I have an old clock (30 day windup) I want to power with a weight that automatically raises a couple inches every 4 hours so I don't have to wind it. The clock will run with a 8 ounce weight hung on an arm extending about 6 inches from the drive wheel. The main drive wheel moves about 180 degrees per day and there are 13 clicks on the drive ratchet per revolution, so each click represents about 4 hours and about 3 inches of distance at a radius of 6 inches. So, the winding mechinism has to pull down 3 inches on the arm at 180 degrees from the weight every four hours, or some combination of radius and distance.
My idea is to construct a solonoid with a strong magnet inside that pulls down on the arm, moves it about 3 inches and lifts the weight up on the other side, but I'm not sure how to construct the solonoid. It needs to be fast acting (1/2 second or less) so the clock doesn't lose a second while power is removed. Seems like the work involved is about
3 watts for 1/2 second (1.5 wattseconds). One foot-pound per second is about 1.5 watts, so 1/2 pound and 1/2 second should be about the same, or maybe 3 watts for 1/2 second ignoring losses. The battery will be 2 lithium cells in series, or about 7 volts regulated down to 5. The pendulum will also be synchronized to a small air core electromagnet controlled by a quartz crystal oscillator for good accuracy.So, the question is, how to construct the solonoid to do the job?How may turns of wire, etc. to make it work? I have a few of those extra strong magnets from disk drives I was thinking of mounting in a tube with copper wire wound on the outside, but I don't have the details (length, turns, etc.) without experimenting. Maybe I can buy something ready made?
Thanks,
-Bill