Instructables

The Stirling Engine, absorb energy from candles, coffee, and more!

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There's energy all around us that's just waiting to be tapped into. Whether it's hot coffee on a cold day, light from the sun, scented candles, waste heat from electronics... there's power to be had! How about we turn it into useful power? Step in the sterling engine.
Ever put a tightly filled balloon in the freezer, then come back and see it largely shrunken? Once you bring it back out into a warm room it expands again. Now what if we could use that expanding and contracting for moving a piston... and you've got the general idea. If you heat the air, it expands, if you cool it it contracts. It's a very simple idea, for a very simple engine.

let's get building!

here' s the video of the build and the engine working!

 
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Step 1: Materials

Required tools:

hacksaw
utility knife
drill
plyers (long nose)
wire cutters
drill bits 1/16, 5/32, 1/2-3/4
drawing compass
ruler

Materials:
CD and case / large plastic jar lid
10x5 inch piece of steel or aluminum two 5x5 pieces are fine, needs to have some thickness
CD tower (or even better) a LARGE 5 inch wide glass bottle. (see picture)
EPOXY (JB weld/ JB kwik AND regular, cheap epoxy. If it says non shrink, don't get it!)
    *there's been a lot of issue with epoxy, I never realized different epoxies would cause such a difference, so I've added a picture of the epoxy. Here's one place to buy it: www.amainhobbies.com/product_info.php/products_id/37084/n/Bob-Smith-Industries-MID-CURE-15-Minute-Epoxy-9oz  Hopefully this clears up the issues!
wire (welding rod is preferred, Stainless steel is best) 1/16 inch stainless or 1/8 steel - MUST BE SMOOTH and straight!
7 inches of PVC pipe
Foam board (5x10 inches or more, two 5x5 pieces are fine)
3/4" copper pipe
oil

(optional)
hotglue and glue gun
fan weights
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horshak4 years ago
I'm feeling like a dummy after reading all your comments and seeing videos on your working engines. I used 1/16 th aluminum for my top and bottom plates. I used brass plates for my stand. I have made my crankshaft out of stainless thicker than 1/16th but under 1/8th in My rods and ends are lightweight model airplane parts. .I have tried to cast my pistons twice with quick epoxy and I'm making my 3rd piston out of JB weld. Everything has been made twice with better quality control. It's ballanced and spins freely and looks quite good. Problem, it won't run at all. My wife says I sound like a hamster in a wheel in the kitchen. Please help!
Do you by chance have any pictures of your design? I was thinking about using Radio Control Aircraft parts on my design as well and would love to see what you came up with.
thecheatscalc (author)  horshak4 years ago
Hey, sorry to hear that you're having trouble! Would you mind taking some pictures? A side picture, a top picture, and anything else important. Maybe even a quick video of it running (or it not!)

Once the JB weld sets, take the copper pipe and hold it up the the light once you've removed the piston, clean the pipe, and put it back in. Check to see how much light you have coming through. If there's a lot, or the piston doesn't slide freely, then there's an issue. Otherwise, put it in the engine and see how well it works.

Also, don't attach the piston to the crankshaft and put the bottom plate on the flame. Does the piston move up? if not, your engine is probably leaking somewhere.

Finally, if you put it on the heat, the engine WILL pressurize, and the piston will move up, and might stay there until the pressure equalizes a bit. Keep spinning it for a few seconds (if it's not even trying by 20 seconds or so, pull it off, something might be wrong.)


found leaks in the displacer by submerging the engine to the top plate in a glass bowl after removing the piston and using my wifes turkey baster to blow air in the power cylinder. Now I get the piston to rise at times but the piston (epoxy) gets sticky and won't work after 1 or 2 tries. I kept sanding down the piston till it wouldn't work any more (the 6th piston).  After heating water in a coffee cup several times in the microwave I had the water explode and I boxed the engine up and dropped it off at a machine shop for them to machine me a aluminum piston. I am now waiting for it to return.
thecheatscalc (author)  horshak4 years ago
Sorry about all the trouble! I hope it works well this time! If they're machining a piston, you might need to get a matching cylinder.

