Wasn’t there a guy named John Neuman (or similar) that had a motor he claimed worked on the energy from ‘pulses’ generated when a circuit is switched on or off?
This would be about in the 70’s or early 80’s
He used to hook it up to a battery to start it, then disconnect the battery and it would still run (no gas or external fuel or wires)
Never knew what happened to that
I have never heard of that one, but it sounds like a classic perpetual motion device.
Some of our fun exercises in physics class involved reading about real perpetual motion devices that have been invented in the past, and figuring out why they wouldn’t work. Some of them are not obvious.