Cheap and Simple Steam Engine

The Idea:
Recently I saw a video of a remote controlled boat powered by a miniature steam engine  and was instantly hooked on the idea.  After doing a bit of research I found miniature steam engines cost hundreds of dollars or require some very advanced skills and tools to build.  Yet looking at the actual mechanism which allows them to run they are really quite simple so I decided to try and make one on the cheap. 

The point of this project was really to see how cheaply and easily a miniature steam engine could be built. I built this engine in one day and for under $10 in materials so I think it's safe to call it a success.

This engine is 7.2cm (2.8") tall.

Some Things to Note:
First off I should state that this steam engine is only a steam engine.  This instructable does not include instructions on how to build a boiler to produce steam.  Instead I run the steam engine on compressed air.  If you don't have a compressor a bicycle pump works well too, it's just a lot more work for you.  ; )

I should also note that even if you did build a boiler this engine probably wouldn't work well because many of it's major components are wood.  In the presence of steam the wood would swell and warp causing problems.  A simple solution to this problem would be to replace the wood parts with aluminum ones.

I am a very visual teacher so be sure to read the 'Image Notes' (hover your mouse over the yellow boxes on the images), it will likely make my instructions clearer. 

How it Works:
You could read my lengthy description below or you could check out the totally awesome animation by the guys over at www.animatedengines.com, find it here! I should note that this animation is of a "double acting" engine, in that is has ports on both the bottom and the top of the cylinder where mine is a "single acting" engine with ports just on the top.  This just means that the engine relies more heavily on the momentum of the flywheel to keep it running but is a lot simpler to build.

This type of engine is called an Oscillating Steam Engine.  If you watch the video below you will see that the cylinder on this engine actually moves back and forth as the flywheel turns (it oscillates!), this action is what opens and closes the ports which let compressed air enter the engine and exhaust air leave. 

The cylinder has one port at it's top which is pressed up against the main body of the engine.  The main body on the other hand has two ports, one for the compressed air and one for exhaust.  As the cylinder tilts to the right it aligns with the compressed air port allowing air to flow into the cylinder and push down the piston.  This causes the crankshaft to turn, thus tilting the cylinder over to the left and allowing the air to exit the cylinder though the exhaust port as the piston comes back up.  Then the process repeats. 




View on YouTube

Step 1: Materials, Tools, and Plans

Most of the materials and tools for this project you will likely already have around the house.  The only things I had to buy were the brass tubing, tubing cutter, and some wire. 

Materials:

• 3/16" Plywood (aprox: 12x8cm)
• Retractable Pen (optional)
• Brass Tubing: (find some at your local RC hobby shop)
            13/32" for the piston and 7/16" x 0.014" for the cylinder
• "Tea Light" candle
• Heavy washers with a diameter less than that of the tea light
• 5 Minute Epoxy Glue
• Plastic Tubing (to connect your compressed air supply)
• HomeDepot sprinkler marker flags or piano wire (~18AWG)
• Floral stem wire or piano wire (~24AWG)
• Q-Tips with plastic tube (not paper)
• Small elastic bands
• Plastic Wrap

Tools:

• Drill (or better yet; a drill press) and bits
• Tubing Cutter ($5) - you should also be able to find one at most hardware stores.
• Pliers and Wire Cutter
• Empty Tin Can
• Razor Knife
• Sandpaper
• Vice (optional)

Plans:

Attached are two PDF files.  "Parts Only With Measurement" includes a layout of all the parts you will need to cut out of wood as well as the lengths for the wire and brass tubing parts.  "Parts Only No Measurements" is exactly the same but without any measurements printed on the page; good for cutting out and gluing to your wood as a guide. 

Some people are having trouble opening the attached PDFs, if you are too try the links below. 

If you can't open the link to the PDF; here is a direct link to it.
If you still can't open the PDF; here is a link to a high resolution PNG image of the plans. 

Step 2: Cut the Piston and the Cylinder

Cut the cylinder and piston from two pieces of brass tubing. They do not have to be exactly the same diameters as I used but the smaller one should fit very snugly inside the larger one and still be able to slide freely. Your local hobby shop should have the correct sizes of brass tubing. 

