess.

FIG. 76
A completed 28mm burner needing only a gas-jet holder and gas jet.

Improve the look of the burner by painting its outer copper parts with black or coloured heat-resistant paint. Leave the brass parts bare or polished, because without a high-temperature etch primer, any paint on the brass will quickly start to look shabby. The finished burner can be seen in Figure 76.

FIG. 77
The 28mm burner alight and correctly set up, showing blue cones and a hot flame.

At last a No. 5 jet can be fitted in the holder and the holder in the gas-jet housing so the jet is half way along the primary air hole. Connect a gas tank of a propane/butane mix, check there are no leaks, turn on the gas and light the top of the ceramic element. Adjust the position of the jet and gas flow so that blue cones form on the surface. Heat will rapidly be generated, as can be seen in Figure 77, and you are finally ready to go.

An Alternative 28mm (1⁷⁄₆₄in) Burner

One particular problem came with building a burner for Tubal Cain’s Trevithick ¹⁄₁₆ scale dredger engine and boiler. The flue has an internal diameter of 28mm, but unfortunately does not stick out beyond the boiler end plate. This is shown in Figure 78. The need, therefore, was for a burner that would plug into, rather than over the flue. A short 20mm (¹³⁄₁₆in) ring of 28mm pipe was cut: this is illustrated in Figure 79 and dimensioned in Figure 80. Push the copper ring into the larger end cap, prior to silver soldering the whole burner. Roughly half the length of the ring must stick out of the 28mm end cap. There is a picture of the finished burner in Figure 81. As it shows, the part of the ring that pushes into the flue should not be painted.

FIG. 78
The Trevithick boiler end plate showing the flue at left, and the connection to the chimney on the right. The solution was to make a plug-in burner as well as a removable plug-in furnace door.

FIG. 79
The copper adaptor ring that can form part of the burner so it can be plugged into, rather than over, a flue.

FIG. 80
The size of the single extra item that will be needed when building the alternative 28mm burner.

FIG. 81
The copper adaptor ring fitted to the 28mm burner so it plugs into a flangeless flue.

Unsurprisingly, exactly the same technique may be applied to a 42mm or 35mm burner using short lengths of 42mm or 35mm copper tube. Again, remember not to paint the bit of the ring that plugs into the flue.

4
Burners to Fit under Boilers

THIS CHAPTER COVERS THE building of two different sizes of round burner and two different shapes of rectangular burner, with one variant. All four are designed to fit in the firebox of either a vertical or horizontal boiler of the appropriate size. Full dimensions are given of all the components, and how they can be assembled to provide working burners for vertical and horizontal boilers that have a firebox.

FIG. 82
Two round and three rectangular burners. Their sizes and shapes suit a wide range of boiler fireboxes.

FIG. 83
A well-used 89mm (3¹⁄₂in) vertical fire-tube boiler installed in a steam lorry. The boiler is heated by a 54mm round burner.

FIG. 84
A 76mm (3in) horizontal boiler fitted with a 70 × 50mm rectangular burner in its firebox.

Ceramic burners for vertical and horizontal model steam boilers built without a centre flue can be either round or rectangular, depending on the size and shape of the boiler firebox, which must include an adequate number of secondary air holes. Figure 82 shows all five of these burners, while Figure 83 shows a boiler that needs a circular burner and Figure 84 is an example of one that uses a rectangular burner to provide heat. All except one of the burners are significantly larger than the 42mm, 35mm and 28mm ones described in the previous chapter.

The round burners are again based on plumbing end caps. The rectangular ones can be folded from 1.6mm (16 SWG) copper or brass sheet, with dimensions to suit the size of the boiler firebox. The round burners are ideal for vertical boilers up to 108mm (4¹⁄₄in) diameter, and the rectangular ones for similar-sized horizontal boilers.

FIG. 85
The simple set of parts needed to mount a burner in a boiler firebox.

Both types of burner require a brass gas-jet housing with holes for primary air, and the ability to adjust the position of the gas-jet holder in the housing. In addition, a length of stainless-steel spring and a small piece of stainless-steel mesh are needed as gas-diffusion components. Mounting the burner in a boiler requires a simple mount of the type shown in Figure 85. It is easily machined from brass strip; dimensions are given in Figure 188 on page 90.

GAS-JET HOUSINGS

The gas-jet housings for the 54mm and 67mm round burners and the three rectangular burners are identical. Figure 86 gives the dimensions, while Figure 87 shows a completed housing. They are made from 12.5mm (¹⁄₂in) brass rod, drilled 8mm and faced each end to 46mm (1¹³⁄₁₆in) long.

FIG. 86
Dimensions of the gas-jet housing that fits both shapes and sizes of burner.

FIG. 87
A complete brass gas-jet housing for either a circular or rectangular burner.

Turn the last 3mm (¹⁄₈in) of length down to 10.5mm (¹³⁄₃₂in) diameter to fit in the hole in the burner body. Cross-drill a 6mm (¹⁄₄in) hole right through the housing, 19mm (³⁄₄in) from the other end, and a second 6mm (¹⁄₄in) hole drilled only in the top of the housing, also 19mm (³⁄₄in) from the same end. Drill and tap a 6BA or M3 hole, 6mm (¹⁄₄in) from the end for the short bolt that holds the jet in position. The housing can then be silver soldered into its round or rectangular housing, but first remove the bolt.

67MM AND 54MM CIRCULAR BURNERS

Figure 88 shows the complete 67mm and 54mm round burners. Figures 89 and 90 provide the dimensions of these two different sizes of round burner. The circular burners can be readily made using 67mm (2⁵⁄₈ in) or 54mm (2¹⁄₈in) copper end caps, depending on the size of burner you require. However, these fittings, as seen in Figure 91, are rather taller than needed so they will have to be shortened. The 67mm end cap is 38mm (1¹⁄₂in) tall, and needs reducing by around 13mm (¹⁄₂in), while the 54mm one needs reducing by 11mm (⁷⁄₁₆in). Large end caps can be expensive if bought from a plumbers’ merchant, but they can be found relatively cheaply on eBay and other internet sites.

FIG. 88
Left, a 67mm round burner, and right, a 54mm one. Both are ideal for heating vertical fire-tube boilers.

FIG. 89
The dimensions of the various components that are required to make a 67mm ceramic burner.

FIG. 90
The sizes of the set of components needed to make a 54mm ceramic burner.

FIG. 91
67mm and 54mm plumbing copper end caps, which form the basis of the round burners.

FIG. 92
An end cap held in a lathe’s external jaws and pressed in place with a rotating Jacob’s chuck. A parting tool marks the desired height of the end cap.

FIG. 93
Finishing cutting the end cap to height with a hacksaw.

The easiest way to shorten a copper end cap is by holding the cap in a lathe and using a parting tool to cut part way through to mark the correct height. This is being done in Figure 92. You can be brave and part the copper right off, but it is difficult material to part cleanly. Alternatively, carefully complete the remainder of the cut with a hacksaw, holding the end cap in a vice and turning it as required with a spacer to stop the gap being closed by the vice. Figure 93 demonstrates how you can do this.

FIG. 94
The end cap clamped to an angle plate. The hole is centre drilled and opened to size. The cap could just as easily be held in a vice on a milling table.

The resulting unit can then have its edge cleaned on a linisher, and a hole drilled for the gas-jet housing. This drilling is easily done by clamping the body to an angle plate (see Figure 94), or holding it in a machine vice, and then drilling the hole 10.5mm (¹³⁄₃₂in) diameter, 8mm (⁵⁄₁₆in) from the underside of the end cap. For those whose chucks have a maximum capacity of 10mm, the hole is easily opened to 10.5mm with a round file, regularly checking for the fit of the gas-jet housing.

FIG. 95
All the metal components for the 67mm burner.

The housing for the gas-jet holder will have been made already, so it can be carefully silver soldered in place on the burner body. When you solder either the larger or the smaller burner bodies, Figures 97 and 98 illustrate how they can be wedged in a vertical position with fire bricks so the gas-jet housing stands upright for soldering. With flux around the joint, it only requires a fairly quick touch of silver-solder rod to complete the joint. Once it is completely cool, any flux can be removed, and the whole assembly cleaned in pickle. Do check you have made a good job of the joint as it must be gas tight.

FIG. 96
The five metal parts needed to make the 54mm burner.

The next task is to prepare the gas-diffusion components. They consist of a length of ¹⁄₂in or 12mm diameter stainless-steel spring of 1.6mm (16 SWG) wire, 70mm (2³⁄₄in) long for the larger burner, or 60mm (2³⁄₈in) long for the smaller one. In addition, a strip of twenty-mesh (twenty holes per inch with a 1.02mm aperture and 0.25mm wire diameter as a woven wire mesh) stainless-steel mesh measuring 15mm (⁹⁄₁₆in) × 40mm (1¹⁄₂in) is needed. Figures 95 and 96 show all the metal parts for the larger and smaller round burners.

FIG. 97
Silver soldering to join the gas-jet housing to the large round burner body.

FIG. 98
Silver soldering to attach the same housing to the small burner body.

FIG. 99
The 67mm burner showing the copper body with the spring and mesh fitted in place. The ceramic is yet to be installed.

FIG. 100
The 54mm burner with its copper body that has had the spring and mesh glued in. The ceramic will be fitted next.

FIG. 101
Left: The finished 67mm burner painted black with its ceramic element fitted; and right: the complete 54mm burner is also black that contrasts with its ceramic element.

Both gas diffusion components can be fixed in place with adhesive filler, as shown in Figures 99 and 100, followed by the ceramic elements that must be cut from a sheet of ceramic honeycomb. Mark the back of a piece of ceramic material with pencil, using the burner body as a template. Then cut out the circle and carefully file or sand it so it just fits in the burner body with 6mm (¹⁄₄in) sticking above the rim. Glue it in place by spreading ceramic adhesive filler around the inside rim of the burner body and the lower side of the ceramic material. Press into place and smooth off the filler with a damp cloth, making sure no gaps are left between the burner body and the ceramic element. The copper can be painted with heat-resistant paint, with the brass gas-jet housing polished. Figure 101 shows the two completed round burners.

FIG. 102
The 54mm burner alight, with far too little primary air and a long yellow flame.

FIG. 103
The 67mm burner burning correctly and covered with blue cones.

For each of these two burners, fit a No. 8 or No. 10 jet to the holder, and the holder in the gas-jet housing so its end is just over half way along the primary air hole. Connect to a gas tank of propane/butane mix, turn on the gas, check for any leaks, and light the flame on the ceramic element. Figure 102 shows that the gas jet is too far in and the burner flame is yellow. Adjust the gas flow and the position of the jet so that blue cones form on the surface of the ceramic, and the whole surface will quickly generate heat, as can be seen in Figure 103.

The larger burner is well suited to vertical fire-tube boilers of around 90mm (3¹⁄₂in) to 108mm (4¹⁄₄in) diameter. The smaller one is ideal for 76mm (3in) to 90mm (3¹⁄₂in) vertical boilers.

