We've long had a clock somewhat similar to this
I don't know whether that's a real torsion pendulum clock, but ours was a pretend version, with an ordinary electronically driven clock dial, and an entirely seperate mechanism (with a separate battery) to make the pendulum rotate.
The other day I had a reaon to take the thing apart (one of the hands had fallen off), and I took a look at the mechanism that drives the pendulum. We'd long since stopped putting batteries in it, since they seemed to run down quite quickly, and when I tried it, it no longer worked.
As far as I could see, the circuit consisted of a transisor, a resistor, and two electrolytic capacitors. There was no mechanical connection between the circuit and the pendulum drive. There is magnet mounted on the drive, suggesting that the circuit produces magnetic pulses - but there's no coil.
I eventually surmised that the required magnetic field is being generated by a track on the circuit board. It doesn't seem very efficient, and perhaps that's why the batteries ran down so quickly.
Anyone familiar with the technique?
Sylvia.