Following World War II, Railroad Watch Standards identified specific serial number ranges that were acceptable to meet a required degree of time keeping accuracy. Presumably, in such identifications, one of the concerns addressed was that of the magnetic fields generated by diesel electric motors. Elvinar had already been introduced and likely other anti-magnetic compounds were also being used in balance spring manufacture. Were anti-magnetic balance springs the only way in which U. S. watch manufacturers addressed the magnetic field problem? If a watch has a serial number which falls within the specified ranges, can one automatically assume (dangerous word) that some sort of effort was consciously made by the manufacturer to offset magnetic field effects? Thanks for any information which you can give me.

Mark,
There is a long history of watch (and case) manufacturers trying to overcome the negative effects that magnetic fields have on regular blue steel hairsprings. Movements using "antimagnetic" hairsprings, often made of palladium, were marketed by Waltham, Paillard and others as early as the 1880s. These hairsprings were very delicate and still had the mid range temperature errors of the steel springs. Another approach was taken to prevent magnetizing movements by the use of "antimagnetic" cases, placing the movement within a soft iron cup which was inside of the case and using a sheet of soft iron under the dial. Thes best known of these were made by Giles, under the name of Giles Antimagnetic Shield cases. Even the late 1960s/70s Ball wristwatches used a mu metal shield around the movement as added protection.
There is a lot more information contained in the Railroaders Corner columns in Aug and Oct 2003 on "Magnetism, Parts 1 & 2".

Late last year I had occasion to operate a diesel-electric motor car 9on a tourist railway). After checking the engine room and just prior to departure I noticed that the 16s Waltham Ball B202005 watch that I was carrying had stopped. I was reduced to keeping time with my mobile phone (cell phone)!

Later investigation revealed magnetisation of the hairspring, no doubt caused by proximity to the main generator during my engine room inspection. This was a matter of chance as I had run the car often without previous dificulty. I was able to completely eradicate the magnetism and to return the performance of the watch to its faultless norm.

Through this experience I learned, in a practical manner, just how important was the development of non-magnetic watches as the railroads entered the diesel age. I continue to use the older watches when operating steam locomotives but I'm afraid it has to be a 992B or 950B when it comes to the diesels.

John Scott

Ed and John;
Thank you both! Ed, from what you have said, I gather that watch manufacturers waged a long drawn-out "combat" with magnetic fields. I have heard of using soft iron shields before, but only in relation to IWC mechanisms. When I have finished re-organizing my office, so I can find things, I shall dig-out the August and October 2003 issues of the Bulletin.
John, now I am curious. Specifically, you named the Hamilton 992B and 950B models. Were they manufactured with a special something that made them more reliable timepieces? Would a combination of anti-magnetic devices afford more effective neutralization?

Mark

I omitted to mention the Ball 999B which is a further model made by Hamilton containing anti-magnetic features identical to those of the 992B and the 950B. These features are a "white" (silver-coloured) alloy anti-magnetic hairspring and an anti-magnetic uncut balance. These parts form the time-keeping "heart" of a watch. The rest of the watch may be thought of as a "engine" to drive the balance and hairspring together with an indication system (dial, hands, etc.) to permit the measured time to be read by the user.

The ant-magnetic technology involved was perfected for the WW2 Hamilton marine chronometers. Thus, we can think of the watches in question as miniature members of the same family as the world-beating marine chronometers developed by Hamilton.

The book "The Science of Clocks and Watches" by A L Rawlings provides much more detail and is highly recommended to all having an interest in the technology of time-pieces.

John Scott

I think it would be more accurate to say that the technology that was "perfected" in WWII Hamilton chronometers was the elimination of the middle temperature error. The nonmagnetic property of the escapement and balance, a separate problem that had been solved effectively enough several decades earlier (as Ed pointed out), came along for the ride. In 1920 Charles Guillaume received the Nobel Prize in physics for his development around 1896 of nickel-iron alloys with about 36% nickel content that showed near zero thermal expansion and nearly invariant elastic properties in a range of temperature around room temperature. These alloys were in fact magnetic, especially at lower temperatures, but less so than conventional hairspring steels, which have a different crystal structure and are very strong ferromagnets.

