Sessions mantle clock

Dave P

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Feb 9, 2007
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I have a Sessions Mantle T&S spring wound clock. I disassembled cleaned it ran it on my test stand through a complete winding. Mounted it back into the case towards the end of the week I noticed it stopped. I knew I had not rewound the clock so I rewound it set the time and thought everything was good. About 4 days into the winding I noticed it was stopped again at the "strike warning position" Reset the time 12 hours later stopped at the warning position, 7 hours later stopped at the warning, 5 hours later stopped at the warning.

Question when I take it out of the case what exactly am I looking for? When I cleaned it The strike side turned very easily I did not see any obstructions, my hands are free and not touching anything. When reseting the clock the previous times I did not notice any real resistance to me moving the hands. The works appear to be mounted in the original holes in the case, setting the clock in beat inside the case was different than on my level test stand but not by that much. Once in beat it ran fine as described above. Dave P
 

R. Croswell

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Dave,

Was the clock working properly before you took it apart for cleaning, or did you clean it because it had stopping problems? When the clock is running, how far does the pendulum swing? When you had it apart, did you polish the pivots in any way? Did any of the pivots seem unusually loose in the holes? Did you remove and unwind the springs and if so, how much did they expand?

The time side or going works is called on to deliver a bit of extra power at the warning to unlock the strike train. The first thing to determine is if the going works is lacking normal power for some reason, or is the strike train requiring more force than normal to unlock. If the pendulum has a nice swing (a couple of inches) and the relaxed spring expanded to 7 or 8 inches, then you probably have enough power. If not, then I would look for a pivot that got bent during assembly, or a verge that may need adjustment.

I think it’s more likely that you will find something binding in the strike train. Start by checking that the count lever or hook is not binding in the slots of the count wheel. You should also see a cam on one of the wheels where a little hook drops at the same time as when the count lever drops into a slot on the count wheel. Then when that happens, the stop pin is captured by a little hooked lever. If the wheel with the stop pin is not “timed” correctly with the wheel that has the cam, it’s possible that the train runs on too far which could cause the little lever to bind in the cam slot, or the count lever to bind in the count wheel. If the problem is not obvious, use a toothpick or small screwdriver to lift the lever that starts the strike and see if you feel excessive resistance. The parts of this strike train must be timed correctly. Don’t try to fix the problem by bending things unless you know that something got bent during assembly. Also, if you find it necessary to move a wheel a tooth or two to get the timing right, be sure to let down the power in both springs first.

I have attached a picture of a Sessions movement that may be similar to yours.

Bob C.
 

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Dave P

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R. said:
Dave,

Was the clock working properly before you took it apart for cleaning, or did you clean it because it had stopping problems? When the clock is running, how far does the pendulum swing? When you had it apart, did you polish the pivots in any way? Did any of the pivots seem unusually loose in the holes? Did you remove and unwind the springs and if so, how much did they expand?

The time side or going works is called on to deliver a bit of extra power at the warning to unlock the strike train. The first thing to determine is if the going works is lacking normal power for some reason, or is the strike train requiring more force than normal to unlock. If the pendulum has a nice swing (a couple of inches) and the relaxed spring expanded to 7 or 8 inches, then you probably have enough power. If not, then I would look for a pivot that got bent during assembly, or a verge that may need adjustment.

I think it’s more likely that you will find something binding in the strike train. Start by checking that the count lever or hook is not binding in the slots of the count wheel. You should also see a cam on one of the wheels where a little hook drops at the same time as when the count lever drops into a slot on the count wheel. Then when that happens, the stop pin is captured by a little hooked lever. If the wheel with the stop pin is not “timed” correctly with the wheel that has the cam, it’s possible that the train runs on too far which could cause the little lever to bind in the cam slot, or the count lever to bind in the count wheel. If the problem is not obvious, use a toothpick or small screwdriver to lift the lever that starts the strike and see if you feel excessive resistance. The parts of this strike train must be timed correctly. Don’t try to fix the problem by bending things unless you know that something got bent during assembly. Also, if you find it necessary to move a wheel a tooth or two to get the timing right, be sure to let down the power in both springs first.

I have attached a picture of a Sessions movement that may be similar to yours.

