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Picture of Simple coke can engine
This is a simple coke can Stirling engine you can make in under an hour. No epoxy or RTV needed, just super-glue. It's all supported by steel wire, with spade connectors for all of the bearings.

Important note: It has been found that aluminium drinks cans need additional cooling around the top because the aluminium is so thermally conductive. Use steel cans if you can, such as Pepsi, Tango etc. Scraptopower has many other plans for simple Stirling engines, have a look here.

Thanks to David Williamson for the diaphragm design/ construction method. Check out his website here!

Materials1 Coke can
  • Steel wire wool
  • 1.6mm steel wire
  • Spring paper clip
  • Normal paper clip
  • 0.4-0.6mm fishing line
  • Super glue
  • Thin cardboard from a cereal box
  • A balloon
  • 6.35mm electrical connector/spade connectors .
 
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Step 1: Open the can with a can opener

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Open the top of the can with a can opener.

Step 2: Bend a paper clip

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Bend a paper clip into this rough shape, this is so that you can tie the wire onto the displacer later on

Step 3: The displacer

Roll the steel wire wool around a bic pen, when it's a little bigger then the can opening, stop rolling the wool and cut it to size. Cut it down to about 2/3rds of the height of the can. Thread the paper clip you formed earlier through the centre of the steel wire wool. Tie on about a foot of fishing line to the hook in the paper clip. Squeeze the displacer into the can. It's a tight fit, but it can be done

 

Step 4: The diaphragm

Draw two circles on the cardboard about the same diameter as the opening in the top of the can. Don't pierce through the cardboard with the point of the compass. Inflate balloon then super glue the cardboard disc onto the balloon, there's usually a slightly deformed part of the balloon - this is roughly the centre. Glue it on here. Deflate the balloon and cut off the neck.Turn the balloon inside out. Cut off the balloon around the centre.Glue the cardboard disc over



Step 5: Fit the diaphragm

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Use a sewing needle to pierce a hole through the centre of the cardboard discs and  thread the fishing line through that hole. Stretch the balloon over the can. Check that the displacer can be moved up and down freely.

Step 6: Cut the main bits of wire

Picture of Cut the main bits of wire
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Cut two pieces of steel wire about a metre long. Mark the approximate length of the bearing supports by making a bend around 15cm from one end.

Bend the wire around the top of the can and twist it  to secure it.

Do the same on the other side.

Step 7: Make the base

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Bend the two 15cm pieces upwards, these will form the bearings for the cranks. The rest of the wire is bent downwards and formed into a big circle to support the coke can. I just twisted the wires together.

Step 8: Cut the bearing supports to size.

Picture of Cut the bearing supports to size.
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Measure from the top of the can and cut the two bearing wires down to about 15cm. Crimp on two spade connectors for the bearing points

Step 9: The cranks

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Cut a piece of the steel wire about a metre long. Bend the displacer crank, this part should be bent out around 25mm.
About 5mm along from this, and rotated around by 90 degrees, start forming the two crank arms for the diaphragm.
The diaphragm cranks arms should be a short a stroke as possible, 2 - 4mm is good.

You should have about 80cm worth of wire left to form the flywheel. About 30mm from the diaphragm crank arm bend the wire in the opposite direction to the displacer crank arm. This is so you can counter balance the displacer it later on. Then about 12 cm along, start forming the circle for the flywheel.

Step 10: The displacer connecting rod

Picture of The displacer connecting rod
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Make the displacer connecting rod as above. To get the right size, thread the cranks through the bearing holes, and line it up as you make it.

Step 11: Diaphragm connecting rods

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The diaphragm connecting rods are made in the same way. Start by forming a half-circle curve on the wire the same as the cardboard disc. You need two of these the same. Crimp connectors on the end.

Step 12: Assembly

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Fit all of the connecting rods on the crankshaft.

Glue the ends of the diaphragm connecting rods to the cardboard discs using super glue. Keep an eye on the fishing line so it doesn't get glued down too!

Step 13: Tie on the displacer

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Tie the fishing line onto the displacer connecting rod. Make sure the displacer is moved all the way up and down by the cranks without getting stuck. When your happy, super-glue the knot so it can't come undone.

Step 14: Secure the flywheel

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Secure the end of the flywheel using a spring clip. This also counter balances the displacer. It's really important that you counterbalance the displacer - the engine won't work if you don't.

It's finished now! All you have to do is light a candle under the coke can and let it heat up. Once it's hot, turn the flywheel to start the engine.


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christpher4 years ago
I gust watched tow helicopters go by woooooooooow
8v924 years ago
Trying to figure out why this engine runs is like figuring out why a bumble bee flys, it should not run but it certainly runs quite well. The counter weight in the center seems to resonate and the flywheel is low mass but high inertia. I am not an expert but there are principals at work here that need to be studied. This is a great example of thinking outside the box.
The principle is quite simple. If I may.... There is a displacer inside the can.
This displacer moves up to allow the air within the can to make contact with the hot can bottom. This expands the air which drives the diaphragm up due to expansion. The displacer then drops to the bottom of the can which insulates the air from the heat thereby allowing the surfaces not exposed to the heat to cool the air which allows the air within the can to contract.
The REALLY cool thing about sterling engines is if you drive the shaft instead of the other way around, it becomes a heat pump! Not bad for 1880's tech!
I did not see the fishing line going to the displacer in the movie so I thought it was resonating somehow. I still think it is a good design and would work with multiple cylinders. Perhaps an affordable and practical vehicle could be built using a stirling engine.
rwcrocker4 years ago
Very cool! We built it today. It took a little more finesse bending wire than I had anticipated. If you don't balance it well enough, it wobbles like crazy on the wire legs even if you're holding the base.

