Introduction
The suspension spring controls the pendulum’s motion and is one of the most commonly replaced parts in mechanical clocks. Choosing the wrong length, thickness, or block style leads to poor timekeeping, erratic pendulum swing, or a clock that won’t run at all. This guide explains how to choose the correct suspension spring for your clock.
Understanding What a Suspension Spring Does
Controls pendulum oscillation
The suspension spring determines how freely the pendulum swings.
Affects timekeeping accuracy
Incorrect thickness or length changes the pendulum’s effective length.
Connects the pendulum to the movement
The top block attaches to the movement; the bottom block attaches to the pendulum leader.
How to Identify the Correct Suspension Spring
Measure the total length
Length determines the pendulum’s effective drop and affects timekeeping.
Measure the spring thickness
Thicker springs make the pendulum swing faster; thinner springs slow it down.
Match the block style
Different movements use different top and bottom block shapes and hole patterns.
Matching the Suspension Spring to the Movement
Identify the movement manufacturer
Hermle, Urgos, and Kieninger use different suspension post designs and block styles.
Match the pendulum leader
The bottom block must fit the leader’s slot or hook style.
Check the pendulum length rating
Suspension spring length must match the movement’s pendulum length specification.
Common Suspension Spring Styles
Hermle-style springs
Use rectangular blocks with specific hole spacing.
American-style springs
Often use simple brass blocks with a single mounting hole.
Anniversary clock springs
Extremely thin and long. Must match the exact torsion pendulum design.
Common Mistakes When Choosing Suspension Springs
Choosing by appearance instead of measurement
Springs that look similar may differ in thickness or block style.
Using a spring that is too thick
This causes fast running and reduced pendulum arc.
Ignoring block compatibility
Incorrect block style prevents proper attachment to the leader or suspension post.
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FAQs
How do I know what suspension spring my clock needs?
Measure the length, thickness, and block style of the original spring or match the movement specifications.
Can I use a thicker suspension spring to improve stability?
No. Thicker springs cause fast running and reduce pendulum swing.
Do all clocks use the same suspension spring?
No. Suspension springs vary widely by movement type and pendulum design.
Why does my clock run fast after replacing the suspension spring?
The replacement spring may be too thick or too short.
Can I trim a suspension spring?
Only if the design allows it. Many springs must match exact block spacing.
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