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The oscillator, or something, in my automatic wrist watch seems to be greatly affected by outside temperature (summer vs winter).

It seems to run fast in the summer, and even faster in winter (The manufacturer said they could adjust it).

Q:  Is this difference with temperature normal/possible?


Q:  What would cause this?  [a poor choice of hair spring material (stiffer in cold = higher rate)??? a poor choice in lubricant???]


As an Engineer, I like to understand causes and effects.

As far as my watch is concerned, I will be surprised if there is a year round fix.


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OK, you asked for it! :)

The bimetallic compensated balance wheel was made obsolete in the early 20th century... Charles Édouard Guillaume won a Nobel prize for the 1896 invention of Invar, a nickel steel alloy with very low thermal expansion, and Elinvar (Elasticité invariable) an alloy whose elasticity is unchanged over a wide temperature range, for balance springs. A solid Invar balance with a spring of Elinvar was largely unaffected by temperature, so it replaced the difficult-to-adjust bimetallic balance. This led to a series of improved low temperature coefficient alloys for balances and springs.

Before developing Elinvar, Guillaume also invented an alloy to compensate for middle temperature error in bimetallic balances by endowing it with a negative quadratic temperature coefficient. This alloy, named anibal, is a slight variation of invar. It almost completely negated the temperature effect of the steel hairspring, but still required a bimetal compensated balance wheel, known as a Guillaume balance wheel. This design later fell out of use in favor of single metal Invar balances with Elinvar springs. The quadratic coefficient is defined by its place in the equation of expansion of a material;

lθ=l0(1+αθ+βθ2){\displaystyle l_{\theta }=l_{0}(1+\alpha \theta +\beta \theta ^{2})\,}l_\theta = l_0 (1 + \alpha \theta + \beta \theta^2) \,
l0{\displaystyle \scriptstyle l_{0}}\scriptstyle l_0 is the length of the sample at some reference temperature
θ{\displaystyle \scriptstyle \theta }\scriptstyle \theta is the temperature above the reference
lθ{\displaystyle \scriptstyle l_{\theta }}\scriptstyle l_\theta is the length of the sample at temperature θ{\displaystyle \scriptstyle \theta }\scriptstyle \theta
α{\displaystyle \scriptstyle \alpha }\scriptstyle \alpha is the linear coefficient of expansion
β{\displaystyle \scriptstyle \beta }\scriptstyle \beta is the quadratic coefficient of expansion
Also the hair spring:
Around 1900, a fundamentally different solution was created by Charles Édouard Guillaume, inventor of elinvar. This is a nickel-steel alloy with the property that the modulus of elasticity is essentially unaffected by temperature. A watch fitted with an elinvar balance spring requires either no temperature compensation at all, or very little. This simplifies the mechanism, and it also means that middle temperature error is eliminated as well, or at a minimum is drastically reduced.

Glucydur is a beryllium bronze; an alloy of beryllium, copper and iron. In addition to its low coefficient of thermal expansion, its hardness (400 Brinell), nonmagnetizability, and resistance to deformation and damage make it suited for making precision parts that must have high dimensional stability. Glucydur is also resistant to corrosion; it is rather inert chemically.

Glucydur was developed about the same time as another non-magnetic material, Nivarox.

Glucydur balance advantages over a nickel balance are simple: Glucydur (or beryllium bronze) resists deformation from temperature change or abuse much better than nickel so the balance wheel stays in balance and therefore keeps more consistent time.
Now for the movements offered by ETA:
The Standard and Elaboré calibers use Etachoc shock protection, a nickel balance wheel with a Nivarox 2 alloy hairspring, a Nivaflex NO mainspring, a steel pallet lever and escape wheel, and polyruby pallet jewels.
The Top and Chronometre calibers use Incabloc shock protection, a Glucydur balance wheel with an Anchron alloy hairspring, a Nivaflex NM mainspring, a Nivarox pallet lever and escape wheel, and ruby pallet jewels.
Anachron is said to be a better performing alloy than any Nivarox incarnation which is why it's used on the Top and Chronometer grades.
The difference between polyrubies and rubies is based in the manufacturing process. Polyrubies are made from powder that's heat pressed into shape. They're translucent, almost foggy. Rubies are cut from a man-made crystal that's formed in an electro-chemical process. They're completely transparent with better consistency.
ETAchoc                            Incabloc
Ok, all this information is a compilation of stuff I've been collecting on my search on the web that throws some light on the answer to your question....Now, the real question here is:
What movement are we talking about? In what conditions do you use it? Has it always behaved that way? It could be simply a magnetized movement or something more serious...which lead to the following extra questions: when was the last time it was serviced?....and by whom?
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Thank you so much for the historical lesson on the progression of material development and selection.  It gave me a good excuse to break out my old Mischke Engineering Design book.

In the next week or so, when I send my watch to the manufacturer to be serviced, I will ask them about the innards of my timepiece.  If I learn more, I will certainly follow-up on this thread.

What I can tell you now is that my watch is made by Reactor.  It is their serial numbered flagship model known as the Poseidon Ti.  It has some sort of newer, more rugged design of automatic winding mechanism from Japan (the back of the watch has a window that lets you see this mechanism).

I bought it new.  It has always been fast. This will be it's first service.

I abuse it.  It endures salt water swiming, snorkeling, sailing. High altitude altitude snowboarding in fridgid conditions. The shock of golf swings, chopping wood, and of shooting firearms.  Vibrations such as chainsaw and grass wip.  It only comes off when I go to bed.  It has become a part of who I am.  If the service cures the summertime one second per hour gain it suffers from, this watch will be close to perfect for me.

Thanks again Bob for your prompt and detailed response.  I doubt anyone else will read this thread, but I certainly foud it interesting and educational.



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Hi E,

I believe my explanation is only good (to a certain point) to Swiss watches. Your Reactor watch apparently has a Japanese Movement...and some of the same model have Quartz which doesn't use a balance wheel. I don't know at this point if your movement originated from Seiko or from Citizen. One thing is certain, it is a good movement, strong and a workhorse. Now, for the sake of curiosity, how long have you had your watch? and, does it winds and hacks?

If I'm not mistaken, if fairly new, it could be one of the new Seiko "replacing" the 7S26 types (I'd say NH35/36...) If old and can wind, it is likely Miyota/Citizen. Now, it is only a guess. Maybe the owners manual or any other paper that came with the watch can shed some light on this matter.

Check this link out since the movement you likely use in your watch is a direct descendant of this Seiko:


In any case, let us know what information you have about your particular watch movement!



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