Torsion clock pendulum project

[EricB]

I like that adjustment device.

The person who purchased the patents for torsion clocks back in 1883 was a marine engineer. He adapted the adjusting screw idea to lifeboat davits and received a patent for that too.

Eric

[Zephyrin]

very nice work on this clock, fascinating mechanism !
In order for the spacing between the two discs to be dead symmetrical,
I wonder if the two opposing threads need to be exactly opposite each other, i.e., start at exactly the same distance on the axle. The same applies to the nuts on the disc supports; otherwise, it seems to me that there could be a maximum definite error of half a thread.

[EricB]

very nice work on this clock, fascinating mechanism !
In order for the spacing between the two discs to be dead symmetrical,
I wonder if the two opposing threads need to be exactly opposite each other, i.e., start at exactly the same distance on the axle. The same applies to the nuts on the disc supports; otherwise, it seems to me that there could be a maximum definite error of half a thread.

Thanks for the comment.

I like a good thought puzzle.

I'm thinking the only important dimension for the threads on each end of the adjusting screw is pitch. In this application, so long as the parts move in opposite directions by equal distance the angular errors in the threaded parts are irrelevant. In operation the pendulum oscillates at only 8 beats (cycles) per minute. Dead symmetrical spacing between the two disks isn't much of an issue at that rate because the variation in positions of their masses by a few threads isn't enough to throw the system out of balance.

Eric

[bent]

A case of perfection being the enemy of good enough?

edit to add:  If it were really important, one could an adjustment screw at the two mass attachment points for the ends of the differential threads, so you could set the spacing as close to equal about the rotation axis as possible.  Then make the differential screws run through a bimetallic rod, like some pendulums use, for temperature compensation...

Sorry, my mind sometimes take the journey down the rabbit hole to ridiculous extremes.

[EricB]

Sorry, my mind sometimes take the journey down the rabbit hole to ridiculous extremes.

Oh, I've been down that rabbit hole a time or two. At one point I was building a test fixture to see how different factors affected the pendulum's performance. What I found was the tiny rare earth magnet I used with the hall sensor to see the rotation was able to induce eddy currents into my aluminum fixture and stop the clock. One day I will start over with a wood frame and no metal near the magnet. One day...

It was fun to try though.

Eric