I like that hot air engine. I like the magnet motor used as a generator too. If you wire 2 of those electric motors together, turn one motor it generates electricity to make the other motor run. A cooling fan on the cold end of the engine makes it more efficient and it runs faster on less heat. Water cooling, tiny water pump, cooling radiator, fan makes it very efficient. I like hot air engines. If you put that little engine inside of an air tank the fill with tank with 100 psi air the power of the engine increases many times because air density increases several times. If you increase atmosphere pressure 10 times a 1/10 HP motor becomes 1 HP.