Un-knurled trundles - intentional?

[Simon Holt]

This is the first time I've encountered un-secured trundles:

This is the centre wheel in a 1930's Jahresuhrenfabrik movement. I didn't realise they were insecure until most of them fell out during ultrasonic cleaning...

The trundles are prevented from falling out in the assembled movement because there is a steel washer between the trundle cap and the shoulder in centre arbor - except in this case two of the trundles were too short and could become unsupported at one end:


Do you think the factory just missed the knurling operation?

Simon

 

[Keith Doster]

This is the first time I've encountered un-secured trundles:
View attachment 714551
This is the centre wheel in a 1930's Jahresuhrenfabrik movement. I didn't realise they were insecure until most of them fell out during ultrasonic cleaning...

The trundles are prevented from falling out in the assembled movement because there is a steel washer between the trundle cap and the shoulder in centre arbor - except in this case two of the trundles were too short and could become unsupported at one end:
View attachment 714552

Do you think the factory just missed the knurling operation?

Simon

For a clock that is 90 years old, those trundles look remarkably good. Untouched. Maybe this was a repair gone bad or incompleted? Do the trundles in the other pinions look as good?

 

[Uhralt]

Are all the other wheels of the clock knurled? If yes, i would think this was a manufacturing fault.

Uhralt

 

[R. Croswell]

......Do you think the factory just missed the knurling operation?

Simon

Just guessing, but I would say no regarding the un-knurled design, also no regarding the unequal length trundles. Looks to me like someone carelessly replaced the trundles not giving proper attention to what the length should be. Sure will make your job of replacing the trundles easier and I would not knurl or change the original design. Apparently the maker intended a smooth surface on that end of the pinion.

RC

 

[Simon Holt]

All of the other trundles are properly secured by knurling. Most are exhibiting wear so I agree that the presence of short trundles in this particular wheel must be a repair done badly. The movement has obviously been apart before.

The movement is otherwise in good condition, needing no bushings (and never having had any done) despite less than pristine pivots!

Simon

 

[shutterbug]

If there's a washer holding the trundles in place, leave it alone. If they are allowed to turn they wear longer with less noise.

 

[Simon Holt]

Yes, a washer holds them in place. Except when you are installing the wheel upside down...

Simon

 

[Uhralt]

Yes, a washer holds them in place. Except when you are installing the wheel upside down...

Simon

What holds the washer in place when installed correctly? Does it hit the plate? In that case i would think that's not original because that would cause unnecessary and unwanted friction. My bet is still a manufacturing mistake.
If the washer is s friction fit on the arbor, then maybe it is original, but the question would be why?

Uhralt

 

[R. Croswell]

We need to see the rest of that center arbor assembly. I’m assuming that the smooth end of the lantern and the washer are part of the slip clutch for setting the time. There must be a spring element that holds the washer against the lantern

RC

 

[Simon Holt]

The clock is now back together so I can't show you the entire arrangement. Here it is during disassembly:

The wheel in question is the centre wheel, with the 4-bladed spring. The washer I mentioned sits on a shoulder on the centre arbor and so the whole arrangement is indeed the slipping clutch for setting the time.

Because the trundles can fall out during assembly, I agree its likely a manufacturing error.

Simon

 

[Uhralt]

These wheels look weird. There is a lot of knurling going on, not only on shrouds but also on wheels. And the knurling looks somehow homemade.
I think somebody has worked on the movement and went overboard with some of the knurling. Why he missed it on this one wheel I don't know.

Uhralt

 

[R. Croswell]

These wheels look weird. There is a lot of knurling going on, not only on shrouds but also on wheels. And the knurling looks somehow homemade.
I think somebody has worked on the movement and went overboard with some of the knurling. Why he missed it on this one wheel I don't know.

Uhralt

Looking at this blow up of the wheel before the escape wheel, the knurling does not cover the ends of the trundles. Looking closer, it looks like the openings were staked after they were knurled, partly obliterating the knurling. We know from the OP's description that some trundles were unequal and/or too short. There seems to be no question that this movement has been messed with, at least the lantern pinions have been messed with.

What I find extremely interesting is the unknurled/unstaked smooth end of the lantern in picture post # 1. It may be argued that perhaps not staking or knurling that end of the lantern could be a factory error or oversight, but it is clear that whoever installed the replacement trundles, presumable the same person who worked on the other lanterns including the example below, is someone who does practice staking trundle openings. I find it rather hard to believe that this was a factory oversight and that the person replacing the trundles would not stake this lantern as he/she did the others to correct the "factory mistake" unless he/she realized and believed that this was not a factory error and was left smooth for a reason.

Trundles falling out would not have been an issue on the assembly line where holding fixtures would likely prevent this. I would agree the design is not very considerate of anyone having to field service this movement. We need to see a second example to be sure.

RC

 

[Simon Holt]

We need to see a second example to be sure.

That would be informative. I expect someone on the forum would remember encountering this before if it was intentional.

Simon