RECTANGULAR BURNERS

Figure 104 shows two larger rectangular burners, which are a nominal 70 × 50mm (2³⁄₄ × 2in), and a smaller one that measures 65 × 25mm (2⁹⁄₁₆ × 1in). They are all relatively straightforward to make. Two require an oblong box that is simply formed from 1.6mm (16 SWG) copper sheet, cut and then bent to shape. The third uses the same thickness of brass sheet.

FIG. 104
The two large rectangular ceramic burners, and one small one.

70 × 50mm Rectangular Burner

Cut out the shape of the burner housing from copper sheet with the four corners removed, as shown in Figure 105. A choice has to be made about whether to fold the boxes with the metal as supplied, or after it has been annealed. It requires rather more force to bend unannealed metal, but the base and sides tend to be flatter. Annealed metal is much easier to bend but tends to distort, though judicious use of a soft-headed hammer readily removes any blemishes. Figure 106 provides the dimensions of the larger rectangular burner. Note that the long sides extend 3mm (¹⁄₈in) beyond the base to allow overlapping corners. Cut the short length between the long sides and the base so that the ends can be correctly folded.

FIG. 105
1.6mm (16SWG) copper sheet cut to size for the 70 × 50mm large rectangular burner.

FIG. 106
The dimensions of the parts required to make a 70 × 50mm rectangular ceramic burner.

FIG. 107
The flat copper sheet in the bender and set to make the first bend.

FIG. 108
Closing the vice jaws to make the first 90-degree bend.

FIG. 109
The result of the first bend is visible as the second bend is created.

FIG. 110
To make the third ‘end’ bend requires using a suitable block of wood as a former and a small length of wood that helps to start bending the copper end before it is hammered over. The fourth bend is formed in the same way.

FIG. 111
To avoid marking the copper with indentations from the head of the hammer, use a protective block of wood.

FIG. 112
The box is completed with the final bend.

FIG. 113
A pair of folded-up brass and copper boxes.

An easy solution to folding the two long sides is with a vice bender, unless you are fortunate enough to have a sheet-metal bender in your workshop. The one used here came from Warco, but a similar one is sold by Axminster tools. Six illustrations (Figures 107–112) show how the bends were made. The first two bends were formed in the bender. The last two were bent by cutting a short length of wood 70 × 50 × 100mm (2¹³⁄₁₆ × 1³¹⁄₃₂ × 3¹⁵⁄₁₆in) to fit inside the box, and then pushing a protective piece of wood by hand, followed by hammering, to force the last two sides through 90 degrees. Figure 113 shows how the overlap of the sides with the ends ensures that any gaps at the corners are easily closed by judicious hammering.

FIG. 114
Silver soldering the gas-jet housing and the corners of a box.

After folding the box, drill a 10.5mm (¹³⁄₃₂in) central hole in one end of the box, 8mm (⁵⁄₁₆in) from the underside of the box, to fit the gas-jet housing. Figure 114 illustrates how the four corners are silver soldered together to seal them, at the same time as the gas-jet housing is silver soldered in place.

Clean the result in pickle once the metal is cool, and then use a file and/or a linisher to provide four sides of equal height. Finally, use a file and wire wool to clean the soldered corners and polish the burner-jet housing to give it an attractive finish. Do check that the joints are well made and gas tight.

FIG. 115
A soldered and cleaned-up box with its gas-jet housing, spring and mesh.

FIG. 116
The burner body now has the spring and mesh glued in place. The ceramic element has been cut to size and is beside it.

Saw a rectangle of ceramic fractionally larger than the internal box dimensions. File a slight taper on the edges so it fits perfectly into the box. Then secure the gas-diffuser components in the case. Figure 115 indicates that you will need a 75mm (3in) long stainless-steel spring, ¹⁄₂in or 12mm diameter of 1.6mm (16 SWG) wire, and a 60 × 15mm (2³⁄₈ × ⁹⁄₁₆in) strip of stainless-steel woven wire mesh (20 mesh with a 1.02mm aperture and 0.25mm wire diameter). Glue both these components in place with ceramic adhesive filler, as shown in Figure 116.

FIG. 117
The copper rectangular burner with its ceramic element fitted. The body has been painted with black heat-resistant paint to finish it.

FIG. 118
The brass rectangular burner with its ceramic element in place and ready for a gas-jet holder and gas jet.

FIG. 119
The black-bodied copper burner alight and providing a lot of heat.

Finally, glue in the ceramic element using the same ceramic adhesive/filler. Ensure no gaps are left between the ceramic and its case, cleaning off any excess filler with a damp cloth. Paint the copper black, leaving the brass gas-jet housing polished. Figure 117 shows a black-painted copper-bodied burner. The rectangular burner bodies can be made from 1.6mm brass instead of copper sheet, but will need polishing rather than painting. Figure 118 is the variant of the burner with an unpainted brass body.

Fit a No. 8 or No. 10 jet to the holder, place it in the gas-jet housing and adjust its position so it fills just over half the primary air hole. Connect up a gas tank, check for leaks, turn on the gas, and light the burner above the ceramic element. Adjust the gas flow and the position of the jet in the gas-jet housing until blue cones of flame appear on top of the burner: then the ceramic element will quickly heat up, giving an excellent heat output. Figure 119 shows the correct gas/air settings for the large rectangular burner.

65 × 25mm Rectangular Burner

A smaller, slimmer, oblong burner measuring a nominal 65 × 25mm (2⁹⁄₁₆ × 1in) is equally simple to construct. Again, carefully cut out the shape in 1.6mm (16 SWG) copper as shown in Figure 120, and fold into the form of an open-top box. Figure 121 shows the dimensions for this burner.

FIG. 120
The copper sheet for the 65 × 25mm small rectangular burner must be carefully cut to size.

FIG. 121
The sizes of the components required to make a 65 × 25mm rectangular ceramic burner.

FIG. 122
Silver soldering the last corner of the small rectangular burner.

FIG. 123
All the metal parts of the small rectangular burner after silver soldering.

FIG. 124
The burner with its spring and mesh fitted in place and its ceramic element beside it.

Folding the box for this burner is very similar to the method used with the larger rectangular burners. However, you will need a piece of wood 65 × 25 × 50mm (2⁹⁄₁₆ × 1 × 1³¹⁄₃₂in) to fit in the box while folding the two short ends. It is certainly much better to fold this box unannealed, as internal access for flattening the sides is limited. It still uses the same gas-jet housing as the larger burners, which must be silver soldered in place, shown in Figure 122, at the same time as the four corners of the box are sealed with solder. However, it uses slightly shorter lengths of spring and metal mesh, seen in Figure 123, again glued in place with your favourite ceramic adhesive filler, as in Figure 124, before the slim strip of ceramic is finally glued in place.

FIG. 125
The small rectangular burner complete with ceramic element.

FIG. 126
The 65 × 25mm rectangular burner alight and covered with blue cones. Its body is painted black.

Either the burner body can be painted black with heat-resistant paint, or left as bare copper. It could even be folded from brass sheet and polished. Figure 125 is a photo of a copper burner painted black. A No. 5 jet is ideal for this burner. As usual, check for gas leaks; adjust the gas flow and the position of the gas jet in relation to the primary air holes to give a covering of blue cones on the ceramic, as can be seen in Figure 126. This is a slim-shaped burner, but despite the reduced area of ceramic, it has an excellent heat output for smaller boilers with a slim firebox; however, it is not as small as those described in the next chapter.

Burners for Mamod and Wilesco Boilers
5

THIS CHAPTER COVERS MAKING one small round and one small rectangular burner, suitable for installation in ready-made Mamod, Wilesco and similar steam-powered models. It describes how to make the various parts, and how to assemble them so as to end up with effective burners. These ceramic burners are a useful alternative to the original methylated spirit burners, and are cleaner burning.

FIG. 127
The two smallest burners are the 35mm round one and the 50mm oblong one.

A small gas-fired burner of suitable dimensions can be used to heat up either Mamod or Wilesco ready-made boilers. They can also be used with similar small commercial boilers, as well as home-made boilers of a comparable size. Their big advantage is that their flame is hot and clean, making less sooty dirt on your model. Figure 127 shows the two designs that can be made: a 35mm (1³⁄₈in) round and a 55 × 15mm (2 × ¹⁹⁄₃₂in) oblong one. The choice will depend on the size and shape of the boiler firebox, which must include an adequate number of secondary air holes; this is not normally an issue with Mamod or Wilesco designs.

FIG. 128
A much-loved and recently refurbished Wilesco steamroller fitted with a gas tank and ceramic burner.

FIG. 129
The 55mm oblong burner with connecting pipe to a small refillable gas tank.

FIG. 130
An early Mamod boiler and single-cylinder engine with its original meths burner; this could be replaced with a ceramic burner.

FIG. 131
A well-used Mamod Minor 2 converted to use a round ceramic burner supplied from a disposable gas tank.

Figure 128 shows a Wilesco steamroller that looks to be in remarkably good condition. It has been fitted with a 55mm oblong burner and the small gas tank illustrated in Figure 129. Figure 130 shows a Mamod boiler/engine combination that still uses a meths burner, while Figure 131 is of another Mamod with the engine on the boiler that has been converted and now runs on LPG supplied to a 35mm round burner.

GAS-JET HOUSINGS

The gas-jet housings for the two burners are similar and are made from ¹⁄₂in or 12mm brass rod. The housing for the round burner is the longer of the two, and Figure 132 provides its dimensions. Face it 71mm (2⁵¹⁄₆₄in) long, and then drill 8mm (⁵⁄₁₆in) diameter to a depth of 30mm (1³⁄₁₆in) from one end and 6mm (¹⁄₄in) diameter from the other end to provide a continuous hole through the housing.

FIG. 132
The dimensions of the gas-jet housing for the 35mm round burner.

The dimensions for the oblong burner are given in Figure 133. Face each end to 41mm (1⁵⁄₈in) long and drill 8mm (⁵⁄₁₆in) to a depth of 30mm (1³⁄₁₆in) from one end and 6mm (¹⁄₄in) from the other to give a continuous hole. Turn the last 3mm (¹⁄₈in) of length down to 8mm (⁵⁄₁₆in) diameter to fit in the hole in the burner housing.

FIG. 133
The sizes of the parts of the gas-jet housing for the 50mm oblong burner.

FIG. 134
Two different brass gas-jet housings, top for the 35mm round and below for the 50mm oblong burner.

For both housings, cross-drill a 6mm (¹⁄₄in) hole 12.5mm (¹⁄₂in) from the thick end and 6mm (¹⁄₄in) from the other; from the same end drill and tap a hole 6BA or M3 for the bolt that allows the position of the gas jet in the housing to be adjusted. Figure 134 is of a pair of completed housings, one for each type of burner. Do not fit the bolt yet. You are now ready to silver solder the appropriate housing into the round or rectangular burner body.

35MM CIRCULAR BURNER

The round burner, seen in Figure 135, is based on a 35mm end cap, with the depth reduced to 17mm (⁴³⁄₆₄in). The easiest way to do this is to hold the cap in a lathe and use a parting tool to mark the correct depth. Then finish the cut with a hacksaw, holding the end cap in a vice and rotating it, with a spacer, to stop the gap closing. Clean the edge on a linisher or in the lathe, and drill an 8mm (⁵⁄₁₆in) hole for the gas-jet housing, with its centre 7.5mm (⁹⁄₃₂in) above the end-cap base, as shown in Figure 136.

