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Antique Clocks/Clock runs slow


Hey Tom.  I have a Gilbert black mantle clock that runs slow.  Adjusting the shaft on the face does not work.  Everything else on the clock seems to work fine.  Construction date looks to be 1909 from the plate stamp.  Is there a way to adjust the speed apart from the adjustment.  Clock loses approx. 15 minutes in 8 hours.  Thanks.

The speed of a clock is determined by the distance between the center of rotation and the center of the pendulum bob. First, be certain the adjuster is working properly then see if the correct pendulum bob is installed. Sometimes, the  pendulum will get lost and a longer or shorter bob will be substituted. Please note the weight of the bob has very little to do with the beat rate of the clock. Merritts ( sells a Gilbert pendulum bob. It is 1-17/32 inches in diameter and weighs 2 oz. Please check and see if your bob meets these dimensions. It has a short bail on it. If a larger diameter pendulum or one with a longer bail was substituted the clock would definitely run too slow. By the way, the part number of this bob is P-527K. It is priced at $4.00 plus shipping.

If everything else seems normal you might have to shorten the pendulum rod. Be certain to remove the entire rod before bending it as the suspension spring could get broken as you shorten up the bend in the rod.

I have seen clocks where the suspension spring was dislodged from its upper slot and hung on the lower slot, thereby slowing the clock down. This happens when a clock is transported with the pendulum bob hanging on the rod. You would definitely want to check to see if this is a possibility. This should be easy to fix.  

Merry Christmas and hope you get your clock working.  

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Tom Williams


I can not think of any questions I cannot answer in regard to repairing antique clocks or radios. However, I am sure there are a few I have not heard and may not be able to answer. If I cannot, I will say so. I have been repairing them since I was a young child.


My experience includes repairing CooKoo clocks, Westminsters, BimBam, almost all antique clocks. I do a bit of repair on battery clocks where the value is sufficient to warrant working on them. I also repair antique (tube type) radios - all makes.

Indiana Historical Radio Society, Illinois Valley Antique Car Club, Military Vehicle Preservation Association

BEE from Cleveland State University

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