# GRIVOLAS PENDULUM

Discussion in '400-Day & Atmos' started by jkfabulos, Jan 26, 2019.

1. ### jkfabulos Registered User NAWCC Member

Aug 21, 2001
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I am restoring a Grivolas pendulum.
It has lead weights attached to the base with screws which I assume are for the course speed adjustment and the fine adjustment threaded unit with small brass weights. My question is are these small rectangular brass weights correct?

2. ### KurtinSA Registered User NAWCC Member

Nov 24, 2014
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#2
3. ### jkfabulos Registered User NAWCC Member

Aug 21, 2001
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Thanks Kurt.
That answers the question. The parts are correct.
However, the blocks should possibly be stacked not spaced which would more closely equal the thicker weights shown on this example,
This would mean moving more mass with each adjustment and would necessarily cause very fine adjustments to be more difficult.
I will try it both ways and see what works the best.
Jim

4. ### KurtinSA Registered User NAWCC Member

Nov 24, 2014
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#4
On those small weights on either side, I would not jamb them together but rather have a slight space between them. If they're too tight, the screw could bind as it tries to turn evenly in both of the weights. Whether they're located close or far apart might not make much difference. The center of gravity of the two weights is likely what contributes to the change in the inertia...at least that seems the case to me at first glance. I'm not about to compute the moment of inertia of each small piece and combine them and then compare that to two weights right next to each other! Maybe your testing will shed some light!!

Kurt

5. ### John Hubby Principal Administrator Staff MemberNAWCC Star FellowNAWCC Life Member

Sep 7, 2000
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Last edited: Jan 26, 2019
The weights are correct. Most of these I take apart have the two weights on each end of the adjusting rod set very close to each other but not touching, I think for the reason Kurt surmised.

I notice the pendulum serial number is 2017. Reviewing my database there is a German Grivolas with a JUF movement and JUF disc pendulum that has this same serial number, which was assigned by Grivolas as a separate and independent series of numbers for their German movement clocks. However, if you have a clock with a Grivolas movement that goes with the pendulum it's not in my database, would like to add if you could forward me the photos or post them here.

6. ### jkfabulos Registered User NAWCC Member

Aug 21, 2001
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I am restoring the clock and will post photos when completed. The movement is also #2017.