FIG. 135
This small 35mm round burner will easily fit into the firebox of most Mamod and Wilesco models.

FIG. 136
The dimensions of the various components required to make a 35mm round burner.

Carefully silver solder the housing for the gas-jet holder on the burner body. Figure 137 shows the burner body wedged upright so the gas-jet housing stands vertically. With flux around the joint and heat, it only requires a quick touch of silver-solder rod to finish the joint. Once completely cool, remove any flux and pickle the whole assembly. Check that the solder runs the whole way round the housing to give a gas-tight joint.

FIG. 137
Soldering the gas-jet housing to the round body with a MAPP gas torch.

The ceramic disc must be thinned, and this can easily be achieved on a sheet of F2/grade 100 sandpaper on a flat surface using a figure-of-eight rubbing motion to reduce its depth to 9mm (³⁄₈in). Then blow away any dust that may have accumulated in the ceramic holes. Mark the back of the ceramic material with pencil using the burner body as a template, cut out the circle, and carefully file or sand it so it just fits in the burner body, with 5mm (³⁄₁₆in) sticking above the rim. Figure 138 shows the burner body and ceramic disc ready for you to fit.

FIG. 138
Two metal components, silver soldered together, a short bolt and a piece of ceramic are all that is required to make the 35mm round burner.

FIG. 139
The finished 35mm round burner with its body coated with heat-resistant paint, ready to have a gas jet and holder fitted.

Glue it in place by spreading ceramic adhesive filler around the inside rim of the burner body and the lower side of the ceramic material. Press into place and smooth off the filler with a damp cloth. Ensure no gaps are left between the burner body and the ceramic, and leave to dry for at least one day. The brass gas-jet housing can be polished, and the copper painted with heat-resistant paint. Figure 139 shows a finished burner.

FIG. 140
With too little primary air, the 35mm round burner produces a soft flame.

FIG. 141
The 35mm round burner correctly burning with blue cones on the surface of the ceramic.

Fit a No. 5 jet to the holder, and place in the gas-jet housing so its end is just over half way along the primary air hole. Connect to a tank of propane/butane mix, check for leaks, turn on the gas, and light the flame on the ceramic element. In Figure 140 there is too little primary air and the flame is burning yellow. Figure 141 shows a correctly adjusted flame, so adjust the gas flow and the position of the jet until the usual blue cones form on the surface of the ceramic. This burner will provide adequate heat for 50mm (2in) diameter boilers.

50 × 15MM OBLONG BURNER

This burner requires the short gas-jet housing shown in Figure 133 on page 67, a short length of stainless-steel spring, and a small piece of stainlesssteel mesh to diffuse the gas beneath the ceramic element. Make the burner case from an 85 × 50mm (3¹¹⁄₃₂ × 2in) piece of 0.9mm (20SWG) brass sheet cut to the size and shape, as shown in Figure 143. Note that the cuts extend below both body sides at both ends. Figure 144 shows the cut brass sheet.

FIG. 142
The finished oblong burner still needs a gas-jet holder and jet before it can be lit.

FIG. 143
The size of the parts needed to make a 50 × 15mm oblong burner.

FIG. 144
There are eight stages involved in folding the burner body from a piece of 0.9mm (20 SWG) brass sheet. First the brass sheet for the body must be carefully cut to shape.

FIG. 145
The sheet is carefully located in the bender in the vice.

FIG. 146
The first bend is easily completed in the folder. Check it is a right angle.

FIG. 147
The second bend can only be started in the bender.

FIG. 148
The part-bent second side needs some further bending.

FIG. 149
The second bend is completed by squeezing it in the vice with a 15mm wide steel spacer.

FIG. 150
The bottom of the casing can then be flattened by hammering with a wooden block.

FIG. 151
The two ends are hammered into position again using the 15mm steel spacer.

The sheet must be carefully folded to form an open-top box. The first bend (Figures 145 and 146) is easily made in the folder, but the second bend can only be started (Figures 147 and 148), completion being undertaken by squeezing it in the vice with a metal spacer 15mm (⁵⁄₈in) wide (Figure 149). The bottom of the casing can then be flattened (Figure 150) before the two ends are hammered into position (Figure 151).

FIG. 152
Silver soldering the corners of the oblong body.

Mount the folded body vertically in a vice, and drill an 8mm (⁵⁄₁₆in) hole for the gas-jet housing in one end, 7.5mm (⁹⁄₃₂in) up from the bottom. Having already made the gas-jet housing, it is time to silver solder the ends of the oblong burner body and the gas-jet housing in a single session. Coat all four corners with flux, as well as the part of the gas-jet housing where it fits into the burner body. A MAPP gas torch provides plenty of heat. First solder the gas-jet housing to the body as well as the two corner joints at that end. Using tongs, turn the burner over and solder the second end to seal it, as shown in Figure 152.

FIG. 153
The complete set of parts needed for the oblong burner.

When the burner body and jet housing have cooled down, the complete assembly should be pickled, cleaned up, the joints checked, and the assembly polished. Then fit the spring in the body, followed by the piece of mesh with an oval cut in the bottom so it doesn’t foul on the spring. These items can be seen in Figure 153, as well as the ceramic cut to size.

FIG. 154
The gas diffusion parts showing the spring and wire mesh glued in place. The strip of ceramic has been cut to shape.

Glue them in place with ceramic adhesive filler, using a wooden drinks stirrer to place the adhesive, as illustrated in Figure 154. Cut the ceramic honeycomb with a slight taper on all four sides where it fits into the burner body. Use ceramic adhesive filler to secure it in the body, and clean off any excess filler with a damp cloth. Ensure that no gaps are left unfilled. Leave the completed burner to dry for twenty-four hours.

FIG. 155
The finished oblong burner is a neat unit that will fit into a narrow firebox.

FIG. 156
The burner with too little primary air and giving a soft yellow flame.

FIG. 157
The blue cones and flames are correct for good heating.

FIG. 158
Still with blue cones, the gas flow has been turned up to increase the rate of heating.

Now it is time to test the burner, which should look like the one pictured in Figure 155. You will need a gas jet and holder, a gas tank, valve and a connecting pipe. Fit a No. 5 jet to the jet holder, and insert it into the gas-jet housing so it covers just over half the primary air hole; then tighten the adjusting screw. Check for gas leaks, then light the burner, and adjust the position of the gas jet and the rate of gas flow until blue cones appear on the ceramic, which will quickly provide a good heat; a soft yellow flame, as seen in Figure 156, should be avoided. Figures 157 and 158 show how the heat output can be adjusted to suit the size of boiler.

FIG. 159
A couple of Terry clips are bolted to the rear of the steamroller. In front of the roller is the gas tank, burner and correctly shaped connecting gas pipe.

This small rectangular burner is ideally suited to heating small horizontal ‘pot’ boilers up to around 100mm (4in) long and 55mm (2in) in diameter. A small rechargeable gas tank, as the one shown in Figure 159, is a good match for this burner, and can usually be mounted at the back of a small car, lorry, traction engine or steamroller.

INSTALLING A SMALL CERAMIC BURNER IN A VEHICLE SUCH AS A STEAM ROLLER

Installing a small ceramic burner in a static engine is quite straightforward, but installing one in a vehicle such as a steam roller can be a little more problematic. Assuming you have selected the shape of burner to fit in the firebox, you will need the smallest refillable gas tank you can find. A small vertical tank is easily installed on the back of the vehicle by bolting a pair of small Terry clips to its back end.

With the tank fitted and the burner in place, use a short length of soft wire to run along the route the gas pipe will follow. Measure the length, and then cut the same length of ¹⁄₈in copper pipe, and bend the pipe to the desired shape. Silver solder a gas-jet holder to one end, and a connector to the gas tank on the other. Then fit the gas-jet holder in the housing, and connect the other end to the gas tank to check the layout.

Remove the burner and gas tank, and connect them together with the gas jet in roughly the right place so that you can turn on the gas, light the burner and adjust the position of the jet and the gas valve to get the desired flame. Tighten the bolt that locates the gas-jet holder in place in its housing.

Now turn off the gas, allow the burner to cool, and refit the burner in the firebox and the gas tank in its clips. Connect the pipe to the gas tank, and check to see if you need to make a small clip to hold the burner securely in position.

Good steaming!

Liquefied Petroleum Gas (LPG)
6

THIS CHAPTER LOOKS AT the various aspects of using liquefied petroleum gas (LPG) to heat ceramic burners. It covers the features of the various gases, how best to contain them, and which are best suited to heating small steam boilers. Various safety issues are discussed, and it is important to apply them. Finally, the chapter also provides information about small gas containers and refillable tanks.

As mentioned at the start of Chapter 2, LPG is used in many applications, including silver soldering. It is also a popular heat source for small steam boilers. For heating these boilers, the gas is available as propane, butane, or as a mixture of the two. It has an unpleasant smell so leaks can be easily detected. LPG burns readily and is denser than air so it pools in low areas. Any leaks present a fire risk. While the physical properties of butane and propane are similar, both gases are poisonous, although butane is less toxic than propane and can be legally stored indoors.

The difference in the properties of propane and butane means that they are particularly suited to specific uses. Propane’s lower boiling point of –42ºC suits outdoor use. Butane does not work well in colder conditions, only vaporizing just above –2ºC, and is best used indoors or outside in the summer months. Otherwise the performance of the two gases is very similar in terms of flame temperature and calorific value.

LPG can be compressed into very small cylinders. It changes easily to a liquid under pressure, so reasonable amounts of gas can be stored in a relatively small volume. However, to work in a ceramic burner, the LPG must be able to boil into a gas. Liquid propane expands 250 times when it turns from a liquid to a gas. When LPG is released from its pressurized canister, it boils, turns into a gas, and in doing so cools the liquid in the container. Thus the LPG temperature will drop some way below ambient, and this can prevent butane alone from boiling and so producing a useful gas supply, even when the outside temperature is significantly above freezing. This can still be a problem with a propane/butane mix when, for example, sailing a steam-powered boat on a cold, windy day.

The ceramic burners described in this book are all designed to run on LPG. Of the various types of LPG, a butane and propane mixture, typically 70/30, sometimes with isobutane, is the preferred fuel to be used in ceramic burners suitable for heating model steam boilers. To provide the gas for the burner either a small disposable canister can be used, or a refillable gas tank can be fitted, and loaded with gas from one of the larger disposable cans. Always fill any refillable tank out of doors so that any inevitable leakage dissipates safely.

In northern Europe, especially in the winter months, the best compromise is the mix of propane and butane commonly found in the small gas cartridges produced for camping stoves and gas lamps. This mix is widely available in small- and medium-size disposable canisters. These canisters can be bought from DIY, camping and caravan equipment stores.

Experience has shown that in operation, particularly in cold weather, gas cylinders can quickly become so cold that their output pressure and rate of gas flow can fall to the point where insufficient heat is available from the burner to keep the boiler steaming at the rate required to drive its engine. For static installations, the solution is simple: place the gas cylinder in a bowl of warm water, and the gas flow will almost immediately increase to its normal level. For installations in boats and land vehicles, the solution is rather harder. One answer is to feed warm air around the gas tank. An option is to install a small electric fan to blow warm air into the compartment containing the gas tank. Another alternative that can help is to run a copper strip from beneath the boiler’s burner to the gas tank to conduct heat from one to the other.

