992B compared to 992E

[ckeithjohnson]

I ran a search o this topic but didn't come up with any thing. Forgive me if this is old thrashed out stuff,but I get the impression that the 992B is the superior watch to the 992E. Is this based on 992B's superior design, if so exactly what features? Or are there performance figures from actual records That demonstrate superiority of the B over the E in the field?

[ckeithjohnson]

I ran a search o this topic but didn't come up with any thing. Forgive me if this is old thrashed out stuff,but I get the impression that the 992B is the superior watch to the 992E. Is this based on 992B's superior design, if so exactly what features? Or are there performance figures from actual records That demonstrate superiority of the B over the E in the field?

[doug sinclair]

Keith,

Superior in what way? There are things I like best about each of these two movements. Mostly from an esthetic point of view in the case of the 992E. But from a practical point of view, the 992E was every bit as capable of keeping to the required time standard as the 992B was later on. I would give the nod to the 992B from the point of view of ease of servicing.

Elinvar was used in the 992E balance wheel and hairspring, and Elinvar Extra was used in the 992B. I have read that the Elinvar Extra hairspring was considered a bit more robust than the Elinvar hairspring.

[Don Dahlberg]

The 992E used a Swiss Elinvar that had some problems. Mainly it was much softer than the old blue steel hairspring. This caused it to sag under its own weight. Elinvar and the monometallic balance had a much smaller middle temperature error compared with blue steel and the bimetallic balance, but it had slightly greater sensitivity to positional errors. The softer Elinvar also is more difficult to work with than blue steel. Watchmakers found it easy to accidently deform and they were then faced with having to true the hairspring again. Many were not very good at truing hairsprings.

Almost immediately Hamilton started work on their own version of Elinvar. They played with the composition a bit, but most of the changes came about from the heat treatments of the Elinvar. After six years of research they came up with a superior version of Elinvar, which they called Elinvar Extra. It had even better temperature characteristics, yet was much more rigid and held its shape. It was introduced in the 992B. Like the Swiss Elinvar, it did not rust and was not effected by magnetism. Elinvar Extra is the main improvement in the 992B over the 992E. Soon Hamilton was using Elinvar Extra in all their watches and in their famous model 21 chronometer.

They also developed new alloys for use for mainsprings and the 992B was adjusted to six positions versus the five positions for the 992E.

There were some other changes in the 992B that may not have changed performance, but made it easier to produce and repair. They went to friction jewels. They changed the way most of the cap jewels were attached to the plates.

Doug's point is well taken. Railroad timekeeping standards had not changed much in several decades. The improvements going from the 992 to the 992E to the 992B was just more overkill in timekeeping ability. Still the 992B was a better timekeeper in absolute terms. Futhermore, as more effort was put into better timekeeping, there was less effort in aesthetics. I think the early 922 models were the most beautiful.

One last change made in the late 40s was the switch to Melamine dials. These dials were much easier to produce with fewer failures in manufacture. Hamilton really thought they would hold up in use much better. They were very wrong on this last point. Melanine did not hold up well with time.

In summary all the 992 models easily exceeded railroad standards. Still the 992B exceeded these standards by more. They gave up some of the beauty of the old watches and the melamine change was a great success for manufacturing point of view, but a failure in longevity.

Don

[Robert Sweet]

Below is the product specification for the 992B.

If we could locate the same for the 992E, we could tell which movement was timed to the closest tolerance.

I know the 950B was timed to a closer tolerance than the 992B.

Robert

http://static.flickr.com/97/206884003_8d16cc16a7_o.jpg