cyma = eta

[gary17]

Hey guys

I am working on a cyma the only markings on the movement cyma R.408.00.

Which is not in cousins or ranfft. So looked around and most people seem to think its a ETA 2722R,2724R or 2728R any way i need a mainspring and they dont make em any more so got measurements of ranfft 1.25x11x0.125 i put these in and it says there is none. It also wants length which i do not know. So what i am asking is what number is it best to fiddle around with so i can get a nearly correct mainspring. Its a nice watch so worth the effort. Its a auto as well.

cheers

gary

[KOwatch]

Take out the mainspring and measure the length.

Go closest shorter mainspring. Shorter, you'll loose  some power reserve but otherwise should be fine.

There are calculations to determine how long based on the area of barrel (see NAWCC website). Input the the ID of the barrel, the OD of the mainspring arbor, and the thickness of the spring. The idea is you fill a certain amount (about 1/2?) of the barrel area with coiled spring, with room for the spring to hold tension.

Altering the thickness will change the torque available; increase, you can add too much and overbank, decrease thickness and you have too low amplitude. If it's a really old watch (not yours) you have to consider this, as older spring material was less powerful for the same thickness. I've read that watches with bad amplitude (or too much) after servicing can benefit from a different thickness, not a common case.

Last resort, you could go for a smaller width, the spring would fit looser in the barrel but one size lower shouldn't really make too much of a difference (so I hear), although technically you want to re-size up the thickness in that case, and there's calculations for that.

The last value you'll see on the cousins website is the size of the mainspring package, which should be equal or closest smaller size to the ID of the barrel.

If you look at some similar ETA models you might get an idea of approximately how long the spring is, often it's listed with ranfft. Unfortunately for you, not for 272x series, nor the 26xx series, but there is for the 25xxs, and the 277x, so you might have some starting points there if the springs are the same for the other dimensions, barrel size, complications and rate.

If you can find your mainspring size measurements, there's other styles of model numbers like the bestfit catalog number (usually a number and a letter), and if you know these you can often find NOS "white-a-loy" springs on ebay or elsewhere. There's scanned documents online from Marshal Handy, Bestfit, General Resorts, Nivaflex that will list more specs on your movement and mainspring.

Like here:

https://watchguy.co.uk/cgi-bin/mainsprings

Some conflicting numbers in multiple entries for the eta2722, but you're seeing ETA2722 numbers similar to the ranfft data, with a length less between 360 and 400mm. Also seems to suggests your GR reference is this one available from cousins:

1.25 x .135 x 400 x 11 Automatic

GR3150X

Which at .135 is thicker than Ranfft's listed .125 (could be an error with Ranfft?), so you'll have to resolve that discrepancy with some more data points. Best to measure what's in there and/or look it up your movement in some more of those catalogues.

Good luck

 

 

 

 

Edited October 25, 2020 by KOwatch

[gary17]

Hey thanks for all the info. But there was no mainspring in it.

cheers

gary

[Nucejoe]

Yes Cyma  R.408 is based on ETA 2724R.  

[KOwatch]

No mainspring? Like the barrel was empty? You can double-check the barrel ID to confirm it's 11mm ID.

The generale resorts catalog (you can download sectons from cousins) seems to think it's the GR3150X. I'd start with that one.

The other bestfit catalogue I'm looking at only goes up to the 25xx series.

There's the older Dennison system of mainsprings numbers, for some watches it's useful to look for those on ebay or somewhere, I think in your case it would be a 39T or a 38T, that's a width 3, thickness 9, length T corresponding to a 1.2 x .13 x 393 mainspring, they go up in whole sizes so it doesn't correspond exactly. There's a 38T in the Cas-Ker catalog, I think I'd stick with the GR mainsprings though.

[AshF]

Sorry to hijack this thread.  I've got an old project CYMA R.421 that I've been trying to find a part for for a few months.  Perhaps this is based on an ETA?  Where is a good place to find out?

[Nucejoe]

40 minutes ago, AshF said:

Sorry to hijack this thread.  I've got an old project CYMA R.421 that I've been trying to find a part for for a few months.  Perhaps this is based on an ETA?  Where is a good place to find out?

Have you checked www.julesborel website, lists many tavaness 420 parts in stock.