For those who prefer a gas tank integrated into the system, particularly for model boat use, a number of designs are available from model engineering suppliers. For those who want a system that controls the gas flow to the burner as the pressure in the boiler varies, one of several commercially available solutions can be purchased, both electronic and mechanical. These are described in Chapter 8.

BASIC SAFETY NOTICE

Here is yet another ‘health and safety’ warning that you should read. Remember to be careful when working with your ceramic burner. Some essential safety precautions need to be observed when using LPG as a fuel for a burner, since it is a potential danger if it is misused.

■Connectors and their associated pipes must be installed correctly, and it is essential to check there are no leaks. Apply soapy water to all joints, and when you turn the gas on, check that no bubbles form. All joints should be inspected frequently to avoid future problems

■LPG is denser than air and will pool in any enclosed area. This includes your workshop, your car or other vehicle, and the inside of your model. Therefore tanks should always be refilled in the open air

■Always use a butane/propane mix. Once a gas tank has been filled, or if the burner fails to ignite and the gas is turned off, allow time for any spilled gas to disperse before any attempt is made to light or re-light the burner

■Ensure that you always shut off the gas valve after use, and remove the connection to any disposable can

GAS CONTAINERS

Gas can be bought in several different sizes of small, disposable self-sealing tin containers. Two of these are shown in Figure 160. The more compact sizes are suitable as a direct gas source for heating a small static boiler, or one fitted in a boat with sufficient space and a boiler feed pump. The following are three practical sizes of gas container:

FIG. 160
100g and 230g disposable containers of a mix of propane, isobutane and butane.

FIG. 161
Top view of an 89mm-long commercial gas tank.

FIG. 162
A very small refillable vertical gas tank.

Alternatively a small commercial gas tank can be bought and filled from a larger disposable tin. Tanks such as those shown in Figures 161 and 162 are primarily intended for use with small marine, rail or vehicle applications. They are made of non-sparking brass and copper, and are silver soldered. The tanks are available in several sizes for use with up to a 60/40 butane/propane mix. They are tested to 360psi (25bar), and are supplied with a test certificate. Four different sizes can be bought from model engineering suppliers:

1in (25mm) diameter by 1³⁄₄in (45mm) high
2in (51mm) diameter by 1³⁄₄in (45mm) high
2in (51mm) diameter by 3¹⁄₂in (89mm) long
2in (51mm) diameter by 5in (127mm) long

FIG. 163
Looking down on a well-constructed home-made copper gas tank.

Some may wish to build a home-made, refillable gas tank from copper or brass, and in theory, making such a tank (with a capacity under 250ml) is a relatively simple task for anyone who has silver soldered even quite a small boiler – an example can be seen in Figure 163. However, testing it is far from simple. The test pressure is just under 27.6bar (400psi), requiring a calibrated test-gauge reading up to 42bar (600psi) – and such an item is expensive. The gas must be at 20ºC, and you will need a club inspector who is prepared to undertake the test and certify that the tank has passed the test. Any gas leak will result in a failure.

Detailed requirements are contained in the Boiler Test Code 2018, Volume 3 – LPG tanks under 250ml. The Appendix summarizes these tests. For all these reasons, it is perhaps sensible and probably less expensive to buy a ready-made gas tank with a test certificate.

FIG. 164
A nozzle to screw on a disposable gas can so a gas tank can be refilled.

Refillable gas tanks incorporate a fitting for a filler nozzle that can be push fitted into it. This allows gas to transfer from a larger disposable gas cylinder into the gas tank. A typical example is shown in Figure 164. There is almost invariably a small amount of gas leakage during the filling process, so do this in the open air, and allow any gas that has accumulated in the vicinity to disperse.

FIG. 165
A gas valve, connecting pipe and jet holder with jet fitted.

FIG. 166
A flexible gas pipe with adapter, jet holder with jet in place, and gas valve.

Whatever the type of tank chosen, you will need a connector, a gas pipe with a gas-jet holder soldered on to the end, and a suitable size of gas jet. In addition, for a throw-away gas tank you will need a gas valve that connects the tank to the gas pipe. Either ¹⁄₈in copper pipe can be used for the gas connection, as illustrated in Figure 165, or choose a flexible gas pipe. Figure 166 shows such a gas pipe, regulator and adaptor, supplied by Chiltern Model Steam. The gas-jet holder is easily connected to it with a ¹⁄₈in nipple soldered on to the ¹⁄₈in copper gas pipe with a ¹⁄₄in × 40ME nut on the pipe the right way round so the nut can be screwed on to the thread of the gas-pipe adaptor. The type of pipe chosen will depend on your particular requirements.

Fitting a Gas Tank to a Wilesco Steamroller

It is not difficult to fit one of the smallest gas tanks to any of the Mamod or Wilesco steamrollers or traction engines. These tanks are small enough to be held by a pair of Terry clips of a suitable size. These can be readily bolted to the rear of the vehicle. (See Figure 128 on page 65.) It may also be necessary to make a small clip underneath in order to secure the gas pipe and ensure the burner sits correctly in the firebox.

CONTAINER SAFETY TESTING

At least every five years, safety checks must be carried out on any refillable gas tank to check for leaks. Disposable tanks are exempt from this requirement. Remove the tank from its location in your model, and also remove any covering, but leave the gas filler valve and gas control valve in place. The test involves filling the tank with your usual LPG, and raising the gas mixture to approximately 20ºC to test for leaks from the fittings. This is most easily done by immersing the tank in a bucket of water at 20ºC and checking for bubbles.

A soap-bubble test is more sensitive, and involves spraying or painting the complete tank with a mix of water, liquid soap and glycerine. Bubbles formed by gas escaping indicate a leak. This test can be carried out with cladding on the tank. Any observable leak is regarded as a failure, and the tank and fittings must be repaired and then re-submitted for a further safeguard test. However, a slow leak from the gas valve to the gas jet is not a reason for failure, but requires a valve change.

7
Operating the Burners

SETTING UP A BURNER is critical to the success of steaming any boiler and powering an engine. Advice is given on the size of gas jet to use with each burner, how to make a gas-jet holder, and how to adjust the position of the jet and the gas flow to it in order to give the optimum heat output from the burner and avoid causing damage to it. Details are also included of installing burners and their pipework, as well as lighting the burner.

Before a new burner is mounted in a boiler, screw the recommended size of jet into the jet holder with a small amount of sealant. Then slide the holder into the brass housing, connect the gas to the holder, and check for gas leaks. There is quite a lot to do if the burner is to work correctly and produce the required amount of heat. In all cases, the way a burner is set up is critical to its efficient operation. It must be fitted with the correct size of gas jet, and it is essential to ensure that the right volume of gas is passing to the burner, and to adjust the mix of the gas with the primary air to the ideal setting by moving the gas-jet holder to the optimum position in the gas-jet housing, so that the burner flame is the right size and colour.

JETS

Gas jets for the ceramic burner you have built come in a range of sizes: 3, 5, 8, 10, 12 and 16. The larger the number, the larger the hole in the jet, and the more gas that can flow through it. Even so, the holes are very small.

No. 3 | 0.15mm hole
No. 5 | 0.2mm hole
No. 8 | 0.25mm hole
No. 12 | 0.3mm hole
No. 16 | 0.35mm hole (this is still less than ¹⁄₆₄ in)

FIG. 167
Four gas jets, one showing the small gas outlet; the others are sizes nos 3, 5 and 12. A No. 10 is screwed into a jet holder.

Gas jets have a 1BA thread so they can be screwed into the gas-jet holder. Figure 167 illustrates a selection of gas jets, including one mounted in a holder. The jets are widely available from model-engineering suppliers and a number of them are listed at the end of this book. To give you some idea of gas consumption with the gas valve fully open, a No. 5 jet consumes about 55 grams per hour and a No. 8 jet around 69 grams per hour. The actual amounts will depend upon the make-up of the gas being burned and the pressure in the gas tank.

For the nine different configurations of ceramic burner, which vary in shape and dimensions, different sizes of gas jet will have to be fitted. They can be screwed into the jet holder with a little sealant on the thread. Secure the holder in the ceramic burner housing tube with a small bolt.

It is important to fit the correct size of jet to each burner. However, you can always try one size larger or smaller to optimise the burner performance for your choice of gas and rate of gas flow.

Burners that plug into the flue |
28mm burner | No. 3 or No. 5 jet
35mm burner | No. 5 or No. 8 jet
42mm burner | No. 8 or No. 10 jet

Burners that fit in the firebox |
35mm round burner | No. 5 jet
50 × 15mm oblong burner | No. 5 jet
54mm round burner | No. 8 or 10 jet
65 × 25mm rectangular burner | No. 5 jet
67mm round burner | No. 8 or 10 jet
70 × 50mm rectangular burner | No. 8 or 10 jet

BRASS GAS-JET HOLDERS

Whilst ready-made gas-jet holders can be purchased, they are also simple to make. All that is needed is a short length of 8mm (⁵⁄₁₆in) round brass rod. The dimensions are given in Figure 168. The holder is 25mm (1in long). After facing the ends, it is drilled 4.5mm for a depth of 20mm (³⁄₄in), and then tapped 1BA to match the gas jet.

FIG. 168
The necessary dimensions for making a gas-jet holder with a hole to connect the gas pipe, through either the end or the side of the holder.

FIG. 169
Two gas-jet holders, the left-hand one with the hole for the gas pipe in its end, the other with the hole in its side. Either is suitable for all the burners described in this book.

FIG. 170
The gas pipe has been soldered to the gas-jet holder and now the nipple is being soldered to the other end of the gas pipe, not forgetting to fit the nut first.

Finally, a ¹⁄₈in hole needs to be drilled for the gas pipe. This can be either cross-drilled 15mm (⁵⁄₈in) from the base of the holder, or through the base itself, depending on how you want the gas pipe to run. These holders are illustrated in Figure 169, and are exactly the same for all the burners described in Chapters 3, 4 and 5. ¹⁄₈in copper gas pipe can easily be obtained from the model engineering suppliers listed at the end of the book, then connect up the gas-jet holder using silver solder. (See Figure 170.)

LIGHTING THE BURNER

While in theory it should be easy to light a gas burner, in practice it is not quite as straightforward. For vertical boilers, the burner is hidden in the firebox and can be lit in one of two ways. With the chimney or funnel removed, as shown in Figure 171, a flame can be applied to the top of the boiler as the gas is turned on. Alternatively a flame can be passed through one of the secondary air holes into the firebox if access to this part of the boiler is possible. In both cases a clear ‘pop’ will indicate that the burner has lit, and carefully looking down the chimney or through the secondary air holes will confirm that the burner is alight.

FIG. 171
Lighting a vertical boiler by removing the chimney and applying a flame that will ignite the burner with a distinct ‘pop’.

