Introduction
Mid‑1800s English fusee clocks, including those by T. J. Wood, use a traditional motion work system to drive the hands. When the hands move too freely or fail to keep time, the cause is almost always a loose cannon pinion, worn friction spring, or wear in the motion work. This guide explains how the motion work functions, how to diagnose excessive hand looseness, and how to safely service the movement.
How Fusee Motion Work Operates
The cannon pinion
The cannon pinion fits over the center arbor and provides controlled friction so the hands can be set without disturbing the train.
The minute wheel
The minute wheel engages the cannon pinion and transfers motion to the hour wheel.
The hour wheel
The hour wheel sits loosely on the cannon pinion tube and advances at a 12:1 ratio.
Friction spring function
A small friction spring or tension washer provides the resistance needed to keep the hands from drifting.
Effect of wear
Wear in any of these components causes the hands to slip or move too freely.
Diagnosing Freely Moving Hands
Check cannon pinion tension
If the cannon pinion is loose on the center arbor, the hands will not stay in position.
Inspect the friction spring
A weak, bent, or missing friction spring is one of the most common causes of drifting hands.
Check for worn motion work pivots
Worn pivots or oval holes reduce engagement between the wheels, causing erratic hand movement.
Inspect the hand collet
Some minute hands use a collet that must grip the cannon pinion firmly. A loose collet causes slippage.
Check for incorrect replacement parts
Non-original hands or motion work components may not fit tightly enough.
Correcting the Problem
Tightening the cannon pinion
The cannon pinion can often be tightened by carefully closing its slot or adjusting its friction fit.
Restoring the friction spring
Re-bend or replace the friction spring so it applies proper pressure to the cannon pinion.
Repairing worn motion work
Install bushings where needed to restore proper depthing and wheel engagement.
Adjusting the hand collet
If the minute hand collet is loose, gently tighten it so it grips the cannon pinion securely.
Checking escapement power
Weak power from the escape wheel due to wear or dirt can cause inconsistent hand motion.
Safe Disassembly for Inspection
Letting down the mainspring
Always use a let down tool to release mainspring tension before removing the plates. Fusee movements store significant power.
Using a movement stand
A movement stand stabilizes the fusee movement, making it easier to inspect the motion work and escapement.
Removing the hands
Use gentle pressure to avoid bending the hand collet or scratching the dial.
Separating the plates
Lift the plates evenly to avoid bending pivots, especially around the motion work.
Inspecting the center arbor
The center arbor must be smooth and free of grooves for the cannon pinion to grip properly.
Troubleshooting Flowcharts
If the hands move too freely
Check cannon pinion → Check friction spring → Check hand collet → Check motion work wear
If the hands slip when setting time
Tighten cannon pinion → Adjust friction spring → Inspect center arbor → Check collet
If the clock stops after hand adjustment
Check for rubbing → Check escape wheel power → Check motion work alignment → Check beat
If the hour hand drifts
Check hour wheel fit → Check cannon pinion → Check friction spring → Inspect wear
If the hands bind
Check dial clearance → Check hand collet → Check motion work depthing → Check pivot wear
Common Mistakes to Avoid
Over-tightening the cannon pinion
Too much pressure can crack the pinion or bind the motion work.
Forcing the hands
Always adjust hands gently to avoid bending the collet or arbor.
Oiling the motion work excessively
Only pivots receive oil. Excess oil attracts dirt and causes wear.
Ignoring friction spring condition
A weak spring is one of the most common causes of drifting hands.
Working without letting down the mainspring
Fusee movements store high torque and must be safely released before service.
Checklist for Final Verification
• Cannon pinion tight but smooth
• Friction spring restored
• Motion work pivots clean and lubricated
• Hands aligned and secure
• Escape wheel delivering full power
• Movement stable on stand during testing
FAQs
Why do the hands move freely on a fusee clock?
Usually due to a loose cannon pinion or weak friction spring.
Should I oil the motion work?
Only the pivots receive oil—never the friction surfaces.
Do I need a let down tool for fusee clocks?
Yes. Fusee mainsprings store significant power and must be released safely.
Can worn motion work cause slipping hands?
Yes. Worn pivots or oval holes reduce friction and engagement.
Why check the escape wheel?
Weak power from the escape wheel can make hand movement inconsistent.
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