This little apha stirling engine appears to be based on an Andy Ross design (see 'Making Stirling Engines'). The small plate on the side reads "P P DEKKER" - presumably the builder. It is very well made, though some parts such as the cooling tank and the saw cuts in the inner sleeve, are not really up to the standard of the rest. The bore is the same as the Ross 35cc engine at 38mm, the stroke however is somewhat longer at 26mm against21.4mm. This presumably a displacement of about 43cc, though I'm not actually sure how to work out the net swept volume of an alpha.
The engine runs, though not as well as it should (now where have I heard that before!). On the basis of the Ross 35cc it should produce 40-50 watts and have a free speed of several thousand rpm. I haven't made any measurements yet, but the speed looks to be in the hundreds rather than thousands and it can quite easily be stopped with a thumb on the pulley. In fact it seems to be a better water heater than an engine at the moment - the waterways are somewhat restrictive so, rather than rely on thermosiphon, I repeatedly filled the tank with cold water letting the other end run to waste. After this single trip through the cooler the water emerged steaming hot!
I believe quite a bit of heat may be being lost by direct conduction from the heater to the cooler - a magnet suggests that the displacer and hot cap are stainless, with the latter's wall thinned down below the area covered by the burner. But the inner sleeve appears to be mild steel and the regenerator matrix looks like copper wire, neither of which would seem ideal - I look forward to a bit of experimentation!
I would be very pleased if anyone can tell me more about this engine or P P Dekker.
A couple of pics in the 'all hot air' album of my webshots page:-