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Quite often on the french visible escapements the jewels have been messed about with to try and get the clock to run. The jewels are held in place with shellac and so only need very light heating to make the shellac soft enough to allow adjustment of the jewels.
This is a deadbeat escapement and quite often when they come in you see some very slight recoil and then shortly after the clock will stop. This is usually due to someone, who doesn’t understand how this escapement works, moving the jewels and adjusting the small turntable that carries the pivot, if the movement has one, to try and get it to run. The turntable does not affect the drop, it is there just to adjust the inside and outside clearance of the jewels and escape wheel teeth.
The jewels are semicircular in shape and when you first start trying to adjust this escapement you imagine that the centre line of the jewel end (where it look like it has been cut in half) is a line that should point directly at the centre of the escape wheel pivot. the jewels usually have a bit of freedom in their holes so when you heat them to adjust them make sure you don’t allow them to sag in a downwards position, they should exit the brass carrier at 90 degrees. If they are very sloppy when heated this could indicate they have been changed in the past and slightly smaller jewels fitted and it could be worth bushing the carrier to give them a better fit. If you notice any fractures or chips in the jewels it is worth replacing them. New ruby jewels can be expensive so if you want to save a bit of money you can make new ones out of steel rod, it works as well but just doesn’t look as nice, you dont have to harden the steel but they will last much longer if you do. Once the jewels are in the correct position you can then adjust the pivot carrying turntable until you get a nice steady deadbeat action. If you find the clock is still stopping it could be down to bent escape wheel teeth, they are very fine and sometimes it is very difficult to spot a bent or deformed tooth. Use good magnification!
One last point worth mentioning is the crutch is usually quite loose, it surprised me how loose they should be as you give the pendulum a good swing and it will put itself in beat.
How was that William?