The cylinder should be 25.5mm long, and the piston 14.5mm. 

Using a Tubing Cutter:
To use a tubing cutter align your cut with the cutters blade and tighten the knob, not too tight though as not to squish the tube. Slowly rotate the tube inside the device tightening the knob every few turns until the blade cuts through the tube.  It may take a few practice runs, I ended up squishing the tube too much several times. 

Scrape out the inside lip of the cylinder with a razor blade to ensure no burs are left to scrape up your piston. 

If you don't have a tubing cutter you can buy one from Harbor Freight for $5. 

Step 3: The Piston

First cut the wire (24AWG) for the piston rod (I used a thin piece of floral wire but any stiff wire will do), then make a 90 ° bend 3mm from one end.

Now take some sandpaper and scuff up the inside of the piston.

Next take a small piece of plastic wrap and cover one end of the piston tube, secure it with an elastic.

Mix some epoxy and fill the inside of the piston tube with it. Be very careful not to get any on the outside of the piston, also try to keep the tube pressed to the table so no epoxy will get out under the edges of the plastic wrap.

Now insert the piston rod (bent end first) straight into the epoxy.

To ensure that the piston rod stays at 90° you may want to push it through a piece of ~0.7mm foam first and glue that in along with the piston rod (see Images).

Alternatively you could try hanging the piston rod from something so that it is just 1mm or so above the table, this will ensure it stays perfectly vertical while the epoxy hardens. 

Step 4: The Flywheel

Start by cutting the crankshaft wire.  It should be a 45mm long piece of ~18 AWG wire.  I used the wire from one of those little red flags you see stuck in lawns to mark the sprinkler system.  If you can't find one Home Depot sells them.  This size of wire is excellent because it fits perfectly inside of the plastic tube that Q-Tips are made of. 

To make the flywheel I popped the wax out of a tea light (candle), inserted the crankshaft wire through a few pieces of wood to keep it from pulling out of the wax and glued them to the crankshaft, then I added some metal washers (to add weight). Next I put all this back into the tea light and poured its melted wax back in to hold it all in place. Hopefully the images below will better explain this process.

To melt the wax I put it in the bottom of a tin can which I had bent a bit of a spout into to make it easier to pour.  Then put the can in a pot of boiling water on the stove until the wax melted.

Be sure to lay down a few layers of newspaper before trying to pour molten wax, I also wouldn't recommend doing this over carpet.  Epoxy could also easily be substituted for the wax, I just didn't have enough epoxy to do it. 

If I were to do it again I would drill a hole through the bottom of the tea light and run the crankshaft wire all the way through so that the motor could be easily connected to another device in order to power it.  If you do this you should probably make the crankshaft wire a cm or so longer. 

Step 5: Make the Wood Parts

The wood parts are to be made from 3/16" plywood. I bought mine from the craft department in Wal-Mart; $3 for a six pack of 7x3" sheets. You could also use aluminum, brass, Teflon, plastic or Plexiglas instead of wood. Just make sure whatever you use it has a nice smooth finish in-between the moving parts.  You will find the plans for the wood parts back on the Materials Page. 

3/16" plywood is easily cut, even with a razor knife. Cut both sides and go over it with the blade several times until the wood cuts. Sand the edges smooth. To cut the round crankshaft part start with an octagon shaped piece and sand the edges to a circle.

Body:
Now start by gluing the part Body 2 to Body 1.  Drill the top two holes with a 3/32" drill bit.  Drill the central hole the same size as the wire you used for the Cylinder Pivot Wire.  Finally Drill the bottom hole the same size as the plastic tube from your Q-Tip. 

Step 6: Cylinder Block

Cylinder Back:
To build the cylinder block start by taking the wooden part "Cylinder Back" and sanding down the center gray area of it by about 1mm. This will make a smaller contact area between it and the body, thus reducing friction.
Now drill out the center hole in this part the same size as the wire you will be using for the "Cylinder Pivot" wire. Now drill out the top hole with a 3/32" bit.
Cut the wire for the "Cylinder Pivot" part and make a 90° bend 5mm from one end. Now, on the opposite side from where you sanded down 1mm on the "Cylinder Back" part you must cut a 5mm long grove from the middle hole towards the top hole, just deep enough for the 5mm of wire to rest in when it has been inserted through the wood.  This is the side you will be gluing the cylinder to. 

