Wood Automata

Tips and Tricks

By Ken Schweim

Table of Contents

Project Design

Operating Frame

Human figures

Cranks and Shafts

Cams

Oscillating Motion

Gears

Levers

Belts and Pulleys

Ratchets

Linkages

Make your own automaton

In the world of automata, a single project is called an “automaton”. An automaton can be defined as a self operating machine or mechanism. In this book an automaton could be defined as a wood project that involves movement of parts. It could be a humorous movement to watch like two people sitting at a table, banging their hands on the table, and obviously verbally attacking each other. It could be an art project with parts that move in a way that is pleasant to watch. It could be a project with parts that move, that simply beg an answer to “how did he do that?” Of course it could be some combination of all of the above.

It is assumed that all the automatons in this book will be made from wood and receive its primary motion from a hand crank. Alternatives could be an electric motor, wind-driven, water-driven, solar driven, or possibly gravity driven.

There is a lot of help on the internet for building wood automata. However, most people have their own project design ideas and that’s what makes it an interesting hobby. Since there is no set pattern or set of guide rules for automata design, I’d like to share my experiences also and offer what I have learned while building my wood automata.

This book will be divided into two major sections. The first section is labeled “Construction Techniques” and will discuss the components of automata and how to apply them to your project. The second section is labeled “Making your own automaton” and will provide detailed instructions to build an automaton, which is a human figure doing push-ups.

To help demonstrate many of the automata concepts I have included reference to two YouTube videos of my own automata. The first video is a somewhat simple project involving one individual doing CPR. The second video is a large automaton which I called “Convolution.” It involves many mechanisms and automata concepts.

The CPR project can be seen here:

http://www.youtube.com/watch?v=01U3XIEdVXI

“Convolution” can be seen here:

http://www.youtube.com/watch?v=fgbUV7xv_sk

I will be making frequent reference to these projects to illustrate various automata concepts.

Building automata requires a basic knowledge of mechanisms. If you are new to this mechanical movement thing, I would highly recommend the following hardcopy books:

Making Mechanical Marvels in Wood by Raymond Levy – I would consider this book an absolute requirement. It provides detailed instructions on how to build many wood mechanisms. The only thing it is missing is human action figures

Cabaret Mechanical Movement – Do an internet search for this title and you will also find “Cabaret Mechanical Theater.” That site will provide an unbelievable amount of information on automata.

507 Mechanical Movements by Henry T. Brown. – Almost every mechanical movement ever thought of is pictured and described.

If you are serious about learning automata, would like to keep up on what others have done, would like to be notified of new ideas, tools, or automata books, consider the following web site as a “must see.” Each day there is a new automaton or book featured on the blog portion of the site.

http://www.dugnorth.com/

As with just about everything created on this earth, there always seems to be another way it could have been done. The internet provides an almost endless source showing examples. Fortunately the site below lists most of them.

http://www.kugelbahn.ch/3_link_automata.htm

The list above will provide more reference material than you can imagine. There are lots of pictures and videos of automata that others have made that may inspire you to develop your own. Deciding on what automaton to make may be the most difficult part of the project. It’s very similar to an artist deciding what to paint. Many of the YouTube videos show the mechanisms in detail. Even though you may have used a mechanism before, you will undoubtedly find a new use or variation of that mechanism. Looking through the internet sites should provide you with all the ideas you need.

I do not claim to be an expert on wood automata. However, my wood scrap box needs to be emptied frequently with my experimenting and I have a real good idea of what doesn’t work. I have spent a considerable amount of time working with wood automata and am satisfied with my personal success. My intent here is simply to share what I have learned.

Creating wood automata does require some woodworking skills and equipment. Hopefully this book will provide the help needed in sharpening those skills for wood automata and help you in deciding which additional tools may be needed.

Construction techniques

Project design

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Selecting the automaton project

So you have decided to try your hand at building wood automata. Where, how do we begin? Automata is actually a form of art which means you get to decide what it is going to be. The project may be something related to your work, hobby, church, something to do with current world events, or maybe you might want to just try to build one similar to something you have seen before. As stated before, the internet has an endless supply of ideas that others have tried. However, just as with any form of art, there is that thrill of success that goes with making something that no one else has.

Number of mechanical movements

You will notice as you browse through the many examples on the internet that the projects with multiple mechanical movements seem to draw more interest. There is a chance however that a very complicated automaton may be overwhelming to the observer. There is also a challenge to make as much happen as possible with one mechanism. This is possible by connecting one action to others so they get a “free ride.” The limit to the number of mechanical movements is usually determined by space available and the power to drive them.

Mechanisms visible or hidden?

This will have a major impact on the scope of your automaton project. There are professionals that are able to hide all of the mechanisms and linkages for the mechanism. This requires far above average skills and I certainly would not recommend this approach for beginners. However many professionals make no attempt to hide the linkages because many in the viewing audience want to see how it was done.  The majority of automatons have their primary mechanisms and linkages visible below the main frame because they are as interesting or even more interesting than the project itself.

Small precision parts not advised with wood

There are several problems with designing small precision parts for your wood automaton. First, they often require special tools. Second, special wood may be required. For example, drilling a hole 1/16” from the edge is very difficult because on most woods it will probably split out so a very tight grained wood is required. Third, as the project goes through an environmental change the wood may change size and either seize up or become too loose. Fourth, if you plan on staining the wood and applying any kind of clear coat your project will be in trouble. The thickness of the clear coat will probably bind any close tolerance movements.

Crank placement

Assuming you are going to use a hand crank for movement, if you are left handed you will probably have the crank mounted on the left side. Will you be the one primarily demonstrating this project or do you intend to possibly sell copies of the project, with the majority of the world preferring right hand? Other options are a front mount, or top mount crank.

Another consideration is the size of the crank. If the crank is placed close to the bottom of the project the crank must be relatively small to allow rotation without scraping the operators knuckles.  If the crank is designed to provide motion to multiple mechanisms, a larger crank would be a good choice.

Design tools

You may be lucky enough to be one of those people that plan things before taking action. If so, here are some design aids that will help you get it all together before you actually start any construction.

Computer Assisted Design (CAD)

I have been using DeltaCad, a relatively inexpensive CAD program I downloaded off the internet that is very easy to learn. It has saved me many hours and materials by determining correct sizes of parts, placements, number of parts, and in many cases point out parts that cannot work as planned. In addition you can draw gears, cams, circles and many other parts that can be printed out and glued onto a piece of wood. Then you only have to follow the lines to cut the parts.

There are also free shareware CAD programs available and I would highly recommend some sort of software to allow you to pre-plan on paper.

SKETCHUP

This program is absolutely FREE and found as a component of GOOGLE.COM. It is a 3-D CAD program and I cannot say enough good things about it. If you take the time to learn this program, your design phase will be as much fun as useful. There are many tutorials online to teach you every aspect of this program. If you learn this program you will no doubt find many other daily uses for it. I would highly recommend that you take the time to learn this program if you are serious about making your own automata.

Use of cardboard and pins or wire

You can model a lot of the mechanical movements by cutting them out of cardboard and watch the actual movement. Stick pins can be used to attach the parts. A piece of Styrofoam from packing material or insulation can be used as the construction frame to allow the stick pins to be easily inserted. With this method it is easy to see if the anticipated movement will work and also determine the correct size for the parts.

Another option is the use of wire for modeling your project. This provides a 3D look at the anticipated parts and a better picture of the full mechanism in action.

Both of these options (cardboard or wire) allow the project to be designed and partially tested sitting at your kitchen table or easy chair before moving to the big equipment.

