A call to say their clock had stopped working - a plea for help - so straight to the Batmobile and off I went.
Upon arrival I was unable to get the clock working (usually the owner has moved it, jolted it etc. and it just needs to be put back in beat, but not this time), so I took the clock with me.
Taking the movement out of the case, an initial inspection showed the cause of the problem, 3 bent teeth on the mainspring barrel.
What had caused this slip is unknown. It could have been a slip of the key when winding the clock, a broken mainspring, or a knock causing the escape wheel to come free, we shall never know…
Removing the back plate enabled me to get access to the offending barrel, and removing the mainspring showed a perfectly normal spring (so that was not the cause). An attempt was made to straighten the three teeth but the final tooth was too far gone and fractured. I decided to replace all three teeth (the same amount of work as for one), this ensured that it there were any weaknesses in the straighten teeth, replacing them would be negated.
The job is quite complex and one of the more difficult skills I have had to pick up. It involves cutting a slot out of the barrel, inserting a piece of brass (filed to be a push fit into the slot) then soldering it in place. Once that is done,marking out the new teeth, cutting and filing them, and then removing all excess metal and cleaning the whole unit.
Once completed, the spring was put back in the barrel, and the movement re-built. The movement was put on a test rig for 2 full revolutions of the barrel to ensure everything was working, the teeth held under the pressure of a fully wound spring, and that the clock kept good time.
