[Smertrios]

BIG STIRLING ENGINE RUNS ON ANY HEAT SOURCE - 850RPM 58cc - FULLY ASSEMBLED | eBay

I watched the video of it spinning a flywheel and have doubt that its 500 watts of power =/ Near the bottom of the auction he claims that if given the right conditions it can produce 500 watts 24 hours a day. That said its the biggest of the relatively cheap and currently produced stirlings I've seen as most are just toys or so well made they cost a fortune.

[UUU]

The whole machine look very much like the "Ky-Ko" fan which would have been powered from a kerosine burner with a wick, so not producing much power at all. Using gas to run it will give more output, but I doubt 500watts. google KyKo fan for more info.

Looking at the crank arrangements, They look a little weedy for that much power.

[RomanLini]

Yeah the crank in the photos looks like a nasty design, and looks sloppy/worn too.

I'm also doubting the "500W output" claim too, even with a 50% efficiency you need to be able to apply a 1000W heat differential to it, or maybe 1300W to 1500W of heat to the hot side? That sounds like a pretty severe flame, and that is only if you get 50% efficiency out of it which is unlikely as most flame sources will dump a heap of heat upwards (lost as convection in the hot exhaust air).