Hi All,

I purchased a very nice 992E in a model 10 case today (2615431). I have read the posts on the solid balance, but, how do I know the hairspring is Elinvar? Is there a way to check. This one is blue

(sorry, this question has probably been asked a hundred times

Bruce
The blue Hairspring is right,they were dyed blue at the factory..

Bruce,
To add to the other comments....

Below is an excerpt from a Hamilton "Tech. Bulletin" showing the pre-Elinvar balance wheel (monmetallic) at top and the Elinvar bi-metallic (brass & steel) split balance wheel at bottom.

Hope this is helpful.

Robert

Hi all,

I double checked the balance wheel and it is solid. I figure if the balance is correct then the hairspring is most likely correct also.. (I just wonder how many 992E's do not have an elinvar hairspring, just a regular one hmmmm )Thanks you all for your input..

Try the ear test....Robert

Robert,

Ear test? different sound than a regular hairspring? what should I be listening for, different pitch? Please explain

Bruce.....Put the complete watch to your ear, and rock left and right. The Elinvar equipped watch will thud. The non Elinvar equipped will ring. Mike C told me about this. Try it!...Robert

You could measure the temperature effect on time.

Put the watch in the refrigerator (sealed in a tight platic bag) for 24 hours and measure the number of seconds lost or gained or if you have a timing machine, measure the rate right after removing the watch from the refrigerator. Repeat the experiment at room temperature. Finally measure the loss or gain near 90F. I have a box with a light bulb as a heat source and a thermostat to control the heat. This time of year, you can just turn off the air conditioning.

A compensating balance with a steel hairspring should have nearly the same rate at the low and high temperature, but be fast in the middle. This is called the middle temperature error. The effect could be as much as a ten seconds middle temperature error.

An Elinvar hairspring with a mononmetallic balance should show only a small increase in rate with temperature amounting to only a couple of seconds or less from 30 to 90 F. This small amount of temperature error should be hard for you to even measure. This is why the Elinvar hairspring and Invar balance was invented.

If you had a steel hairspring on a monometallic balance, the watch would slow down a huge amount with increasing temperature. This would be like the old solid balances from the 1850s before the compensating balance was commonly used. We are talking about minutes in rate change from 30 to 90F.

Don

Don, I think Roberts thud experiment sounds easier

Bruce....You can tell which is which with your eyes closed and the case back on..Give it a try and report back......Robert

I hear a thud with a steel hairspring. That is the old test for endshake in a balance. Oh well, I have old ears. I'll have to try it with my 992E.

Seriously, run the watch cold and at room temp. If you have a steel hairspring in a monometallic balanced the temperature error will jump out at you.

Don

If it's Elinvar it is also non magnetic.
To make an easy and accurate test:If you approach a magnet to a steel hair spring it tends to be attracted to the magnet. Don't get too close! about one inch's distance is safe and causes no magnetization of other steel parts in the mvt.
Of course if it is Elinvar you see no movement of the hair spring.

Robert, I thought I heard a thud but wasn't sure. I tried Peters idea. I had a small screwdriver that had become magnatized. I checked a junk movement and sure enough the hairspring moved towards the screwdriver. I tried this again with the 992E and it did not budge. This screwdriver is very, very small so I did not run the risk of magnatizing the rest of the watch. I am gonna try the hot cold test next..

Put the thing through a demagnetizer and see what effect it has on hairspring?
Jim.