Antique Clock Suspension Spring
Most used on round antique clock movements. These clocks were popular prior to 1950 and goes way back from there. It is called a suspension because it suspends the pendulum in the air. It is called a spring because it flexes back and forth. If a spare spring is ordered it would be a good idea. One can be put on the bottom of the weight section of the clock for next time. That way the search to find the next one will be saved.
Clock Pendulum Suspension Spring
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. Likewise, if the clock is running fast then turn the rating nut to lower the pendulum bob.
Most common springs
By and large, suspension spring A is the most common style suspension spring. Of course, it is most likely the one by default. 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. The A3 size is for grandfather clock units with a larger pendulum bob diameter. This size can also be seen on Grandmother clocks with larger bob diameters. The larger A3 is used with large bob diameters so the bob will not wobble front to back. If using a pendulum with a bob of 8 1/2 inch diameter or larger please order Suspension A3 for this reason.
Not as common
Urgos uses the single hook style as seen in picture suspension B. However suspension A was the very most common to use. Very old antique round movements mainly use Suspension C and Suspension D. These are mainly French clocks and US made units made prior to 1945.