The last design option is the use of standard paper, pencil, ruler, and compass. You can still save a lot of time and frustration by using these tools to design the parts

The size

You have to decide on the approximate size of the project before you begin. One of the determining factors will be the answer to the question “what will you do with this thing when it’s finished?” Do you want to be able to move it easily to show it to people? Will it end up on a shelf or hang from a wall? If it is a small project, you may be able to make it from scrap pieces of wood which gives you more incentive to experiment.

Operating Frame

Most wood automatons have a standard frame arrangement. The mechanical movements are on top of a frame and the mechanics to make it happen are inside the frame. Other options are mechanical movements in front and the mechanics in back which looks like a thick picture frame or mechanical movements on one side and the mechanics on the other side. As you saw in my “Convolution” YouTube video listed above, I simply made a six-sided cubed frame with the movements on the outside and mechanics on the inside.

Finally, although a clear design will make your project much easier, you can just “go for it” with just an idea. Because most wood automatons are small, the cost of the material is minimal, so “trial and error” design may work out just fine for you.

Operating Frame

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The most common operating frame is a flat surface with an area underneath designed to hold the mechanisms as shown in the example from CPR I shown below.

The “flat surface” however could be the bottom of a lake, a cow yard, construction site or whatever your imagination allows. The frame could also be an irregular shape such as a bridge girder, ship mast, athletic equipment, military equipment, etc.

When deciding on the frame layout, be sure to consider the angle of motion (crank) in relation to the figures. With just a little planning you can avoid having to make a 90 degree change in motion or some other angle. Most automatons have all of their mechanical parts lined up on common or parallel shafts. If you design your frame to access the mechanisms from an odd angle you will create a lot of work for yourself.

Try to keep all the action figures in one common area. If your action figures are located a relative long distance from each other you will have to consider belts, chains, driveshafts or some other means to deliver the motion to each figure. You can see an example of that in my Convolution project shown below.

Here you can see a driveshaft, a long crankshaft, and a wood chain used to access mechanisms located a distance from the home crank position. 

An interesting operating frame is a wall hanging. As mentioned before, it may just look like a thick picture. The action figures are on the front and the mechanicals are behind the picture. The crank can be located anyplace but is usually located on the front.

One last consideration in your frame design is the possibility of adding a motorized option. You could attach a motor to run the automata instead of a crank to allow observers to push a button rather than turn the crank. This is very common in places where automata projects are on display to the public.

Human figures

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This topic could be an entire book by itself. We can begin by answering the question “How realistic do you want this to be?” The answer to that is completely controlled by your own skill level. There are many human figure automata projects that use a very basic block form of human design. A simple rectangular wood block is used for the head and another for the chest. The legs and arms can be simple pieces of dowel rod or long wooden blocks. The other option is to try to make all the pieces more life-like. That requires smaller joints, tapered limbs, a lot of sanding, and a few other things.

Body proportions vary significantly. The drawing below will give you a rough idea of the proportions. The unit of measure is the head.

You may want to make some body parts larger than normal to connect them to the motion. Some parts are made larger to show humor such as an exaggerated smile or pain in a swollen hand. A long neck may be necessary to allow a unique head movement. For the best realistic proportions simply measure your own body. Your wrist is probably close to your waist line. Your shoulders are wider than your hips and simply standing in front of a mirror will give you the proportion information needed. You will find that you can have considerable freedom in selection body proportions and still make your project look normal.

The theme and motion are more important than the detail. You can always ask for help from a wood carving friend to bring it to life. Another way to bring life to your form is with paint. You can paint in the details as needed, such as eyes, shoes, shoelaces, clothing, etc. If you have sewing skills, or can get somebody to sew for you, you can make clothes for the figures which will make the figures much more realistic and at the same time hide much of the mechanisms.

Tip: When making wood action figures, try to cut all the pieces from the same wood stock. Mismatched wood pieces give the appearance of a piece that was added as an afterthought.

Our discussion will only involve the basic block forms for the figures and concentrate on the action. Let’s start with the arm movements. There are three main movements to work with here, and they are the shoulder, elbow, and wrists. You have to be an extremely gifted individual to animate individual fingers. We’ll work on the shoulder first.

Shoulder joint

Generally speaking, the shoulder movement is in one direction, front to back or side to side. This is option one:

The arm is held in place with a piece of wood dowel. The size of the dowel is totally dependent on the size of your figure. For example if your figure is ~6” tall, a 3/16” wood dowel would work well. To make this joint, drill a 3/16” hole through the shoulder and at least ½” into the side of the chest. The hole in the arm piece should be one drill size larger than the shoulder drill to allow the arm to pivot without restriction on the wood dowel pin. After you drill the holes in the shoulder, cut the slot in the armpit.

Tip: Drill the hole before you cut the slot on any joint. This will prevent the drill from “chipping out” as it passes through the slot.

Another option for the shoulder joint is to pin the arm directly into the side of the chest. Drill a hole in the arm slightly larger than the size of screw you intend to use to hold it. Slightly countersink the hole. Use a wood screw to attach the arm with the screw head recessed into the countersunk hole but loose enough to allow free movement of the arm. This type of joint provides 360 degree movement if necessary. This is a very common shoulder joint.

There is one more option that I have used to provide much more movement with the arm. That involves the use of screw eyes found at most home improvement centers. Screw one screw eye into the side of the chest. Screw another screw eye into the end of the arm. With needle nose pliers, temporarily open the loop on one screw eye slightly to connect the two and then re-close the loop. This option does not look as good but adds the benefit of much more motion rather than just front to back. If skills are available, adding clothing will completely cover the mechanism.

Elbow joint

Moving on to the elbow we are a little more limited. Basically we are connecting two shafts.

You can see that the upper arm section has a slot and the forearm section has the narrow strip which fits into the slot. The upper arm section with the slot has a hole drilled into which is the exact size of the pin. The narrow strip has a slightly larger hole to allow free movement of the forearm. This joint may require detailed sanding to increase the angle of the bend. Simply locate where the two pieces make contact and sand as needed.

Another option for the elbow joint is the use of two screw eyes as described in the shoulder joint.

A final option is a combination of the two above. You can make a slot in the upper arm section and use a screw eye on the forearm section. The pin can be either a small piece of wood dowel or a piece of wire.

Wrist joint

The wrist joint options are the same type as the elbow joint.

Hip joint

The hip joint is determined by the action required. If your requirement is only to have the upper body pivot on the legs or to have the legs move as one unit, the option shown below can be used.

If your project requires each leg to move individually, you have several choices. The option shown below is probably the most popular. This option provides up to 360 degree leg rotation if required. To add realism, you can round the top of the legs. You can also recess the upper leg into the upper body. Countersink the screws as shown.

The last hip option shown below can also be used. As stated before, drill the holes before you make the slots to prevent chip-outs. You may want to drill the hole through the entire body. Then if you need to remove the pins for some reason, you can push the pin out from the other side.

Tip: To remove a pin that is flush with the surface, drill a small hole into the end of the pin and insert a screw part way. Then just pull on the screw to remove the pin.

Knee joint

The options here are the same as the elbow joint.

Foot joint

The options here are the same as the wrist joint.

Tip: Paint or varnish on the contact part of the joint will probably disable the movement.

Head

The head can easily be created as part of the chest block if there is no movement involved. Another option is to make the head separately and attach it to the chest using dowel rod as the neck. There are several benefits to making the head separately. One, if you make a mistake with the head you only have to replace that part of the figure. Two, the head can be rotated to any position you want. Three, you can change your character by switching to a different head.

