Hot air makes the wheels (and propellor) go round

As promised, here's the engine which runs on air. My colleague Malcolm Rowney built it a couple of years ago and shows it at model engineering displays around East Anglia. The engine is a Stirling engine, and I think it would be accurately described as an external combustion engine.


Don't ask me to explain how it works: I think you need to know about the theory of gases. Yes, probably only A-Level physics stuff, but I've forgotten most of it! The main components seem to be metal tubes suspended in the top of a wood burning stove; a couple of pistons mounted one above the other in one cylinder;


and an ingenious rhombic drive to convert the up-and-down movements of the pistons to rotary motion. The photo above is looking down onto the rhombic drive mounted directly above the cylinder. The engine is driving a water pump and a dynamo. The stove will burn anything, but is usually fired with scrap timber. You might just be able to make out another important feature, between the yellow chimney and the aluminium box housing the gears: a kettle.

Here's Malcolm on the Thames in a boat powered by a Stirling engine. Malcolm, I hope you don't mind me borrowing your picture.


Advantages of Stirling engines (as far as I can tell): quietness and high efficiency.

And here's Malcolm himself, demonstrating it on YouTube (not one of my films - apologies for the muzak):