Poised Collets and Gibri's balance spring weights

[D.th.munroe]

I've had some of these questions for years, but my mind has been wandering while working lately (not alot of challenging stuff).
One question was about Hamiltons use of poised balance spring collets to get closer positional rates, and why it didn't seem to be adopted more? Was it not enough of an improvement? And what watches used them?

I was also thinking about Gibri using weights on the spring itself and from his description of where they were put, it seemed to me that the weights were possibly balancing out the poise of the collet achieving close the same result.
I wonder if Gibri had thought of poising the collet, he may have done that instead of the weights?

Gibri's book was one of my first watchmaking manuals, for anyone else who wants to read the whole book.

Practical course in adjusting, comprising a review of the laws governing the motion of the balance and balance spring in watches and chronometers, and application of the principles deduced therefrom in the correction of variations of rate arising from want of isochronism, change of position and variation of temperature .. : Gribi, Theo. (Theophilus) : Free Download, Borrow, and Streaming : Internet Archive

Book digitized by Google from the library of the University of Michigan and uploaded to the Internet Archive by user tpb.

archive.org

Dan

 

[DeweyC]

Dan,

Thank you for that link. He really laid the foundations of modern watch theory but does not seem to get much credit. A lot of companies dropped posied pallets shortly after his analysis of poising vs increased mass (momentum) was published. I think I remember reading it and IIRC it is the complete version of the series he did for one of the 19th cent horological journals ( I have the series on a HD I cannot access).

Poising at the collet. Wasn't that a mid century thing? I think Elgin used it wrist watches?

I have to read the treatise and think how it all fits with what I think I know about adjusting. My books are in storage, but did Jendritski mention it?

Thanks for the puzzle.

 

[DeweyC]

Yes, that is the complete series from Jewelers Circular Keystone. I use that book as a reference for discussions regarding watch theory.

Are you wondering how poised collets would fit in with his analysis?

I do know the effect of mass distribution increases as the distance from the axis. So small changes to the poise at the collet would have a small impact compared to the distribution of mass at the rim. I wonder if the impact was even measurable?

Besides, we concentrate our efforts on timing on the distribution of mass on the rim. Which would seem to swamp any benefit of poising at the collet.

I know Hamilton made a big deal about this on the M22 but I wonder now if it was just marketing for the benefit of the USN. After all, these were kept dial up unless something went seriously wrong.

I know Hamilton played these games. When I purchased my 500 M21s from the USN in the 1990s, I copied all the production cards for them at the NAWCC. Almost all of them had "bruised pivots" which needed to be corrected. What in the world is a bruised pivot and if there were so many, why not correct the issues around handling that caused it! There were other comments that were repeated word for word but I cannot recall them. Bruised pivots stuck in my mind.

 

[roughbarked]

Would a bruised pivot be what is otherwise known as a riveted pivot?

 

[D.th.munroe]

I was thinking basically the same about the (oh I should've said "counterpoised") collet, wouldn't it just have been so small that a couple degrees, if that, turn of a screw would've countered the effect.

This is where I read about Hamilton using them. More info than I remember. 1946 HIA Journal Archives page 28 of September and page 9 of October 1946
Dan

 

[D.th.munroe]

And thank you Dewey, I know you know more about timing than I do.
It was your mention and praise of him a few years ago reminded me I had that book and made me reread it.
I don't remember if Jendritski mentioned either, I dont own his books yet, I have read them but not in many years.

I was more thinking about if Gibri's weights were actually indirectly compensating for lack of poise of the collet or if it was about the weight of the spring itself.
Dan

 

[DeweyC]

And thank you Dewey, I know you know more about timing than I do.
It was your mention and praise of him a few years ago reminded me I had that book and made me reread it.
I don't remember if Jendritski mentioned either, I dont own his books yet, I have read them but not in many years.

I was more thinking about if Gibri's weights were actually indirectly compensating for lack of poise of the collet or if it was about the weight of the spring itself.
Dan

Dan,

You just brought this to mind. Somewheres (Jendritski) there is a photomicrograph of a balance spring with mass added to the spring near the collet. I forget the purported purpose. But I think it was related to your question.

 

[D.th.munroe]

I'm guessing it may have, starting on page 79 of the above Gibri book, he talks about his reasoning and experiments (I should've pointed this out earlier as well oops)