Four Dualtetrahedron pendulum wobbles..?

MuseChaser

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Feb 5, 2019
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One of my recent and beginner successes is a Henn mini with a four ball pendulum... discussed in another recent thread. It's running very well and keeping good time, although as others have noted it's pretty fussy with being setup absolutely correctly. Unlike my other three currently workign 400-day clocks, though, the pendulum wobbles back and forth like a drunken sailor. At first, I thought it might be where I had it situated and that it was reacting to folks walking by, but I put another mini (Schatz) right next to it and that one is rock steady. Pulled the Henn pendulum and noted that two of the four weight arms were binding, so I fixed that so that all four arms freely moved with then time adjustment dial was turned, thinking that it was out of balance, but that didn't solve it although it's still running well.

Is there anything that causes that wobble OTHER than an out of balance pendulum? Other than what I did, freeing up those stuck arms, how would I go about ensuring the pendulum IS balanced? I checked the spring to make sure it was centered in the bottom block directly above the pin, and it looks as if it is... anything else?

Thanks for any help.. I'm getting seasick watching this thing for two days...
 

Wayne A

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Sep 24, 2019
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Check where the suspension spring is clamped in the lower block, it needs to be in the center of the pendulums axis of rotation or your going to get wobble. Also the spring should be strait in the bock and not off at an angle. If all thats good check that the pendulum arms are at the same level and not bent.
 
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MuseChaser

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Thanks, Wayne. Checked all of those things and all looked good, although this is a miniature clock and I had to use a full-sized bottom block. It hangs true, but it'd probably be better to use a correct block. Does it matter more than cosmetically, as long as it fits into the pendulum and is centered on the rotation and vertical spring axis?

Solved the issue this morning, after having, for my first time, completely disassembled a pendulum (from a different clock successfully rebuilt yesterday) to polish, and saw exactly how they work. On a hunch, I took out the lead weights on this misbehaving wobbly clock this am and sure enough, two weighed 34 grams, and two weighed 33 grams. They were placed so that the like-weighing weights were side by side instead of across from each other. One of the little rubber washers that keeps things from rattling had been placed under the weight housing instead of on top of the lead weight itself inside the top housing, too, so I know someone had been in there previously and messed with it. I put it all back together with the matching pairs across from each other and the rubber gasket washers in the correct spot.

NO WOBBLE! :)
 

Wayne A

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Well a couple of grams sure will make a difference! I've ran across the paired weights before but they were in the proper spots. Definately want to be sure to stop the weights from wiggling about in the housings or your going to have a tough time regulating it.

The larger block will work and as you say its cosmetic.
 

MuseChaser

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Tight fitting blocks (top and bottom) can lead to reduced extra "motion" with the pendulum.

Kurt
Kurt, thanks for chiming in... no pun intended (maybe... hehehehe). Just to clarify, do you mean that tight-fitting blocks are desirable in order to reduce wobble, or that they are not because they may reduce rotation? I thought I had read in the Terwilliger book and maybe elsewhere that the top block, especially, needed to be loose enough to pivot freely on the affixing screw. Not arguing... I'm a total beginner and just trying to learn. Thanks!
 

KurtinSA

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Certainly the top block needs to be able self center on the pin, but I don't think there should be extra space so that the blocks wallow as the pendulum and suspension spring turns.

Kurt
 
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Wayne A

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On sloppy saddle to block clocks I'll use a little brass shim stock thats bent a little to at as a spring and shim to stop any play in the block.
 

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