Seth Thomas 48R movement troubles and spring replacement

[R. Croswell]

I had a clock with this ST No. 48R movement in about 15 months ago. It needed a time side main spring, one bushing, and the usual cleaning and oiling. I used the ¾" x 0.012" x 90" spring suggested in the spring charts. It seemed to run OK but was not a real strong runner but was stable and ran two full weeks without issue so I sent it out.

It came back last month stopping periodically. Quick check - nothing obvious but it stopped before 8 days. Thinking that a 0.012" spring might be a bit weak for a clock with some age on it, I ordered a 0.014" and planned to install that after cleaning the clock and oiling it. The movement had some previous bushing work by someone else but it looked well executed and I didn't see anything that looked like a depthing issue, no "pivot poop", just nothing.

This is the model with the stationary "spring boxes" (cups) screwed to the back plate. It is NOT the model that has the separate plate for the spring boxes and the little spacers that get lost easily. Got the spring in OK although it fills the box a bit more than I would like but It winds OK. So I assemble just the lower part of the train to check for smooth running (already checked the upper part) but there seemed to be excessive friction and occasional "griping". Without spring everything seemed to turn smoothly. Then I noticed that with the spring in place there was zero end-shake on that main arbor. There was also zero or near zero clearance between the coils of the spring and the main wheel, obviously a problem.

But how could this be? The spring chart calls for a ¾" wide spring and the winding arbor seems to have space for a ¾" wide spring, so what's going on? I thought the spring was all the way into the spring box and the hole in the end is large enough to allow a little side to side positioning. Closer inspection revealed that the outer coils of the spring were "riding up" on the radius at the bottom of the spring box which was causing the interference and friction. The solution I found was to grind the width of the spring down a bit for the length of the first three coils on the side that would go to the bottom of the spring box. The movement is back together now and has normal end shake on that arbor and is running strong again. The sketch images illustrate this all be it a bit exaggerated.

So my questions is; has anyone else run into this issue with a No. 48 and how did you resolve it? Was the original spring used by Seth Thomas actually ¾" wide? Were the ends of the original springs modified in some way? Or is there just something I'm missing here?

RC

 

[shutterbug]

I can imagine an issue after several days of running, but that's quite strange. Good sleuthing to sort it.

 

[harold bain]

RC, although some ST movements use an 11/16" mainspring, the specs on this one are for a 3/4" spring. Never run into this problem with a 48 movement.
With two different springs and the same problem, something is not right.

 

[Bruce Alexander]

Never ran into it either. Ditto on the sleuthing. Perhaps this 48R solid front plate version calls for a different dimension. Did you happen to measure the pre-existing MS? If I ever run into it, hopefully your prior experience will "click". Thanks for sharing.

 

[R. Croswell]

Never ran into it either. Ditto on the sleuthing. Perhaps this 48R solid front plate version calls for a different dimension. Did you happen to measure the pre-existing MS? If I ever run into it, hopefully your prior experience will "click". Thanks for sharing.

I will check my shop notes to see. I know I trashed the old spring that I removed but no way to know if that onen was original.

RC

 

[bangster]

How did you grind it?

 

[R. Croswell]

How did you grind it?

With the spring captured in the spring box and all the coils tapped down as far as they would go with a brass punch (the outer turns protruding above the rest as in the sketch post #1) I simply used a bench grinder and ground off the protruding part. Once that was done, I removed the spring from the barrel and while holding it so there was a slight curve to keep it from chattering, lightly touched any uneven places. Finally smoothed the sharp edge with a fine sanding disk in a Dremel tool.


Re post # 4 - I checked my notes and could not find any comments about the spring I removed other than that I had replaced it. Like the "old gray mare", my memory ain't what it used to be. There was some obvious reason to replace the spring and I just assumed that the 3/4" wide spring in the table would be correct. In retrospect I can't help wonder if the supplier of the table (I believe LaRose) simply listed the closest available size for ST round movements of this general style? ST must have provided for some way to keep this from being an issue. Or perhaps is was a problem for ST that was corrected when the two-part frame and spacers were introduced which would add just about the amount of space needed? Or perhaps they didn't use the 3/4" spring or modified the original? In thinking back several years ago I recall that I did own a tambour ST with the same 48L movement. I checked my library of photos of that clock and it to had a busted main spring. Of course I cant tell the size from the photo, but my records indicate that I used a Merritts MS-202 3/4" x 0.012" x 90" replacement spring. Curiously that clock always seemed to run weaker that I thought it should as everything about it was original and showed very little wear. I never did discover why it seemed to have a somewhat weak action but someone came along and made me an offer "I could not refuse" so I let it go. I bet it had the same issue.

RC

 

[harold bain]

Seth Thomas had a list of springs for their movements that is included in Tran Duy Ly's Seth Thomas book, volume two. That is my source, and likely LaRose used the same chart.

 

[R. Croswell]

Seth Thomas had a list of springs for their movements that is included in Tran Duy Ly's Seth Thomas book, volume two. That is my source, and likely LaRose used the same chart.