The situation for a burner that plugs into the flue of a horizontal boiler is very different, as lighting from the top of the chimney often fails to ignite the burner. Tests were made with a glow plug, as used in model internal combustion engines. The plug glowed a bright red/yellow when connected to a low voltage battery and was installed at the other end of the flue to the burner. Unfortunately the experiment proved to be a total failure and the gas never ignited. While spark ignition might have worked, the complexity and expense of such a solution made it impractical.

FIG. 172
Inserting a lit burner into the flue using a heat-resistant red glove. It is the flexible gas pipe that makes it simple to remove the burner, light it, and then plug it back into the flue.

This means that flue-mounted burners need to be pulled out of the flue, lit, and then pushed back into the flue. This implies the use of a flexible gas pipe to make this task significantly simpler. In addition, lighting the burner outside the flue means that heat-resistant gloves must be used when lighting the burner and pushing it back into the flue. (See Figure 172.)

ADJUSTING THE BURNER

It is very important to position the gas jet correctly, and this is shown in Figures 173 to 179. Adjust its position in the housing so that the air holes are about two-thirds blocked by the jet. The end of the jet holder should stick out of the brass housing by about 8mm (⁵⁄₁₆in). Tighten the adjusting screw; it is easier if a nut spinner is used for this.

FIG. 173
The jet-holder housing with the tip of the jet set half way across the primary air hole.

FIG. 174
The ideal starting point, with the jet just more than half way across the primary air hole.

FIG. 175
The jet less than half way in will give a little too much primary air.

FIG. 176
Too little primary air, with the jet blocking most of the primary air hole.

FIG. 177
The jet is too far out, allowing too much primary air into the burner.

FIG. 178
There will be far too little primary air as the jet is much too far in.

FIG. 179
The jet is much too far out and effectively not visible through the primary air hole.

FIG. 180
The yellow flame indicates too little primary air (the jet is too far in) on this 42mm burner.

Always check valve and pipe connections with soapy water to ensure there are no gas leaks. Slowly turn on the gas and light the burner. Set the gas valve to give a reasonable size of yellow flame, as shown in Figure 180.

FIG. 181
A nice set of blue cones is a good indication of the correct position of the jet and also the optimum flow rate of gas.

Allow the burner to warm up for about half a minute. The screw can then be loosened and the jet moved out a little until a stable blue flame is obtained, with small blue cones burning over the surface of the ceramic. (This is not an easy task, really requiring you to have three hands protected with heat-resistant gloves. You have to hold the gas-jet housing making sure not to cover the air holes, while at the same time positioning the gas jet correctly and tightening the bolt.) Finally retighten the screw to secure the jet holder firmly in place. This will ensure the optimum air/gas mixture is obtained. The resulting correct flame can be seen in Figure 181.

FIG. 182
Too much primary air (the jet is too far out). The ceramic is glowing red and there is a serious risk of blowback.

A soft yellow flame indicates insufficient primary air, and the jet holder needs moving out until there are small blue cones over the ceramic surface. With the gas jet too far out, the ceramic can glow bright red, as Figure 182 demonstrates, and after a while the burner may well overheat. This is accompanied by a change in tone to a ‘roaring’ sound. When this happens, gas is burning inside the burner, which can quickly damage the burner. This only seems to occur when using some commercially built ceramic burners, but it probably also applies to other types of ceramic burner.

FIG. 183
The blue cones on the 57mm round burner are clearly visible through the holes in the firebox of this vertical boiler.

FIG. 184
The bright red colour visible through the holes in the firebox of this 108mm boiler indicates too much primary air, and the likelihood of blowback destroying the burner.

The way to avoid this is to move the gas jet in a little until a blue/purple flame is observed, and not an overall red glow. This way, good heat is produced and the burner will work properly without overheating. Do not move the jet holder any further out as this will result in a blue flame moving on the burner surface, which indicates rather too much air. Figure 183 shows the view through the secondary air holes of a vertical boiler where the burner flame is set correctly, while Figure 184 shows the burner glowing bright red, when it is in danger of destroying itself.

Note that if a jet is partially blocked, or if there is any other similar problem with the gas tap or gas pipe, or gas leaking around the jet threads, problems may also occur, and it may be impossible to adjust the burner to give a correct flame.

Once the burner has been warmed, the ceramic will start to burn with brilliant blue cones, the flame will become purple, and the heat output will rise. At this point heat transfer to the water in the boiler will be optimal, and you can wait until the pressure gauge starts to rise, indicating that steam is being generated.

Clearly it is much easier to set up the burner before plugging it into the flue or placing it in the firebox. Once the ideal gas-jet position has been established, fully tighten the securing screw and try the burner in the boiler.

Burner Blowback

On any of the burners that fit under boilers, rather than fit into horizontal flues, burner blowback is indicated by a sudden roaring noise. This means that the flame is now also burning beneath the ceramic, and it will rapidly damage and then destroy parts of the burner. Immediately turn off the gas and allow the burner to cool down. (Interestingly, this phenomenon has not been found to occur with burners that plug into flues.)

FIG. 185
A commercial 2in (51mm) round burner, with its gas-diffusion components totally destroyed by blowback.

FIG. 186
The same commercial 2in (51mm) round burner with its ceramic honeycomb and gas-diffusion components replaced. It looks good after repair in the author’s home workshop.

FIG. 187
The commercial 2in (51mm) round burner is burning well, although the gas tap could be closed a little.

Damage can involve crumbling of the ceramic element, or even breaks in any gas diffusing components, such as a spring and wire mesh. Fortunately it is not a difficult task to replace any of these parts and fix new ones in place, though it will normally require fitting at least a new ceramic element. Figure 185 shows a commercial burner relit after it suffered from blowback and its internal parts were seriously damaged, while Figure 186 shows the same burner repaired using a custom-cut piece of ceramic honeycomb. In Figure 187 the whole ceramic element is producing heat after what was a relatively simple repair.

Experiments suggest that the cause of burner blowback is normally too much primary air. To avoid blowback, always set the gas-jet holder further in than the optimum, and then carefully and slowly move it further out to get the best possible blue flame. If you have experienced blowback, before attempting to relight the burner, make sure that the gas-jet holder is moved a little further into its housing. After relighting the burner, recheck the flame and readjust the position of the gas jet in the housing until it is burning correctly.

Boiler Howling

Any horizontal boiler with a flue, into which the burner is plugged, has the potential to howl. The problem is caused by the acoustic characteristics of the flue and chimney/funnel combination. Its length, any obstructions such as Galloway tubes, super heater or bends, can interact with the velocity of gas and air flow through the flue. It may also be altered by changes in atmospheric conditions such as humidity, pressure and temperature. While howling is not an uncommon problem, it is relatively straightforward to solve by trial and error.

You can try increasing the size of the gas jet and reducing the flow at the gas valve. These two measures should enable you to set the blue cones on the burner, but with the speed of the gas coming out of the jet reduced. Increasing the gas jet one or two sizes should quickly resolve the problem without altering the heat output of the burner. It is a simple question of balancing the variables, jet size, the amount the gas valve is open, and the associated air flow and the amount of noise from the flue. However, do warm up the flue first at a low gas setting before any work to eliminate howling is carried out.

BURNER INSTALLATION

After setting up the burner correctly, turn off the gas so the burner can cool before installing it in the firebox of the boiler or plugging it into the flue. It is essential that plenty of fresh secondary air can enter the flue or firebox. Only the smallest 28mm burners have secondary air holes bored in their outer casings – the other flue-mounted burners obtain sufficient secondary air through the gas-jet housing.

The larger burners and the two smallest flatbottomed ones sit in the fireboxes of their boilers. It is important to ensure that these fireboxes have ample air holes. Too much air is not a problem, but too little will inhibit effective burning, will reduce heat output, and in severe cases, can cause damage to the burner.

FIG. 188
Making a mount to hold a burner in a firebox requires two lengths of rectangular brass rod and two bolts. The size of the central hole must match the diameter of the gas-jet housing.

FIG. 189
A 54mm burner attached by a mount to the baseplate of a 102mm (4in) diameter vertical boiler.

Figure 188 shows the dimensions of a two-part burner mount, which can be used with the ceramic burners that fit into the firebox of a vertical or horizontal boiler. The critical dimension is the diameter of the hole, ¹⁄₂in or 12mm, depending on the size of metal used to make the gas-jet housing and its height from the bottom of the mount. Both these measurements need to match the dimensions of the burner. The mount will also need to be fixed to the boiler base plate. The mount clamps the burner firmly in place in the correct position. Figure 189 shows a typical example of a burner with its mount attached to a base plate for a vertical fire-tube boiler.

FIG. 190
A 42mm burner connected to a horizontal boiler flue via an adapter ring.

Clearly all the smaller burners that feed heat into a circular flue use a different mounting system. They either plug over their boiler’s flue, incorporate a copper ring so they can plug into the flue, or, for some sizes of flue, plug into a brass adaptor ring that fits over the flue. This adaptor can easily be made on a lathe, boring one end to the flue diameter and the other to the burner diameter. It is beneficial to fit a pair of small bolts to hold the adaptor in place on the flue and the burner. An example can be seen in Figure 190.

PIPEWORK AND VALVES

When connecting a gas source to a boiler burner take care that the joints are all gas tight. It is sensible to apply soapy water to each joint and to ensure that when the gas is on, it is not blowing any bubbles. A manual gas valve that is screwed on to a disposable gas tank, or a similar valve fitted to a refillable gas tank, controls the gas flow. Normally ¹⁄₈in outsidediameter copper pipe should be used to connect the gas to the burner. One end usually terminates in a manual screw fitting that goes on to the gas valve; the other joins to the gas jet holder. However, sometimes you will need to use ¹⁄₄mm × 40ME coned connectors.

FIG. 191
Commercial steam plant in an attractive launch with the burner and gas tank both visible.

To make a neat pipe run, a pipe bender such as the one shown in Figure 21 on page 19 should be used. A very tidy marine installation can be seen in Figure 191, where all the various steam and gas pipes are neatly fitted in place. The steam pipes have ‘fake’ asbestos insulation covering them.

For static installations and also for testing burners and boilers, a flexible gas pipe can be a great advantage. It is ideal for connecting burners that plug into a round flue, allowing you to light the burner before plugging it into the flue using protective gloves. It is also an advantage for some static installations where the burners sit in the boiler firebox, as the gas cylinder can be readily moved to the preferred position.

A manual gas valve will only allow the heat input to be set to match the expected steam output to the engine approximately. A radio-controlled gas-tight valve driven by a servo will give rather better boilerpressure management. Alternatively, a commercial gas regulator can be fitted, which varies the gas flow to maintain the steam pressure in the boiler. The next chapter gives more information about these options.

GAS SEALANTS

When installing gas jets and connecting up gas pipework, the use of a gas sealant is recommended to make the joints gas tight. Loctite 542, Heldite or Rocol pipe-jointing compound are all suitable and only need smearing on the joints to provide a gas-tight seal. They are available from plumbers’ merchants and DIY stores.

IGNITERS

Matches or a lighter can be used to ignite a burner in a vertical boiler, but a better solution is to use an igniter such as the one shown in Figure 192. These igniters burn lighter fuel (butane), which can be easily topped up from a lighter-fuel can. Ignition of the gas is by a piezo-electric crystal. The burner in a vertical boiler can be lit by removing the chimney, holding the lit igniter to the chimney mount, and turning on the gas. A distinctive ‘pop’ will indicate that the burner has been safely lit.

