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Carriage clock cannon pinion clutch


StuartBaker104

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Working from home during lock down means my spare room workbench is back in use as a desk :(, but looking at the collection of carriage clocks waiting attention and the “need” for a desk clock inspired me to choose a project for the Easter weekend.

I picked the one I thought would be least troublesome - probably no more than 20 years old but somewhat gummed up and obviously revived by its former keeper by the liberal application of car engine oil.  The mind boggles, but the stuff was everywhere, including dried up residue on the balance wheel, and sadly had eaten away at the lacquer on the plates and the base of the case.

No matter, it all came up bright and shiny in the end, and the timegrapher said all was steady as a rock, so I got it back in the case ready for the bench to go back to office mode.

This morning it had lost about a minute and continued to lose ever so slightly all day, but I left the timegrapher on it all day which said it was running fine. I can only think that the cannon pinion (if that’s the correct name on a clock) is slipping. It is loose enough that the hand setting can be turned by hand without a key. The resistance is provided by a curved circlip, which was pretty stiff to remove and refit, so I’m not sure how I’d increase the resistance. I could clean out the grease, but assume the cannon is supposed to be lubricated?

Anyone got any previous experience of this?

I did also think the balance amplitude a bit low, but not had many lever platforms to compare against.

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Edited by StuartBaker104
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Thanks both, it’s been consistently losing just under a minute a day. I’ve moved the regulator to correct by that much. So it now shows +55 secs/day on the timing machine and I can confirm later when it’s run for a bit, but that should be enough to get it to keep time.

Still loads more adjustment available - see before and after positions below.

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That's a very modern platform, you have two adjustments on that one, the long tail and the one that the hairspring goes through, they are independent of  one another or they can work together. What type of oil did you use on the platform?

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The platform is a modern Swiss 11 jewel with beat correction probably by Gorge.S.A, typically the amplitude on these is around 270 to 300,  the regulator arm moves the index pins by friction so once correct rate has been established the  regulator arm can be moved back to the center position while holding the index to maintain its position. To adjust beat the  ring holding the mainspring stud is rotated.

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3 hours ago, oldhippy said:

That's a very modern platform, you have two adjustments on that one, the long tail and the one that the hairspring goes through, they are independent of  one another or they can work together. What type of oil did you use on the platform?

Yes, quite a young clock to go with it too. I used 9010 on the balance and escape pivots and 9415 on the pallet stones. The pallet pivots are dry.

1 hour ago, wls1971 said:

typically the amplitude on these is around 270 to 300

Thanks - that was my expectation, but the amplitude is a little low on mine, varying between 250 and 270. It’s the same upside down, but drops by 15-20 degrees when on side.  Timing variation in positions is trivial, beat error tuned out to zero and the timegrapher trace is pretty much dead straight so I wasn’t concerned about the platform performance.

After adjusting the rate as above, all stayed on time for the first 4 hours, but it’s then lost 30 seconds in the last half hour, which is what makes me suspect the canon pinion. Will keep monitoring it, but won’t have time for any disassembly before the weekend :(

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Well I took this apart again yesterday to look at the canon pinion.

I cleaned the grease off the pinion and replaced with automatic mainspring braking grease, then moved the bent circlip round so the ends of it sat on the pinion leaves rather than in the gaps, which increased the slipping torque. I thought it might slide back down, but seems pretty planted there.

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So that all made no difference whatsoever, and it still loses time when the timing machine says it isn’t, and I’m pretty sure it isn’t slipping now.

I did a train count to make sure I had the right ratios for an 18,000 vph escapement and now I don’t really know what else to look at.  I can’t think how the escapement could look ok on the timegrapher and then lose time. I do have a spare new platform which should fit. Probably needs a clean and oil first, but I could give that a go...

 

 

 

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Remove all that grease. Tiny drops of oil about two is all that is needed. You might have opened that clip a tiny bit when removing it. Those new clips are not good, thy squeezing it a little or better still as as watchweasol suggested replace it with a new clip. I also agree it is not the platform, it is all to do with the friction tight center wheel. 

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Thanks, will see what I can do to tighten that clip some more - the resistance comes from the bow in the clip - it doesn't grip the shaft radially. Turning it over makes it looser because it has less to rest on. I may have to fit a small shim under it, as there is some wear on the face of the groove it fits in.

I can’t find them on Cousins. They appear to be these, made by a company called Rotor Clip https://www.rotorclip.com/cat_pdfs/be.pdf.

I can find some larger ones for sale, but will need to strip it apart again to take measurements before I go hunting for the exact part if I need to replace it; unless someone knows where to buy them in clock sizes https://www.raptorsupplies.com/en-gb/rotor-clip/be-25st-pa

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7 hours ago, wls1971 said:

Are you sure the wheel is not slipping where it is riveted to the pinion on the arbour ? 

Well, I wondered about that and then when I scratched my head really, really hard, I concluded that would make it run fast, not slow, since the power drive from the barrel would not be properly stopped by the escapement. But I will check anyway because I may not have scratched my head hard enough!

What has just occurred to my is that since this is a carriage clock, I have great visibility of the movement, so I can set the minute hand to be in line with a spoke on the centre wheel. I can then be absolutely certain if the canon pinion is slipping as they will go out of alignment.

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Well that experiment worked. Definitely able to see that the minute hand got left behind by the centre wheel.

When I get a moment to take this apart again, I guess there are 2 potential problems... too little friction between the centre wheel and the centre shaft, or too much friction between the centre shaft and the movement plates.

More to come...

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  • 2 weeks later...

Hopefully sorted now. Back together and on test..

Once stripped down, I measured the circlip and compared against this table https://www.rotorclip.com/cat_pdfs/be.pdf. It seemed to be within all the tolerances,  so not distorted, but at the lower end of the defined curvature, which is a 0.010” range.

There is some wear to the groove in the centre wheel, so I made o 0.005” shim and fitted it between the centre wheel and minute pinion. This increased the friction quite a bit, so now just have to wait and see how it keeps time...

 

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