Making the mouth move is an advanced technique. To make the mouth move you have two basic options. One, hold the head and move the mouth. Two, hold the mouth and move the head.

If you choose option one, to hold the head and move the mouth, there are two primary considerations. One, how will you hold the head and two, how will you move the mouth. With this option the neck will probably be abnormally small to allow the mouth to move in front of it. Refer to the example shown below.

The area of the jaw will have to be removed first. You have the option of cutting straight across the jaw and make the whole lower half of the face act as a jaw, or cut a rectangular piece into the lower face from the lips down to the chin. If you prefer the second option, you can make the head in three pieces, right side of the head, left side of the head, and the center of the head. Then you can glue the head parts together.

Tip: Make as many cuts, holes, and shapes as possible before you trim the part to its final size.

Depending on your needs and skill, you can make the new jaw a simple solid piece of wood that fits reasonably into the jaw opening. This would be usable to show someone talking. Otherwise you can make a hollow jaw which would be more realistic for someone eating or drinking. Either way, drill the pivot hole in the jaw piece before you trim it to final size. Drill a small hole in the back of the jaw piece and insert a piece of wire. Epoxy the wire in place. A mechanism will pull down and push up on the wire. Therefore the wire must protrude through the back of the head. The neck however is directly in the way. Make a slot in the neck to allow the wire to pass through. Form a loop on the end of the wire. Now you can attach the mechanism to the wire. Another option here is to add another screw eye to the back of the head near the top and attach a spring from it to the mouth pivot wire. Then the mechanism will only have to pull the mouth open and the spring will shut it.

If you decide to use the option where the head pivots instead of the mouth the mouth portion is attached to the neck as shown below.

The mechanism is attached to the back of the head to raise and lower the upper jaw.

If you want the head to bob back and forth, make the neck flat and make a slot in the upper body. If you want the head to rotate side to side, refer to the section on “Oscillating motion.”

As stated before, a figure can be made up of plain wooden blocks and your project then can just concentrate on the mechanism. Covering your figures with clothes can make your project much more realistic. Painting the figure is a personal choice. As you go through the examples found on the internet you will find many projects that are well above average that have no paint.

Tip: All of the joints described above will work just as well on animal figures and other action projects.

Cranks & Shafts

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Crank

The crank on wood a automaton is usually a very simple part.

The shaft is usually a wood dowel rod. Shafts smaller than 3/8” are fragile but can be used for small projects or projects with few action figures. Shaft sizes of 3/8” and ½” are very common. It is rare to find a shaft larger than ½” in wood automata.

The crank handle can be made from ¼” – ½” wood stock. The size of the crank handle is determined by several things. The first one is the amount of motion that will be created by turning the crank. If you have a lot of action figures, a larger crank handle would be an advantage because, assuming your action figures are all wood, wood on wood creates a lot of friction. Another consideration is the crank placement. If the crank is placed close to the bottom of the project, your hand may hit the bottom surface while cranking. You may also find it difficult to transfer the motion if the crank is located an excessive distance from the action figure.

The crank handle is another piece of wood dowel, ¼” – ½” in diameter. You can make this more elegant by placing a knob here instead.

Shafts

My area of interest is primarily wood automata and therefore most of my experience has been using wood shafts. I use dowel rods for the shafts and they are usually oak or poplar, in my part of the world anyway. The biggest problem with wood shafts is binding. As stated before, you have to be aware that although dowel rods look round, that is not necessarily the case. If your wood dowel binds in the support, you can do several different things to correct it.

1.       You can try sanding the shaft until it turns smoothly in its mounting hole.

2.       You could make the mounting hole one drill bit size larger. 

3.       You could use a round file and gently enlarge the mounting hole until the shaft no longer binds.

4.       Baby powder often acts as a good lubricant.

5.       You can polish the shaft with an automotive clear coat polish

Most automata makers will use wood dowels for the axles. They are readily available, are usually nice and smooth, and not expensive. However there are some problems that you must be aware of with using wood dowels for axles.

1.       Wood dowels are often not true round. This is more noticeable on the larger sizes. Your application will determine if that is a problem or not.

2.       Wood dowels are rarely straight. This becomes a problem when the mounts are located a distance from each other.

3.       The given diameter sizes may vary depending on the type of wood. In my experience I often find the oak dowels to be slightly larger than the poplar dowels

4.       Wood dowels bend easily. If your project requires a significant distance between mounts, the bend could cause a problem.

Cams

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Cam: An eccentric or a wheel with one or one or more offset curves, mounted on a rotating shaft, used to produce variable or reciprocating motion in another engaged or contact part.

This is a subject where we can finally begin to create movement. A shaft will rotate the cam. For the remainder of this book we will refer to any rotating shaft as the “axle.” In the example above, the axle is off-centered. The cam then will provide up and down motion to be used by your action figures. Actually the cam will only provide the “up” motion and rely on gravity to do the “down” motion.

The amount of lift from the cam can be calculated using the dimensions shown below. Just subtract the length of “A” from the length of “B”. In the example below the cam lift would be 1 ¼” (1 5/8” – 3/8”) with a cam size of 2”. The range of motion then would be 3/8” above the center of the axle to the top of the cam for a total of 1 ¼”.

Placement of the hole is determined by several factors. To make the smallest cam possible the hole must be placed as close to the edge as possible. If it is too close to the edge however the wood may chip out especially when inserting the axle. The farther you place the hole from the edge the stronger the cam will be but the larger your cam will be.

Cams are not always a linear up and down motion however. There may be a need to have the peak of the “up” motion held for a little longer than expected. For example, an arm is raised to take a drink. The drink should stay in place long enough to take a gulp. The example shown below will add extra “dwell” time. Notice in this example as well as others below that the axle is in the center and the “lobe ” (action raised section) was added.

If you needed a series of short quick actions, for example a dog barking three times with each single turn of the crank, you could add three bumps on the cam. That cam would look something like this:

There are potential problems with the “bumpy cam” however. Even though the bump is small, the lever may take excessive rotation to clear the bump. In addition, depending on the location of the bumps, the lever may actually encounter two bumps at the same time as shown below.

One option to minimize the problem is to have only the tip of the lever contact the cam as shown below.

One method used to avoid the problem is the use of a “roller cam follower” on the lever as shown below.

Each bump on the cam can be modified as required. There may be a need for a sudden stop for a motion as in perhaps something slamming shut. The cam shown below has a gradual rise and a sudden fall so the arm falls straight back down to the cam.

You can also use the bumpy cam concept to create multiple actions on the same cam. The cam shown below could be used to create the motion of a mouth taking a big bite and then chew three times.

The “bumps” can also be created by making depressions in the cam as shown below. There is a restriction with using depressions on a cam and that is the slopes of the depression must not be sharp or the action will not be able to slide over them. Use of the roller cam follower shown above would be an excellent choice here.

The cam shown below uses the side of the cam to provide side-to-side motion. This option is very popular for projects that require a small amount of side movement. This cam I call a “Wedge cam” or “Wobble cam.”

Although this cam rotates on an axle as they all do, the width of the cam is variable so the action is taken from the side of the cam. The cam will push the action out but you have to provide the return which can easily be done with a spring. You can also add another wedge cam on the other side of the action to return the action.

Although the wedge cam is designed to have the action taken from the side of the cam, you can still add any of the options above to have the cam perform more than one action.

The last cam action can provide a 90 degree turn as shown below. The cam rubs against a disk usually held down by gravity. The rotary motion of the cam is converted to a circular motion on the disk. If your project requires precision movement this option may not be your best choice. However this cam action is very popular.

