Replacement of Mainsprings

Vint

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I would like to know the wisdom of of replacing vintage clock mainsprings having a little less power opposed to purchasing a spring of equal power. I have a clock that was built in the late 1800’s and I’m questioning the impact the new spring will have on the clock as a whole. Any thoughts or advice on the matter is most appreciated.
Thank you.
 

Mike Phelan

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I would just replace like for like, assuming that new springs are available. Generally (in UK, anyway) new springs aren't as good as the originals.
 

Willie X

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So, what exactly is the problem? No problem ... then I guess you are preparing to do some experiments?
You will need a 1/4" drive torque wrench with a 7/16" deep well socket and a set of standard hex type let-down tools. This will take the guesswork out of your experiments. Willie X
 

R. Croswell

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I would like to know the wisdom of of replacing vintage clock mainsprings having a little less power opposed to purchasing a spring of equal power. I have a clock that was built in the late 1800’s and I’m questioning the impact the new spring will have on the clock as a whole. Any thoughts or advice on the matter is most appreciated.
Thank you.
We should probably assume that the original manufacturer selected springs that in the day had the proper amount of power for that clock. If the springs are not broken and do not have any cracks I would not change them. If they were OK for 150 years the maker must have done something right. As far as replacing old springs with different size (strength) springs, it really depends on the particular clock, and the type of springs it has. Many American open spring clocks can benefit from springs that are size thinner and a bit longer. Some like the Sessions two-train chime clocks need all the power they can get and do not do well "lighter" springs. If the spring is a barreled it is usually best to replace with the original size. We may be able top give better advice if we could have more information about the clock, including pictures.

RC
 

Vint

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It’s a matter of curiosity mainly as I’ve learned how to replace loop and hole mainsprings. I was wondering how a new a new source of power ( a spring) actually affect a clock, say is 150 years old in terms of the strength and overall condition of the clock parts. Thank you gentlemen for your candid responses.....I value your opinions and do you’ve answered my question. I think I’ll do a little experimentation,lol!
 

shutterbug

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In my shop, I don't replace mainsprings unless they are broken, cracked, or show signs of other damage. I have used springs that have all of the symptoms of what many repairmen call "set" mainsprings. I have found that if the movement is repaired properly, a "set" mainspring has no issues running the clock for the length of time it was designed for. For some American movements, I will use weaker springs .... but only if the original is broken.
 

SuffolkM

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A few thoughts, in favour of keeping old springs:
  1. I think the temptation of new springs is to 'add more power' and rescue a clock that's not running reliably due to a 'set spring'. Is it really set? It's not that common. Provided the movement is correctly serviced, and the spring was the right one to start with, that isn't usually the root cause. Basically, there's usually no good reason to add more power. The problem is elsewhere, and the problem could be back soon. Fitting a new spring to overcome a fault with upgraded power is likely to accelerate that fault's development.
  2. I'd argue it's a useful property that old springs have less 'excess' power. Adding more power than necessary increases wear on the pivot holes, creating new faults and bringing forward the date of the next service. Even though this might seem to be someone else's problem (and I do understand the temptations of fitting new springs), a gentle old spring running a clock nicely is a really fine outcome.
  3. I know of some elderly folk who have commented on the fact they preferred their old clock being easier to wind before the spring was changed! It's surprisingly difficult for some people to turn winding keys on new springs. (As an aside, this is another reason fusee clocks are so wonderful to own).
  4. There's autenticity and originality in an old spring. The really old ones are antiques in their own right, and do not belong in the bin.
  5. You're saving money if you keep the old spring and service it instead.
I hope that's a few good reasons to consider, before putting in an expensive, stiff-winding, brutal pivot mashing fault-amplifying new spring. ;) Ok, maybe I'm over-egging it. And, obviously, any doubt at all about the safety of a spring's condition must win the day.
 