FIG. 192
A low-cost piezo-electric igniter. It is filled with butane lighter fuel at the bottom, and has a slider to vary the flame size and another to lock the trigger. It is ideal for lighting the burners in boilers.

For flue-mounted burners, provided the chimney/ funnel can be removed, sometimes the burner can be lit at the bend on the end of the flue. Otherwise the burner will have to be lit outside the flue and then quickly fitted in place. Use heat-resistant gloves in order not to burn your fingers, as the burner body can quickly heat up.

STORAGE

When not in use, it is a good idea to store the burner plugged into the flue or fitted in the firebox of the boiler to protect the ceramic material.

Gas Control
8

WHILE THE GAS CONTROL to a burner can always be set up manually, this chapter describes a number of mechanical and electronic automatic gas-control systems that are much more important where the steam plant is fitted in a vehicle or boat. A number of different systems are described so that an informed choice can be made; also described is a radio-controlled gas cut-off valve.

FIG. 193
A 54mm round burner heating a 102mm (4in) vertical boiler for a test run with a small single-cylinder mill engine.

Any ceramic burner requires a gas tank to hold its fuel, but some sort of gas-control system will also be needed. This may be just a simple on/off valve that is built into, or screws on to the gas tank, with a pipe that runs to the gas jet in the burner (see Figure 193). Such a valve can be used, partly open, to set the rate of gas flow manually. This can only be done by looking at the burner, although this can be difficult in some installations. For running a static steam engine and boiler combination in the workshop, this is usually an adequate approach. However, it is less than satisfactory in a mobile application such as a steam launch or a small steam lorry. Thus your chosen solution may also be a more complex one that senses boiler pressure and varies the gas flow to the burner in order to maintain the required pressure.

The type and size of gas tank depends both on individual choice and on the environment in which the burner is intended to be used. For a static application, a disposable gas-can with a simple gas valve can be fitted; the valve can then be manually operated to increase or decrease the gas flow to the burner and thus maintain pressure in the boiler as the engine consumes steam. Equally a refillable gas tank with a similar gas valve can be fitted.

In both cases, if the safety valve starts to lift with the engine running, it is a simple matter to turn down the gas flow so that the ceramic burner provides rather less heat to the boiler. Similarly the gas flow can be turned up if the boiler pressure starts to fall. All this assumes that the boiler and engine are a good match.

For marine applications and for small-scale steam lorries and traction engines, as well as small-gauge locomotives and other mobile applications, it is essential that the gas supply is exhausted before all the water in the boiler has been used. This implies fitting a relatively small gas tank to supply the burner. Its size depends on the water capacity of the boiler it heats, whether a boiler feed pump is fitted to the engine, and the volume of its water supply as well as the size of the engine, its steam consumption, and the way it is operated. An oscillating engine will always have a significantly higher steam consumption than a side-valve one and will require more heat from the burner, all other things being equal.

Do you plan to run your engine mostly at full power, or much of the time well throttled back, or even at times stationary? Think about these variables carefully and decide the size of the gas tank accordingly.

Having chosen the gas tank, a connector and valve will be needed regardless of whether a boiler pressure-control system is fitted as well. The decision to install one is often price dependent, as a complex gas-control installation is not cheap.

AUTOMATIC BOILER CONTROL

There are several commercial solutions that aim to provide a constant boiler steam pressure regardless of steam consumption. There are both electronic and mechanical systems that fit between the boiler and the gas tank. An electronic gas valve automatically controls gas flow to the burner using a pressure sensor fitted to the boiler. It reduces the gas flow to just a pilot when the pressure is sufficient. The chosen pressure can be set with a screwdriver adjustment on the electronic control box. However, a servo will have to be provided in order to move the gas valve, although this servo will not be connected to, and will operate independently from, any radiocontrol system that may be fitted.

The alternative mechanical solutions use a flexible membrane, connected to boiler pressure, to control the flow of gas. The required pressure is set using a simple screw adjustment. The advantages and disadvantages of the two different types of system and their cost are likely to affect your choice. When looking at electronic systems, remember there will be a battery to charge or replace, and the cost of the extra servo. Balanced against this are the simpler controls that you may find are easier to adjust on electronic solutions.

ELECTRONIC SYSTEMS

Using a pressure sensor fitted to the boiler and a battery-powered electronic control box, a servo (independent of any radio-control system) automatically adjusts gas flow to the burner via a servo-operated gas valve. The movement of the valve reduces the gas flow to just a pilot when the pressure is sufficient, and increases it again when the pressure falls. The chosen pressure can be set with a screw adjustment on the electronic control box.

Stuart Electronic Gas Valve (EGV)

The Stuart EGV comprises six items, which, when correctly connected together, aim to regulate the gas flow to the burner. They are the pressure sensor, the control box, the gas valve, the gas connecting pipe, the battery holder, the switch and the wiring cable. A four-page leaflet covers the installation and setting up.

FIG. 194
The Stuart EGV comprises a gas pipe, the electronic control box, boiler-pressure sensor and lead, battery box, gas valve and switch harness.

FIG. 195
Diagram showing how to connect the Stuart electronic gas valve.

Figure 194 shows the various components of the Stuart EGV system. You have to provide your own servo to move the gas valve in response to signals from the control box. Four fully charged AA batteries will also be needed to fit in the battery holder. As can be seen in Figure 195, the pressure sensor screws into a spare ¹⁄₄in × 32 ME threaded bush on the boiler with the usual sealing precautions. The white and black wires from the sensor go to terminals 1 and 2 on the control box. The red and black wires from the battery switch go to terminals 3 and 4. The servo plugs into the three-pin servo connector. The two sets of three pins enable the direction of movement of the servo to be reversed if required by the installation. The servo and the gas valve are connected by a short wire link.

The supplied gas pipe runs from the valve on the gas tank to connection A on the Stuart gas valve, while your own gas pipe runs from connection B on the Stuart valve to the burner. When switched on, the LED (light-emitting diode) illuminates for some five seconds while the servo moves to each end of its travel. Then the LED flashes.

The gas valve has two controls. The lever arm is servo controlled (you provide the servo) and sets the gas flow to the burner. The knurled knob is used to set the gas flow to the pilot so that, even with the lever arm moved to the ‘valve closed’ position, a pilot gas flow can be set to the burner so that the flame does not go out. The valve connects directly to the gas tank, with its other connection to the burner. The short connecting gas pipe joins the valve to the gas tank. The gas jet in the burner needs a gas pipe and connector, which can be screwed into the valve output.

The servo fits between the gas valve and the control box. It is connected mechanically to the valve and electronically to the box. As you have to provide the servo you could use a spare from your radiocontrol system.

FIG. 196
The Stuart EGV neatly installed in a steam launch.

The control box gets its power from the battery box via a switch and cable harness. An LED flashes when the gas valve is fully open, and goes out when the gas valve is closed, with gas flow continuing just to the pilot valve. The pressure sensor screws into a ¹⁄₄in × 32 ME threaded bush in the top of the boiler, and also connects to the control box. The boiler pressure can be varied with the screwdriver adjustment on the control box. The practical layout of the complete Stuart EGV can be seen in a steam launch in Figure 196.

Clevedon Steam Electronic Gas Regulator

The Clevedon steam electronic gas regulator (EGR) works in a similar way to the Stuart electronic gas valve. Figure 197 shows the various parts that make up the EGR. It consists of an electronic control box, a pressure sensor and lead, a gas-control valve, a gas supply pipe, a switch lead and a comprehensive set of instructions covering safety features, tools and equipment required, fitting and setting-up instructions, and an initial boiler test.

FIG. 197
The Clevedon electronic gas regulator showing from the top the gas pipe, the electronic control box, the gas valve and mounting bracket, the boiler pressure sensor with connecting wire, and the battery connector, leads and switch.
CLEVEDON STEAM

It requires a complete battery pack of four rechargeable or dry cells, using the supplied plug and switch to connect into the EGR. The boiler-pressure sensor screws into a spare ¹⁄₄in × 40 ME bush at the top of a vertical boiler, or a similar tapping in the dome of a horizontal boiler. Alternatively the sensor can be a ¹⁄₄in × 32 ME. The burner will reduce to a pilot flame either when the pre-set pressure is attained, or if the boiler runs out of water.

The gas valve looks completely different from the Stuart one, and comes with a mounting bracket. The supplied gas pipe connects this valve to the gas-tank valve. You will need to provide a pipe to connect the Clevedon gas valve to the gas-jet holder. A red LED lights on the control box when the gas valve is open, and two screwdriver adjustments allow you to adjust the maximum boiler pressure and the amount of gas to the pilot flame. Mount the control box where it can be easily accessed, both for initial setting up and to check while in use. Locate it away from direct heat or steam.

FIG. 198
Connecting the parts of the Clevedon electronic gas valve/regulator.

When you have decided the positions of the gas valve, tank and burner, you can then decide how to mount the gas valve and where to put the servo. Preferably a Futaba or Hi Tec servo should be used as they have the wires to the plug in the correct order. If another make is used, the wires may need rearranging in the plug. A straight-type servo arm will be needed. Ensure that the control lever of the gas valve and the servo arm are at the same height and in line at their ends. Connect the servo lead to the one set of pins on the control box, the switch plugs into the other set of control-box pins, and a fully charged battery pack to the input end of the switch lead. Figure 198 gives details of how to connect the various parts.

Full details are given of how to connect the servo to the gas valve, and how to set up the movement correctly to ensure an adequate pilot flame.

MECHANICAL SYSTEMS

All the mechanical solutions use flexible membranes inside a gas-pressure regulator valve. One end connects via a steam pipe to a fitting on the boiler in order to sense the steam pressure and thus control the flow of gas. The required boiler pressure is set using a thumb-wheel adjustment on the regulator valve. Figure 199 shows typical examples of these solutions. When the desired pressure is reached, the regulator reduces gas flow to a pilot and vice-versa when the steam pressure falls. There are several different valves available that all work on a similar principle.

FIG. 199
Installation will need to be planned if a mechanical gas regulator is to be used between the gas tank and the burner, with a connection to the boiler steam.

Forest Classics offers the Bix boiler-pressure regulator, while Antón in France produces a similar mechanical solution, as does Microcosm from China.

However, these last two use a different layout to the Bix solution. All the devices automatically vary the burner flame to try and maintain the boiler pressure. However, the Bix burner does not have an adjustment to set the pilot flame; the other two do. In practice it may be slightly tricky to ensure the burner operates satisfactorily under changing gas settings.

Bix Boiler Pressure Regulator

The Bix 029 automatic boiler pressure regulator, illustrated in Figure 200, automatically adjusts the gas flow to the burner to keep the boiler at the pre-set pressure. The pressure can be adjusted using the knurled adjustment knob within the range 10lb to 90lb/sq in (0.7 to 6bar). The unit is 40mm high, 33mm wide and 19mm deep (1⁹⁄₁₆ × 1¹⁄₃ × ³⁄₄in). All three connections are ¹⁄₄in × 32 ME: one to the gas tank, one to the burner and the top one to the boiler.