Cylinder Head:
Start by drilling out the 12mm hole in the cylinder head before you cut out the square around it, unless you have a drill press such a large hole will be hard to align with a small piece of wood. This also helps it from splitting on you. Now cut out the 2.5mm deep grove in the other Cylinder Head part.

Cylinder Block:
The next step is to glue the two cylinder head parts, the brass cylinder tube, and the cylinder back parts together. You may want to press some foam into the end of the cylinder tube to prevent any epoxy from dripping into it before gluing.
Epoxy the cylinder head to the cylinder then both of those to the 'cylinder back' so that they are centered horizontally and the bottom of the cylinder is aligned with the bottom of the cylinder back. The 2mm deep grove you cut in the second cylinder head piece must also line up with the top hole in the 'cylinder back'.

Step 7: Crankshaft

I added a small circle of wood around the outer hole in the wooden crankshaft part.  This gives the piston rod a little more clearance and prevents it from creating more friction rubbing on the crankshaft.  See the Image below.
Next drill the outer hole in the wooden crankshaft part the same size as your piston rod wire, then drill the central hole in that part the same size as the wire used for your crankshaft. 

Now epoxy the part "Brace" to the flywheel side of the body just under the hole for the crankshaft, I also added a small brace to the piston side of the Body.
Now epoxy a Q-Tip tube into the hole though the body and to the top of the brace. You can now insert the crankshaft through the body, add a few washers made of free spinning Q-Tip tube between the flywheel and the body. Add more Q-Tip washers on the piston side to provide proper spacing so the face of the wooden crankshaft part will be under the center of this piston.  This also helps prevent the wooden crankshaft part from accidentally getting glued to the body.
Finally trim off any excess length of crankshaft wire as it will collide with the piston rod if it sticks out at all from the face of the wooden crankshaft part.  Now glue the wooden crankshaft part to the metal crankshaft wire (the other end of which is secured in the flywheel), fixing it in place.

Step 8: Finishing Up

Piston:
First make a 90° bend in the piston rod 20.5mm from where it enters the end of the piston. Now insert the piston into the cylinder, then simultaneously push the cylinder pivot rod and the cylinder rod through the body and the crankshaft respectively. You will likely have to turn the crankshaft to make the hole for the cylinder align with the bend in the cylinder rod.

Now you just need a way to hold the cylinder tight up against the body. I used a spring from a retractable pen held in place with a screw on "prop-saver" from a model airplane. I also found just putting an elastic band around the piston and body worked quite well... if not better than the spring, this option is also much easier to remove than if you glued a cap on the cylinder pivot rod.  An elastic or two should really be all you need here.

Air Supply:
Lastly you need to connect one of the top two holes on the flywheel side of the body to a compressed air tank or pump. To do this I just glued some plastic tubing to the body; just do whatever works best for you. This motor works quite well for me on ~15psi. Turn on the air and give the flywheel a quick flick and the motor should start, if not try flicking it in the other direction. If you line it up just right the motor will even start without you flicking it.  Switching which hole the air goes into will reverse the direction of the engine's rotation.

Troubleshooting:
If your motor does not run first make sure everything spins fairly easily when turned by hand. If it doesn't try figure out what is stopping it.  Next make sure that you did not accidentally get glue in any of the holes that supply air to the motor.  Lastly try running the motor on higher PSI.  Other than that there isn't much more I can suggest.  You can try posting any questions in the comments, I'll see what I can do but I'm no expert on the subject. 

Final Thoughts:
Over all I am very pleased with how this little motor came out.  It runs very smoothly, looks good and was really easy and cheap to build.  Some possible improvement include; the use of bearings to reduce friction, waxing the wood where it rubs together, or replacing/coating the wood with a layer of Teflon which would greatly reduce friction and help with the air seal. You might also try making the air input/output holes a little bigger and upping the PSI for more speed. 

