Anyone have a copy of the original "992E and 992B accuracy comparisons" topic?


Here's why I'm asking...

The other night I was overtired and posted in the wrong topic. When taking out my post
I mistakenly removed not just my post but the entire topic. Our software team assured
me they could restore the topic, but those efforts were unsuccessful.

We have made progress in piecing it back together. If anyone made a copy og posts not
included below we can restore that information. Send it to ihc185@roadrunner.com
or call 440-461-0167 and we'll work on this together.

I promise to be far more careful in the future!

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Here are the first two postings:



Michael Sherwood
IHC Member 892
Posted May 21, 2007 00:10


If I am opening a subject that has been discussed prior, please point me in the right direction. I am perplexed over the 992E and its accuracy versus the 992B. The latter being a more technologically advanced design with the pressed jewel settings that don't require any adjustments. In fact, from my research on this forum and elsewhere, I find that a 992B can be disassembled and interchanged with another's parts without much change in behavior. Absolutely astounding.

To my question: How does a 992 with the Elinvar balance compare in accuracy to the 992B and which makes the better "daily driver" (I fear I have just opened Pandora's favorite box). Curently I am carrying a 992 that pre-dates the 992E and I enjoy the age factor not to mention the nice damaskeening of the wave and flower variety - they look so nice.

But, I want the greatest accuracy. I think the 992E must be a little more accurate than the 992B based on cost but I might be wrong. Please give me your thoughts. Thanks,

Mike

Posts: 6 | Location: Plano, Texas in the USA | Registered: February 02, 2007

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Matthew E. Sutton
IHC Member 481
Posted May 21, 2007 03:01

From what I gather, the only difference between the 992 and 992E was the evolutionary hair spring. The 992B went a step further with the interchangable parts, some re-engineering AND the Elinvar hair spring. Not so sure about accuracy, but consistancy of the time keeping properties of the movement has many factors to determine performance such as the use application, degree of quality servicing, etc. In my opinion, for a daily carry, I prefer the early 992B because parts are semi-available, and the model #15 case is post 992E. This case is stainless steel and perfect for modern daily carry. I do not think you can go wrong either way as long as you are happy carrying what you have.

Posts: 356 | Location: Havre De Grace, Maryland USA | Registered: March 14, 2005

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Robert Sweet sent us the 992B Specifications he posted...

Thanks to Norman Bliss who had eMail Notification turned on for the later
days of the "992E and 992B accuracy comparisons" topic we have the posts
that follow. If anyone else has any additional ones please do send them along.

Thank You Norman!

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Donald B. Dahlberg
Posted May 29, 2007 13:28


The sixth postion adjustment is very difficult and actually comes at the cost of the other positions. The reason has to do with the inner terminal of the hairspring where it attaches to the collet. When the balance is at rest the hairspring should come out of the collet and head upwards. This is toward the stem, when stem is up on a open face watch. When you have the stem down, then the hairspring comes out of the collet and heads down, causing a terminal end error.

You can compensate for a terminal error by creating some positional error in the opposite direction. So you are giving up some accuracy in positions that are most used to get less error in a position that you hardly ever use.

Look at the Hamilton standards that Robert gave you for the 992B. Notice that a 10 second range was allowed between any of the first three positions. This really means 10 seconds between pendant up compared to the dial positions. This rises to 15 seconds when we add the pendant left and right positions and 20 seconds when we add the pendant down position. So the adjusting is still oriented to get the best timing in the most common three positions.

Here are the 992 standards:
Six seconds between dial and cock positions.
Ten seconds between all five positions.

See that the 992 was actually adjusted to better timekeeping over the five positions (10 versus 15 seconds per day). No standard is reported for the 6th position for the 992, but we know they gave up 4 seconds on the pendant up and 5 seconds on the pendant left and right positions to bring the pendant down position to 20 seconds on the 992B.

The important thing about the 992B is the great reduction of the middle temperature error. A compensated balance with a steel hairspring was adjusted to keep good time at low and high temperature. This created a middle temperature error. So a watch that is right on at 50 F and 100F, would run fast by 4 to 5 seconds at 70F. The effect was even larger for higher and lower temperatures. With a Swiss Elinvar hairspring the temperature error was only about 1.5 second from 40F to 120F, and most of this was at the very high temperatures. I believe the error was even less with Elinvar Extra. This is a huge improvement.

So it is not enough to say a watch is adjusted to six versus five positions. The question is to what tolerances. How is the watch going to be used? A Hamilton Model 21 chronometer was not adjusted to close positional error, because it was expected to run dial up only. It was gimbled to do so. There is no better mechanical timekeeper, but it would keep terrible time pendant up.

The 4992B master navigational watch, which is essentually a 992B, was adjusted to within 5 seconds over the three positions (remember the 992B was 10 seconds over these positions). This was because the watch was expected to be kept mostly dial up and sometimes pendant up. I am sure the 4992B would not pass the 992B standards in the three positions. You improve things in some positions at the expense of other positions.

Finally, I must repeat that all of this positional error stuff means nothing for a watch that has not been factory adjusted in decades. You can adjust a 992 to 992B standards and visa versa. You can even adjust a 974 to 992B standards if you know what you are doing and have several days to work on it.

You cannot get a 992 to have the small temperature error of a 992B, no matter how much adjusting you do. Steel cannot perform like Elinvar.

Don

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Robert M. Sweet
Posted May 29, 2007 17:46


Don,
Thank you very much for sharing the 992 specification and all the other great info.

Robert

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Lindell V. Riddle
Posted May 29, 2007 18:24


You guys are amazing.

Great information!