I hope it all goes well!
thank you for replying. I just cast my 6th piston as both I made with JB Weld were bad. I used 60 min epoxy this time and got what looks to be an excellent piston. Engine still doesn't work. I went around the displacer looking for bad joints with the epoxy to the bottom plate and tried to seal up questionable areas and reduced the crankshaft dips as was someone elses video. Still doesn't work.I tried your suggestion of disconnecting the piston and don't see any movement. I am now going to submerg the engine in water and try blowing thru the piston cylinder to see if I can see bubbles indicating leaks.......................horshak
How long is the pipe? I can't size it up and I only have a limited supply of spare pipe. I don't need an exact measurement, I just need an approximate measurement. Thank you!
Doddity4 years ago
how much is this in cm the calculator doesn't seem right
Doddity4 years ago
Could you use fimo
martinhui4 years ago
I'm thinking to build one to drive the model boat with rc, but I see that the fixture is big enough to hold in a small boat, do you think there is other version to fit and if the output power is partically to drive.
rumania4 years ago
dispacer can do other material, or even preserve
vijks4 years ago
thanks for the instructable, but can you help me more on the calculations part? the way you choose the dimensions of the pistons (power as well as displacer)? you can also mail me to vijaytheonly1@yahoo.com i am tryin to build this engine on my own, but without any calculations i am feeling hampered. please help me on this
booyah-boy6 years ago
would it be alright if i used poltstyrene instead of foam board?
Polystyrene foam is fine. Things to watch: 1. There needs to be a gap around the edge of the displacer piston (the big one) to allow air to move around it. 2. The power piston (the small one) needs to be a snug fit in the cylinder, but not so snug that it won't move. It should slide easily without allowing air past it. You should be able to suck it from one end of the cylinder to the other with your mouth. 3. If the displacer touches the bottom plate and the bottom plate is too hot, styrofoam will melt and stick. You can try glueing a sheet of paper onto the bottom side of the foam with PVA glue to protect it. 4. Air leaks will stop the engine from running. 5. As you rotate the crank, the displacer should come close to, but not touch the top or bottom plates. If it does, the engine won't run. 6. Similarly, the power piston should not touch anything at the end of its travel Basically, you're trying to get no air leaks and nothing catching or binding as the engine turns
Alterman5 years ago
Does this part have to be plastic? If I use metal or another heat conducting material will the machine still work ?
The displacer cylinder needs to either be made of a non-conducting material (plastic, glass, rubber, etc) or have a non-conducting spacer separating the upper section from the lower section if you use conducting materials (metal) to make the cylinder. The fundamental idea is to have distinctly separate "sides" of the cylinder, one to collect energy, and one to disperse it, in a manner that is controlled by the position of the displacer, in order to facilitate the contraction-expansion cycle of the enclosed gas.
What kind of power can you get out of this thing? For example, could it pull its own weight and then some to make a miniature train, given adequate heat?
guhan4 years ago
what can i use instead of foam board

theruss0074 years ago
I don't know much but from what I have learned couldnt you replace the aluminium circles with copper. That way the heat from the source heats the air better. and the top would allow the cold side to cool off quicker for the next cycle. Plus could a heatsink help cool the warm air that has rushed to the top of the displacer.
Wesley6664 years ago
I was planning on making a Stirling Engine, but I had some questions.

I designed mine to use 2 cylinders, opposed 180° on the crankshaft.  I was using one as the heated end, the other as a cooling end with a regenerator between them.  My idea was to add a mini heat sink that would be liquid cooled to remove more heat.  After that, the air would be sent back through the regenerator to slightly warm it before going back into the heated cylinder.  The regenerator is one part that conducts heat from the warmed side to the cool side, but both pipes are sealed to that air exchange between sides only occurs by passing into the cooling cylinder.  The heat removed by the liquid cooled heat sink would be removed by another heat sink cooled by a fan driven by the crankshaft.  The liquid coolant would be moved by way of an electric pump, or mechanical pump driven by the crankshaft.  Any pointers or thoughts on this would be helpful. 

