A question for the chronograph experts

[Yoda]

Guys, I admit that I haven't worked very much on chronographs for a while and now I have an Omega 321 in pieces, nothing was assembled. I wonder if this particular part really is a part of that movement, I can't seem to locate a logical spot for it? To me, it looks more like a part for a rotor in some automatic movement.

20181018_135947_resized.jpg

[unreformed66]

That's the little drive wheel that goes on the end of the mainspring arbor and is held on by the funny looking spring that mounts to the mainspring barrel with two very tiny screws.

[unreformed66]

Here's a picture I stole from the internet.

[Yoda]

Oh, that's where it sits, thanks a lot! It wasn´t quite obvious, but I did wonder what the heck that spring plate was doing.

[unreformed66]

I recognized it immediately but I've done service on 4 Speedmasters in the last couple of months so it was fresh in my memory..... And you're quite welcome.

[Yoda]

Tearing down the Omega 320 again, damn...LOLOL!

[unreformed66]

I actually really like those Lemania movements. And believe it or not I like the 861 better than the 321 as far as servicing them goes.

[Yoda]

Did Lemania make those for Omega ?

That was news to me.

Same here, I like the 860 series better.

[unreformed66]

Yes, almost all vintage Omega and some Tissot movements were by Lemania. The 320 and 321 are based on the Lemania CH27 (or 2310) and the 861 is the Lemania 1873. The Omega automatics are also actually by Lemania, I'd have to look the caliber number up. Patek used Lemania movements as the base for some of their chronographs as well but re-worked them to meet the Geneva Seal standards (Solid banking, no wire springs and etc.). Knowing this has helped me source parts at much better prices through the years.... Of course now the lower end Omega chronographs are using ETA 7750 movements but the Lemanias are still in the higher end ones.

[Yoda]

You live and learn, thanks for the education!