Synchronome Synchronome Slave - gravity problems!

puffernutter

Registered User
Aug 13, 2015
16
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I have had one slave that always gains time, initially I thought the set up was wrong and it was over-reaching and pulling two teeth rather than one, however, having now observed it on the bench, and I had to have it vertical to see the problem, when the minute had gets beyond 1/4 past, gravity takes over and it will drop two or three teeth.

Looking at the back of the clock mechanism, the reason is that the arm to the left (gravity controlled only as far as I can see and opposite to the arm attached to the solenoid armature) fails to stop the wheel moving just one tooth.

Is that because the end of that arm is worn and needs a touch with a file to be sharpened, the brass toothed wheel is worn (less likely I suspect) or could I add a little weight to that arm?

I hope that makes sense

Peter
 

John UK

Registered User
Mar 25, 2006
118
5
18
The minute hand on a Synchronome should be 'balanced'. Normally on a standard factory pattern hand, there is a small counterweight made of lead riveted to the hand. See attached pic (and I apologise for the poor quality!). Sometimes the 120 tooth driving wheel is counterbalanced instead - and if this is the case, clearly the hand has to be fitted in the correct (of 4 since it is a square shaft) position. Where the coiunterbalance is on the 120 tooth wheel, it can be either added cheese head (or similar) screws around the rim, or sometimes a 'filled in' web on the wheel.

In order to experiment, 'Bluetac' adhesive putty can be used on the 120 tooth wheel.

IMG_3362.jpeg
 

puffernutter

Registered User
Aug 13, 2015
16
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1
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Thank you for that detailed response. I have had a close look at the mechanism and there is no evidence of any weights on the minute hand, nor is there anything on the driving wheel. However, looking at the original mechanism (that I replaced), there is a piece of brass strip on the driving wheel. I have also noted the minute hand is held on by a grub screw that was loose.
So, I wonder if the minute hand had become loose, moved around the shaft, so it was no longer balanced and that gave rise to the loss of time keeping.

It's all back together now, the minute hand opposite the balance weight and tightened on the shaft. When I get time I'll put it back in the circuit and see if it keep time!

Thank you again for taking the time to respond.

Peter
 

John UK

Registered User
Mar 25, 2006
118
5
18
I hope you will find it now works correctly. The hands do need to be reasonably correctly balanced. I'm surprised that a grub screw is used. Synchronome usually used a square shaft and a square collet in the hand and the hand held in place by a tapered pin in the square shaft.
 

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