As a general rule, the size of the cam should be as large as you can make it considering the size of your frame and cosmetic concerns. The larger the cam the easier it is to make a smooth trouble free operation.

Oscillating Motion

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Oscillation – repetitive variation of some measure about a central value

A dual rack and pinion setup shown below is one form of oscillating motion. It involves a partial set of gears that engages the top gears and moves the rack to the right and then engages the bottom gears to bring it back the same amount. You can attach the action figure to either the top or the side of the rack.

The photo is taken from my Convolution automaton.

The wedge cam discussed earlier can be used in a variety of ways to produce an oscillating motion. In the example below, applying the action to both sides of the wedge provides a solid side to side motion.

The next option I call a “Peg cam.” As shown below, the cam rotates on an axle mounted in the center. The action is attached to a peg is mounted off center on the side of the cam. This option almost always requires a movable joint at the end of the shaft to couple to the action. Please note the joint shown here has been rotated 90 degrees for better viewing. The Peg Cam mechanism can provide positive vertical or horizontal movement depending on the mounting of the linkage. There is one serious restriction with this option however, and that is this cam has to always fit on the end of the axle. Otherwise the action lever will not be able to make a 360 degree rotation. This type of oscillating motion is very popular.

A variation of the Peg Cam is shown below. The slot in the lever follows the offset peg in the cam. The advantages are a positive up and down motion. In the photo below there are two action take-off points. You can watch them in action in the CPR 1 video. This option also requires this cam to be mounted on the end of the axle.

There is an option to get around the ”end of the axle” restrictions noted above with the peg cam and that is a crankshaft. The crankshaft shown below is similar to the type commonly used in automotive engines.

The crankshaft is made with one long shaft on top and one short shaft on the bottom. The space between the sides is slightly larger than the width of the connecting rod to allow free movement of the connecting rod. The photo below shows the crankshaft before the final cuts.

After the glue dries, cut the top shaft as shown below.

Although a crankshaft looks easy to make, it does take a precise woodworking effort. The crankshaft is mounted as one continuous shaft. If the holes on the sides of the journals are not matched up perfectly the ends of the crankshaft may not remain inline when you cut the crankshaft as shown below (top view).

In addition, you must insure that the space between the journals are exactly the same on both ends to avoid the problem shown below (side view).

Tip: You can often experiment with the various parts involving pieces of dowel without using glue because pressure fit is adequate.

Unfortunately when working with a crankshaft you almost have to glue the parts before you can test them out. Because of that, you have to “commit” the connecting rod permanently as soon as you glue the crankshaft together. To avoid that, you can make the connecting rod in two parts that are screwed together. The sequence is shown below. Cut the connecting rod as one solid unit (step #1). Drill two holes (step 2). Then saw the “Cap” part off. Using two small screws, re-connect the cap (step #3. Now you can drill the connecting hole in the connecting rod (step #4). The hole should be slightly larger than the shaft on the crankshaft. With this setup you can remove the connecting rod as you experiment or if you change your mind on the design.

Gears

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How to make a wooden gear

Gears, in my humble opinion, are really not difficult to make. If you have access to a CAD program your job will be MUCH easier. Everyone has access to SKETCHUP because it is free and available from Google. The only negative to SKETCHUP is it takes a while to learn. You can however concentrate only on those components of SKETCHUP to make a gear. The most primitive, yet very effective, method to make a gear is using a standard grade school compass, pencil, and paper.

I am not an engineer. What I’m about to share works for me. I know there is some very hi-tech terminology used in designing gears but I’m not interested in learning another language.

The size of the gear of course is your choice but when working in wood I would recommend nothing smaller than 1 ½” diameter. In my world, the size of the gear is the diameter. For my purposes, the diameter of the gear is measured in the middle of the teeth.

The actual size of the gear is generally not important and is usually controlled by how much room the gear will take in your project. What is extremely important is the size in comparison to the gear it will mesh with. We will discuss that after we learn how to make the gear.

To draw the gear we will use the most inexpensive equipment available, a compass and protractor as shown below.

So the first step is determining the diameter of the gear. The next step is deciding how many teeth the gear will have. As a rule, in my world anyway, I try to have at least 8 teeth on a gear. You are simply going to have to experiment here to determine the correct number of gear teeth for your specific project. The more teeth you have the more precise the mesh will be. However it will be more difficult to make a nice smooth mesh because of the precision involved.

After you decide how many teeth you want, divide that number into 360 to determine how many degrees of a full circle each tooth will occupy. Divide that number by 2 to find the half way point between the gear teeth.

For example, if you have decided that you would like 16 teeth on your gear, divide 360° by 16 which equals 22.5°. Each gear tooth then will be 22.5° wide. We divide that number by 2 which gives us 11.25°, which is the half-way point between each gear tooth.

Draw a circle for the diameter of the gear. Use the compass to draw the circle. Draw a horizontal line from the center of the circle to the outside on either the left or right side. For our example, using your protractor, rotate 11.25 degrees either up or down. Draw another line from the center to the outside. Continue until you have all the lines drawn as shown below.

Determining the height of the gear teeth is not an absolute. The smaller the gear height, the more precise the gears have to be and the mesh of the gears becomes more critical. As discussed later, the location of the mounting hole in the center of the gear is critical. If the center is off by just 1/16” the gear will wobble 1/8”. When two gears mesh, if both gears are off by 1/16” on center it is possible there could be a ¼” gap between them or the gears will bind.

The greater the height of gear teeth, the less precise they are. If you require precision movement of your figures it is best to keep the height of the gear teeth as small as possible. In my experience I have found that gear teeth height of 3/8” is most common for me.

To create the height of the teeth we need to draw an inner circle as shown below. That means, if I intend to have a gear tooth height of 3/8”, the inner circle must be ¾” smaller than the outer circle. For example, let’s suppose you wanted to make a 3” diameter gear with 3/8” teeth. You would draw a 3” circle, place the lines corresponding to the placement and number of the teeth, and then draw a 2 ¼” diameter inner circle. At any one point then, the outer circle would be 3/8” larger than the inner circle.

Now we can draw the teeth. At this point it should be clear why we divided the number of degrees for each tooth by 2. Now we have an exact halfway point between each gear which will be the low point. Draw diagonal lines from the tip of each tooth to the inner circle at the half way between point between each gear tooth. Your gear design should now look like the one above.

Cut the design out of the paper. Leave a generous edge around the design. Glue the paper design onto the wood with either a spray adhesive or a light touch of glue.

The type of wood you use for the gear is not critical. I never use anything less than 3/8” thick. It would be really unusual to use wood greater than ¾” wide.

The next step is to drill the center hole.You now have to decide if the gear will rotate on the axle or if the gear will be attached to the axle and the axle will rotate.

wThe diameter of the hole is determined by the diameter of the shaft it will rotate on.

The exact center of the gear hole is very important here. If the center is off by just 1/16”, the gear mesh will fluctuate 1/8” total. That means at one point the gears will have a perfect mesh and 180 degrees later they will be 1/8” apart.

Using the paper design as a guide, cut around the outside circle leaving a little edge outside the outer circle all the way around. It should now look like the example below.

Now we can use a disk sander to smooth edges and form a more perfect circle. A method I use to insure the center is using a jig as shown below.