Bob C.
Thanks Bob, I took the clock apart because it did not run. It had been completely re bushed, but the bushings on one of the plates were all long, but flat on the inside of the plate. I debated about making them flush and making an oil sink in each one , but decided against that. May do it now that I'll be taking it apart again. Pivots were all very smooth and shiny, no pits, no groves that I could see with a 4x loop. I pegged all the pivot holes. I thought the spring looked fine when I was cleaning it and I used clock spring oil to re-oil it. Pendulum has a good solid swing, but was very sensitive to put into beat. The strike operation is a little different than yours it did not look like the wire lift lever operation as yours, and no it is not a rack strike. I'll try and get a picture. I'll keep you posted. DAVE
 

Dave P

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OK Bob, I was able to take a couple of pictures. I took the works out of the case, I could not find where it was bound at all. When it was in warning I could lift the count lever and every thing remained in place. As soon as I moved the minute hand the clock struck, very easy to lift every thing. I placed the clock on my test stand and really had to have the clock in perfect beat to get it to run. I wound the spring 3 or 4, 1/2 turns and got a good solid beat. I think my main spring may be weak. Also noticed that I had failed to oil the pivots so I did that, I thought American clocks could run dry? Not that I'd want to do that just thought they could. We'll see what happens over the next couple of days. Dave
 

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R. Croswell

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Dave,

The end of the pivots should pass all the way through the bushing. If they don't, at some point a "ridge" will develop that will later cause a problem. Cutting the bushings flush with the plate and making an oil sink would be the proper thing to do while it's apart.

There are dozens of minor variations in strike mechanisms, but they all have to do basically the same operations. In any case, there will be a means of stopping the strike train without binding the count hook in the count wheel. I would make sure that part is in time and working correctly.

An "expert" would not have left the bushings standing tall like that, so you might want to take a look at how tight the pivots fit the holes. With the power let down, you should be able to move the arbor side to side and see the movement if you look very carefully. Along the same line of "non-expert" bushing, if the installer carelessly reamed an out-of-round hole without first making it round and centered over the original hole, the bushing may have drifted off-center and could be causing a depthing problem. Make sure that all the wheels and pinions are meshing at the correct depth. This alone would not cause the clock to stop at the warning, but it could drain power from the movement and make it unstable.

Now that we know that the clock has been "previously worked on" by persons unknown, almost anything is possible. I would try turning the minute hand slowly toward the hour and just before the lifting part drops to start the strike, hold the fan so it won't move and gently try to raise the lifting part a bit more - it should not be bottomed out against something. That is, there should be a little "headroom" or travel space left at the drop off point. Another thing to check would be the little brass helper springs on some of the levers in the strike mechanism. The ends of these frequently break off during assembly/disassembly. If the person doing the job just pulled them tighter to form a new end hook, then the spring may be causing the lifting lever to exert excessive pressure on the cam (the cam turned by the minute hand that starts the warning).

Bob C.
 

R. Croswell

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Dave,

You posted your pictures while I was editing my reply, so some of the comments above don't apply.

If the spring is weak, the clock would typically work ok right after being wound but develop problems a few days later - before the end of the week. It's beginning to sound more like a time side problem if the strike releases easily. Sounds like your clock is very unstable and ready to stop with the least provocation. How are the pallets and the escape wheel? - any ruts in the pallets - any crooked teeth or rounded points? Does this movement have a recoil or half-deadbeat escapement? Is there a small clearance between the pendulum leader and the loop at the end of the crutch? You don't want it to bind here. You may be able to move the verge a tiny bit closer to the escape wheel - as long as the teeth don't snag on the pallets. A little change can make a big difference in some clocks. It needs to be pretty close to right for the clock to run well.

Bob C.
 

shutterbug

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I'd check for smooth surfaces at the J hook and all corresponding surfaces (pins, levers). You may have a rough surface that won't smoothly move during warn.
 
C

clockdaddy

You've been given some excellent tips. Read the information very carefully and thoroughly understand exactly what each person is explaining.
One point of clarification, if I may. To check the tightness of the pivots, clamp the mainspring and let down all the power. While holding the movement laying flat (either front down or back down) in you hand, use a small screwdriver or tweezers, lift each wheel upwards and let it fall.
If you lift the wheel and it sticks the least bit then there is a binding problem. Flip the movement over and do the same thing from the other side.
Friction is the enemy of the clock. Anywhere you can reduce friction is helpful. The pallets should be polished smooth. Anything less than a mirror finish creates friction.
Check the spring on your stike hammer. Many enthusiast want to hear a louder strike and will put on a heavier spring wire or put the exixting wire very tight to get more tension. Too much tension creates pressure against the center shaft thus creating presure on the minute hand.

CD
 

harold bain

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Dave, you said the movement ran for a week on your test stand. Check that the movement feet sit flat to the case before putting screws in. If they don't there may be some twisting of the plate when you tighten the movement down
 

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