The Big Ben Chime alarm was introduced in 1931, and made until 1956. (A new Chime Alarm movement with single key wind and one mainspring for time and alarm was introduced in 1956 for the Clock Of Tomorrow. A later Chime Alarm movement was used in some style 8 Big Ben alarm clocks.)
The Big Ben Chime Alarm movement uses some of the same time parts as the Baby Ben movement:
- Balance and spring;
- Escape Wheel;
- Fourth Wheel;
Most Westclox pivots are polished, hard steel wire. The third through fifth (escape) wheel and pallet pivots are made this way, but they may wear their pivot holes enough to need bushings.
Westclox center wheel arbors are made of turned soft steel wire, and are not finished very well. Some are rough, and left the factory that way. They may cause bad wear to the front center wheel pivot hole, requiring a bushing. The back center pivot can wear, but unless the wear is super-bad, I prefer not to install a bushing, as a bushing may pop out when removing the time set knob.
Typically, I do the following pivot work to a Chime Alarm movement:
- Sharpen the balance staff pivots (if necessary) and polish them;
- Polish the balance end screws;
- Smooth the center arbor pivots with a pivot file, then polish them;
- Bush the front center wheel pivot hole;
- Bush one or both time third wheel pivot holes;
- Bush zero, one or both time fourth wheel pivots holes;
- Bush the time fifth (escape wheel) pivot holes;
- Bush the pallet pivot holes (this helps the clock run a lot better, as it reduces power-losing side-to-side motion of the pallet arbor.
I use KWM-sized “American System” bushings. These are small and blend in well.
- Center Wheel front pivot: #26 bushing, shorten in the lathe to be just slightly longer than the plate thickness, then insert and rivet flush with the front and back of the plate.
- T3 (time third wheel): pivot diameter about .69mm; bushing #6.
- T4 (time 4th wheel): pivot diameter .5mm, bushing #5.
- T5 and pallet pivots: pivot diameter .39 mm, bushing #59.
I use small cutting and smoothing broaches to enlarge the holes to the finished size.
I use oil sink forming tools to shorten the bushing on the outside of the plate (I leave the bushings slightly long to reduce future wear). I use the oil sink forming tool on the inside of the plate to match the original shape.
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