If you have any comments, questions, or suggestions please don't hesitate to put them in the comments.  I'll do my best to respond to them. 

I hope you enjoyed my instructable and I wish you a successful build.

Comments

[patrickpow]

Will it matter if the copper tubes are bigger diameter and height wise than those you showed.

[liam2317]

I actually used brass tubing for this little engine, I bet copper will work fine too though so long as they fit together very closely and still move freely. The diameter really shouldn't matter much (within reason) so long as there is still a very close fit between the two. Height wise; unless you scale the other parts you will run into problems. Just make everything bigger to match the scale of your tubes and everything should work great.

[Kevin12345]

Digging in my old broken VCR i found the video head and the first thing that popped into my head was "flywheel". just a thought..

[Bilal k Abbasi]

nice one .....:-)

[woodstockbirdy]

Umm I Know this is kind of late to ask but the last steps you wrote but there are no pictures. I think you probably did that because you were already done. But I don't quite understand how the final assembly goes together. Could you please add one or two more pictures just to clear up. Thanks

[lost2010]

How is this a steam engine if you are using compressed air? this is a waste because its pointless to use a machine to run another machiine.

[fishhsifboy]

it uses the same principles as an oscilating steam engine so hence technically it is but as the maker said, a lot of parts are wood so if you want a genuine steam engine use metal.

[fishhsifboy]

it uses the same principles as an oscilating steam engine so hence technically it is but as the maker said, a lot of parts are wood so if you want a genuine steam engine use metal.

[Billgun21]

This is a steam engine, If you built a small boiler and everything to go with it it would run it just as well as the compressed air. But homemade boilers are risky and dangerous if you're not experienced. So using a air compressor is safer and easier (And cheaper)

[Everett_McKinley]

but not as cool besides the boilers don't generally burst like a frag, their seams split and vent steam. sorry if you wanted shrapnel but chances are you'd just get burned.

[MIRAMANALI]

hi this project looks really cool i am planning to use the basics to make one for a geared bicycle so that i can use its gears as helping hand for the engine(reducing the load). instead of a single acting engine i want to make a double acting engine but am confused whether adding one more inlet and outlet as above hole on bottom side of the plank will do the job? ,sealing the cylinder from bottom of course with the valve u have shown above and running the piston rod through the plank of that valve (the hole will be lined inside with rubber just to prevent air leaks because of piston rod)

[egustys]

Best way using propseivers (last foto)

[Daniel Deacon]

you could also use a hacksaw but that might be abit more trikey and not get such a good finish

[akidrick]

how did you cut the ply wood

[Daniel Deacon]

cut the ply with a saw. cut roughly around where you need to cut. make sure you have drawn out the patten onto the wood exactly right then make a waste line and the exact line cut in the middle of the waste line and the exact line when this is done sand it down till it is perfect. make sure you don't go over the exact line or you will need to start over. it would be good if you used a small saw unless you are very careful. you could also use a copping saw or jigsaw but that might be abit more tricky

[sam D]

Love this build. White nylon cutting boards from the junk shop - which are high density PE might be an alternative for the wood. Low friction, good durability and high temp resistance.

[planetroverrobo]

I'm thinking about building a steam powered boat. And I like the idea of this steam engine but my idea of a engine is where there is olive oil burning boiling 2 quarts of water. when the steam becomes pressurized it will be pushed out of a two way valve so it creats pressure to push boat. But this engine has to carry a model boat, car battery, live camer, antena for radio control, ROV (which has camera on it), 200ft cable to power ROV, 200ft cable to carry information from ROV camera to model boat. Which engine would be better the one I thought about or the one liam2317 made?

[liam2317]

Sounds like a pretty complex project already, may as well save yourself the trouble and just go electric. You would need a pretty big steam engine to move around all the things you listed at a decent speed. Unless you have a very specific reason for using a steam engine I would definitely just use an electric motor if I were you.