On a scrap piece of wood, drill a hole, close to the edge, with the exact diameter of the shaft. Insert a scrap piece of appropriate sized wood dowel into the hole. Set the gear onto the shaft. Make sure the gear spins easily. Clamp the board in position next to a disk sander as shown below. Turn on the sander and slowly spin the gear. After each rotation move the gear a little closer to the disk sander and repeat the sanding. Use the outside circle on the paper for a guide.

Now you can cut the gear teeth. If you follow the paper design closely, the tips of the teeth will now have a sharp edge. They have to be sanded down because the wood tips are very fragile and the gears are difficult to mesh with a sharp tip. Trial and error is the best method I have found for determining how much to sand off the tips. Use the sanding jig described above to sand the gear tips. Obviously you will have to have two gears so rotate them together and sand the tips as necessary to allow a smooth rotation. As you gain experience with making wood gears, you will have a good idea of how much to remove from the gear teeth tips. On future gears you may find it easier to just make another circle on your drawing to showing the sanding point on the teeth.

The last thing we have to do to make a gear is find a way to attach the gear to the axle. The easiest method is simply glue the gear to the axle. However I cannot believe how many times I have had to remove a gear while building the project. To make construction easier, I always add a wood collar to attach the gear. The wood collar can be made from a scrap piece of wood as shown below. You could also use a piece of wood dowel. The diameter of the collar should be ~ ½” larger than the size of the shaft it’s mounted on.

Drill a hole through the center the same size as the gear center hole. Insert a temporary shaft through the collar and the gear to line up the parts and glue the collar to the gear. Remove the temporary shaft ASAP so it doesn’t get glued in place. After the collar is installed, slide the gear onto the shaft into its final position. Then drill a 1/8” hole through the collar and the shaft. Cut a small piece of 1/8” wood dowel for a pin and insert it through the hole as shown in the photo above. I generally make the 1/8” pin a little longer than needed because, as stated before, I’m always finding a reason to remove the gear while building the project. You could also use a set screw here instead of the 1/8” pin, and if you choose that option, I would recommend using two, one from each side.

Gears in Action

Gears provide a rotary to rotary transfer of motion. At the same time they may also provide a change in speed and/or change in direction. The gears shown below show a simple transfer of motion.

One additional thing to remember about a simple two-gear transfer of motion is that the second gear will rotate in the opposite direction as shown with the arrows above.

If you need to just transfer motion, both gears must be identical. There is a need quite often however, to have some of the action elements operating at a slower (or faster) speed than the hand crank speed. If you want to transfer motion and change the speed of the gears, we need to talk about gear ratios.

For example, if you would like one of your action elements to operate at ½ the speed of the crank, we have to make a set of gears with a 2:1 gear ratio. To do that, one gear must be exactly twice the size and have twice as many teeth as shown below.

If the smaller gear is the driven gear, the larger gear will turn at ½ the speed. In the example below, the small gear is the driven gear. It is not as common to have the larger gear as the driven wheel.

Changing the gear ratio will also increase the force. If you have a larger object, or one that is more difficult to move, you can use a gear reduction to make it easier to turn.

There is often a need to change the directions of the shafts. A 90 degree turn is all we can do with common tools. One option is a different type of gear construction which is very similar to the old Tinker Toys. The gears are made from pegs as shown below.

Each peg is a piece of dowel rod. The gear is designed on paper exactly as we did above. Drill the center and cut out the basic circle as described above. With a pencil, draw a line across the outside surface for the tip of each tooth. Draw a line around the outside surface exactly in the midpoint of the width. You should now have intersecting marks for each peg. Drill a hole for each tooth ~3/8” deep. As a rule of thumb, the length of each tooth should be a maximum of the the distance between the midpoint of the teeth. I have found that 3/16” – ¼” dowel work well for the teeth. Use the smallest diameter dowel rod you can. It is important to round off the tip of each tooth.

Tip: Placing the pegs in a perfect line around the outside surface is very difficult with normal equipment. The peg alignment shown below is typical. The drill bit always seems to go where it wants to go. In most cases however, the peg gear will still work.

To complete the 90 degree turn, make another gear. You will have to experiment with exact placement of the 2 gears to get the best gear match. The 90 degree gear set is shown below. This option is easy to make but not very impressive.

There is another variation of the 90 degree turn which is shown below and is actually more common. This version works the best with small diameter pegs. To maintain the strength needed with the small pegs they are often made from metal such as nails. This version of the 90 degree turn also requires the tips of each peg to be rounded and very smooth.

An example of this version of the 90 degree gears is shown below as part of my Convolution project. Note that I also added a 2:1 gear reduction so the large gear will operate a ½ the speed of the crank. A gear reduction is necessary quite often to present a more natural movement. Also please take note of the rounding on the end of each tooth.

This option requires some experimenting with spacing of the pins and the proximity of the the gears to each other.

There is a third option and in my opinion, the most reliable opinion. This option uses two gears with relatively wide spacing of the teeth.

Because the grain of any wood changes around the perimeter of the gear, the strength of the gear teeth will vary. To compensate for that I use plywood which maintains consistent strength no matter what the angle.

The gears are cut using the same technique described earlier (draw on paper, past pattern on wood). Depending on the workload of the gears, I would recommend making each gear tooth at least ¼” wide and 3/8” tall. Less than that makes the gear very delicate but it depends on your workload requirements. If the gear teeth are going to be ¼” wide, the space between the teeth must be at least ¼”

If your requirements are only for a 90 degree transfer of motion, just make a copy of the gear for the second one. I find that this is also a good place for a gear reduction if needed. Whenever possible, do not add another set of gears just to reduce or increase speed. If you are going to add gear reduction/increase, draw the smaller gear inside the larger one to save time. Make a pattern on paper for both gears and glue them to the wood as shown.

Tip: Drill at least a pilot hole in the center for the axle before you start trimming the board and cutting the teeth. It’s easier to drill with a larger piece of wood. Also, if you remove the paper pattern by mistake, it is very difficult to find the exact center and that is an important requirement on a gear.

A band saw to cut the teeth. Cut down both sides of the teeth and then “nibble” away the space between. It takes only a few minutes to cut out each gear.

The gears must be filed/sanded smooth for proper operation. The tips of each gear tooth must be rounded so they can easily slide in between the teeth of the other gear. The sides of each gear tooth must also be rounded slightly as shown below.

The final step is to attach a wood collar to attach it to the axle as shown above. The collar can be made from a piece of wood dowel as shown or any scrap piece of wood. There are two methods to attach the collar to the axle. In the example above, both collars are attached by drilling a common hole through the collar and axle and inserting a piece of 1/8” dowel rod. An alternative method is drilling a hole all the way through the collar before it is installed on the axle, and using set screws on both sides of the axle.

Rack and Pinion

The last gear action we’ll look at is the rack and pinion combination. This gear set will convert a rotary motion into a straight horizontal or vertical motion.

The example above can be seen in action on the Convolution video.

Gear mounts

Mounting the gears requires a lot of thought. If you decide to mount the gear attached to an axle on one side only as shown below, the gear must be attached very close to the mount. If the axle is wood, the axle will bend easily so mount it as close as possible to the mount. The hole in the mount also must be slightly larger than the axle to allow the axle to turn easily. Unfortunately this allows the axle to “wobble” slightly and increases significantly as you get further from the mount.

At this point we have to also look at another concern, and that is, do we mount the gear to the axle and spin the axle, or do we mount the axle and spin the gear? If the gear is used only to transfer motion, it can spin on the shaft. If the gear provides the motion, it must be mounted on the axle.

If the gear must be mounted away from the mount, or several gears mounted on the same shaft, a second mount is used as shown below.

