Build a Coke Can Stirling Engine

The Stirling engine is a heat engine invented by Robert Stirling in 1816, it's different from your car engine because the fuel is burned outside of the engine, which makes it much easier to build. There are Stirling engines which will run on the heat of your hand, although they are a little harder to build. The Stirling engine makes a cool addition to any hobbyists collection of "things I've built!". I've since published a few different Stirling engine plans, take a look at my site to see them! There's now two how to videos with an updated construction method. Enjoy! I also have these engines for sale on my website here.

How does it work ?

This engine uses air which is repeated heated and cooled. To allow the air to be heated and cooled the coke can contains a displacer which is like a loose piston that can move up and down forcing the air around the engine. When the air is heated it expands pushing the diaphragm (balloon) outward which turns the cranks. When the cranks turn they move the displacer down so that the air is near the top where it is cooled causing it to shrink and pull the cranks back, which of course moves the displacer upwards allowing the air to be heated at the bottom, this repeats over and over!

What you need:

3 X Coke cans
1 X Balloon
2 X Spoke nipples
4 X 5A Electrical terminal blocks
Fine steel wire wool
1mm steel wire (about 30cm)
Thick (1.6mm) Copper wire or 1.6mm - 2mm steel wire
Plastic Drinks bottle cap.
1cm length of 20mm Dowel rod (you could carve this as you only need a tiny amount!)
Super Glue
30cm of Electrical wire (we want the outer insulation, so 3 core mains will be fine!)
Fishing line about 30cm long
Small scrap of inner tube rubber about 2cm square.
Small weights for balancing (5p 2p nickel etc)
3 CD's
A Lyles syrup tin or other tin for the firebox
Drawing pin
Super Glue

[optional]

Red temperature resistant silicone
Tuna can for a water Jacker

Step 1 Prepare 2 of the coke cans

Next you need two coke cans with their inside of their tops cut off. Use the tin snips to cut them, this will leave a lethal jagged edge which you must clean up either using a metal file or a small flap sander (could also use a Dremel)

Then cut the bottom off the cans using a Stanley knife. Try not to crease the metal as this will reduce the chances of it being airtight.

Comments

[flybynightenterprises]

This is the coolest engine and I really want to build one but frankly I can't follow the instructions. I would probably understand if I had ever build one before.  Is there a diagram somewhere for this design?  For instance, does the balloon go on one of the cans that were modified in step one?  Which end?  Where is the third Coke can?

[scraptopower]

I drew a diagram for you, I think it should be easier to follow the instructions once you have the parts in front of you

[flybynightenterprises]

Your sketch is very much appreciated, I should be able to figure it out now.  Time to start rounding up materials

[cayson]

hey i had the same problem and thanks for drawing that out!!!

[DieCastoms]

I think you should maybe re-draw this diagram on the computer (not that it doesn't look pretty darn good the way it is) and include it in your 'Ible. The directions make a lot more sense with the drawing.

[scraptopower]

Thanks for your comments! I'll try and do that when I get time.

[killersquirel11]

Looks like a beta sterling engine, unless I'm mistaken.  This picture from the wikipedia article might help

[flybynightenterprises]

The animation is very cool and helpful also!

[killersquirel11]

Yeah... I've done a fair amount of research on these, even made one in Autodesk Inventor as a final project in a high school class, but never actually got around to making one...

[gafernandesil]

Why you didn't just remove the top of the can (the can that displacer runs) to put the displacer and the diaphragm? I didn't understend the need to remove the bottom.

[scraptopower]

Originally, I didn't think that the displacer would be able to fit through the smaller hole and still work. But I was wrong :)

You can keep the can whole and just squeeze the displacer in, like I did in my other simple coke can engine.

[nizarhaddad]

thanks man because of you now i have a Stirling engine, but next time you do something try to use things you can find it around you in your home because i bought epoxy from a market, so what i mean is to use thing don't need epoxy if you can, just

[nerfv8]

have any tips on building 1

[ccrh2008]

I tried to make this one and it did NOT turn out well but I went on your website and found the engine that used only super glue and steel wire, much harder for me to mess up on. XD

[smorchhale]

is there any alternative for iron wool?
actually iam unable to find iron wool in my city.....

[pushp8890]

can i use cotton wool instead of steel wire wool?????????????????????????

