Most visitors online was 1660 , on 12 Dec 2020
Hi TT - attached cabinet photo.
View attachment 620873
Thanks Joe - the controller is fitted on the top of the case in the recess flush with the top.
I didn't think I would find a pendulum so was thinking about making one - if I can find details on the suspension spring mounting.
That is going to be a challenge. Pendulums are very complicated. I would look for one first. All things have a temperature coefficient, usually expanding when warmer. The glass jars of an IBM mercury compensating pendulum are graduated, meaning the inside bottom is smaller than the inside top. This means when the ambient temperature gets warmer, the mercury as it expands, will raise the center of gravity [of the mercury] more than if the jars had straight sides. This will tend to speed the clock up. Even an Invar steel pendulum rod, as it expands will get longer which tends to slow the clock down. They figured out the correct balance to make it work. Hence the compensating mercury pendulum. Wood has a better expansion coefficient than steel, and is also cheaper, so it was often used in clocks until Invar steel was discovered.They also did some neat tricks with multiple rods, some dropping down to hold rods going up to cancel the expansion problem.I would like to make a mercury compensating pendulum if possible...
Opps, my mistake, the inside diameter is 1.800 inches, not 0.180 inches. The thickness of my suspension spring and pad is 0.088" so a slot between .088" to .100" should be fine. The pendulum should easily drop over the pin. Joe"
The glass jars are 7-1/4 inches tall, and fit inside the cups with an inside diameter is 0.180”.