Gruen hand setting problem

[chrisdt]

Hi all,    I;m fairly familiar with canon pinions, removal, tightening loosening etc until I came across this Gruen 790 CD. The symptoms are very (almost impossible) difficult to adjust the hands. This movement is new to me so any help with the problem would be good. Would it be the CP? or something else. Either way partial disassembly would be required. The movement is is in generally good shape so Ive never known a CP to be this tight..

 

Edited July 10, 2021 by chrisdt

[Nucejoe]

 Gruen 790 CD is an A Shieds 2066, with the offset canon pinion which is a culprit on such AS movements, remove, tighten, clean and grease the canon pinion.

Is this giving you problem?   Heres a picture and the subject has been discussed on the forum many

times.

Good luck

[chrisdt]

Thanks for the info and pic but surely the CP must be too tight and will need a reamer

[oldhippy]

This type can be very troublesome, not easy to remove and tighten up. If you can get a replacement I recommend you do so. 

[chrisdt]

Thanks for the info and pic but surely the CP must be too tight and will need a reamer

[chrisdt]

Thanks OH I will take your advice

[Marc]

One way to check to see if there is too much friction in the canon pinion is to pull the crown into the hand setting position, and with the watch running, gently move the hand backward via the crown. If the cano9n pinion is too tight then you will be able to stop the watch, and in extreme cases make it run backwards, just from the crown. If you can't do either of these things then the problem is unlikely to lay with the CP.

Incidentally, if it is the CP then a replacement may well be cheaper than the broaches needed to ream the original out.

Edited July 10, 2021 by Marc
additional comment

[oldhippy]

26 minutes ago, Marc said:

One way to check to see if there is too much friction in the canon pinion is to pull the crown into the hand setting position, and with the watch running, gently move the hand backward via the crown. If the cano9n pinion is too tight then you will be able to stop the watch, and in extreme cases make it run backwards, just from the crown. If you can't do either of these things then the problem is unlikely to lay with the CP.

Incidentally, if it is the CP then a replacement may well be cheaper than the broaches needed to ream the original out.

By doing that it is possible to damage or break the teeth of the  wheel it engages with.  

[Marc]

4 minutes ago, oldhippy said:

By doing that it is possible to damage or break the teeth of the  wheel it engages with.  

really?

I suppose if the CP slipping clutch was literally welded tight then maybe....  but rather unlikely, especially if the advice I gave to just "gently move the hands backwards" was adhered to...

As always in watchmaking, if the force required to achieve a particular objective seems excessive, then it probably is and damage could result. However, since the OP is familiar with CPs and their tightening and loosening etc, I would imagine that he is in a position to determine what constitutes "excessive" force in this instance.

Incidentally, there is a scool of thought that refers to the ability to stop a movement via the crown courtesey of a "too tight" canon pinion as a "poor man's hack", and it is a facility that I have often taken advantage of without any detrimental effect on the watch what-so-ever.

I think that as a diagnostic test to assess whether or not the CP is too tight my advice stands, although perhaps I should have said "so long as you don't force anything".

[oldhippy]

Never force a movement to do something it is not meant to do like running backwards. 

[chrisdt]

Not forced it but it is at the point of not being able to move the hands at all with the crown but with slight pressure on the crown the watch will stop.....

[oldhippy]

As I said I  would replace it. Something clearly is not right with it. 

[Nucejoe]

I try a bit of penetrating oil on the CP before tearing the whole movement apart. 

 

 

 

[chrisdt]

Not forced it but it is at the point of not being able to move the hands at all with the crown but with slight pressure on the crown the watch will stop.....

[chrisdt]

Bit late for that Nucejoe....Just hope I remember where everything goes !!!!!

[chrisdt]

Can anyone please tell me the easiest way to remove offset canon pinion with the minimum of disassembly presumably from the rotor side?

[oldhippy]

As far as I'm aware you can only remove the cannon pinion from the calendar side.  

[Nucejoe]

 I,d be more concerned about good results, there is no gurantee you will get the right friction with a broach alone.

I made me this contraption, the screw provides with a micrometer action and it might take several tries to get it right.

so you best have both parts out to clean and have max control over what you are doing as following broaching you might end up retightening.

 

 

[nickelsilver]

If this is like many other AS movements I've seen, you have to get the offset center wheel out to access the cp. To take the cp out you have to take out the automatic mechanism, and the bridge over the gear train.

 

When you have the center wheel out, if you grasp the upper pinion firmly with tweezers you can turn the wheel and pull it off of the pinion. Clean everything, then grease with whatever- preferably Moebius 9504 but any grease, including Vaseline, will work. This should fix your high friction problem.

[chrisdt]

On this movement there seems to be a circlip on the end which I cant seem to find in any pics including Nucejoes above.

Totally lost with this. How do I set the friction?