[mustang6618]

to those who want to know what it does, all the displacer does is moves the heat from the bottom to the top of the chamber. since the sting is "bendable" it allows it to fall on its own.

[electrowizard]

it seems to me that this part dose not make any scene,you have no upward push,the displacer is meant to move up and down and is attached to the crankshaft,the wire connecting the displacer and the crankshaft is the main force behind the movement,if you use something like fishing line,how do you get any upward force?

[mustang6618]

the string pulls the hot displacer up and causes pressure moving the diaphram. when it cools the diaphram goes down and the string lets the displacer fall on its own.

[scraptopower]

The displacer does not product any power/force, so the line needn't be solid. All of the power comes from the diaphragm.

[electrowizard]

Hmm,ok,when I build it it will make more sense to me,big visual Lerner,ok,thanks.

[The_DonuT]

Can you use steelwool with soap thingy in? it's the only sort i got

[wudaal]

do we need to put some water inside the presure cylender? I mean is it steam or only dry air in the cylender? I made one following your instructions but nothing happened to the balloon.

[SirNoodlehe]

Can I use cotton rather than steel wire?
thanks

[or_ford98]

wow, that looks proffesional :)))

[bustedknuckles]

SOMEONE PLEASE HELP. I BUILT A STIRLING ENGINE LIKE THE ONE IN THE TWO PART VIDEO ABOVE. IT LOOKS AWESOME, BUT I CANT GET THE DARN THING TO RUN!!!!!!!!!!!!! HOW CLOSE DOES THE CAN NEED TO BE TO THE HEAT, HOW TIGHT DOES THE BALLOON NEED TO BE, AND HOW SHOULD I ADJUST THE DISPLACER. I'VE TRIED TO MAKE IT AS CLOSE AS POSSIBLE TO THE VIDEO, BUT THE FACT IS, I"VE GOT ABOUT 10HRS IN THIS PROJECT AND IT'S JUST A PAPER WEIGHT!

[davidofff]

My engine has too much friction, when I turn the wheel, it just stops. Is there a solution?

[scraptopower]

It could be the crankshaft isn't straight or the balloon is too tight. But without having it in my hands it's hard to say.

[electrowizard]

I hace mine put together,but I find it very hard to turn the crankshaft,is this normal?

[scraptopower]

It could be the crankshaft isn't straight or the balloon is too tight. But without having it in my hands it's hard to say.

[electrowizard]

*have*

[truest1]

hey, i was wounderin what the temp is for the hot side and the temp for the cold side is ?

[scraptopower]

It's only the temperature difference that matters. Around 120c difference should make it work nicely.

[slatinski]

Ok how to do it?If I make the piston never to touch the bottom then the crank cant get all the way up?

[scraptopower]

The displacer must be too tall or the crank arm for the displacer must be too long. You'll have to adjust one or the other, the displacer is is easier to adjust though.

[slatinski]

Okay one question-the balloon has a hole for the tread but is this hole letting hot air escape?if not how the tread can moove freely wihout loosing hot air?

[atayman]

http://www.youtube.com/watch?v=MJcKlxNkhr8

i went with 2 cds on each site to keep it from falling over. I tried making the sterling fan at first and failed this worked first try. the cds are attached with a stick as a dowel. I just went and cut a branch with the right diameter. thanks for the instructions!

[atayman]

http://www.youtube.com/watch?feature=player_embedded&v=MJcKlxNkhr8

a video of mine thanks for the plans a little drop of oil on the fishing line really lets it slide on the balloon

[atayman]

thanks for the upload mine worked first try! the heat created a very tigh seal on the bottom on the displacer chamber then it stopped working seems it was too sealed up. so a tiny push pin hole in the bottom and all is goo again. Here is a video. I used brass tubing and parts from a hobby shop. I went with 2 flywheels both 2 cds on each side so it wouldnt fall over. The cool water holder is a 1 litre soda bottle.

[jaipai]

Very Nice .
Here is some more info on Stirling engines.
A Small Free-Piston S t i r l i n g R e f r i g e r a t o r
http://www.archive.org/details/nasa_techdoc_19860012245
by
A. K. de Jonge
(14th I n t e r s o c i e t y Energy Conversion Engineering Conference,
Boston, Mass, Aug. 5-10, 1979)