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Gilbert Parisian Pendulum Problem

ssohner

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Dec 19, 2015
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After cleaning and reassembling my Gilbert Parisian clock, the pendulum did not seem to be able to change the rate even though the pointer was moving when the rating knob was turned. After reading a thread started by imreman in 2012 I tried balancing it to see if turning the knob would change the balance point. I concluded that the lead bob inside was not moving up or down.

I finally got the courage to open the case and discovered that the female threads in the lead bob are stripped. I can’t separate the threaded rod (inside the case) from the rating knob on the outside. I tried heat and a couple different penetrating fluids with no luck. The threaded rod does not seem to be any standard thread. It measures 32 threads per inch and major dia. 0.099 inch (about 2.52 mm).

Any ideas how I can restore this pendulum’s functionality?


DSC_0773.JPG DSC_0774.JPG DSC_0776.JPG
 

bruce linde

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if the threads on the rod are ok, lead is soft... couldn’t you also just whack on the end of the bob a bit to close up the hole and then re-tap?

you could also cut off the rod and replace w something slightly thicker,,, and re-tap the holes in the bob and knob.

(p.s.: don’t quote me... hobbyist, not professional!)
 

R. Croswell

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I've never had to do this repair but along the line of what Bruce said, perhaps put some grease on the thread and with the rod in the lead use a flat punch to compress the lead around the threaded rod to reform the threads?

RC
 

bruce linde

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I've never had to do this repair but along the line of what Bruce said, perhaps put some grease on the thread and with the rod in the lead use a flat punch to compress the lead around the threaded rod to reform the threads?RC

clever... even though i’ve done similar w crutch forks (for example) i didn’t even think of it for this... doh!
 

shutterbug

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I wonder if the rating unit screws out of the case? If you can get that out, you should be able to try the suggestions above.
 

ssohner

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Thanks for the suggestions. I used my lathe to turn down a lead fishing sinker to fit the hole, chamfered the top and bottom edges of the hole and peened over the insert in hopes that I could use the rod to rethread the insert. But it was awkward working with the threaded rod trapped in the case and ultimately unsuccessful. I was hoping someone might know how the knob is attached or suggest how to removed it.
 

Arlington_VA

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after looking at this for a few minutes I offer:
1. your threaded rod is a #3 gauge diameter. This size screw usually has 48 not 32 TPI.
2. Because of #1, you are not very likely going to be able to find any tap to re-tap the lead and finding or making a nut that could be fitted into the lead is a challenge.
3. The aforementioned "hit it with a punch" method would make it as good as new, which, as you can see, was not all that great. Looking at your pic, it looks like someone ran it all the way up, then gave it a few extra gentle twists and stripped it out. Lead is just too soft to thread an adjustable bolt that gets exercised through
4. A suggested "improved" repair method would be, to replace the shaft with a standard size (either metric or English), then fit a nut to the lead and re-tap the brass nut / star wheel.
 

ssohner

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Still struggling with how to separate the threaded rod, the gear, and the adjusting knob from the case without doing irreparable harm.
 

wcampbell

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I have restored this type of pendulum before. You do not want to replace the threaded rod. The thread pitch in relation to the dial indicator on the front of the movement is designed to give you a fine adjustment 0-95 changing the thread will also cause the indicator to beyond its range. The reason why the threads strip in these pendulums is because the weight is bottomed out making contact with the brass case as they keep trying to thread it in the same direction. All you need to do is compress the lead enough to slightly distort the led bore were the rod was threaded into. then a gently thread the rod back into the lead weight. the threaded rod will act as a tap creating its own threads. once you have created the new threads, thread the weight to the bottom move the little indicator so that it is pointing to the zero then reseat the weight to engage the indicator gage. thread the weight back up so that it is in the center and thats it. resemble I have attached some pictures for you to see before and after.

1.jpg 2.jpg 3.jpg 4.jpg 5.jpg 6.jpg 7.jpg 8.jpg
 
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ssohner

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WCampbell,

Thanks to you, SUCCESS! Great pictures and great explanation It was a bit of a challenge getting the threads started. The thread is left hand, and there is very little clearance between the end of the rod and the arbor for the pointer. But some fiddling and judicious use of force got the job done.

Thanks again for your help.

Steve Sohner