Cannon Pinion problem.

[fjseal]

Hi all,

On a Std 96-4 movement the hands turned too easily and the second hand did not stop with back pressure on the winding stem, so I removed the cannon pinion and tightened it a little. On refitting it the cannon pinion does not rotate with the minute wheel, so could the centre pinion be distorted, or is the cannon pinion too tight. The watch performs ok in other respects.  Any ideas?

Thanks.

Frank.

 

[Marc]

I have just checked the layout on an ST-96 from my parts bin (essentially the same movement) to verify that it uses a conventional cannon pinion layout and not an indirect set up. 

The cannon pinion takes drive from the centre wheel pinion and transfers it to the minute wheel. The only way in which the minute wheel can be turning is if it is correctly meshed with the cannon pinion and the cannon pinion is turning too. The only issue that you would have if the cannon pinion was too tight would be that it would be difficult to set the time and the watch would stop when you did so.

When you say that the watch performs ok in all other respects do you mean that the both the minute wheel and the hour wheel are turning normally? If so then the cannon pinion must also be turning.

Can you confirm exactly what is turning and what is not. You might find it helpful to track the power through each wheel from the centre wheel pinion to the hour wheel, one wheel at a time.

[fjseal]

Thanks for your reply Marc. The watch was running ok before I removed the cannon pinion to tighten it; the minute and hour wheels were both turning. Now, when in time setting position, nothing turns, it is all jammed. I will look closer later today, thanks.

[Marc]

Ok, if everything is jammed up in time setting position then it may well be that the cannon pinion is now too tight.

How did you go about tightening it? and how difficult was it to reinstall?

The other possibility is that some of the wheels aren't meshing properly, always worth a check.

 

[fjseal]

Marc,

Thanks for your replies. I tightened the cannon pinion by sliding it over a needle and squeezing it with snips. I must have overdone it, so i managed to spread it by sliding a larger needle through the pinion and gently tapping it on the jaws of a mini vice. I attach a photo of what I mean. It may seem crude, but now I can turn it and will re-assemble the watch and see if it is okay.