FIG. 200
The Bix mechanical gas regulator is a neat unit.
FOREST CLASSICS

When the boiler pressure reaches the level that has been set with the control wheel, the gas supply to the burner is reduced to an amount set by an internal pilot valve. This keeps the burner running at a low heat output until the boiler pressure drops again. The main gas supply is then restored and the cycle will automatically repeat itself.

To set up the unit, connect the valve to the gas tank, boiler and burner, as shown in Figure 199. The valve will work upright, inverted, or on its side. Undo the control wheel fully and ensure that all the connections are gas tight before lighting the burner. When the boiler reaches the required pressure, turn the control wheel until the burner output reduces to just the pilot flame. It may be necessary to make some fine adjustments after using the regulator a few times.

The Antón Bi-Membrane Gas Regulator

Atelier Antón is a French company based in Aquitaine in the south-west of France. It offers a different mechanical way of regulating boiler pressure: a two-membrane gas regulator.

FIG. 201
The Antón bi-membrane gas regulator uses a totally different layout to the Bix one.
ATELIER ANTÓN

FIG. 202
The parts of the Antón bi-membrane gas regulator.
ATELIER ANTÓN

The Antón twin-membrane regulator, shown in Figure 201, makes it possible to regulate the pressure of the boiler by acting on the gas flow to the burner. The operation of this regulator is governed by two membranes and a gas-regulating valve, the steam pressure being on one side of one membrane, the gas pressure on the other side of the other membrane. When the boiler reaches the selected operating pressure, the burner automatically turns down. The regulator thus saves the gas while maintaining boiler pressure. It also saves water consumption by avoiding the inadvertent discharges through the safety valve. In Figure 202 the various parts of the regulator are named.

The gas regulator employs a double compensation spring. It provides greater flexibility of gas control, with a pilot light even when gas flow is reduced to the minimum. This is beneficial with varying throttle settings. The pilot-light adjustment screw and the pressure adjusting nut can be altered easily when the regulator is installed in a boat or vehicle.

Microcosm P5 Steam-Controlled Gas Regulator

Microcosm is a Chinese company based in Foshan some 50 miles (80km) north-west of Hong Kong. They do all their trading on eBay, and experience has shown that they are a reliable supplier with quality products.

FIG. 203
A Microcosm P5 regulator showing its construction, knurled nut and screwdriver adjustment.

FIG. 204
The parts of the Microcosm P5 steam-controlled gas regulator.

The P5 gas regulator shown in Figure 203 controls boiler pressure by varying the gas flow to the burner. Its operation is controlled by a pair of membranes and a gas-regulating valve. Steam pressure acts on one membrane, while gas pressure operates on the other membrane. When the boiler reaches the pressure that has been selected by turning the boiler pressure adjusting wheel, the gas to the burner automatically reduces, lowering its heat output. The controls and connections can be seen in Figure 204. The regulator reduces gas consumption and stops the boiler wasting water by discharging steam through the safety valve.

FIG. 205
Microcosm’s P5 mechanical gas regulator fitted on this steam plant. The connection from the gas tank is at bottom left, and the output goes straight to the burner gas jet. The insulated pipe feeds boiler pressure into the regulator.

The regulator has two simple operator adjustments: one that sets the boiler pressure, and the other to adjust the gas flow. The operating pressure of the regulator is 5 to 90psi (0.34 to 6.2bar). All three connectors to the regulator are ¹⁄₄in × 40 ME. The one on the long side connects directly to the gas tank. The adjacent one on the end goes straight to the burner. The one at the other end is fed with steam pressure from a tapping in the boiler. Figure 205 illustrates a typical installation of the regulator in a steam launch.

GAS CUT-OFF VALVES

When installing a steam plant in a boat, the question of safety arises: how do you turn off the gas if the boiler runs out of water? The solution is to use a radio-controlled cut-off gas valve: this requires an additional servo, and the risk of battery or radio failure still remains.

Antón Radio-Controlled Gas Shut-Off Valve

The shut-off valve pictured in Figure 206 fits between the gas tank and the burner or, assuming either a manual or electronic gas regulator is fitted, either between the regulator and the burner, or between the gas tank and regulator. The valve is operated by a radio-control servo. The radio channel should be a switched one so the valve is either open or closed. It should employ a standard servo capable of providing a force of 3kg (6.6lb) pushing directly along the axis of the valve. Antón emphasizes that in the open position, it is important to ensure the servo arm is in line with the operating rod on the valve to minimize the power consumption of the servo. Figure 207 shows how to install the valve.

FIG. 206
The Antón servo-operated gas cut-off valve is a useful safety feature.
ATELIER ANTÓN

FIG. 207
Installing the radio-controlled Antón gas cut-off valve.

This valve can also provide an additional benefit! At the end of an outing on the water, you can turn off the gas shortly before you berth your boat. This enables you, at your leisure, to put your transmitter down safely, take the boat out of the water and finally turn off the gas valve.

Conclusions

YOU WILL NOW HAVE discovered that, in model engineering terms, there is nothing particularly demanding about making a ceramic burner. The materials to make the component parts are readily available, and the various parts are not difficult to produce in the home workshop using hand tools and a lathe to make them. Only for the 28mm burner is access to a milling machine and rotary table needed.

FIG. 208
Which of these eleven burners will you choose to build to heat your boiler?

Figure 208 shows all the burners that you will have read about, and asks which one you will choose to build. Your choice will really depend on the size and type of boiler you wish to heat, and whether it has a flue running through it or a firebox underneath it.

Assuming you have no basic experience of silver soldering, the burners described in this book provide an excellent opportunity to learn this skill as they are not difficult to solder, and do not require a great amount of heat, nor a large hearth. Hopefully you will feel sufficiently confident to start building a burner to fit your own boiler, whether it is a small burner that slots into the flue, or a circular or rectangular one that is mounted in the firebox.

It should be apparent that some of the materials for the parts that are needed to make one burner will actually be sufficient to make a number of burners. Examples include the honeycomb ceramic, high-temperature adhesive/filler, and heatproof paint. In addition, end caps are often supplied in pairs rather than as single items. Thus, if you can interest friends or fellow club members to build a burner at the same time as you do, or to use ones that you have built for them, you can then reduce the overall cost of each individual burner.

Setting up a burner to optimize its heat output is not difficult, and only requires the right jet located in the optimum position in the gas-jet housing, no gas leaks, and the correct amount of flow from the gas tank. Hopefully the illustrations provided in the book will help you to achieve the settings correctly so that the heat output of your burner is optimized.

Manual control of the burner is fine for a static boiler, but some form of automatic control of the burner heat output is very desirable, particularly for use in model boats or land vehicles. 8 has reviewed the majority of the available systems, both mechanical and electronic, so it is up to you to decide whether you want one, which one you would like to fit, and whether you feel that it represents good value for money.

FIG. 209
A home-built steam plant heated by a 67mm round burner. The gas-jet housing can be seen towards the bows of the ship at the bottom of the vertical boiler. The burner is fed by the vertically mounted gas regulator, with a steam pipe running up to the manifold on top of the boiler.

There is huge satisfaction to be gained from building your own burner to use with any steam plant, but particularly with a boiler and engine you have also made yourself. Figure 209 shows the author’s own home-built steam plant for a 760mm-long steam launch.

Finally, do remember to heed the safety warnings given in various parts of this book so that you can continue to enjoy the great hobby of model engineering.

APPENDIX

Summary of The Boiler Test Code 2018, Volume 3

THE ORANGE COVER OF Part 3 of the Boiler Test Code 2018 is illustrated. If you wish to build your own refillable gas tank, you should download this part of the Boiler Test Code 2018, which is not copyrighted, and is available at no cost from https://www.sfmes.co.uk/ydrRoot/committees/boilerSC/Forms/testCode2018_volume3.pdf

The Test Code has been prepared by the following bodies:

10¹⁄₄in Gauge Railway Society
7¹⁄₄in Gauge Society
Association of 16mm Narrow Gauge Modellers
Gauge 1 Model Railway Association
Midland Federation of Model Engineers
Model Power Boat Association
Northern Association of Model Engineers
Southern Federation of Model Engineering Societies
Walker Midgley Insurance Brokers

A tank may be of any shape, with a maximum capacity of 250ml, and designed to be refillable from a commercial canister of LPG. It shall be constructed of brass or copper to satisfy the requirements of the test procedures set out in this code.

The testing shall comprise a hydraulic test followed by a safeguard test. The object of the hydraulic test is to verify that the structure of the tank suffers no undue permanent distortion. The objective of the safeguard test is to verify that the tank is leak proof at the specified pressure, and that there are no observable leaks from any fittings. Any observable leak or undue residual distortion of the tank shall be regarded as a failure.

Repeat tests shall take place following any repair to the tank, in which case the tank will be considered new, and the full sequence of tests described in paragraph 6.1 of the code should be carried out.

The maker or owner/user must ensure that the tank is only used with butane or a butane/propane mix below 40 per cent propane, and never exceeds a temperature of 60ºC. Every tank shall be indelibly marked with a unique identification number. The form and position of the marking shall not damage or compromise the structure of the tank. The tank shall also carry a mark indicating the type of LPG for which it was constructed.

THE ROLE OF INSPECTORS

Inspectors are appointed by the associations, and may test a tank only if its maker or current owner/ user is a member of the associations. Inspectors undertake their duties on a voluntary non-commercial basis, and all examinations and tests are carried out entirely at their discretion. Inspectors will only test and certify a tank that they feel competent to test, based on their own experience. A test certificate will be issued only by an inspector. Inspectors shall not inspect their own work, unless that work has already been tested and passed by another inspector.

HYDRAULIC TEST

The tank should be without fittings, and unmounted in order that it may be inspected all round. If this is impractical, the agreement of the inspector will be required before the test can proceed. This requirement applies to both initial and any subsequent hydraulic tests.

The specified initial test pressure for the hydraulic test of the tank, as described in this code, shall be 400psi gauge pressure. This will apply for all tanks, regardless of whether they are intended to be used for butane only, or a butane/propane mix with a maximum propane content of 40 per cent. The test gauge range should be approximately 1.5 times the pressure of the test (for example, a range 0–600psi will be satisfactory for test pressures up to 400psi), and within the previous two years should have been checked and calibrated to within ±2 per cent, either against a currently validated dead-weight test apparatus or against other traceable equipment. The test gauge may also be calibrated by a commercial test facility, which will provide a calibration test certificate.

The tank shall be indelibly marked with a unique identification number. The form and position of the marking shall not damage or compromise the structure of the tank. The tank shall also carry a mark indicating the type of LPG for which it was constructed.

The procedure shall consist of raising the hydraulic pressure from zero to the test pressure, stopping at several intermediate pressures for careful visual examination until the full test pressure is attained. Each test pressure shall be held long enough to investigate any distortion of the vessel, and to confirm that any fall in pressure is not caused by structural weakness, and that there are no observable leaks.

SAFEGUARD TEST

The tank should be unmounted but with the gas filler valve and gas control valve in place. The tank shall be filled with LPG of a type specified by the maker or owner/user, and the gas mixture should be at, or raised to approximately 20ºC to test for leaks from the fittings. Any observable leak shall be regarded as a failure, and the tank and fittings shall be repaired and then resubmitted for a further safeguard test.