In fact, the temperature invariance of invar is brought about precisely by a transition that occurs in the alloy between a strongy magnetic and a weakly magnetic phase! Somewhat below room temperature, a change in magnetic ordering in the crystal lattice of the material occurs from a highly magnetized state, in which the local magnetic moments of adjacent atoms are strongly aligned, to a weakly magnetized state with reduced local ordering. Some magnetic ordering persists above this so called Curie Temperature, however, to temperatures as high as 230 degrees Centigrade. Thus, as the temperature continues to increase beyond the Curie Temperature (Tc is below room temperature), the continuing reduction in the residual magnetization density induces a contraction in the crystal lattice that is nearly sufficient to offset the natural tendency of the material to expand due to increasing lattice vibration. This results in a net near-zero thermal expansion coefficient over a certain temperature range. (It is noteworthy that Guillaume himself was unaware of the underlying cause of the behavior he observed and so effectively exploited. The current physical picture of the "invar effect" was pieced together by later researchers using experimental probes and a modern theory of "critical phenomena" [phase transitions] that did not exist in Guillaume's time.)

Pardon my long digression. Returning to the original subject, my point is that if nonmagnetic behavior had been the main engineering objective, palladium hairsprings would have sufficed without additional development effort.

Clint

Not to jump topic even further, Clint, but on that tact...were the Hamilton 4992B's and 3992B's subject to this same 'anti-magnetic' application as your mentioned marine watches, since they were in close proxmity to radio gear and the like in their use as navagional tools during the war?

Regards! Mark

Ed;
I re-read my August and October 2003 Railroaders Corner columns and can say that at least they mean more to me now than they did when I originally read them. The choice to shield or spring a movement to provide an acceptable degree of magnetic protection certainly appears to have been a dilemma.
John;
Your indication of what to expect to see, “a "white" (silver-coloured) alloy anti-magnetic hairspring and an anti-magnetic uncut balance” confirms thoughts my concerning regarding the out-come of the anti-magnetic controversy, but the details of the anti-magnetic technology that Hamilton perfected is now more alluring than ever.
Clint;
You appear to have addressed the details of anti-magnetic technology perfected by Hamilton, but not being a metallurgist, I will not claim to understand all of the nuances of what you have said. There is, however, a nagging question that you may be able to answer. Blued steel, carbon steel and stainless steel are all ferrous metals affected by magnetism. What though is the special property of stainless steel that would allow it to be used as a case material (Hamilton’s case style #15 is a good example)? My best guess is that is would react like soft iron.

P. S. John, I am still hunting for a copy of Rawling’s The Science of Clocks and Watches, but thus far have only found one available for $150.00!

Many questions have been asked. I'll try to address them all.

Blued, carbon and stainless steels: "Blued steel" is not a particular kind of steel. It is merely a steel that has been heated in an oxidizing atmosphere (i.e., air) to form an optical interference film on it's surface. When the oxide film that develops on a heated metal surface achieves a thickness equal to one half of a wavelength of a specific color of visible light, the surface will strongly reflect that particular wavelength of light. That's because parallel light rays of the same wavelength reflected near normal incidence from the front and rear surfaces of the film will be in phase and will thus reenforce one another (i.e., they will "interfere constructively" with one another) while the reflection of other wavelengths of light will be reduced by destructive interference. As I recall, blue light has a wavelength of about one micron or a bit less, so the surface is held in the flame until a half micron thick oxide film is grown. Other colors, in fact all colors in the rainbow, are possible at least in principle. For instance, Howard heat tinted his dial screws to a "wine" color.

As for carbon steel, all steels actually contain carbon. The basic alloying ingredients that turn ordinary iron into steel are carbon and oxygen. Thus all steels, including the simplest, contain these 3 elements. High carbon steels are hard and relatively brittle, but keep a fine edge and are often used for tools, especially cutting tools. Lower carbon steels are softer (i.e., they are more easily scratched) but tougher (i.e, fracture resistant) and stronger (i.e, can bear greater loads). More complex steels have additional alloying constituents, such as chromium (as for example, most stainless steels), molybdenum and tungsten (which increases tensile strength), etcetera. Stainless steels tend to work harden fairly rapidly, which makes them undesirable for most applications other than where high corrosion resistance is at an absolute premium.

