Seth Thomas 8 Day Four Sided Top Shelf Clock

January 21, 2009 | By | 1 Reply More

I recently overhauled this Seth Thomas shelf clock. This clock has an excellent movement design, as it runs very efficiently, allowing the use of thin mainsprings to reduce wear. Both the time and strike mainsprings in this clock are the original springs, and measure 11/16 inch wide and 0.015 inches thick. This is much thinner than the so-called standard American clock mainspring of 0.018 inch thick. These springs provide approximately half the force of the thicker mainsprings, yet the movement takes an excellent pendulum motion (plenty of overswing or supplementary arc). The good efficiency arises from the use of a semi-deadbeat instead of a recoil escapement, and the use of 4 instead of 5 wheels in each gear train. This movement has stop works to keep the mainspring tension more constant. I set up the stop works so that when the spring winding is stopped by the stop works, the spring is unwound 1 turn.

The video below shows the action of the escapement, starting from minimum pendulum arc:

The video below shows the escapement action when the clock is fully wound. Notice that the escapement is very nearly deadbeat, there is only a slight recoil on the exit pallet near the end of its travel:

The video below shows the escapement action when the clock has run down 7 days:

The video below shows the pendulum motion when the clock is fully wound:

The video below shows the pendulum motion when the clock has run down 7 days:

The video below shows the clock striking (it strikes only on the hour):

Here is a closeup video of the striking, showing the action of the count wheel and the locking cam:

Job 4654.


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Category: American Clock Repair

Last updated: November 26, 2009

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  1. ClockInfo.com » Blog Archive » Noah Pomeroy Semi-Deadbeat Escapement | February 9, 2009

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