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I just overhauled a Seth Thomas “Giant No. 1″, having an oak case 25-1/4 inches tall (job no. 4433). The movement is marked “8 1/4″ but it is the same movement later called No. 89. It has between-the-plates escapement, and the plates measure 5-5/8 inches tall and 3-5/8 inches wide.

According to a repair label, it had been repaired in 1979. It had two of the overpowering USIBEL FRANCE mainsprings, 0.0180 and 0.0185 inches tick, for the time and strike, respectively.

Both mainwheels had quite noticeable tooth wear. The strike mainwheel had about twice the wear of the time mainwheel, so I turned the strike mainwheel over so the unused tooth surface could be employed. I judged that the time mainwheel would work okay as is. The time second wheel had quite a bit of wear, so I turned it over.

The previous repairer had installed 2.7 mm tall KWM bushings, which I replaced with 1.8 mm tall KWM bushings (except for the verge pivots, which get 1.4 mm high bushings). I polished the train wheel pivots before installing new bushings.

I discarded the too-strong mainsprings and used the following springs:

Time: 3/4 x 0.0155 x 96 inch Merritt’s mainspring

Strike: 3/4 x 0.0165 x 96 inch, from R & M (or Merritt’s brown box)

Even with this thin mainspring for the time side, the pendulum motion is excellent, the running arc being about 3 times the escape arc.

Note: I first tried a .0155 inch thick spring for the striking. The striking did run for at least 9 days, but the striking sounded slow, and the customer decided he wanted a faster strike. The 0.0165 inch thick spring should not cause excessive wear, but time will tell. It will certainly be better than the .0185 inch thick mainspring!

So far, the .0155 inch to .0158 inch thick mainspring has been perfect for the time train. For the strike train, it is satisfactory, but the striking speed may be too slow to suit some people. On a ST “Giant No. 1″ oak shelf clock I am currently repairing, I am going to try an (approximately) .0165 inch thick spring, as the customer does not want the striking to be too slow. (At this moment, a .0155 inch thick Merritt’s spring is on the strike side, and it IS strong enough to power the strike for at least 9 days, but the striking sounds slow.)

I’ll post again when this job is complete.

I just finished a New Haven oak kitchen clock (my job no. 4333). The movement has 4 pillars and the dimensions are 4-9/16 x 3-1/4. The time mainspring is held by a separate short pillar attached to back plate. This movement has thin springs for time and strike. The two springs are both old but they are different, so I don’t know which one (if any) is original. The spring thicknesses are:

Time: 0.0165 inch

Strike: 0.0160 inch

This clock has nice old thin springs, and the pendulum motion is good, and so is the striking speed.

For future reference, some of the pivot diameters are:

T5F: 1.2 mm
T4F: 1.2 mm
T3F: 1.2 mm
T2F: 1.55 mm

I just completed the overhaul of an Ansonia iron cased mantel clock (my job no. 4422). It has the common 4 pillar 8 day time and strike movement of dimensions 5 x 3-1/4 inches. In this clock, a previous repairer had replaced the srike mainspring with one that is 3/4 inches wide and .018 inches thick. The time spring was an original that is .0153 inches thick.

When assembling the movement, I put the original thin mainspring in the striking side, and for the time mainspring used a spring 3/4 inches wide x .0138 inches thick by 120 inches long (no. 77.303 from R & M Imports). This spring gives a good pendulum motion of just over twice the escape arc. It will run the clock reliably without causing excessive wear.

I just overhauled an Ansonia oak shelf (kitchen) clock (my job no. 4357). It has the 4 pillar 8 day time and strike movement of dimensions 5 x 3-1/4 inches. The original mainsprings in these clocks are 3/4 inch wide and typically about .0155 inch thick. The previous repairer had installed a time mainspring .0185 inch thick! The loop end of the spring is labeled “USIBEL FRANCE”. I replaced this spring with a new spring that is 3/4 inch wide, .014 inch thick and 108 inches long. The pendulum motion is great (running arc slightly more than twice the escape arc).