The axle mounts are often referred to as “pillow blocks.” If two mounts are used, extra care must be taken to make sure the axle holes are exactly the same.

Tip: Drill both mounts at the same time to insure identical hole placement.

Even with extra care you may find the axle binds when the mounts are positioned a distance from each other. The reason for that is the wood axles are rarely straight and the problem increases with distance. As you apply pressure of any kind on the axle, depending on the distance and size of the axle, it will bend. It may help to add an additional mount in the middle. However each additional mount will add friction.

Levers

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Just about every automaton has some form of lever involved. As shown below, there are three points to discuss.

The “motion” is provided by the power mechanism, usually a crank. The “action” is attached to the action figure. The “fulcrum” is the pivot point.

The motion is often received from a cam. The cam can push up from the bottom or down from the top. If you push up from the bottom, you will probably have to include some method to bring it back down on the reverse side of the cam action. One possible method is to attach a spring. Another method is to attach a weight of some kind and allow gravity to bring it back down.

If you push down from the top there may be enough weight in the action figure to allow gravity to bring it back up. Otherwise you can also use a spring or weight here also.

The action end of the lever is often attached with wires, dowel rods, or attached directly to the action figure.

The fulcrum is a very important part of the lever design. The height of the fulcrum could decide how much movement there will be on the action end. The placement of the fulcrum will have a major impact on the amount of action movement.

With the fulcrum arrangement above, it would require much less motion power to apply the action. This could be used to apply motion to a heavy action figure. It could also be used to reduce the amount of movement from the motion. A large push downward on the motion end would give much less movement on the action end. This arrangement is not common.

The fulcrum arrangement above requires more motion power but increases the action swing. This can be used very effectively to provide a wide action swing using a relatively small cam for motion power. This arrangement is very popular.

The next lever example is used quite often. In this arrangement the fulcrum is at the end of the lever.

Here the position of the cam (motion) will determine how much action will be available. As stated before, raising the lever with a cam under the lever can often use gravity to bring the lever back down. Placing the cam on top of the lever to push down may require a spring to bring the lever back up.

Belts & Pulleys

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It is often necessary to transfer the motion to another area beyond the range of a simple gear-to-gear. Using a belt with pulleys may be the answer.

Belts

1. The most obvious advantage of a belt is the ability to provide motion to a mechanism almost any distance from the motion source (Crank?).

2. You can change speed by using different size pulleys

3. You can change the direction of motion by twisting the belt

4. You can change the angle of motion depending on how you position the pulleys.

Additional pulleys can be used to guide the belt in awkward places.

Of course there has to be some disadvantages.

1. A method must be developed to maintain tension so it doesn’t slip. A very common method is the use of a tension idler pulley as shown below.

The idler pulley has a spring attached so it always applies pressure on the belt. In the world of automata that requires substantial mechanism which really doesn't help make the project interesting.

Another method to maintain tension is to mount the axle on a movable mount as shown below. One or both mounts are attached to a shaft with a set screw.

One mount could also be attached to a frame with slots and screws. This has a tendency to get bulky but is more dependable than attaching the mounts to a shaft.

Another solution to maintain belt tension is to use a belt that stretches like an O-ring or commercial rubber belts such as found on some vacuum cleaners. A belt can be made from common elastic material and easily sewn to size. Then you can find just the right tension to provide movement with minimal tension.

2. Another concern with using belts is, since tension must be maintained to prevent slippage, extra pressure is applied to both axles. Since this is a wood project, increasing pressure on a wood-on-wood movement may increase friction which could make it more difficult to turn the crank. You can minimize this problem by using metal axles or nylon bushings.

3. If you are not using a tension idler, there is always a concern about the belt stretching.

4. The last disadvantage is the loss of precise sequencing. Since belts are subject to some slippage, it may be difficult to make events always happen exactly when desired.

If you use string to make the belt there are several considerations. The first one is to use string that has a rough surface (not smooth) to help prevent slippage. The second consideration is to choose a string that will not stretch for obvious reasons. Another concern is trying to tie a knot that will make the string tight on the pulleys.

I have made a belt out of leather from an old leather coat. Then I made a wood sprocket and punched corresponding holes in the belt. If you would like to experiment with this concept, keep in mind that you only need one sprocket for a positive drive. All the other pulleys or wheels just go along for the ride.

Pulleys

If you have a lathe (metal or wood) it is a very easy task to make a pulley. If you don’t happen to have a lathe however you can still make a pulley with relative ease. A lot depends on what you are going to use for a belt. If you are going to use string for the belt you only need a small groove around the perimeter of your disk. For that application you can make a disk with a hole cutter. Then mount a bolt in the center of the disk and insert the bolt into your drill press. Hold a file, rasp, hacksaw blade, or similar against the wheel center as it spins.

If your belt is larger than string you can easily make the following pulley.

Cut three disks. Disk 1 and disk 3 are the same size and disk 2 is a little smaller. Using a temporary axle for alignment, glue all three disks together as shown.

Tip: Glue a rough material to the outside surface of Disk 2 to minimize slippage of the belt. The “rough material” could be leather (smooth side down), sandpaper, emery cloth, etc.

If you have a need to use string with a pulley (or any other application), getting just the right tension on the string is a problem. I suspect there are knots available that will allow you to slide the knot to get the tension desired but it’s beyond my skill. The use of a “Ferrule” may be the solution.

For my applications, the ferrule is a piece of tubing that is crimped to hold two elements together. I use a small diameter aluminum or brass tubing found at hobby stores. Cut a small piece ~3/4” long or whatever suits your needs. Use whatever you have on hand (tip of Phillips screwdriver, nail, pointed punch, etc.) to flare out the ends so it doesn’t cut the string. Place both pieces of string in place and then, using a pliers, pinch the tubing just enough to restrict the movement but still allow movement with sufficient force. When the tension is correct, pinch the entire tubing length to make a permanent setting.

Ratchets

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A ratchet is somewhat like a gear with the exception of the fact that it is not necessarily matched with another gear.

The pawl is connected to your choice of an oscillating drive mechanism which is described later in this manual. The mechanism must provide a back and forth movement. The pawl is pulled backward just enough to drop into the next tooth of the ratchet. Then the ratchet is pushed forward the length of one tooth. The detent provides a solid lock so the ratchet can’t move backwards. Although this option utilizes a spring to hold the detent in place because it’s on the bottom, you could just set the detent on top and let gravity drop it into place.

The ratchet has several uses and is used quite often in automata.

1. It can be used to prevent turning the crank backwards. In that use there is no pawl so the gravity detent works well placed on top. It also makes a clickity-clack sound that most people like to hear.

2. Another good use for the ratchet is to slow things down.

In this configuration each revolution of the drive wheel will move the ratchet only the length of one tooth. In the example above, the drive wheel would have to turn eight times to get one complete revolution of the ratchet gear which gives us an 8:1 gear reduction. This movement obviously will not produce a smooth movement but in many automata projects that is not a problem. An example of use here may be to move a fish across the bottom of a lake. Instead of one crank to get across the lake, it would take eight cranks.

Linkages

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Cam linkage

A very common challenge in automata is finding a way to connect movements or connecting the mechanism to the action figure. We have already discussed the Cam so let’s look at options to connect the cam to the action figure.

The cam shown below is cam linkage in its least complicated form. This cam linkage is used in the project at the end of this manual.One end of a shaft rides on the surface of a cam and the other end is connected to the action figure. The axle is offset on the cam.

