Clock Rate Adjusting Questions

[bbodnyk]

I am in the process of getting a Seth Thomas weight movement working. Currently I've bushed the escape wheel holes which were pretty bad. Prior I could only get it to run by using a fine wire looped around the protruding end of the escape wheel pivot to pull the pivot into position and it would run for a minute or two. Now the escape wheel seems to run fine. Unfortunately I inadvertently left the suspension spring somewhere. Meanwhile I'm using a different suspension spring; I'm using a 0.003" one.

I have been having a heck of a time trying to get it to run more than a few minutes over the last few days until this morning when all the planets seemed to line up correctly and I believe I have it running. So in getting it going I have a number of questions.

1. In watch repair a test for the freedom of the train is to wind the watch one click without the pallet fork in place. The escape wheel should turn freely and then reverse slightly. Is there a similar test one should do for clocks? How can you tell enough power is getting to the escape wheel?

2. Are thinner suspension springs used on longer pendulums and thicker ones used on shorter ones?

3. The pendulum amplitude has to be a function of the spring thickness and bob weight. On a normal recoil escapement is the correct amplitude the one that minimizes recoil? If so how critical is the bob weight? I assume the correct bob weight is the also one that minimizes recoil?

4. How critical is the beat error?

Thanks!
Bruce

 

[Randy Beckett]

I would think the .003 would work fine.

I don't know of a reliable standard test for testing the train freedom other than to power the great wheel by hand with the verge removed and make a judgement call. It should move move freely and smoothly with little pressure.

Make sure the escapement is adjusted correctly. The standard most often quoted on a recoil is to move it deeper in the wheel until it won't escape, then move it out just enough to escape.

On a recoil escapement, having a pendulum bob heavy enough to minimize recoil will likely make it unreliable, and especially sensitive to beat adjustment, even though with perfect adjustment it "might" make it slightly more accurate. However I would be surprised, especially being weight driven, that it would be observable. I believe it needs to have a little overswing(recoil) to run reliably.

If this is the same movement from a previous thread you may want to reference those pictures or repost them for others more knowledgeable than I. Recoil escapements aren't my best game.

 

[Scottie-TX]

2. Are thinner suspension springs used on longer pendulums and thicker ones used on shorter ones?

3. The pendulum amplitude has to be a function of the spring thickness and bob weight. On a normal recoil escapement is the correct amplitude the one that minimizes recoil? If so how critical is the bob weight? I assume the correct bob weight is the also one that minimizes recoil?

4. How critical is the beat error?

Thanks!

Let's start at the top. Thickness of suspension spring has little or nothing to do with pendulum length. It has more to do with weight of pendulum. It must be strong enough to hold the pendulum and thin enough to have low resistance.
2. Suspension thickness has little to do with swing amplitude. It does affect it a little but the biggest factor is power applied. The more power, the bigger the swing.
3. In any recoil escapement you always want to maximize recoil. Recoil provides the impulse to the pendulum. The smaller the impulse the weaker the swing.
4. Bob weight surprisingly has little to do with swing amplitude or required power to run the movement. Bob then also has little to do with amount of recoil.
5. Beat error. Well I think you know this answer. Beat error is VERY important.

 

[shutterbug]

Well, bbod - watches are just very small clocks. The principles you've learned with watches will serve you well with clocks. Trust your instincts and have at it. You'll be fine.

 

[bbodnyk]

Well, bbod - watches are just very small clocks. The principles you've learned with watches will serve you well with clocks. Trust your instincts and have at it. You'll be fine.

My instincts tell me that I should bush the remainder of the time train pivots to maximize the power getting to the escape wheel. I plan on getting the original suspension spring back today. I also need to make sure the verge is located correctly. The piece the verge pivots on was removable and when putting the clock back together I put it back where I thought the original position was. Since I bushed the escape wheel I imagine the verge might needs it's position adjusted accordingly.

 

[harold bain]

These weight movements like loose bushings. Too tight will rob power. If they are not ovalled, they are usually OK.
Test running this movement out of the case can give you false problems or not show problems, in that they are meant to be run with the weight pulling up on the movement using a pulley on the top of the case.
It's unlikely bushing the escapewheel made enough of a position difference to require moving the anchor, if you've properly centered the hole to it's original placement. These movements are overpowered, and should work very well once overhauled.

 

[bbodnyk]

Luckily I didn't have the bushing size I needed for the movement so after a day or so looking at the movement I finally discovered my problem with getting my ST to run. The culprit was the clutch of the verge that loops around the pendulum rod. Mine was too tight and gripping the rod. As soon as I open it up, the clock started to run. Interesting how regardless of how overpowered a clock might be, the tiny amount the pendulum was constrained was enough to keep the clock from running.

Thanks to everyone!
Bruce

 

[harold bain]

It appears the rod may be thicker than the original would have been. Good sleuthing, it doesn't always take a major problem to stop a clock.