After completion of the hydraulic and safeguard tests, safety checks shall be carried out on the gas tank at no longer than five-year intervals, or when the model is next used if greater than that time interval since previous use.

SAFETY CHECK

A safety check shall be conducted at five-yearly intervals. It shall take the form of a leak test.

Where reasonably practicable the whole of the tank shall be examined visually by removal of any covering. Where this is not possible, the accessible tank joints and unions should be sprayed or covered with soap solution to reveal any leakage.

Any leakage observed must be corrected before any further use of the tank.

CERTIFICATES

The certificate used as part of this code will be given to the owner/user of the tank for safekeeping, and will be common across, and available from the associations. Each certificate shall bear the following information:

■The name of the club/society and organization issuing the certificate

■The name of the owner/user

■The location where the test was carried out

■Identification of the system that the certificate relates to, for example the boiler number

■The maker of the tank

■The tank identification markings

■Material(s) used in construction

■Date of construction, if known

■Test pressure of the test just completed

■Signatures of the inspector and the witness

■Notes and comments where applicable

List of Useful Contacts

FINDING THE RIGHT COMPANY to supply the various parts needed to build your own burner can be time consuming. The list below summarizes the products each company sells, and provides full details regarding how to contact them, and how to access them on the Internet. Not mentioned is eBay, which can be a wonderful and often low-cost source of many of the materials needed to build a ceramic burner.

ATELIER ANTÓN

La Jarrie No.13
17380 Puy Du Lac
France
Tel: 0674517485
www.anton-vapeur.fr

Antón supply model boiler kits and parts, steam engines, refillable gas tanks and gas valves, including shut-off valves. The owner has said that health problems and a shortage of machinery have forced a considerable reduction in production.

AXMINSTER TOOLS & MACHINERY

Axminster Tool Centre Ltd
Unit 10
Weycroft Avenue
Axminster
Devon
EX13 5PH
Email: sales@axminster.co.uk
www.axminster.co.uk

Axminster can provide many types of machine tools and a range of ancillary items.

BETTS COUNTER

49–63 Spencer Street
Birmingham
B18 6DE
Tel: 0121 233 2413
Email: webenquires@bettsmetals.co.uk
www.bettsmetalsales.com

Betts deals with the jewellery trade and can supply blocks of ceramic honeycomb.

BLACKGATES ENGINEERING

Unit 1
Victory Court
Flagship Square
Shaw Cross Business Park
Dewsbury
West Yorkshire
WF12 7TH
Email: sales@blackgates.co.uk
www.blackgates.co.uk

Blackgates is a specialist model-engineering supplier of metal materials and fasteners, drills, taps and dies, gas torches, silver solder and flux.

CHESTER MACHINE TOOLS

Clwyd Close
Hawarden Industrial Park
Hawarden
Nr Chester
CH5 3PZ
Tel: 01244 531631
Email: sales@chestermachinetools.com
www.chestermachinetools.com

Chester offer for sale a wide range of machine tools and a large array of ancillary items.

CHILTERN MODEL STEAM

6 The Pingle
Rugeley
Staffordshire
WS15 2UR
Mob: 07941 800103
Email: sales@chilternmodelsteam.co.uk
www.chilternmodelsteam.co.uk

Chiltern specializes in steam engines, boilers and accessories. They can supply flexible gas pipes with a regulator and adaptor.

CLEVEDON STEAM

15 Lusart Drive
The Lizard
Helston
Cornwall
TR12 7RS
Tel: 01275 340048
Mob: 07818 044 648
Email: clevedon.steam@uwclub.net
www.clevedonsteam.co.uk

Clevedon supplies a wide range of steam engines and boilers as well as fire-tube and pan burners, gas tanks, gas jets and gas-jet holders, gas refill valves and adaptors as well as electronic gas regulators.

COLLEGE ENGINEERING SUPPLY

Barnfield Industrial Estate
Speed Rd
Tipton
West Midlands
DY4 9DY
Tel: 0121 530 3600
Email: sales@collegeengineering.co.uk
www.collegeengineering.co.uk

College Engineering sells a wide range of metal sheet, tube, strip and bar.

COOKSONGOLD

59–83 Vittoria Street
Birmingham
B1 3NZ
Email: info@cooksongold.com
Tel: 0345 100 1122 or 0121 200 2120
www.cooksongold.com

Cooksongold is the UK’s largest one-stop shop for the jewellery maker, and is able to supply blocks of ceramic honeycomb.

CUP ALLOYS (METAL JOINING) LTD

154 Mandalay Road
Pleasley
Mansfield
Notts
NG19 7TJ
Email: sales@cupalloys.co.uk
www.cupalloys.co.uk

CuP Alloys supplies a wide range of soldering items including gas torches, flux and silver solder, as well as brazing hearths, vermiculite block and cleaning salts.

ETSY IRELAND UC

66/67 Great Strand Street
Dublin 1
Ireland
Tel: 0353 1 513 7100
Email: legal@etsy.com
www.etsy.com/uk

Etsy supplies the jewellery trade, and can deliver blocks of ceramic honeycomb.

FOREST CLASSICS

Unit 2B
The New Building
Ellwood Road
Milkwall
Coleford
Gloucestershire
GL16 7LE
Tel: 01594 368318
Mob: 07778 950725
Email: info@forest-classics.net
www.forest-classics.co.uk

Forest Classics markets a range of Bix burners, gas tanks, pipes, jets, gas valves and adaptors, as well as an automatic boiler-pressure regulator.

GREENWOOD TOOLS LTD

2a Middlefield Road
Bromsgrove
Worcestershire
B60 2PW
Tel: 01527 877576
Email: greenwtool@aol.com
www.greenwood-tools.co.uk

Greenwood tools specializes in providing quality turning, boring, parting, threading, milling and drilling tools, and also indexable inserts.

MAMOD LTD

Summit Crescent Industrial Estate
Summit Crescent
Smethwick
Warley
West Midlands
B66 1BT
Tel: 0121 500 6433
Email: info@mamod.co.uk
www.mamod.co.uk

Mamod produces a large number of ready-to-run static steam plants, land vehicles, marine boilers and engines as well as ceramic burners, gas tanks and fittings.

THE MESH COMPANY (WARRINGTON) LTD

Unit 1
Farrell Street
Warrington
Cheshire
WA1 2WW
Tel: 01925 406602
Email: sales@themeshcompany.com
www.themeshcompany.com

The Mesh Company specializes in selling a huge range of meshes made from many different metals.

MICROCOSM

Dong Tu Jin
No.2 Lane 4
Zhang Cha Bi Tang Bei Bian Xin Village
FoShan
Guangong China
www.microcosm-engine.com

Microcosm is a Chinese company that offers many different model steam boilers, engines, and accessories including burners, automatic boiler-pressure regulators, valves and fittings.

NOGGIN END METALS

Ashdown
10 Boon Hill Road
Bignall End
Stoke on Trent
ST7 8LA
Tel: 01782 865 428
Mob: 07763 847 983
Email: mike@nogginend.com
www.nogginend.com

Noggin End offers many different types of sheet metal, tubes, strip and bar.

RDG TOOLS LTD

Unit 7/8, White Lee/Burnley Road
Mytholmroyd
West Yorkshire
HX7 5AD
Tel: 01422 884605/885069
Email: rdgtools@aol.com
www.rdgtools.co.uk

RDG offers a wide range of engineering products for model engineers including machines of all sizes and an extensive range of tools.

SCREWFIX DIRECT LTD

Trade House
Mead Avenue
Houndstone Business Park
Yeovil
Somerset
BA22 8RT
Tel: 03330 112 112
Email: online@screwfix.com
www.screwfix.com

Screwfix stocks most DIY products and materials including propane and MAPP gas torches, high-temperature paints and sealants.

SOLDER CONNECTION LTD

Unit 5
Severn Link Distribution Centre
Chepstow
Monmouthshire
NP16 6UN
Tel: 01291 624 400
Email: sales@solderconnection.co.uk
www.solderconnection.com

Solder Connection offers a complete range of silver solders and fluxes.

STUART MODELS

Grove Works
West Road
Bridport
Dorset
DT6 5JT
Tel: 01308 456 859
Email: sales@stuartmodels.com
www.stuartmodels.com

Stuart Models is renowned for its range of model steam engines and boilers, but can also supply ceramic burners, refillable gas tanks and valves, electronic gas regulators, gas jets and pipes.

TOOLSTATION

Express Park
Bridgwater
TA6 4RN
Tel: 0808 100 7211
Email: info@toolstation.com
www.toolstation.com

Toolstation stocks a wide range of DIY items including MAPP gas and propane torches as well as high-temperature paints.

HS WALSH & SONS LTD

Hunter House
Biggin Hill Airport
Churchill Way
Biggin Hill
Kent
TN16 3BN
Tel: 01959 543 660
www.hswalsh.com

Walsh supplies jewellery tools and equipment including ceramic honeycomb.

WARCO

Warco House
Fisher Lane
Chiddingfold
Surrey
GU8 4TD
Tel: 01428 682929
www.warco.co.uk

Warco markets many different machine tools, and useful accessories to use with them.

WILH. SCHRÖDER GMBH & CO. KG (WILESCO)

Schützenstraße 12
58511 Lüdenscheid
Germany
Email: info@wilesco.de
www.wilesco.de

Wilesco supplies a wide range of model stationary steam plant, mobile and ship boilers and engines.

Index

adjusting the burner 85

Antón. 98, 99, 102, 107

automatic boiler control 94

Axminster 56, 107

Bix 98, 108

boiler blowback 15, 88

boiler howling 89

boiler test code 105

burner installation 90

ceramic 1, 3, 20, 22, 48

ceramic saw 16, 21, 38, 45

Ceramix 13, 22, 23

citric acid 32

cleaning 25, 28, 30, 31, 60

Clevedon 96, 98, 108

cutting lubricant 16

disposing of sulphuric acid 32

electronic gas regulator 96, 98

electronic gas valve 94, 96

end caps 6, 13, 16, 17, 43, 48, 50, 104

flux 37

gas containers 78

gas control 93

gas diffusing 13, 20, 23, 38, 41, 48, 55, 70, 88

gas jets 82

gas leaks 27, 39, 43, 46, 56, 60, 64, 69, 74, 77, 78, 80–82, 104, 105, 106

gas shut-off valves 102

gas tanks 79

igniters 92

installation 76

LPG 8, 9, 15, 19, 25, 26, 34, 67, 77, 78, 79, 81, 105, 106

Mamod 5, 6, 11, 15, 20, 65, 67, 81, 109

Mapeflex Firestop 13, 22, 23

MAPP gas 25, 26, 27, 29, 38, 70, 110

mesh 20, 60, 109

microcosm 98, 100, 109

Noggin Ends 109

paint 24, 38, 60

pipe work 91

safety 26, 78, 81, 106

silver solder 5, 25, 31, 44, 76

silver soldering 5, 25, 44

Stuart 39, 94, 96, 98, 110

sulphuric acid 32

Vitcas 13, 22, 23

Warco 56, 110

Wilesco 5, 6, 11, 15, 20, 65, 67, 81, 111