IWC barrel conundrum

[Bill241]

I recently acquired a fairly early British-retailed ‘Peerless’ IWC pocket watch, with cal 52 movement. This was bought as a non working watch for restoration, but to my surprise, it wound up and ran. As the intention was to service it,  I then immediately but gently let down the mainspring, which then at that point failed. Thankfully, no damage to the barrel or teeth on the adjacent wheels. 

The barrel set up is quite odd- it is original to the watch (same serial number scratched inside it) and appears to have holes for a T-end mainspring (by my measurements, the correct one is 2.30 x 0.21 x 540 x  17). At some point in the past, a rivet has been fitted in the recess in the barrel. Very crude work that is  definitely not Probus Scafusia! 

The old steel spring was not a hole-end spring, which wouldn’t work as the rivet is in a recess. Instead, a bridle was riveted to the spring and the bridle rests against the rivet. 

My question is how best to make the best of a bad job as I would prefer not to replace the barrel. I am thinking either put in a new spring with bridle, or to try to remove the dodgy rivet without destroying the thin barrel wall, and put in a T-end spring? 

What’s the safest way to remove a steel rivet from the barrel wall? 

 

 

Edited October 29, 2024 by Bill241

[AndyGSi]

15 minutes ago, Bill241 said:

by my measurements, the correct one is 2.30 x 0.21 x 540 x  17

Ranfft shows the mainspring as H6.5 2.35 x 0.21 & H6 2.05 x 0.20

watchguy shows the following with a DB end termination.

Edited October 29, 2024 by AndyGSi

[Bill241]

Hi Andy, 

Thanks for this. It isn’t a DB end on this watch as there are round holes rather than rectangular slots in the barrel and barrel lid. In about 1917, I believe IWC changed the design of the ratchet and crown wheels on the cal 52 from a single large fixing screw to the more elegant square arbor and three small fixing screws. I suspect the design of the mainspring fitting in the barrel was changed around the same time. 

I am happy that 2.30 is the right height. The old spring is the right thickness but too short - even in its weakened, set, state, and the movement dirty it was running an amplitude well over 300 degrees. As such I’m concerned about the risk of overbanking if the new spring is too thick and too short (I must re-read Hooke’s Law). 

Bill

[AndyGSi]

The thickness is all you need to worry about when it comes to amplitude.

[RichardHarris123]

If you go for the removing the steel pin option, I  would drill it out using progressively larger drill bits. The hole could then be soldered shut.

[nevenbekriev]

My advice will be to leave the rivet as is, may be just carefully file the outside if it protrudes and is not smooth.

[RichardHarris123]

Which spring would you use? @nevenbekriev

Edited October 29, 2024 by RichardHarris123

[GPrideaux]

If the barrel is brass and the rivet steel, you could perhaps dissolve it with alum. When enough material is gone is should drop out.

[Bill241]

28 minutes ago, nevenbekriev said:

My advice will be to leave the rivet as is, may be just carefully file the outside if it protrudes and is not smooth.

Yes, I think I will do this as I don’t want to risk warping the barrel. The outside of the rivet is flush with the barrel. The T end fitting is to the right of the rivet and so that shouldn’t interfere with the new spring. 

The cal 52 movement strikes me as being very well made and certainly over engineered! 

10 minutes ago, GPrideaux said:

If the barrel is brass and the rivet steel, you could perhaps dissolve it with alum. When enough material is gone is should drop out.

I actually do have some alum powder somewhere, and I hadn’t thought of that. Certainly less destructive than using punches and eliminates the risk of a slipped drill. 

My only concern is there appears to be solder around the rivet which I imagine was added for strength. I don’t want to lose that. 

[praezis]

1 hour ago, Bill241 said:

I actually do have some alum powder somewhere, and I hadn’t thought of that

And what to do with the resulting hole? Soft soldering will be a worse botch than a rivet. Silver soldering will include unpredictable danger for the barrel.

3 hours ago, Bill241 said:

The old spring is the right thickness but too short - even in its weakened, set, state, and the movement dirty it was running an amplitude well over 300 degrees. As such I’m concerned about the risk of overbanking

Same question again: which lift angle did you use?

Frank

[Bill241]

Hello Frank, 

I’ll leave the hole ‘plugged’ with the steel rivet and will only remove it if somehow it works loose in future. It is very firm at the moment. 

I admit my timegrapher was set to the default 52 degrees and the watch was only running for a few minutes before I decided to let down the mainspring. I must look up the lift angle for this movement- the H7 variant of cal 52.

[Bill241]

Just by way of an update, I successfully fitted the new mainspring with T-ends. No filing of the ends was necessary and it is a good fit. 

If of interest (as these threads pop up in Google searches), the spring reference is GR6449T. this is for the earlier (pre 1907) H7 variant of cal 52. 

I did leave the now redundant rivet in place but conveniently the force of the new mainspring against the inside wall of the barrel made it pop neatly out. 

Edited November 1, 2024 by Bill241