Why is it like this?

[Shane]

looking through my spares, in an attempt to find a barrel cover for another watch, I came across these.  I didn't remove them from anything, I probably just received them in a box of miscellaneous watch parts from Ebay or the like.  Does anybody have an idea about what the extra details do and what they might be from, age, excreta?

Thanks.

Shane

[nickelsilver]

That's where the maltese cross would be mounted. It limits the number of turns you can wind up and also allows prearming the batrel

[watchweasol]

It is a s Nicklesilver says  the maltese cross (stop work),  a mainspring pre loading and protection device as you cant overwind I think it was a six turn limit depending on the design.

[nickelsilver]

The most common Maltese stopworks allow 4 turns, most springs develop 6 or 6.5 turns, so the weakest turns on both ends of wind are avoided.

The gear ratios between barrel and center wheel are also changed so that a useful power reserve is obtained on 4 turns.

Some maltese cross allow 5 turns, but more than that and the Maltese style geometry doesn't work reliably any more.

[Shane]

Thanks, that gives me something to look into.

[nickelsilver]

Ha should have said "weakest and strongest" above.

Finding a compatible cross and finger in the wild will be next to impossible, they usually need to be made.

[Shane]

I found pictures illustrating what they looked like in several other posts.

I remember seeing some of the other components involved whilst previously sorting through boxes of miscellaneous parts.

It would be nice if I had enough parts to make a complete assembly.

Was it just a mechanism to reduce the likelihood of a broken mainspring until better manufacturing processes rendered it obsolete or did it have some other benefit?  

 

Thanks for your time.

Shane

[Shane]

I suppose a better average spring rate, which would result in a more accurate watch throughout the day.   Sacrificing some duration in favor of  accuracy wouldn't be a bad thing and was probably considered a significant improvement.

Thanks again.

[nickelsilver]

10 hours ago, Shane said:

Was it just a mechanism to reduce the likelihood of a broken mainspring until better manufacturing processes rendered it obsolete or did it have some other benefit? 

 

It was to use a more consistent power from the spring. In the pic (from Vintagewatchstraps - great site) you see a typical graph showing power from zero to full wind. The stopworks allow using just the "good" part.

 

They do also help protect against broken springs, though that's not their purpose. Since there will always be a wrap of spring in the barrel wall at full wind the stress on the hook (whatever form it may be) is greatly reduced. This is an issue in old clocks in particular; I see some 250+ year old Neuchateloise clocks fairly regularly and they are always missing the stopworks. These old boys have tremendously powerful springs, but run a full 8-9 days on just 3.5 turns of spring. They invariably have simple hole end mainsprings, and after hundreds of cycles getting that hole stressed (with the stopworks missing), one day, maybe, BOOM.

I always remake them when missing, even if the customer refuses, just out of respect for the clock. In the pic you can see it's a different type of stopworks, simpler than Maltese cross but very effective. The partial gear has a friction spring to maintain its position, where the Maltese uses the geometry of the cross to hold position.

[Shane]

On 2/2/2020 at 9:28 AM, nickelsilver said:

the maltese cross would be mounted. It limits the number of turns you can wind up and also allows prearming the barrel.

On 2/2/2020 at 11:06 AM, watchweasol said:

he maltese cross (stop work),  a mainspring pre loading and protection device as you cant overwind

 

Good morning, Nickelsilver and Watchweasol.

I always find your posts to be informative and worth reading.

I will preface my following comments and questions with (the information I found didn't mention the incredibly strong mainsprings of some clocks and was just focused on vintage pocket watches).

The Maltese cross seems to be a mechanical means of averaging the mainspring's influence, with regards to amplitude, for more accurate time keeping.  As with most compromises, you must give up something in return... runtime.

As better metallurgy, manufacturing, design and understanding brought mainsprings with a more consistent power curves into both production use and replacement availability, many of these Maltese crosses where removed and discarded.  If, a NOS spring (of the original material and design) was found, it probably wouldn't be the best of ideas to use because of age harding and embrittlment of the steel.  I would be afraid of a significantly shortened service life before the inevitable and catastrophic failure.

I am on the fence between preserving the historical accuracy of an antique and improving an instruments ability to perform its intended function.  If the modifications started so long ago (when this was accepted practice) was it wrong?  Is the evolution of any individual time piece acceptable if better accuracy and higher stamina are the end results?

I myself would not modify one if I received it in original condition but I also would not carry it around running and if I received one that was modified well before my father was born, I probably wouldn't go out of my way to restore it.

What are your thoughts?

Thank you.

Shane 

[watchweasol]

Hi  I think the simple answer is that if the clock/watch is fitted with the stop work then it should remain regardless of whether the mainspring is changed for a modern one. The watch/clock was designed that way and should remain so.

If you come across a watch/clock where the stop work has been removed one has to ask why. Did the repairman not understand the principal and therefore removed it ? was it broken and the repairman couldnt/wouldnt find the relative parts or his customer /client not want to pay the extra costs involved  in sourcing the parts. There are many IFs and BUTS, but in my opinion if thats how it was made thats how it should remain if only for Historical accuracy and authenticity. 

I hope this answers your question, bear in mind this is only MY opinion others may differ.