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

Step 3 Cut displacer

This is pretty easy, pull out your foam board and compass. Using the top cut from the CD tower, span the compass from the middle to a fourth of an inch from the edge (2.25" to be exact). Draw two circles on the foam board (make sure to mark the middles!) and cut out. I'd suggest cutting the two circles roughly then use a jigsaw or the like to finish the cut smoothly. If you don't have one, the scissors will work fine.

Stack the two circles, then, using matching electrical tape, tape them together around the circumference. If you want you could glue them together, and it's not going to cause a problem.

Comments

[Mr. Z]

Would styrofoam work for the foam board?

[rumania]

dispacer can do other material, or even preserve

[booyah-boy]

would it be alright if i used poltstyrene instead of foam board?

[mrwolfe]

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

[lecrosskid65]

ok so i going to build one of these engines for a school project but im slightly confused. does the displacer have to be airtight withen the cd tower piece?

[Rotten194]

The idea is the air flows around the piston to the cooling chamber, so no. It CANT be airtight.

[dauty]

no. in this design, the idea is that it isn't

[corpz192]

I don´t get it, why the actual diameter of the displacer is 4.5" if the chamber is 5" ¿does the displacer need to be airtight?. thanks for your help

[seabeepirate]

If I understand correctly the point is actually to make sure the displacer is NOT airtight. The only purpose of the displacer is to move air from one end of the chamber to the other, while the piston actually uses the pressure of the heated air to turn the flywheel and in turn the displacer. Once the piston has been driven to it's highest position the flywheel carries the displacer to the hot side, moving the air to the cold side, as the air cools it contracts and draws the piston back down(or at least in a perfect stirling it would do this). Again the flywheel will move the displacer, this time to the cool side, move the air to the hot side, causing the air to expand and build pressure to move the piston, starting the cycle over again. Hope that helps :)

[seabeepirate]

I feel I should specify, that when I write displacer I only mean the piston itself and not the chamber. It is important to keep the chambers as airtight as possibly, but air inside the chamber should move freely around the displacer piston.

[lecrosskid65]

also hahaha i forgot to say this engine is the best looking/working one i have seen on the internet. most people that build stirlings like these often run at like less than 20 rpm but it looks like this one does a much better job.

[jdivy]

How thick is your styrofoam board? I assume it is not all exactly the same thickness. Mine, doubled as per the plans, is 3/4 of an inch. Is that right or should I make the displacement chamber taller?

[Zerog]

Hi, I've tried to make the stirling engine according to your instructions, but it doesn't work. I especially don't know the high of the displacer, I haven't found it anywhere... Is it possible to create it from polystyrene? Thanks a lot.

[thecheatscalc]

the displacer should be half the internal height of the enclosed chamber. polystyrene might work... but the requirements are: 1- must be stiff (not going to expand or contract with the air) 2- must be light 3- should be able to take a bit of heat w/o melting. as for your engine, have you made sure there aren't any leaks? that's a large problem, I'd suggest going around the edge of the top cylinder and sealing it up again with even more hot glue. Yes, again. I found I had leaks I couldn't see on mine but were affecting the performance a good bit. Also, make sure nothing is sticking in the engine. When you spin the wheel, how does it go? It should feel spongy as you turn it. biggest thing to check is the piston. It's the most critical component on the engine. PS: when you try to run it, does it move? does it act like it almost WANTS to run? if that's the case, make sure the flywheel is balanced properly and if it still doesn't quite turn over, the "steps" on the crankshaft are probably too deep. Make another with shallower steps.

[Zerog]

Hello

So I pasted whole motor once again but nothing happend. The worst thing of all is I dont know where I’ve made mistake. I think that ancillary piston is OK. It goes very gently (if it goes more gently it wont be caulking anymore). I thing that the problem is in main (working) piston. Maybe it has wrong height ( smaller than half space which is made for piston), and it is made from styrofoam so that is not so good as well. It is a fact that it is really light. I had it made from hard paper before, but I thought that was so heavy.PS: The worst thing what pissed me off is that the motor dont want to work at all so I think that it couldnt ne working anyway. But I have no problem with caulktion.

Look on my pictures zerog.cz/engine pls

[thecheatscalc]

hmm... it LOOKS like it should run... what're you running it on? try putting ice on top of the cold plate. try this to make sure everything's sealed. pull out the epoxy piston and bite it like you're blowing a balloon and... blow. take some soapy water and smear it around any glue seams. see what happens. The ONLY thing left that I can think of is the epoxy piston. When you push it in the tube does it spring back a bit when you let go, or stay put? Also does it move up when you heat the bottom plate (not attached to anything) or stay still, or worse, sink? if either of the latter two are the case, you'll need to re-cast the piston... file down the sides a bit, take off the tube, and set it on a piece of wax paper. Put a splotch of epoxy in the tube (mixed, and the tube is oiled) and just shove the piston down there and squish the epoxy around it's edges effectively re-sealing the piston. Another thing you could try is a copper cylinder instead of your aluminum one. PS: here's a stupid question (like the "is it plugged in?" question) have you tried turning the flywheel both directions to get it to start? it'll only run in one direction and if you turn it the wrong way it won't go... :P One final question: does it make a wet "gluga gluga gluga" when you spin the crankshaft? Sorry you're having such a hard time with this... We'll get it fixed though!