This tambour mantel clock has the unusual feature of quarter-hour striking. It does bim-bam striking on the first, second and third quarters, and strikes one rod on the hour (see video below). The mahogany case is 9 1/4 inches tall and 19 inches wide. The dial is silver plated brass with applied bronze numerals. The minute track in 5 inches diameter, and the minute hand is 2 1/2 inches long.
The dial has no maker’s name, just “Made in U.S.A.” at the bottom. The label inside the back door says:
THE PLYMOUTH CLOCK
Plymouth was a division of Seth Thomas, which marketed clocks made by Seth Thomas, but with the Plymouth name instead of Seth Thomas.
This clock uses the later type of Seth Thomas mantel clock movement (made in USA), as described in Plymouth (by Seth Thomas) 1940 Mantel clock, modified to strike quarters instead of just hour and half-hour. The model number 4601 is stamped on the back, as is the date code 11 39 (November 1939).
Repair job 5939. I polished the pivots and installed 20 bushings. There was lots of bearing wear due to the strong mainsprings that this movement uses. The time mainspring was replaced in the past, and I replaced it again with a thinner one (Empire 280-17-505 11/16 by 0.0163 by 96 inches, shortened by 13 inches). The strike mainspring is the original one measuring 11/16 by 0.018 inch.
This movement has rack and snail strike. To allow for quarter-hour striking, the following changes were made from the hour and half-hour strike movement:
- The lifting cam on the front of the center arbor has 4 lobes of equal length (instead of 2 lobes) to activate the strike every quarter-hour;
- There is a quarter-hour snail on the rear of the center arbor. This controls the number of quarter-hour strikes, from 1 to 3;
- There is another cam on the rear of the center arbor (between the quarter-hour snail and the back plate). It has one lobe that holds the rear hammer up on the hour so that it cannot strike. Thus, the hour strike is on only one rod, and the first, second and third quarters strike bim-bam on two rods);
- There is a lever on the rear strike hammer lifter lifted by the cam mentioned above;
- There is a rack tail on the rear of the hour rack arbor that bears on the quarter-hour snail to control the quarter-hour strike.
When assembling the movement, set the hour snail so that the front rack-tail can fall into the notch between the 1:00 and 2:00 steps on the first, second and third quarters. If there is clicking when the rear hammer strikes, grease the rear end of its lifter.