We added a 15 mm strip of wet paper towel around the top of the can to act as a better heat sink - it helped a lot.
Thanks a lot for the great instructable!!
scraptopower (author)  rwcrocker4 years ago
Wooo! First person to build this ? Please share some photo's if you can :)

The paper towel is a good idea!

Thanks!
Middle School Science Fair, here I come!!!!
Awesome!
I had never even heard of a Stirling Engine until this instructable.
My kids and I will have a blast (in a good kind of way) with this.
I think it's AWESOME that you are introducing your kids to this!
Not only is this device classified as an external combustion engine and is truly a flex fuel technology which can even run on solar or geothermal heat.
In fact, any heat difference between the "hot cap" and "cold cap" will make it run. This goes all the way back to 1880's Scotland and I have read that it was devised to take the place of the dangerous steam engines used in coal mining at the time. Not a bad job of design by a monk of all people.
Ther is a wealth of history associated with this device.
One last thing, it has been said that this device is one of the most thermally efficient engines ever devised. Good luck with the Science Fair!
T0BY1 month ago

You have done really well here! You have taken what could be potentially a very complicated engine and made it very simple. What an achievement!

can i use a steel wire instead of fish line and tell me how it works??????

I used dental floss - it's stronger than thread

Could somebody suggest an alternative to coat-hanger wire please? Steel coat-hangers are no longer commercially available in the UK.

I tried using a bicycle spoke but it was too hard to bend into the small part of the crank.

I just used garden wire - it's about £1.25 from Wickes of a £1 from Aldi (when they have it)

snoopindaweb4 months ago

~(:-})

Sandyho8 months ago

I tried and failed on first attempt....:-( I need urgently for school project.........pleeeez help ! )

I couldn't get the connectors, so made eye hooks ...I read some where you said it adds to friction.....but mince rolled freely when fully connected up......

This time I will reduce the length between the two bearing points and see if it works......while trying I want to any other loop holes.......is it possible to test the movement of diaphragm by heating BEFORE connecting the cranks ?( It is very difficult to assemble w/o connectors ! ) It appears a bit stiff to me.....but it does rise almost a cm when pulled up. ....I saw the picture posted earlier where the pulling the fishing line brought the diaphragm up......it doesnt happen in my case.....is it OK ?

the diaphragm crank throw seems very small for the gas to move it....? As I understand this is what makes the crank rotate....I am using Aluminium PEPSI ( no steel cans where I live ) can I will add wet towel on top if required........lot of work for 5 hours and no result ......really hurts !!!

ssuseelan1 year ago
Hai wit respect
I like to know if I can replace the 'fine steel wool' thing here.
I am unable to find it.and also can you suggest me a way to find it? please!

thankyou
Would ring terminals do I couldn't find spade connectors
great instructable.one question.can i use cotton instead of steel wool?in our county steel wool is not available.so..............
tojo132 years ago
Where and how does the displacer connecting rods go?
rikardom3 years ago
Awesome!
tobune3 years ago
Very good concept. Trying to make it reality now.
tokin3 years ago
Cool!
mattle tokin3 years ago
Yes it is!
stumitch3 years ago
fantastic! i want to build one!
teniva3 years ago
Just love it and I certainly must try it
begunia3 years ago
Amazing work my friend!
kuruting3 years ago
Amazing...
lepar3 years ago
Awesome work. Thanks for sharing it with the community.
merkuri23 years ago
Interesting I must say.Trying to make it now.
kokina23 years ago
You are awesome and creative!
torina23 years ago
Excellent work!
Chowmix124 years ago
I really want to do this project. I have all the things but the wire. Would paperclips work as wire? By the way, would a few drops of water make Stirling engines more effective? I know steam is 100 times the volume of water.
scraptopower (author)  Chowmix124 years ago
I wouldn't have thought paper clips would be long enough, even un-wound. You could try adding another coke can on top for the bearings like my other instructable "make a coke can Stirling egnine" . You can get this kind of wire at garden centres and the like, it's not usually expensive, don't get the really thin 1mm stuff though as that won't work.

My engines that have had small water leaks all splutter to a quick death, maybe it would work but you need to be quite precise in the amount of water :)
the paperclips worked for the crankshaft, I made a flywheel of cardboard and glued it onto the crankshaft. For some reason I couldn't get the engine to work.. I gave up on it...
sandra-14 years ago
Very cool! We built it today.
MCzone4 years ago
learn to measure
how does 15 cm get that far
you made me waste 30cm of wire.
MCzone MCzone4 years ago
oh im sorry i made the mistake
scraptopower (author)  MCzone4 years ago
Use it for the connecting rods.
I started using it for the stand and the loop above the basket <:(
wiinick MCzone4 years ago
I almost id that too, but my base looks nothing like the picture, but does it work, yes.
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