Dave Ware writes: The flywheel travels down an inclined track, rolling on its axle. It picks up speed slowly as it overcomes the inertia of the flywheel. One turn of the flywheel only advances it the circumference of the axle. When it reaches the end of a track, it is spinning rapidly. It fall off the end of the track and on to the beginning of the next track. Its spin tries to take it up the new track, but a stop prevents that. Eventually it stops spinning and then slowly begins to spin in the reverse direction and down the new track. This continues for 4 tracks. At the end of the last track it falls into a cage.
The bottom of the cage has two insulated strips wired in series with an A58 motor and transformer. The flywheel completes the circuit when it sits in the cage. This causes the motor to wind a string around a pulley and raise the flywheel to the top of the structure and dump it onto the top track. The flywheel then starts its journey over again. Meanwhile, the cage returns to the bottom under its own weight, spinning the unpowered motor backwards.
The flywheel is made of 4 MH wheels mounted on a short axle. Prewar wheels were used as they weight more and thus provide more inertia. P17 spooked wheels highlight the action.