Here is a question for those of technical bent.

I have two cal 354 movements, one in a Seamaster and one in a Constellation. They are both from the 1950s, the Seamaster is about a year older. But the Seamaster does not hack - if you turn the hands backward when setting the time the second hand keeps right on going. Here it is -



Whereas the Connie does hack - if I turn the hands backwards the second hand stops, and you can set the time precisely to the radio time signal (remember that?) or these days to the internet clock. Here it is -



Now then, does anyone have any ideas why this should be so? And if you have 354s, do they hack?

John

 

my technical bent is pretty straight. Id just like to point out that both of those watch movements look like they belong in the omega museum. Really nice, thanks for sharing.

 

Be VERY careful about forcing a watch to run backwards. Not so good for the escapement. And these didn't 'hack' - they just happened to be more directly connected to the keyless works for lack of a better discription.

 

Exactly right - the tightness of the cannon pinion will determine if enough back pressure can be put on the train to stop the movement. The OP didn't mention how much wind was on the watch when you tried to stop it, so if you only tried this at full wind, then try letting the watch run down past 24 hours and see if it stops then. With less torque from the mainspring going to the train, it will be easier to stop it when the watch has run down closer to the end of it's power reserve. If that works you can set the time, then immediately wind it.

And Dennis is correct - you don't want the watch to run backwards or you risk damage to the pallet fork jewels....for this reason I tend to err on the side of the cannon pinion being loose.

Cheers, Al

 

How interesting. And thank you, everyone.

So as I understand it, there may be nothing actually wrong with either movement - it is just that one has the cannon pinion set slightly tighter than the other?

John

 

Correct. If the movement that does stop runs backwards at any point though, I would consider the cannon pinion too tight.

Cheers, Al

 

Thanks to the op, interesting thread