Metallurgists often divide steels into two broad categories called "ferritic steels" and "austenitic steels." Ferritic steels have the "body centered cubic" crystal structure, which is to say that the atoms comprising it are organized such that the material can be viewed as a repeating array of cubic unit cells consisting of one atom at each of the 8 cube corners and a ninth one in the geometric center. Ferritic steels are said to be "ferromagnetic," meaning that once magnetized they retain a sizable and essentially permanent macroscopic magnetic moment that persists unitl it is erased by another sufficiently strong applied field. Most steels used in watches are ferritic. The bcc crystal structure of ferritic steels turns out to be intimately related to the feromagnetism of these materials. Austenitic steels, which include most (but not all) stainless steels, crystallize in the "face centered cubic" structure and are "paramagnetic," which means that the magnetization density induced by an external field quickly dissipates after the field is removed. (As the name implies, an fcc structure is composed of cubes with one atom at each of the 8 corners and one at the center of each of the 6 cube faces. It so happens that the fcc structure does not produce unpaired electron spins or a net magnetization density.)

As for the need to insulate certain Hamilton watches from radio equipment, it turns out that equipment operated via direct current power sources poses a much bigger magnetization problem than alternating current driven sources. That's because the magnetic field associated with an AC source reverses many times a second, which tends to strictly limit the degree of magnetization imparted to surrounding metal objects. In fact, the impetus for developing nonmagnetic watch escapements in the US dates to the period when DC was still being seriously entertained as an alternative to AC for large-scale electric power generation and distribution. After AC definitively won this debate, interest in nonmagnetic watches declined. That said, WWII era military aircraft were known to use quite a lot of DC power. Thus, my answer to Mark's question is a definite "maybe."

Clint

Mark

I wish you luck in your search for the book. It is worth the effort.

JBS

Thanks, Clint....I think.

Regards! Mark

I work with Diesel Electric locomotives on an almost daily basis, and have had no trouble with magnetism so far. While I have carried a 992B for most of the last ten years, I have used many watches that were not elinvar equipped during that time, with no ill effects. Maybe modern locomotives are better shielded than older ones, but Union Pacific still has some old ones as well. A while back, I used a GP40 that was manufactured in 1965.

Clint;
Thanks! That does explain quite a bit. Austenitic steel, being “paramagnetic” then releases magnetic influence in much the same way as would soft iron. In that instance an austenitic steel watch case would provide much the same kind of protection as that which would be provided by the Giles case shield that Ed and Kent wrote of in the October 2003 Railroaders Corner column.
If my extension of Clint’s information is valid then, Mark C., the Hamilton 3992 (I do not know about the 4992), offered in a chrome case would be equally protected.
Don;
(Or do you prefer Donald?) Your comments about using an unaffected GP40 are interesting. By GP, I am supposing that you mean Girard-Perregaux. Recently, I acquired a GP99 which is by no means a railroad watch. After some digging around, I had accumulated enough information to ask Girard-Perregaux what sort of balance spring was used in their finish work on the base ébauche. Their response was:
As far as we know from such an old movement, we used an anti-magnetic balance spring.
Their response made sense as Europe has continued to use DC power. Your GP40 is likely similarly equipped.
John;
The hunt for the book continues. Borrowing the book from the NAWCC library is decidedly the short-term answer. However, I have learned that the British Horological Institute is the publisher and a more realistically priced copy may be obtainable from them.

No, a 'GP' designated locomotive that Don mentions stands for "General Purpose", and is what EMD calls those particular locomotive models. He was using a 'General Purpose' model 40 EMD diesel locomotive built in 1964. Don is a UP locomotive engineer.

Thanks for the info too, Mark. The 4992B is housed in the same chrome base metal case as the 3992B, so must have had the same protection.

Regards! Mark

Actually any metallic case that is not itself magnetic, such as austenitic steel, or chrome, or nickel, should provide at least some protection from external magnetic fields. When an external magnetic field impinges on an electrically conducting body, the field induces eddy currents in the surface of the body that produce internal magnetic fields tending to cancel the applied field. The shielding effect is strongest in the best conducting metals. That is why sensitive scientific laboratory equipment that one must shield from the Earth's magnetic field is often enclosed in a copper mesh basket for that purpose.

Clint

When Hamilton released their Swiss Elinvar hairspring and Invar balance they gave 15 advantages to the change. The fact that the watches are undisturbed by magnetism was listed as number 1. The fact that they did not rust was number 2 and the smaller temperature error was number 3. Watches already kept acceptable time.