 

Refer to the picture below to get an idea.  As well I did not include the crank shaft, flywheel, fan, etc… in the picture:

Stirling.bmp
The two objects that consist of 2 triangles and a black ball are check valves so movement is only in one direction.
orion224 years ago
Interesting Application: Attach the Stirling Engine to a Wimshurst Machine.

ok, i will do it again. but can you show me how can i do the small poston. i am in Vietnam so it is difficult to find to right meterial. after finish the machine work by using hot water or fire.
the first time, i did finish but the small piston is no smooth so it did not work. the small piston with the hole has to have the small space or not.
123.png
the second one
i am thinking of using test tube as piston cylinder and silicon gel for moulding my piston i think it should work..
anyway will try it this evening..
i have done all it but it does not work. can you tell me about the size of the small piston. my teacher said i have to do the big piston and the small piston have to equal about the kg. it is hard to move. i am so disappointed. so can you show me clearer. please. i am very interest in it.
thecheatscalc (author)  hayketban7894 years ago
I'm not sure I understand the 'equal about the kg' part, (supposed to be the same weight?)

However, both should be as light as possible. If one or the other is very heavy, it'll mess up the engine.

The 'Hard to move' part worries me though. Does your piston slide smoothly? the engine should NOT be hard to move at all! It should turn easily.

If there's a specific part of the rotation that it sticks, or becomes hard to move at, check that out. There is likely a problem there. Either the piston isn't smooth at that point, the displacer is hitting the top or bottom, or a shaft is rubbing.
sorry. can you tell me about how to do poston. waht kind glue can i make a piston.
i done it by using glass to do piston but it does not work.  so can you tell me why and what should i do.thanks 
thecheatscalc (author)  hayketban7894 years ago
I'm not sure I understand exactly... For the piston, go back to the materials page, I updated the epoxy with the exact type I used.

Glass piston? I'm not sure I understand, did you grind the glass? or have a glass test tube? or what?

If you have a picture that'd be great!
illumin5 years ago
if thermal expansion is an issue, why not use non-shrink? That part isn't clear to me, but i'm the new guy for just that reason :-)
Just a guess, but probably he used what he already had in the house.
You mean the piston? Yeah, Actually I chose that epoxy because it had been sitting around for a few years, and... well it worked. When I tried fast epoxy, it never worked right, because it shrunk too much, and the 24hr epoxy never cured. Although it was too tight anyways.

It can't be perfectly secure, because the pipe isn't perfect, and small defects would catch it. However, too loose and it won't run.
i have the 4 minutes epoxy .. i also have a 5 minutes epoxy >>> does it mean it'll shrink too much??
i cant find any different epoxy other than the ones i have...
also how do i glue the wire in??
thecheatscalc (author)  kawaiiushii4 years ago
good question, I personally used a toothpick laid over the top of the casting cylinder, and secured the wire with tape until the glue set.
thecheatscalc (author)  kawaiiushii4 years ago
I need to add this to the parts list, but here's the actual epoxy I used:

http://www.amainhobbies.com/product_info.php/products_id/37084/n/Bob-Smith-Industries-MID-CURE-15-Minute-Epoxy-9oz?utm_source=Google-Base&utm_medium=cpc&utm_campaign=Product-Feeds&source=google_ext

Anyways, give it a try! The main point of this instructable is to use what you've got!

Here's the deal, if it does shrink too much, you could try putting something in the middle of the epoxy (ie a smaller solid cylinder) to reduce the overall shrinkage.
 can the hot and cold pistons be separated.
    what i mean that when u heat up from down all the inside air is being haeated while if u made two of the piston in wich u used the foam in as i think with the upper cold part and the beneth hot part .

   [please answer me on my mail.  hamadaranger_95@hotmail.com)
    
Eddiepers4 years ago
should i modify the cast piston diameter if my "main" cyinder is 6 inches across instead of 5 inches?

thanks
how did u stick fly wheel with the crank shaft?
all you need to do is take a cd and tape some cardboard to it and then drill a hole in the center and glue it.
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