Perhaps the original ST springs had a narrower end hole that forced the outer coils down over the radius of the spring box? Guess I'll have to look for another 48 movement and see how it is.

RC

RC

 

[kinsler33]

Aha. I have a cantankerous Seth Thomas 48J that came with the note, "Sometimes runs." I replaced its 3/4" mainspring with another, and it still runs--sometimes. It has those 'spring boxes,' which look like barrels but are a lot less fun on the winding machine. I shall check for mainspring ride-up, and thanks very much for this.

Mark Kinsler

A dose of humility with every clock...

 

[Jay Fortner]

To RC and anyone else that runs into this problem I just finished one where the nests were cupped outward at the hole where the arbor goes through. The fix was quite easy. I just had to flatten the bottom of the nest so that it sat flat against the back plate. When I took it apart the nest was right up againt the MW and after flattening the bottom I had close to a 1/16" gap between the nest and the MW,plenty of clearance for the spring.

 

[harold bain]

Good information, Jay. A very likely cause of the problem noted.

 

[scott64a]

Good info, Jay/
That would surely cause the spring to ride awkwardly.
R.Croswell... You mention the bushings had been redone by someone else, and that they looked to be free or bushing crud or whatever...
but it's been my experience with these little pain in the donkey movements that if each and every bushing isn't buttery smooth, it'll stop and start seemingly with the change in wind direction.

I'd suggest polishing the pivots to mirror shine and checking end shake, and go through the bushings with a very strong magnification and light present. If there's any bit of rough in them, it'll have you going insane until they're round and burnished properly.

 

[Tinker Dwight]

Ok, What is a nest? I'm not sure I've seen that
term used on a clock before that wasn't caused by some
small stinging beast.
Tinker Dwight

 

[Jay Fortner]

Ok, What is a nest? I'm not sure I've seen that
term used on a clock before that wasn't caused by some
small stinging beast.
Tinker Dwight

A stationary barrel that is attached to either the front or rear plate.
I have worked on clocks that were in storage that had dirt dobbers,guinee wasps and german roach nests in them. Florida is the land of bugs!

 

[Tinker Dwight]

A stationary barrel that is attached to either the front or rear plate.
I have worked on clocks that were in storage that had dirt dobbers,guinee wasps and german roach nests in them. Florida is the land of bugs!

Ah! like on a ST124.
I was in Florida for 4 years. A friend asked me to help fix her
old Mercedes. It had been unused for three years.
I finally told here that the risk was too high.
One rattle snake, three scorpions and two black widow spiders
later.
Tinker Dwight

 

[Jay Fortner]

Ah! like on a ST124.
I was in Florida for 4 years. A friend asked me to help fix her
old Mercedes. It had been unused for three years.
I finally told here that the risk was too high.
One rattle snake, three scorpions and two black widow spiders
later.
Tinker Dwight

What!,no cow killer ants or brown recluse spiders? That would have been an easy job.
I got into a nest of baby brown recluse spiders a couple years ago,they got up under the sleeves of my shirt and tore me up good. The cure is scrub the wounds till they bleed and pour the bleach to them. The venom is an acid based enzyme.

The ST 120 uses them too. I've yet to do one yet but I've seen some german made clocks here on the MB with them.

 

[harold bain]

I have worked on clocks that were in storage that had dirt dobbers,guinee wasps and german roach nests in them. Florida is the land of bugs!

A few years back a customer sent me a Schatz cuckoo clock that had been stored in a shed. The top of the case, and much of the movement was covered with a mud dauber nest, it was like concrete to remove. Came from Texas.

 

[shutterbug]

A couple of years ago, I had one that had several dead lizards in it!

 

[Jay Fortner]

Yeah Harold,I've got a 1977 Viking GM that the original movement had dirt dobbers in it. The owner cleaned out the nests,oiled it with WD-40 and ran it until it quit. That movement is toast,ground into dust.

 

[harold bain]

Mine had a better outcome, movement just needed a few bushings after a thorough cleaning.

 

[Bruce Alexander]

Nice catch Jay. I've seen the brass around the spring hook deformed of course, but I've never seen the type of situation you encountered. What tools/method did you use to reshape it?

 

[Jay Fortner]

I used my 21"drill press with a piece of 1/2" brass bolt chucked in the chuck. The head of the bolt has been turned round and the top surfaced flat. I laid the nest on the table,open side down and pushed the bottom flat.
You could also use an arbor press or a piece of wooen dowel and a hammer.

 

[Bruce Alexander]

I used my 21"drill press with a piece of 1/2" brass bolt chucked in the chuck. The head of the bolt has been turned round and the top surfaced flat. I laid the nest on the table,open side down and pushed the bottom flat.
You could also use an arbor press or a piece of wooen dowel and a hammer.

Thanks for getting back to me Jay. Just wondering how you went about it. I would probably use the end of steel round stock that I use for riveting spring hooks. That and a small hammer or course. You know how us newbies like to pound on stuff!