Elinvar Extra was a Hamilton variant on Elinvar that corrected some problems they had with Swiss Elinvar. Swiss Elinvar was very soft and actually changed shape with gravity. This caused greater positional errors than they had with blue steel. It was also hard to work with because it could easily be distorted. Elinvar Extra had all the advantages of the Swiss Elinvar without the disadvantages. It was first released with the 992B (1940)two years before the war broke out and work began on the model 21 chronometer (1942). The watch application came first.

The other companies also used various versions of Elinvar. It was being used in all kinds of watches including wristwatches by mid 1930s.

The chemical composition of Hamilton Elinvar Extra is
Iron 47.17-47.31%
Nickel 42.94-43.07%
Chromium 4.85-4.99%
Silicon 0.48-0.53%
Carbon 0.041-0.046%
Manganese 0.61-0.63%
Titanium 2.66-2.84%
Aluminum 0.40-0.48%
Cobalt 0.28-0.30%

The heat treatment and cold working were major parts of the secret.

Don

Mmm! Hoof-in-mouth! Yum, yum! I wonder if the folks at Girard-Perregaux would be as amused at my gaff as I am. My apologies, Don; no insult was intended.
Mark;
When you speak of a chrome base metal case, what would have been used as the base metal? Brass or a yellow colored metal was used in gold-filled cases; and I know that brass was also used as a base metal in less expensive chrome cases (such as one finds housing New Haven mechanisms).
Don;
Could (and was) Elivar Extra be considered as a 'rival' material of Elgiloy? Elgiloy was advertised primarily as a rust inhibiting alloy; but I do not recall if anti-magnetic properties for it were also claimed.
Clint;

quote:

Actually any metallic case that is not itself magnetic, such as austenitic steel, or chrome, or nickel, should provide at least some protection from external magnetic fields.

In the rough-and-tumble of daily use it would seem that the attraction of a stainless steel case would be in its durability. Is that a logical conclusion?

Thanks all. I appreciate your patience with what has likely seemed an endless stream of questions.

Mark, personally I have no clue what the base metal is on my 4992B.

Regards! Mark

Fair enough. Thanks for responding.

Very interesting, Don. It is puzzling that Hamilton should tout a solution to a problem that had been solved much earlier and was already declining in practical importance due to the switch from DC to AC. Perhaps palladium (which is even more corrosion resistant than elinvar) hairsprings had some performance, or cost issues that elinvar addressed, though I am not aware of any performance issues with palladium. Palladium is certainly expensive, but how much does a hairspring weigh? Was it wanting in tensile strength?

Don's statement that watches already kept time well enough is certainly true. On the other hand, for that very reason watchmakers had for decades been pushing popular notions of "qaulity" that had progressively less and less to do with timekeeping ability. (For example, the actual advantage offered by the last two jewels in a 23 jewel watch would be very hard indeed to demonstrate using any practical standard.) Whatever Hamilton's stated rationale was for introducing elinvar on watches, the elimination of the middle temperature error was clearly their motivation for using elinvar on navigational chronometers, where incremental improvements in timekeeping accuracy still made a practical difference. As far as watches were concerned, I think Hamilton was simply hard up to offer the watch-buying public something "new," or at least different from their competitors.

Clint

Clint,
My understanding (based on hands on experience - don't ask!) is that Palladium hairsprings would kink and bend if you just looked at them the wrong way. They were extremely fragile when handled. A lot of watchmakers didn't like working on them as they would get out of round so easily and it was a time consuming job to get them back into shape. When Hamilton first introduced their antimagnetic hairsprings in the 992E, they dyed them blue so that watchmakers wouldn't think they were the old troublesome Palladium springs. After the trade got used to the more modern alloy hairsprings, Hamilton let them remain their natural silver color.

The main problem for RR men is a Diesel's electro-motive equipment, and that, in large part, was still DC until well after WWII. I believe even AC locomotives today rectify the output of their alternators to provide DC to the traction motors, so there's still a lot of DC around. There are also a lot of old generator diesels around.

Also, concerning WWII aircraft, all electronic equipment was very well shielded. You couldn't have RF (radio frequency) energy from one unit interfering with another, and magnetic fields had to be minimized so as not to throw off the magnetic compass (I believe the main compass would have been a gyro, but the magnetic is always the back up).

Norman

Ed and Norman,

Thank you both for your very interesting and enlightening posts.

Clint