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The amazing Pringles Stirling engine

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The amazing pringles Stirling engine, made from cardboard Pringles tube. When I saw this video by MarekSHayward I just had to have my own! It impressed me seeing a Stirling engine made mostly out of cardboard, something which wouldn't normally be workable in an external combustion engine.  This is a really easy to build Stirling that should be accessible to almost anyone.

How does it work ?

This engine uses air which is repeated heated and cooled. To allow the air to be heated and cooled the pringles tube 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!

Materials :

  • 4 x Pringles tubes, clean and dry
  • 1 x Balloon
  • 1 x Air freshener lid/ small aerosol lid
  • Cardboard from an old shipping box
  • Several plastic straws
  • General purpose adhesive
  • Hot melt glue
  • Fishing line (the creator of the original engine used cotton thread instead)
  • Cotton wool

Tools :

  • Scissors
  • Compass
  • Drill (with 2mm and 5mm drill bits)
  • Mark pen
  • Pencil
  • Ruler
  • Pliers
  • Box cutter
  • Hot melt glue gun







 
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The3rdPunch3 years ago
What does it do?
scraptopower (author)  The3rdPunch3 years ago
It spins! Powered by a candle!
ok im gonna use this for my science fair project so if you could explain a litte more that would be awesome. thank you for answering.
scraptopower (author)  The3rdPunch3 years ago
It just works by heating and cooling the air, when the air is heated it expands pushing the balloon out, and when you cool the air down, it contracts returning it back to the start. The displacer just moves the air from the top to the bottom and vice versa so that it can be heated/cooled.
we have to put the card board having srtaw in both sides between cotton
The3rdPunch3 years ago
for the displacer tube, what size should that be?
scraptopower (author)  The3rdPunch3 years ago
It doesn't have to be exact, but it should 2 - 4 mm smaller than the main pringles tube and 2/3rd of the height of the tube that it's moving in. BTW I just found out, the fishing line I used is about 0.4mm diameter.

I have followed the instructions verbatim and yet my engine does not work. I have checked for air leaks and there is none. I do find the displacer kind of heavy tensing too much the fishing line. I have tried several lengths to see if that fix the problem but the engine does not work.
Any suggestion ?
scraptopower (author)  Epoxy piston3 years ago
It's probably that the hole around the displacer wire is too big - this seems to be where everyone is getting stuck. What diameter is the fishing line that you used, or what weight is intended for ?

Maybe your displacer is too tall and is getting stuck somewhere. Have you tried it with a slightly bigger heat source to see if it works with that ?
rimar20003 years ago
Very good work, congratulations!
scraptopower (author)  rimar20003 years ago
Thanks!
if the fire burn all the engine than
goa6043 years ago
damnit out of all that i dont have a ballon .
anyway that is a great instructable very easy to understand with parts you really do find around your house .
scraptopower (author)  goa6043 years ago
Thanks, I'm sure you'll be able to pick up a balloon somewhere ?
The3rdPunch3 years ago
How exactly does it work?
yoshhash3 years ago
brilliant! I'm not sure why but it seems easier to understand this instructable than the other ones with pop cans.
Please explain a couple things though: the displacer sits inside the displacer cylinder, is that correct? and if so, I have a hard time believing that whatever pressure might build up in the heated compartment wouldn't escape past the 3 mm gap. Is this something I just needn't be concerned with (and just build it because it works), or do I have the concept wrong?
scraptopower (author)  yoshhash3 years ago
I think you've got the concept wrong, the air has to be able to leak around the displacer, if it can't the engine won't work. The displacer just moves the air from the top to the bottom and vice versa, all of the pressure acts on the diaphragm turning the engine.

But make sure the outside of the displacer cylinder is airtight or it won't work.

Let us know if you build it !
coppaj3 years ago
This is really cool - my son is going to build this for his science fair project. Great job!
TheGeek19843 years ago
There's one thing that I can't wrap my head around, step 9, the final picture. Does that mean that the crank should be in the 'down' position (roughly like this |_| ) and you glue the coins on top of the fly wheel? I'm sorry, there's some things that I can visualize with two words, but some things are difficult. It's an awesome project and I'd like to build one, but this one thing is confusing me for some reason...
scraptopower (author)  TheGeek19843 years ago
You have it exactly right! I tried to make it simple, but I think I over complicated explaining it ! I'm not too good at explaining things.
Kiteman3 years ago
How did you fit the displacer inside the cylinder, if they're both made of cylinders of the same diameter?

scraptopower (author)  Kiteman3 years ago
It's cut down the side of the tube in step 2 so you can roll it into a smaller diameter, to fit round the cardboard discs that are 6mm smaller than the Pringles tubes. Hope this is clear Kiteman.
Yes, I should have read that more closely.

Thanks.
la-main3 years ago
For the first time i have all the materials at home to build one of these. :D

Thank you
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