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I repaired this Seth Thomas Adamantine clock last week. The movement is No. 89C, a popular movement for mantel clocks, using a semi-deadbeat escapement. This one needed a lot of work, including making a new dial (it had a terrible replacement dial), making a new front strike mainwheel bushing, and replacing both click rivets and clicksprings (the clicksprings were the unreliable flat steel type, one of which was broken). I routinely replace these with round spring wire springs. See the slideshow below for photos of some of the repair steps. Here are some movies of this clock in operation:

The time mainspring is 0.016 inch thick (thinner than average) yet the escapement takes a great motion!

Here is a slide show of some of the repair steps:

Job 4767.

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1. Seth Thomas Sparta Adamantine Mantel Clock
2. Seth Thomas Adamantine
3. Mainsprings for Seth Thomas Adamantine, 89C Movement
4. Seth Thomas 8 Day Four Sided Top Shelf Clock
5. Seth Thomas Mantel Clock Glass Sizes

I did not repair this clock, just oiled the bearings and regulated it. It has the model name “Sparta” and a date code on the bottom.

The date code is 1901

This movement with the escapement at the back was used until about 1901 in Adamantine mantel clocks. It was superceded by the no. 89 movement. Note: the brass j-shaped turnback lever is not in the correct position because the previous repairer assembled it incorrectly. The long part should be on the left (time train side) and should have free movement toward the time train. See this post for how it should be.

Related posts:

1. Seth Thomas Adamantine
2. Mainsprings for Seth Thomas Queen Anne, Time and Strike, with Second Hand
3. Mainsprings for Seth Thomas Adamantine, 89C Movement
4. Mainsprings for Seth Thomas No. 89 Movements
5. Seth Thomas Giant No. 1

As received: the time mainspring was 3/4 inch wide by 0.0175 inch thick, and the strike mainspring was 0.0165 inch thick. There was very bad T4F pivot hole wear. The strike train had virtually no wear.

Showing front time pivot holes 3, 4, and 5 before bushing. Note excessive wear on #4

After the overhaul, (I did no bushings on the strike side), the pendulum motion was excessive, and the striking sounded sluggish. I swapped the time and strike mainsprings, and then the pendulum motion was excellent (could still have been less) and the strike sounded fine. Here are the final values of the mainspring sizes (remember that these are ORIGINAL OLD mainsprings, if they were being replaced, thinner spring should be used):

Time Spring: Original old 3/4 x 0.0165 inch

Strike Spring: Original old 3/4 x 0.0175 inch

The bottom of the clock showing date code “6091L” which means December 1906.

My job no. 4487

Related posts:

1. Seth Thomas Giant No. 1
2. Mainsprings for Seth Thomas Adamantine, 89C Movement
3. Mainsprings for Seth Thomas Oak Kitchen Clock
4. Mainsprings for Seth Thomas No. 89 Movements
5. Mainsprings for Seth Thomas Queen Anne, Time and Strike, with Second Hand