I have seen (and discarded) these thick USIBEL FRANCE mainsprings many times before. They were sold by clock parts suppliers such as S. LaRose as “mainsprings for 8 day American Clocks” and sometimes described as the finest mainsprings, made in France. I guess they were fine for many repairers, as they are so strong that they will make a clock work without being correctly repaired! I have measured some of these springs to be as thick as .019 inches! Just by winding the clock, you can feel that they are way too strong. If used for too long, they will cause severe wear to the mainwheel teeth.

The force that a mainspring provides is proportional to the cube of the thickness: .0185 cubed divided by .0155 cubed is 1.7, so the USIBEL spring is providing 1.7 times the force of the original spring (actually it is even worse, as modern steel is better than steel made 100 years ago. So the new .0185 inch thick spring is probably at least twice as strong as necessary.

I used a no. 77.303 from R & M Imports that is specified as 3/4 x .017 x 120 inches. The springs I received have an actual thickness slightly less than .014 inch, and I shortened a spring to 108 inches and re-attached the loop end. This spring seemed so weak when uncoiled that I wondered if it would have enough power! But it works great for the time train, as mentioned in the first paragraph. NOTE TO MYSELF: Next time, leave the spring 120 inches long - there appears to be plenty of room.

Note: R & M has a no. 77.301 mainspring that is specified as 3/4 x .014 x 108 inches that may be German made, and seems stronger than the spring discussed above. I like the 77.303 the best.

It is interesting to compare the force provided by the USIBEL spring to the force provided by the .014 inch thick spring: .0185 cubed divided by .014 cubed is 2.3. This mean that the USIBEL spring provides approximately 2.3 times the force of the .014 inch thick spring. A clock running with the thick spring will wear itself out prematurely!

If you have an heirloom antique American clock that you want to pass down to future generations, make sure your clock repairer does not (or did not) install mainsprings that are too thick. Original mainsprings should be kept in the clock, unless there is a good reason for replacement (broken, too strong, rusted or damaged).

Merritt’s Antiques has the P1496 mainspring in the red, orange and yellow box again! Last week I received 12 of them. I took two springs, measured them to be .0158 inches thick, cleaned and lubricated them, and installed them in a Seth Thomas 89C movement in an Adamantine mantel clock (my job no. 4396). These springs are perfect for this type of clock. The pendulum motion is good but not excessive.

After a clock movement has been repaired, it should look like it has always been well taken care of, and not show obvious signs that it has been “repaired”. As part of this, the cleaning process should not be harsh. For typical American antique clocks, I use “Historic Timekeepers” cleaning fluid (available from Timesavers as part #17863 and #17864). I scrub brass parts such as plates and gears with a fine brass bristle brush (stock #16.310 from R & M Imports). This results in a uniformly clean finish that is not too shiny (some repairers polish the brass parts with metal polish, but this leaves the parts looking too shiny, and American clock parts never looked this way when new. It is customary to polish the back of the back plate of a round French movement, and Vienna regulator movements look great when polished).

Some repairers use an electric motor powered rotary brass brush to polish the brass parts. I DO NOT like the way this makes the movement look, and so I am opposed to this practice.

This note concerns a Revere A/C electric mantel clock with 60 RPM Telechron motor (yes, 60 RPM or 1 revolution per second) made in the late 1920’s. The movement is 5-3/8 inches tall and 5 inches wide and is labeled on the back:

1334428
1615664
PATENTS PENDING

REVERE CLOCK CO.
CINCINNATI O.

This movement relies on the second hand to reduce the endshake of the hour wheel. If the second hand is pushed all the way in, the rack tail will rest on the snail when the rack is released. With the second hand off, the hour wheel may move forward, and the rack tail can slide behind the snail, particularly at 1:00 and 2:00. So if you are testing the clock with the second hand off and hear it striking too many times, don’t be alarmed! Put the second hand on and all should be well.