In the example above, the linkage needs a little extra help. There is nothing to hold the linkage in position over the cam. There has to be something mounted just above the cam’s highest point to hold the linkage in place. It most often is a piece of wood with a hole in it large enough to insure there will be no friction with the linkage passing through it. It could also be wire loops. The linkage must be held firmly exactly on top of the cam or it will not work.

Another area of concern with the Cam linkage is the use of gravity. The linkage example above is dependent on the weight of the action figure to hold the linkage against the cam. When the cam is rotating down, the linkage must not have any friction to prevent the linkage from following the downward movement.

A slightly modified version of cam linkage is shown below and provides positive movement both up and down. It is a mechanism called the “Scotch yoke.”

The Scotch Yoke uses a peg cam which rotates on the center axle and the slider follows the offset peg. The slider is held into vertical position so the linkage can only go straight up and down. The photo below is from my Convolution and shows a horizontal movement with movement fixed on both sides.

Another variation of cam linkage is shown below.

The cam provides positive side-to-side motion, again with the slot following the peg in the cam.

To connect the linkage to the mechanism or action figure I use the simple wood connector shown below.

Most of my projects use 3/16” or ¼” dowel rods for linkage. The linkage shaft has to fit tight so I drill the same size hole in the connector as the shaft.  I usually use a 3/16” pin so I drill the same size hole in the connector and a slightly larger hole for the matching action figure. In other words, the pin never rotates in the connector. In most cases I can pressure fit the dowel rods into the connector while I build the project and then glue them in place when I’m certain everything is working properly

Driveshaft

A driveshaft is useful if you need to transfer motion in a somewhat straight line. The driveshaft provides a very solid transfer of motion.

The example above is from Convolution and transfers power from the front panel to the back panel.  Notice that all the movable parts are pinned together with 1/8” dowel rod. The movable parts on each end of the driveshaft are called universal joints, or U-joints. Each U-joint is two U-shaped pieces with a common square block to join them. The plans for the U-joints are shown below.

There is a ¾” x ¾” x ¾” block that is common to the two U-shaped pieces as shown above. A 1/8” hole is made in the center on two sides. To make a complete driveshaft, you need to make four U-joints, two center blocks, and one shaft.

Tip: Whenever dowel pins are required, make them at least ½” too long to allow easy removal while building and testing.

Bell Crank

A bell crank will change up and down motion to side to side motion. It got its name from an application a long time ago when people would pull down on a rope to ring a bell. They would pull down on a rope connected to a bell crank which would then hit the bell with a sideways motion.

With the bell crank you also have opportunity to increase or decrease the range of motion by changing the length of either side.

Wood connectors and shafts

Wood connectors and shafts provide an endless variety of linkage options. Consider the photo below taken from my Convolution project.

Another concern with linkages is finding a method to hold the connectors. In the example above, I made small square caps and drilled 3/16” holes on one side. Then I can just pressure fit them onto the 3/16 shafts. Commercial caps are available also in most home improvement centers that are much more elegant but take more room.

A common problem with using wood shafts for linkage is determining the correct length for each piece. I have found the simplest solution is to make them too long and see how the action performs. Each shaft should fit into the connector reasonably tight without glue which allows testing and experimenting before final assembly using glue.

Using wire for linkage

There are a number of advantages of using wire for linkage.

1.       Wire is usually purchased in 100’ rolls or more so one roll would provide enough for years of projects.

2.       Wire is easy to work with.

3.       Wire is less obvious to the observer which makes the project look more realistic.

If wire is used in linkage there is going to be an action joint on one end at least. A common method used to connect wire to a wood object is with a screw eye. You can either wrap the wire around one side of the screw eye as shown or form a loop on the end of the wire.

You could form the end of the wire into a loop and fit it into a slot in the wood which has a pin in it. Then you only have to be concerned about forming the loop so it’s only slightly larger than the pin diameter.

One disadvantage of using wire for linkage is the possible loss of solid predictable movement. When wrapping the wire for the connection, it must allow enough room for friction free movement. That may cause an undesirable amount of play in the linkage.

Make your own Automaton

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Now we get to the fun part, building your own automaton. The automaton is a figure doing push-ups as shown below. Your own version can change significantly depending on your skills, tools, and imagination.

The operating frame dimensions are shown below. The top and bottom pieces are ½” and the ends are ¾”. The top piece has a slot to allow the connecting linkage to pass through. Drill a 7/16” hole on each end of the slot as shown and then take out the wood between them.

I would strongly recommend you have the grain vertical on the end pieces. If not, they will split very easily when attaching the tops and bottoms. Drill a 25/64” hole as shown in one of the end pieces for the crankshaft to pass through. Before you assemble the frame, pre-drill the holes to help prevent splitting. Attach the top and bottom pieces to the end pieces with 1 ¼” screws. Note the relation of the location of the slot in the top and the hole in the end.

Using masking tape, make a mark across each corner joint. The operating frame will be disassembled, probably more than once, and the marks will be used to re-assemble. Even though you have carefully drilled each hole so they are identical on each side, if you don’t re-assemble exactly as it was initially, it is possible you will have screw holes that will not line up and the edges will be offset.

The action figure is made from standard 1 ½” pine (2 x 4, 2 x 6, etc.).

The neck hole is ¾” diameter and is centered on the top of the figure. Draw diagonal lines from each corner to find the center. Drill the ¼” hole in the chest for the push rod as shown. Then make all the rest of the detailed cuts. Round off all the corners except the top of the shoulders and the tips of the shoes to make the body more realistic. The tips of the shoes will be used as pivot points with cloth joints. The shoulder tops will be rounded after we attach the arms. You can cut/carve a small notch around the middle of the figure at the 3” point to make a waist line.

At this point you may want to consider painting on some gym trunks and shoes or whatever cosmetics you have the time, skill, or desire to add. Of course if you have any wood carving skills you can add a lot to the figure.

The neck is made from standard ¾” dowel rod. Start with a piece 1 ½” long.

The head is made from 1 ½” pine. The dimensions for the head are shown below. If you have any expertise at woodcarving, or know someone that has, this is one area that can really add to the looks of your project. The head as shown below however will work just fine.

The print on the left is the block outline. The dotted line on the right print show the neck hole and cosmetic cuts/sanding. Make corner cuts/sand on the front/back, side/side, and top/bottom edges so the head looks round. Using a utility knife, make the nose about 3/8” wide in the center by trimming off the sides.  If you want to go one step further, you can make small oval shape pieces and glue them on for ears as shown in the photo below. Sand the leading edge of the ears to make them look more realistic.

Using the neck cut previously from ¾” wood dowel, attach the head. Adjust the length of the neck to what looks good for you.

The arms are the “action” part of this figure. We’ll start with the upper arm part. This part will be attached to the upper body as part of the shoulder. It will be attached with a pin for the arm to rotate on. The print below gives the rough block dimensions for the upper arm.

The arms are made from ¾” stock. Try to match the grain and color of this stock to the grain and color of the main body. Although the instructions will only reference one piece, remember that there are two arms so make two of everything. Cut a block 2 1/8” x 1 ¼”. Drill the 3/16” pin hole first so it doesn’t chip out when you cut the slot. Stand the block on end and cut the slot. The pivot hole size is your choice. The hole must be just slightly larger than the pivot screw to allow the upper arm to move easily. I used an 8-32 x 1 ¼” screw to attach the arm to the body. Countersink the hole just enough to hide the head of the screw.

The finish cuts for the upper arm are shown below.

