When my friend and fellow horology enthusiast Andy showed me this old Jaeger cockpit clock I was immediately intrigued and interested. It was a complete non runner, and I had not worked on one of these before, but being a classic car enthusiast myself I was very keen to work on this piece.
The clock was produced by British Jaeger Instruments Ltd. The firm was based in London as indicated on the dial.
This is a picture of the Jaeger Instruments catalogue of that era.
The back of the clock has a window to allow regulation of the clock by the user (to make it run slower or faster). The winder would have protruded under the dashboard of the car to allow the user to wind the mainspring. The power reserve is 8 days on this model.
I start by removing the clock from its case.
I then carefully remove dial and hands.
The movement can now be taken out of the case completely.
This it the winding mechanism. It looks pretty robust.
With the movement out of the case, I start by conducting an overall appraisal of the movement. This is a non runner, so I try to figure out as much as I can before starting stripping it. A quick check on the endshake of the balance wheel confirms that the staff has a broken pivot.
So I proceed with the removal of the balance wheel from the platform escapement.
I source a replacement balance staff.
I then carefully remove the hairspring from the balance wheel. It is a friction fit of the hairspring collet on the balance staff.
I then remove the roller from the staff. I use a special tool produced by Bergeon for this, the Platax tool. It is very handy but unfortunately it has now been discontinued.
And finally the old balance staff is out.
With a bit of zooming you can just about see the broken pivot, sorry this would have been worthy of a macro picture!
The assembly of the new staff can commence. I use my staking set to rivet the staff on the wheel.
With that done, before going any further, I check the fit of the new balance staff on the platform escapement. There is no point doing any more work if it is not right at this stage. The balance is turning freely and true with the correct endshake, so I am happy with that.
I then fit the roller back onto the balance staff, and then fit the balance spring.
With this repair done and the balance reassembled, the clock is ticking again, so I now proceed with the “conventional” service, and strip all the parts to clean them. During disassembly I inspect all the parts, and find that the pivot holes in the plate are in reasonably good condition, so my guess is that clock has not seen a lot of use.
After cleaning, I reassemble and lubricate the movement. Assembly is quite straightforward with the platform escapement which just bolts onto the rest of the train once assembled.
The clock keeps good time with good amplitude, and goes through its 8 day power reserve without any issue, so the job is done!
I would like to thank Andy for entrusting me with this project, it has been a pleasure to work on something a little bit different.