R. Croswell

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I was wondering how a new a new source of power ( a spring) actually affect a clock, say is 150 years old in terms of the strength and overall condition of the clock parts.
Old brass clock movements do not become weak and fragile with age. So there is no need to reduce spring power to protect the clock movement just because of its age. The big enemy of mechanical clocks of any age is wear. Reducing spring power can reduce loading and wear if the clock was significantly over powered originally. If the clock already has significant wear, reducing the spring power may cause a clock that was running OK to stop running. If the movement is overhauled and worn pivot holes properly bushed a small reduction in power may prolong the useful life of many parts including the clicks and click wheels. Adding length to the spring becomes possible when the thickness is reduced, and the added length may flatten the power curve a little and improve time keeping.

Perhaps the most important consideration when replacing mainsprings is to not install a more powerful spring in order to make an uncooperative clock run. Fix the reason the clock won't run and keep the original spring unless it is broken.

RC
 
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Vint

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In my shop, I don't replace mainsprings unless they are broken, cracked, or show signs of other damage. I have used springs that have all of the symptoms of what many repairmen call "set" mainsprings. I have found that if the movement is repaired properly, a "set" mainspring has no issues running the clock for the length of time it was designed for. For some American movements, I will use weaker springs .... but only if the original is broken.
This is most interesting and it is information I am interested in knowing. Which American movements in particular would you use a weaker spring?
 

Vint

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In my shop, I don't replace mainsprings unless they are broken, cracked, or show signs of other damage. I have used springs that have all of the symptoms of what many repairmen call "set" mainsprings. I have found that if the movement is repaired properly, a "set" mainspring has no issues running the clock for the length of time it was designed for. For some American movements, I will use weaker springs .... but only if the original is broken.
A few thoughts, in favour of keeping old springs:
  1. I think the temptation of new springs is to 'add more power' and rescue a clock that's not running reliably due to a 'set spring'. Is it really set? It's not that common. Provided the movement is correctly serviced, and the spring was the right one to start with, that isn't usually the root cause. Basically, there's usually no good reason to add more power. The problem is elsewhere, and the problem could be back soon. Fitting a new spring to overcome a fault with upgraded power is likely to accelerate that fault's development.
  2. I'd argue it's a useful property that old springs have less 'excess' power. Adding more power than necessary increases wear on the pivot holes, creating new faults and bringing forward the date of the next service. Even though this might seem to be someone else's problem (and I do understand the temptations of fitting new springs), a gentle old spring running a clock nicely is a really fine outcome.
  3. I know of some elderly folk who have commented on the fact they preferred their old clock being easier to wind before the spring was changed! It's surprisingly difficult for some people to turn winding keys on new springs. (As an aside, this is another reason fusee clocks are so wonderful to own).
  4. There's autenticity and originality in an old spring. The really old ones are antiques in their own right, and do not belong in the bin.
  5. You're saving money if you keep the old spring and service it instead.
I hope that's a few good reasons to consider, before putting in an expensive, stiff-winding, brutal pivot mashing fault-amplifying new spring. ;) Ok, maybe I'm over-egging it. And, obviously, any doubt at all about the safety of a spring's condition must win the day.
Can an old spring be serviced if it is ‘set’ but in great condition? How can one tell if there is still enough life in a spring to reuse it?
 

R. Croswell

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This is most interesting and it is information I am interested in knowing. Which American movements in particular would you use a weaker spring?
The presumed "standard spring" for American open spring movements such as many so called kitchen clocks, black mantel clocks, and some wall clocks is 3/4" wide 0.018" thick and 96" long. With few exceptions a spring that's 0.018" provides a lot more power than required to run these clocks. A few clockmakers used lighter springs. Seth Thomas used 3/4" x 0.016" x 108" in their popular # 89 movements. Waterbury used even thinner springs in some of their kitchen clocks. If I replace a 0.018" spring in an ordinary 8-day time & strike clock I will usually replace with a 0.016" or 0.0165" thick spring 102 to 108 inches long. If I replace a 0.012" or 0.014" I would use the original size. Same for a Seth Thomas # 89. If I had to make a rule I would recommend replacing 0.018" original springs in ordinary American 8-day time and strike movements 0.016" or 0.0165" springs and for all others replace with the original size keeping in mind that the spring one finds in the clock may not be original.

