have new disks made. The playing time for a disk of this size is about a minute. This particular music box includes a disk-changing mechanism that can cycle through a dozen disks, lifting each in turn into position to be played. Grandma's music box doesn't work enough to play disks -- yet -- but here's a YouTube video of a similar model that shows the basic operation.
The mechanism itself is fascinating (or a nightmare, depending on perspective). A strong spring motor turns slowly; the turning barrel for the motor has a number of cams cut into it; each cam moves one end of a lever that, through various linkages, is translated into the proper motions at the proper time. In one sense, I am incredibly lucky. The box is stopped at the point in the cycle where all of the interesting things involved in changing a disk are happening. This makes it possible to manually move the followers into the depressions in the cam and watch the corresponding levers move. If the mechanism had stopped in the middle of playing a disk, working things out would have been much more difficult.
Perhaps the most interesting item is the governor that controls the speed of the spring motor. The critical piece of it is that gold-colored widget near the top of this photograph. The video linked above includes a brief shot of the governor in operation. It spins at high enough speed that air resistance becomes a factor. That air resistance is transferred back to the spring motor through a set of gears that provides a few-hundred-to-one mechanical advantage. An ounce of pressure at the governor translates into tens of pounds of resistance that the spring must overcome, slowing it down. The governor has two spring-loaded wings that unfold when it spins too rapidly, increasing the resistance and slowing the motor. I'm not sure that I ever knew enough physics to actually write down a set of equations describing the system. Or to prove that there's a single stable equilibrium for it.
So, what worries me most about the problems involved in restoring this disk player mechanism? The people who have provided me information thus far all seem to be significantly older than I am, and I'm no longer young.