[planetroverrobo]

ok thanks. I'v decided to go electric any ways also I'v decided to take everything of what I listed. Instead I made a pontoon boat puting 4 D cells or C cells and a small solar panel to rechage batteries. Thanks anyways though

[steve-lane]

(removed by author or community request)

[liam2317]

In the final picture on Step 8 you can clearly see how the air hose (it's the clear tube which is connected to the white plastic tube by a smaller, black piece of heat-shrink) is connected to the motor. You will not need to drill any holes in the brass pipe.

[steve-lane]

(removed by author or community request)

[liam2317]

You can download the PDF attached to Step 1 which is titled "Parts Only With Measurements.pdf" or you can get them from the attached image of the plans.
Here is a direct link to the large image of the plans.

[Sky Woulf]

if using seeam (bolier problems aside) you could use an old model airplane trick..... in a gas powered model airplane we coat our "wood" engine compartment and fuel tank compartment and the firewall with painted on 30 min epoxy (find it at your local automotive parts store) and this completely seals the wood from "Any" moisture, solvents, etc. (also has high temp restance somewhere around 1300 degrees F i think) so if you were to coad ALL surfaces of your wood like that you could (I think) run low presure setam in this motor. then you could try to run it off a stovetop tea kettle with a stopper and a hose. just allow for the pressure to build before starting!

[liam2317]

I think this would probably work quite well. If someone does try this I would definitely recommend coating the parts with epoxy either before, or as you assemble them (you could even use the epoxy coating to glue the parts together as well as seal them!).

[sbinc028]

what's the spring for?

[liam2317]

The spring is used to push the cylinder head piece up against the main body piece to provide a good tight seal between the two. In the pictures though, you can see I replaced the spring with a small elastic band that goes around the whole steam engine. The elastic seemed to work a lot more efficiently than the spring did.

[flowerman7]

Nice project! for the piston could you cast it out of J-B weld like many people do when building stirling engines. How airtight doues the pison and cylinder actualy have to be? Thanks

[liam2317]

I tried casting a piston out of epoxy as well but found that the brass tubes fit much better, were much easier to make, and seemed to have a lot less friction. My guess would be that it would still run if it leaked a bit but the more air tight the better!

[David97]

I have been talking to my teacher who has done a night course on building a steam engine. I have made 2 double acting engines to put on a model train.
I was going to run it with a boiler and a RC system. The boiler was going to be designed like a real one. Here’s what I thought of doing.

[David97]

I fogort to say the two engines would have a shaft between them to stop the steam taking the easyst route and olny going in circles

[GillesBathory]

the 2 pdf's "Parts Only With Measurements.pdf" and "Parts Only With no Measurements.pdf". The links dont work, how can i get them ?

[henrib736]

How many psi's does this run on?

[liam2317]

See the last step under the heading "Air Supply" for more info, but it runs well on ~15PSI.

[fuzzyguy]

The valve is tge 2 pieces of wood. as the piston is tilted by the crankshaft to the power stroke side it's 1 hole lines up with the hole conected to the air supply. As it passes by the bottom of it's stroke the 1 hole startes to line up with the other hole in the back piece. This hole allows the air to escape as the piston comes up. The spacing of the holes on the back piece are all important to how the engine runs.

[riverreaper]

could you vent the escapeing air in a way that it flicks it to start it ? sorta like the air compressor large in air to a fine out , simmlar to how they jet air to cut with only not that fine.

[liam2317]

I bet you could, maybe making some kind of little steam turbine like device could do it... hmmmm good idea!

[liam2317]

Thanks for the great description!

[DehLeprechaun]

first how would i hook up steam to it? second is it possible to hook 2 or more to one crankshaft? and third do you think it would work for a boat or car propeller/wheel respectively? thanks

[liam2317]

Unless you know what you are doing a steam boiler can be rather dangerous, even a miniature one. Be sure you do your reading and use the proper safety precautions if you do build one. Hooking up steam would be quite easy, just attach your boiler to the same port that the compressed air would normally be attached. As noted in the instructable using steam with an engine made primarily of wood will cause warping/swelling problems so replace with wood parts with something like aluminum. You should be able to add pretty much as many cylinders as you want, you probably wont get much more speed but you should get lots more torque. I think that this motor would definitely work in car or boat... or train. I am planning to eventually build one with twin cylinders using aluminum and putting it in a small remote control boat.