There are a few special cases such as brass main springs (in some very early spring powered clocks) which were very thick and when replaced with steel should be much thinner. The same applies to the early so called wrought iron springs that tend to be thick and rough. A somewhat thinner modern spring will produce the same power.

As for making the clock easier to wind, I recommend the wide wing winding keys available from most suppliers.

RC
 

Vint

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In my shop, I don't replace mainsprings unless they are broken, cracked, or show signs of other damage. I have used springs that have all of the symptoms of what many repairmen call "set" mainsprings. I have found that if the movement is repaired properly, a "set" mainspring has no issues running the clock for the length of time it was designed for. For some American movements, I will use weaker springs .... but only if the original is broken.
This is good advice. Are mainsprings repairable?
 

SuffolkM

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"Set but in great condition" is not so common! Springs become set when they are left unused for a long time (often you will find lots of gunge crusted onto the spring leaves too - oil that has broken down is rather a thick, tar-like substance which eventually goes very hard). You can of course go to the trouble of cleaning this up. The big indication that a spring is set is that the diameter of the spring is not much more than the diameter of the barrel (or if it's an open loop, that when you unwind the spring it looks like it it's still mostly wound, with very little resistance to being wound again). You may also see that part of the spring looks right, and then it suddenly transitions to being very tightly wound (usually near the centre). I don't think you can fix this, personally. I know others have advocated flattening out the spring etc. but I would call it a day and buy a new one.
 

shutterbug

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I used to feel the same way as Suffolk, and mostly because that's what a lot of repairmen say and do. But after the spring market was saturated with crappy springs made in India, I stopped doing it. Time has shown that a spring will retain enough power to run a clock for the intended run time even if it meets the criteria he mentioned above. The sad reality is that the old used 100 year old spring is probably much better than the modern replacement would be.
 

SuffolkM

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Do you have access to Trifix springs in the States, Shutterbug? I haven't seen any dodgy springs from them, and the UK wholesalers carry virtually everything under that brand.
 

shutterbug

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I've never heard of them, Suffolk. So I'm guessing they are not available here. The ones coming from Germany are pretty good. The problem is that most suppliers won't disclose where they get their springs from.
 

Bruce Alexander

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This is good advice. Are mainsprings repairable?
What type of problem repair are you referring to?

Do you have access to Trifix springs in the States, Shutterbug? I haven't seen any dodgy springs from them, and the UK wholesalers carry virtually everything under that brand.
Timesavers mostly sells mainsprings manufactured in China. China can certainly manufacture quality products but if their customers want "cheap", they'll get "cheap". One should always measure newly acquired mainsprings to make sure they are the dimensions ordered.

I asked Timesavers if they might offer Triflix. They said they would look into it. I would definitely order them if they were offered domestically since that should reduce the shipping costs. As things stand now, I'll only order Triflix from Cousins if I'm working on a German movement and there are no domestic springs that are comparable to the original. It can be expensive, but not as costly as trying to use something that isn't suitable.
 

SuffolkM

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Trifix are Swiss made, not expensive, and have an excellent reputation. Fingers crossed for a source in the USA for you, as these springs would seem to be very much preferable based on what's been said here lately.

I've been doing some mathematics research on springs today. I'm trying to arrive at a formula for the stored potential energy (I'm getting close, but it's all subject to a fiddle factor for the quality of the materials). I'll share a spreadsheet if I get something useful, but I think what I'll get is probably just rules of thumb (there's no point going into differential equations or finite element analysis, surely).

One thing to call forward is that the force (per unit length) of a spring is proportional to the cube of the spring's thickness. Changing from 0.35mm to 0.45mm spring thicknesses more than doubles the spring torque!
 

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