Antique Clock Suspension Spring
Most round antique clock movements use this spring. These clocks were popular prior to 1950 and goes way back from there. It is known as a suspension because it suspends the pendulum in the air.
The second part of the name is spring because it flexes back and forth. It would be a good idea to order a spare spring . One can be put on the bottom of the weight section of the clock for next time the spring breaks. That way you will have a spare and will not be without the use of your clock.
Clock Pendulum Suspension-Spring Information
The following is a discussion on clock pendulum suspension-spring information. Naturally, suspension springs do not have to be exact in length. If the clock runs slow, simply raise the pendulum bob with the rating nut at the bottom.
Most common springs
If the old suspension spring looks similar to this one then it is right. As a general rule of thumb, small mantle clocks take suspension A1, wall clocks and small grandmother units will take suspension A2.
This size can also be seen on Grandmother clocks with larger bob diameters. Use the larger A3 with large bob diameters so the bob will not wobble front to back.