Hamilton Balance Wheel Patent:

PapaLouies

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I assumed that Patent No. 2356911 covered the 992B Balance Wheel because it was filed Aug 1, 1941 and approved Aug 29, 1944 long after the 992B Balance Wheel was created.
The Patent was authored by William Ogle Bennett Jr., who was in fact the chief physicist for the Hamilton Watch Co. from 1932 to 1946.
For this discussion I will refer to the second generation 992E Balance Wheel as the 992E-2.

On the first page of the pdf of the Patent is a sketch of a Balance Wheel that could depict the 992E-2 or the 992B.
In the first paragraph of page 2, Bennett describes the adjustment of the Balance Wheel to compensate for the short comings of the "Elinvar" hairspring to increase in strength under the action of heat.

Bennett described the Balance Wheel with a monometallic rim of stainless steel and a crossbar formed of Invar.
I think it's unlikely that Bennett would not know the existing metal composition of the 992E-2 Balance Wheel.
It would not surprise me if Bennett had been the original Architect of the 992E-2 Balance Wheel.
I suggest that Patent No. 2356911 covers the 992E-2 Balance Wheel and no other.
Regards, P/L
Please see my Threads: Hamilton 992B: and 992E ca. 1938:
 

thesnark17

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Surely the primary application of that patent was to the Model 21 and 22 marine chronometers. They feature an Invar and stainless steel "ovalizing" balance with Elinvar hairspring, which use case was described using almost that exact wording in the patent application. The patent timeframe also lines up nicely.

I don't see that it has to have anything to do with the 992E at all. Though I suppose it could. Is the late 992E balance bimetallic?
 
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PapaLouies

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Hi thesnark17,
A breath of fresh air.
It's obvious you know precisely what I'm saying, apparently unlike many others.
You have proposed an alternative view that I think does not recognize the following.
The Hamilton Model 21 and 22 marine chronometers have Elinvar Extra hairsprings, not Elinvar hairsprings that require balance wheel adjustment to compensate for Elinvar, as stated in Patent No. 2356911.

The term bimetallic balance also was used to describe a cut balance made of brass and steel.
If by bimetallic balance you mean stainless steel and Invar, then yes my 992E-2 has a bimetallic balance wheel.
A photo of my 992E-2 balance wheel ca. 1938.
IMG_2052.JPG
Regards, P/L
This arrangement of the screws 5 plus the more delicate adjustment ‘afforded by the thread ed holes 4 and the possible movement of the screws in the holes toward and away from the center of the wheel, provides ready and accu rate balancing of the expansion of the Wheel with the increase in strength of the hairspring. A hairspring of material such as “Elinvar” is one which may increase in strength under the action of heat.
 
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thesnark17

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Yes, by bimetallic, I meant "made of stainless steel and Invar" (to compensate for the Elinvar hairspring).

The M21 and M22 did use this principle, at least the earlier ones did. I would not be surprised to find that Hamilton switched them to Elinvar Extra once it became available - it is the superior material and these were superior timekeepers - but they were advertised as carrying stainless steel/Invar balances (which presumably would have to be altered if using EE hairsprings).

My point with my statement was that the patent clearly has application to movements other than the 992E - but that doesn't mean that it doesn't apply to the 992E. I am not a Hamilton expert - my collection includes zero Hamilton railroad watches - but I am fascinated by the process of Hamilton's (and others') application of new materials to reduce the middle temperature error. Thus my interest in the discussion, as the M21 and M22 are the only watches that I have ever heard of that employ the principle of an ovalizing balance.

If your 992E balance is stainless steel and Invar (I'm sorry to say that I don't know how to tell that from a picture), then it is certainly covered under that patent. And that makes me interested in picking up one myself. The M21 and 22 are far more expensive!
 
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PapaLouies

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The Model 21 began with Elinvar Extra, see Bulletin June 2005 Vol. 47 No. 356 beginning with page 325.
Regards, P/L
 

thesnark17

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Ok, I have checked and you are right about the Model 21. That's what I get for not being an expert - I generalized the M21 and M22 together.

Since the M21 uses Elinvar Extra, it shows that the bimetallic balance can still be used/still has value over solid Invar type even when an Elinvar Extra hairspring is employed, at least on a watch where adjustment to temperature is the primary source of error.

Nonetheless the Model 22 was advertised as having an Elinvar (not Extra) hairspring, see for example the advertisement featured in this link:

1942 Model 22 Marine Chronometer
 
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PapaLouies

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patent for review....

still unsure of motive.
What does motive have to do with anything?
I guess if this was a Murder Trial motive would be of interest to the Hamilton Experts.
P/L
 

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