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Clyde Roper
Posted May 29, 2007 22:04


Agreed, great information! I was especially interested to learn that the 4992B and 992B were adjusted to different specs and the model 21 chronometer also. GREAT stuff and thanks.


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Robert M. Sweet
Posted May 30, 2007 16:06


The S.S./Bunn Special advertisement below is used to promote the 6 position adj. over the 5 position.

Robert

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Michael Sherwood
Posted May 31, 2007 20:09


Hi Everyone,

I'm really enjoying and learning everything I can from the posts.

Now back to those 992Es - I just realized (and have no idea how odd this might be) that I have somehow acquired two Es from the same production run (3rd run). They are not consecutively serial numbered but still in the same run per the books. Given I don't know how many Es were produced in total, I still find it amazing that I somehow acquired 2 from separate sources so closely numbered.

Just more trivia: the first one is housed in a genuine Hamilton Mainliner case and the second is in the Keystone Mainliner style (Railroader??) case - both look so much alike you need to see them side by side to appreciate the differences (This has been discussed elsewhere in 185 and when I read it I immediately checked them out - yep I'm now an expert in this area.)

Having these 2 Es from the same nursery makes for a nice family and I refer to them as "Jack" and "Jill".

These coincidences really make studing and enjoying our hobby so interesting. I appreciate having so many experts around. Thanks for your help.

Michael


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Robert M. Sweet
Posted May 31, 2007 21:04


Michael,


Quote:

"Given I don't know how many Es were produced in total, I still find it amazing that I somehow acquired 2 from separate sources so closely numbered."


Roy Ehrhardt book, Hamilton "Production Figures with Grade and Serial Numbers" indicates there were a total of 60,997, 992E produced. I'm not sure if this total includes several 992 non-Elinvar movements that was upgraded to Elinvar.

The original "Mainliner" case was only used with the 950E movement which was produced from 1937-39.

Robert


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Lindell
Thank you for your efforts to restore this topic.

Below is some information about Elinvar and Invar.
while most people know these alloys have low coefficients of expansion their knowledge ends there. Hopefully people will find this information interesting.
Bob
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From Wikipedia, the free encyclopedia
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Elinvar is the name of a type of metallic alloy with a modulus of elasticity which does not vary with temperature; the name means elastically invariable. It was invented by Charles Édouard Guillaume, a Swiss physicist who also invented invar, the alloy of nickel and iron which has a small temperature coefficient of expansion. The initial use of elinvar materials was in watches which required that a mechanical vibration rate not change with temperature changes. It was also used in producing antimagnetic watches, though not so often as some other alloys with this properties (Nivarox, Glucydur, Invar).
Elinvar consists of 59% iron, 36% nickel, and 5% chromium.
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Invar, also called FeNi, is an alloy of iron (64%) and nickel (36%) with some carbon and chromium. This alloy is known for its unique properties of controlled coefficient of thermal expansion (CTE). It was invented in 1896 by a Swiss Charles Edouard Guillaume, who later received the Nobel Prize in Physics in 1920.
Due to its low coefficient of thermal expansion at room temperature (about 10-6 K-1 in length; some formulations have negative thermal expansion, NTE) it is used in precision instruments (clocks, physics laboratory devices, seismic creep gauges, shadow-mask frames,[1] valves in motors, antimagnetic watches, etc.) However, it has a propensity to creep.
Although Invar is today a widely used material in many industries and applications, this is a particular trademark of a French company named Imphy Alloys: this company originates from Aciéries d’Imphy (a small city near Nevers, France) where the alloy was initially industrialised after its invention. The generic reference for Invar® is FeNi36.
There are variations of the original Invar material that have slightly different coefficient of thermal expansion such as:
• FeNi42, which matches the CTE of silicon and therefore is widely used as lead frame material for electronic components, integrated circuits, etc.
• FeNiCo alloys — named Kovar or Dilver P — that have the same expansion behaviour as glass, and because of that are used for optical parts in a wide range of temperatures and applications, such as satellites.



Physicists consider true ideal Invar to be the pure bi-metallic alloy with stoichiometry Fe65Ni35 that has the face centered cubic crystal structure, since this laboratory alloy has all the essential properties of the commercial varieties. The Invar problem of physics has been to discover the microscopic mechanism that gives Invar its exceptional thermal properties. It was established early on that Invar behaviour is directly related to and dependent upon the alloy's ferromagnetism however the exact mechanism has been the subject of much research and debate, including several international conferences on the subject. The dominant theories of Invar were recently critically reviewed.[1]
All the iron-rich face centered cubic Fe-Ni alloys show Invar anomalies in their measured thermal and magnetic properties, that evolve continuously in intensity with varying alloy composition. Recently it was advanced that Invar behaviour was a direct consequence of a high-magnetic-moment to low-magnetic-moment transition occurring in the face centered cubic Fe-Ni series (and that gives rise to the mineral antitaenite), however this has now been shown to be incorrect.[2] Instead, it appears that the low-moment/high-moment transition is preceded by a high-magnetic-moment frustrated ferromagnetic state in which the Fe-Fe magnetic exchange bonds have a large magneto-volume effect of the right sign and magnitude to create the observed thermal expansion anomaly.[3]

Elinvar Extra was:
Iron 47.17-47.31%
Nickel 42.94-43.07
Chromium 4.95-4.99
Silicon 0.48-0.53
Carbon 0.041-0.046
Maganese 0.61-0.63
Titanium 2.66-2.84
Aluminum 0.40-0.48
Cobalt 0.28-0.30

The tempering process was very complicated.

Elinvar Extra was affected less by temperature or magnetism than the original Elinvar. It also was more rigid. The isochronism characteristics were also better. Oil that got on the hairspring was of less concern because the coils were farther apart and the springs more rigid. They did not easily stick together.

Don