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Cool $20 Gift for the Guy who has Everything - Page 2 — Parallax Forums

Cool $20 Gift for the Guy who has Everything



  • The_Master, FYI Stirling engines can be very efficient if they are operated across a large temperature differential, such as several thousand degrees. They are theoretically more efficient than steam engines because you don't lose the power driving the working fluid across its phase change (boiling it). And their advantage over internal combustion engines is that, being external combustion, they can use any heat source.

    The down side of Stirling engines is power density, unless the working fluid is at very high pressure. Boiling water wastes energy to create the steam but you can get a lot of steam from a little water; in a Stirling, the working fluid is always a gas and so you have what you have to exert forces on the power cylinder.
  • ercoerco Posts: 19,989
    My brother has a different/better/costlier version of this $20 Sterling engine. It has a metal upper plate (plastic in the cheapie) which transfers heat more efficiently. He says it will run just off the heat from his hand.
  • Request a video from him!
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,049
    edited 2019-01-25 01:57
    I opted for the metal version, which arrived today. It was thinking that, with metal top and bottom plates, the heat conduction would be better, and it would run longer. And it was only a few dollars more.

    It's a bit fussy to adjust, though. The metal stanchions are formed sheet metal, which I had to bend slightly to keep the flywheel between the main piston housing and the other piston rod without rubbing on one of them. The fact that the flywheel is a little wobbly didn't help much either. Then the tension against the pointed ends of the flywheel spindle has to be just so to keep them centered in their conical divots without being too tight.

    But I did get it to work. After running for awhile, I noticed that it was making rubbing/squeaking noises. So I added a drop of 3-in-1 oil to each shaft end and to each crank. That quieted things down, but mainly it let the engine run far longer to the point that it was like watching slow motion before it finally stopped.

    What a cool thing!


    Addendum: One thing I've noticed with this unit (and maybe it applies to the plastic unit, too) is that you don't want the water to be boiling hot. On mine, if the water is too hot, the foam displacer piston will tilt on its axis, rendering it ineffective, and the motor will stop.
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