Pendulum micro-adjuster

[GregS]

My seconds beating pendulum has a micro adjuster roughly 12 inches from the pendulum hook. This adjuster just does not seem to work the way I envisioned it. So, I am thinking of moving it from the hook end to a few inches above the pendulum bob.
What do all of you think of this idea? Do you have alternate ideas I should consider?
Thank you for your help,
Greg

 

[John MacArthur]

What is it not doing? Conventional wisdom has the weight trays for minute adjustment at midway between suspension and c.g. of the bob. I'm not sure why this would be different. What material is the rod and compensation?
Johnny

 

[John MacArthur]

OK, now I looked at your pendulum thread from earlier this year. I am somewhat confused as to how it is expected to work. In that thread you say " Section A grows downward, section B grows upward", however section B has a lot more mass expanding upward than section A has expanding downward, even though both have the same vertical dimension. This will for a given temp change move the c.g. of those two sections substantially upward. The third section will of course add more to the compensation. My guess is that your bob is between somewhat and moderately over-compensated, which could be contributing to your rating anomalies.

In my Strasser type bob (https://mb.nawcc.org/threads/6-regulator-with-mods.185536/#post-1558001) I was very careful to set the top of the compensation sleeve exactly in the middle of the mid-support of the two cylinders. However, the length I calculated for the compensation sleeve was for mild steel, and after I and made and installed it out of 12L14 I discovered that that alloy has a moderately different c.e. than mild steel, and there was some minor error in the compensation. Live and learn....do it better next time.

Johnny