Vintage Omega Geneve Seconds Hand Issue

[AdamC]

Hello,

I have been asked to fix a problem with the stem of an Omega Geneve that wasn't engaging to set the hands and wind. Fair enough, I'm becoming a little more experienced now after six months of tinkering and soon identified that the winding pinion had popped out of its housing and fouling the calendar wheel teeth - presumably someone else had removed the stem before! Anyhow, fiddly but I fixed the problem, reassembled, and everything tested out okay (winds, hands set, and calendar quick set works).

The problem now is that when I fit the second hand it keeps falling off, though while laid flat face up, the second hand moves around the dial normally. I've added a couple of photos, just in case you can spot anything. I must add that I ordered a set of used replacement hands, thinking that the second hand hole (if that's the term) had become worn and too large for the pinion. However, the replacement hand makes no difference. So am I now correct in looking towards pinion wear that's driving the second hand through the cannon pinion? Am I doing anything obviously wrong that you may be able to provide a tip for. I am using a proper Horotec hand fitting tool in an attempt to press the hand fully home, though afraid to exert much force in case I damage anything.

Any help would be greatly appreciated.

Thanks,
Adam

[canthus]

It is likely that the second hand shaft is pushing down so the hand is not fully going onto it.  The second hand pinion is held in mesh by a flat spring which sits on the other end of the shaft.  This needs to be supported when fitting the second hand so that it allows the hand to be fitted without moving down.  This spring can be seen when the rotor bridge is removed, see near the centre of the pic attached.

[clockboy]

1 hour ago, canthus said:

It is likely that the second hand shaft is pushing down so the hand is not fully going onto it.  The second hand pinion is held in mesh by a flat spring which sits on the other end of the shaft.  This needs to be supported when fitting the second hand so that it allows the hand to be fitted without moving down.  This spring can be seen when the rotor bridge is removed, see near the centre of the pic attached.

I would say that is the issue the pinion needs to  be supported when fitting the centre seconds hand much the same as some chronographs (thinking of the ETA 7750) that really need a dedicated movement holder to support the centre pinion.

[AdamC]

Okay. I have taken the rotor off and the drive wheel and now have what's shown in the photo. So rather than just dive in, when you say rotor bridge, I'm assuming I now need to bite the bullet and remove the two screws holding it on. It just looks quite different to your photo (accepting that it's a different movement). Presumably I'm going to have to remove a number of wheels underneath looking at those pivots?! Apologies for probably ask ing the obvious  

[AdamC]

Bit the bullet and removed the rotor bridge. I think I can see the flat spring hiding further down underneath that centre pinion. I've circled it in red. Just in case anybody's got a pointer to watch out for, I'll leave this one till tomorrow now. 

[AdamC]

Couldn't wait with getting this far. Tricky but did it. Thanks gentlemen!

[rodabod]

I could be wrong, but the movement you posted may be a “directly driven” seconds type, as opposed to the indirectly driven types posted beforehand from a 500-series. 

For the 500-series, you can get away with fitting the seconds hand once the rotor is assembled as it supports the friction spring. Another alternative is to use a firm case cushion. 

Edited March 28, 2018 by rodabod