The notch near the 3/16” hole is determined by the amount of movement needed. As a general rule, if the required joint movement exceeds 45 degrees you will have to make a notch as shown. The depth of the notch is determined by trial and error. In this project the upper arm and forearm end up almost parallel to each other so the notch is significant. The dotted lines show suggested rounding for a more realistic look. After you attach the arm you will be able to see what surfaces need to be rounded off and how much for a more realistic looking arm.

The forearm rough block dimensions are shown below. Note that the hole for the connecting pin is slightly larger than the corresponding hole in the upper arm. The connecting pin will pressure fit into the upper arm and the forearm will rotate on the pin.

The bottom of the forearm will narrow down to form a wrist connected to the hand. After you make the hand piece you can determine how much you need to narrow down the bottom of the forearm.  The print below shows the finish cuts for the forearm.

Again, the notch near the hole here will be determined by the amount of movement needed. After you connect the upper arm and hand you will be able to round off the arm parts as desired. Temporarily connect the forearm to the upper arm with a piece of 3/16” dowel. Make sure the joint moves without restriction.

The dimensions for the hand are shown below. The hand is made from 3/8” stock.

A screw eye will connect the hand to the forearm. The size and depth of the slot in the hand will be determined by the size of your screw eye used. Sand and round the edges of the hand. Temporarily attach the forearm to the upper arm with a piece of 3/16” dowel. Attach a screw eye to the bottom of the forearm. Using a piece of 1/8” dowel, attach the hand to the forearm. Test the complete arm for unrestricted movement. The entire completed arm is shown in the photo below. Note the joints, rounding and sanding.

Now is the time to finish with the cosmetics. My choice was to show a sweatshirt, sweatpants, and shoes. I therefore painted the upper body and arms the same color. The sweat pants were painted a different color as well as the shoes.

Now we can move on to the mechanical movements. The figure will receive motion from a standard cam. Since the figure will raise about 45 degrees off the surface, and the connecting rod is attached to the figure, the connecting rod will change the contact point on the cam as it goes through the cycle. To accommodate the variable contact point, the cam was made a little wider than I normally use (1”). The dimensions for the cam are shown below. The surface of the cam must be extremely smooth. The connecting rod will ride on this surface. Any imperfections here could easily disable the mechanism.

The shaft mount has a hole that must be located in the exact same vertical location as the hole in the end piece. The dimensions for the shaft mount are shown below. After cutting the mount, round off the corners as shown.

The crank shaft is a piece of 3/8” dowel, which is initially 8 1/2” long. One end will extend out beyond the side of the pillow block so slightly round off one end of the shaft for a finished look. The other end of the shaft is attached to the crank. The crank handle is a piece of ¼” dowel, ~2” long.

The crank can be made out of any ¼” – ½” stock. The dimensions for the crank are shown below. Round the crank edges as shown in the dotted lines.

The photo below shows the crankshaft parts and completed assembly. Do not glue the crankshaft parts until final assembly.

The last piece is a 3 ½ ” piece of ¼” dowel to be used as a connecting rod from the figures chest to the cam. The length will be cut to an exact fit during assembly. The connecting rod will have a “skid plate” attached to the bottom to ride on the cam. Without the skid plate it would be very difficult to get the connecting rod to follow the surface of the cam. The skid plate is a ¼” piece of wood, ¾” x 1 ½”. Drill a ¼” hole in the center to insert the connecting rod. Slightly round the edges of the skid plate for better appearance. Insert the connecting rod into the skid plate. Make sure the connecting rod does not extend beyond the bottom surface of the skid plate. The connecting rod with the skid plate attached is shown below on the completed project.

We are now ready to assemble the project. Do not use any glue until everything is working to your satisfaction. If you haven’t already, assemble the four sides of the operating frame. Sand any edges that don’t match perfectly. Glue the ¼” dowel handle into the crank. Glue the 3/8” crankshaft into the other side of the crank. Insert the crankshaft through the hole in the end piece and the pillow block. Position the pillow block as shown below.

The pillow block should be in the center of the bottom frame piece so the crankshaft holes are aligned. Clamp the pillow block into position. Turn the crankshaft. If it does not turn easily, slightly enlarge the holes in the pillow block and end piece. After you find the correct pillow block position, lightly mark the position of the pillow block on the bottom frame piece.

Push the crankshaft through the openings until the crank is ~1/16” away from the frame side wall. The crankshaft will be held in place by a 1/8” wood dowel pin beside the pillow block as shown in the diagram above. Make a mark for the 1/8” hole so the pin will be ~ 1/16” away from the pillow block as shown.

Slide the cam onto the crankshaft. It should fit tight and will take a little extra effort. Clamp the pillow block into position as previously marked. Position the cam as shown above.

Position the cam at its lowest point. Set the figure into position as shown above. The bottom of the shoes of the figure should be 3/4” from the edge. The nose of the figure should be ~1/8” from the top of the operating frame. If not, adjust the length of the connecting rod until the nose is ~1/8” from the frame.

Lightly hold the figure near the toes while you turn the crank. The figure should easily ride up and down on the cam. If it does not ride easily, make sure the surface of the cam is as smooth as possible. You could try coating the cam surface with an automotive clear coat wax.

If everything checks out, mark the position of the cam on the crankshaft. The crankshaft will be held in place horizontally by the position of the crank next to the frame side piece, and the 1/8” pin on the side of the pillow block.

Remove the crankshaft. Drill the 1/8” hole through the crankshaft for the pin using the mark made previously. Attach the pillow block with two 1 ¼” screws on the bottom plate. Countersink the screws so the frame sets flat on a surface.

Insert the crankshaft through the frame side wall. Slide the cam onto the crankshaft. Slide the crankshaft into the pillow block. If the cam is not tight on the crankshaft, apply glue and using the marks made previously, slide the cam into position. Insert a piece of 1/8” dowel into the crankshaft in the hole near the pillow block. With the crank handle installed and the pin in place, the cam should not move out of position. Turn the crankshaft and make sure it continues to turn smoothly.

The shoes on the figure are attached with two small brass hinges as shown below. The brass hinges are used to help insure the body moves straight up and down with minimal side to side movement.

Fasten the hinges to the tips of the shoes first. Then stand the figure into position on top of the frame and attach the hinges to the frame. Lay the figure down and insert the connecting rod from under the top plate into the chest. Rotate the crank so the cam is at its lowest point. Remove both arms. With the cam at its low point, the skid plate should be resting on the cam and the nose on the body should be approximately 1/8” from the top frame piece. You should now be able to easily turn the crank and observe a nice smooth operation.

Now attach both arms. You will need to experiment to find the position where both hands are flat on the top frame piece while still allowing full up and down movement of the body. Mark the hand positions and then glue them to the top frame piece.

I would like to add one final piece of general advice here. Do not use any glue until you have to. When working with wood, you will often find that two parts will fit together reasonably snug with just a pressure fit, especially when working with wood dowels. Although you may be an expert with design equipment, wood dimensions are not precise. In the world of wood, 1/16” is not a reasonable measurement. Therefore the parts may not fit exactly as planned and may require adjustments from the original design. Try to make the glue operation your final step.

Your project is now complete. Hopefully this project will be enough incentive to get you started in the world of automata, and the tips and tricks provided will allow your imagination to produce some interesting, fun, and quality automata.

In Conclusion….

As stated previously, this book is an attempt to share my experience. In addition to many hours of experimenting I read everything I could find on automation and mechanisms. It is reasonable to expect that you may think of better, more efficient methods to accomplish the steps above. You may also disagree with any of the above. I welcome any suggestions, criticisms, corrections, etc. that you may be willing to offer.

calliopeguy@hotmail.com