Clock Mainspring Break Damage

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Clock Mainspring Break - Damage Assessment

When a mainspring breaks within a clock movement, it could cause damage. This damage could be within the movement itself or to the clock case. However, it is uncommon, but sometimes even the sides of the wood case can sustain damage when a mainspring breaks.

The German movement

As for the movement itself, we need to check the gear teeth and the gear arbors. Any damage will be on the lower part of the gear train if anywhere. Initially, the teeth of the gear that the mainspring is on, is a good place to start.

The next gear up is also a frequent damage area. As you go up the gear train, to the smaller wheels, damage is unlikely. So the force of the breaking impact happens in the lower wheels, typically the main wheel and the next one up.

Antiques with lantern pinions

Lantern pinions are the type of gear that is made of vertical wires instead of teeth. So it would be the smaller side of the two intersecting gears and would be going up the train not down. Thus the vertical wires within the circular brass bushings act as teeth instead of having a gear.

Subsequently, the advantage is the wire will spin within the bushings and decreasing friction and wear. However, not all clocks have lantern pinions, this would apply to some antique American time strike units only.

Lantern pinion damage check

If the clock has lantern pinions it is possible that some pins have bent or broken off completely. It would happen on the next wheel up from the mainspring gear, or main wheel.

Therefore, the impact of the main wheel from the break jolts the next wheel up with such force the pinion cant withstand the impact often. These are not so easy to repair if the pin breaks, it requires the removal of the pinion and the dismantling of the pinion to restore it.

So the gear or wheel, comes out, remove the pinion via a staking set. Repair this with the same steel rod size to make it perfect again. If the pin is just bent sometimes you can straighten it again with needle nose pliers for a quick fix.

Checking arbors and pivots

Meanwhile, assess the damage to the arbor of the next wheel up from the main wheel. Often it will be bent from the impact of the mainspring breaking and you would need to straighten it again if possible.

Furthermore, it is best to remove it and roll the arbor's long side on the table and see if it rolls straight.

Also, and just as important, check the skinny ends of the arbor known as the pivots. These are the skinny ends of the arbor that stick into the movements outer main brass plates.

If these are bent, the clock will not run. They need to be straight or the clock will have too much resistance in the gear train for the clock to function under the power of the new mainspring.

The teeth of the gear wheels

Lastly, inspect the teeth of the gears on both the main wheel where the spring was, and the next wheel up. Ordinarily, bent teeth are common but not as easy to correct.

Otherwise, bending back and reshaping them with a needle file sometimes works, other times the wheel needs a chunk cut out and you replace it by soldering new teeth in place.

Wooden clock case inspection

At any rate, make sure to get the movement out with no further damage to the clock case. Then check the condition of the case to be sure it does not need attention. It may need glue or nails to make it more secure as the impact of the spring breaking could loosen the boards.

To much information

On the other hand, if this is not in the realm of interest in learning about and experimenting with, please send us the movement instead. We will take care of everything for a fee. Please email a pic of what is going on to [email protected] so we can quote.

The content of this website is copyright by Clockworks and written by James Stoudenmire in year 2022

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1 year ago

I have a clock (German, I think) that needs a new spring barrel. It has some stripped teeth. The only marks on the movement is a number 23 on the back plate. 23 is also on the barrel cap.

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