Here's a photo of the original weight driven clock for the 60-inch. We found it 
near the back door of the 100-inch dome, solving a mystery of whatever happened 
to it.

The drum, with the grooves in the foreground is where the cable and (2000#?) 
weight was wrapped to provide the driving force.  The smaller gears to the left 
are part of the rewind mechanism that hauled the weight back up.  The big 
weights, upper center were the governor, the speed regulating system, amazingly 
accurate over a fair range of loads.  The thing, with the brass gears to the 
right, looking like a car transmission, is the mechanism for fine adjustment of 
the drive rate and motion of the telescope.  The disk at the end is probably the 
electrical slip ring that gets juice to those fine adjustment motors.  The cage 
containing the speed governor is about 4X4 feet.

This should have been left in place with a way to engage it when the computer 
stuff croaks.  There is a motor over at the 60-foot tower that I was told was 
one of only two in existence, the other in the Smithsonian.  Long after the 
instruments at the tower were "modernized" the motor was still there with a belt 
lying on the floor nearby.  "If our high-tech systems give up, we can plug this 
in, replace the belt and keep on going."