Algodoo

A spring engine so powerful that it probably couldn't be used in a vehicle. There is so much crazy energy that the engine oscillates between 150 and 250 rad/s. It's really stable though, so don't worry about it going crazy and exploding.

Just start the simulation and have a look at it. I don't really feel like making it moveable right now, but if you bug me about it I will.

Uses a readable scripted ratchet, so you've gotta have 'godoo 2.0.0 or higher.