Balance wheel issues

sjaffe

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Dec 25, 2012
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My dear niece asked if her Uncle Stan could fix an old clock she recently received from her grandmother. The "case" is like a porcelain vase. The movement has no markings, but is similar to an alarm clock movement. I assume it is a 30 hour with a balance wheel and hairspring, probably early 20th century. It is probably not worth much, but I am considering it as educational experience and hope I might get a little help with some aspects that are baffling me.

Before I disassembled it, the first problem was the safety pin used for the winding key handle. I formed a replacement from a piece of brass round rod. After disassembly, cleaning and reassembly, I was able to get it running, but at best I could only get about fifteen hours running time. The mainspring was 9/32" x 0.014" x ~22"(?) I found a 9/32" x 0.012" x 27" so replaced with this. After uncoiling the new one it was obvious the originally was badly set. The new spring now will run for over 24 hours.

It took a while to get it running. I believe there was a beat issue. I moved the hairspring where it was clamped and that provided a way to center the balance wheel pin in the pallet fork. I couldn't find any written info on this adjustment. If you know of any books or websites that explain this, please let me know. I'm thinking this is very similar to an alarm clock movement, so something that details these might help. I recall I read a book that had a few pages about alarm clocks (was it DeCarle?)

I had to rotate the pallet arm on the pallet arbor to get the movement in beat. I just rotated it until the I got an even pallet/escape wheel contact between entry and exit.

Initially the exit pallet pin would sometimes hang up on the escape wheel impulse surface. I touched up the escape wheel impulse surfaces lightly with 400 grit sandpaper. This helped a lot, but was still sometimes hanging up. I bent the exit pin pallet ever so slightly and that seemed to fix.

My MicroSet is showing a rate that varies widely at each impulse (13800-14350 BPH). The pallet arbor pivot hole in the plate is round, but may be worn. I can see the arbor "jumping" as it rotates, so I'm thinking if I bush this it will stabilize the rate. The pivot is ~0.020", so thought this might be challenging to make a bushing of this size. Suggestions?

Last problem: after winding the mainspring, the balance wheel does not start on its own. I need to give it a push.

I didn't phrase the above as questions, but please read it as such and any suggestions or sources of info would be most welcome. I'd like to use this as a learning opportunity and hopefully the answers might help others in a similar situation.

Thanks,
Uncle Stan
 

bangster

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See Beat setting 101. Scroll toward the end. It's necessary to set the balance a degree or two OUT of beat, in order for the movement to self-start. If it's exactly in beat, there's no waiting impulse to get it going.
 

R. Croswell

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One indication of the "health" of a clock like this is the amplitude of the rotation of the balance wheel. When this clock is running how many degrees of rotation does the balance have from one extreme to the other? If it is "weak" it may not self start even if the beat is set properly. 400 grit paper is awfully rough for polishing balance wheel faces. One can usually obtain 2000 or 2500 grit wet/dry from auto supply stores that sell body repair and touchup paints. Bushings are available for 0.020" pivots but is very important to exactly center that bushing on the original hole. I would be more concerned about the condition of the points of the balance staff and the "cups" into which they fit.

RC
 

Jay Fortner

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Feb 5, 2011
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Just to add,judging by the rates you've given the BPH on that clock should be 14,400. That is a very common beat rate for pin pallet clocks.
 

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