Hermle pendulum length?

[rison123]

Have Howard miller schoolhouse clock with a Hermele movement. Their tech department told me the specs were 43cm for the pendulum drop. Where is that measurement applied? From the release at the top of the movement or from the bottom of the suspension rod where the pendulum hooks on? I have the data, just don't know how to apply it

Tom H

 

[Tinker Dwight]

Re: Hermele pendulum length?

I think most German are from the suspension
post to the bottom of the bob. I believe some
may be from the center shaft to the bottom of the bob.
I have never heard them use the length from
the hanger down but then I don't pay that much
attention to the numbers.
If you know the beat rate I can tell you what it should
be.
Tinker Dwight

 

[Dave Diel]

Re: Hermele pendulum length?

Rison,

I happen to have a Hermle 1051-030 43cm on the test stand at the moment. From the center of the post that holds the suspension spring to the end of the pendulum rating screw threads is 40.6cm. That's not a mistake, I double checked. Since the clock cares about the location of the center of mass of the pendulum, not the actual length, the manufacturer's rating is only a guide. For your reference, this particular clock has a 3" diameter metal bob on the bottom of the pendulum.

 

[rison123]

Re: Hermele pendulum length?

Thanks guys that is really helpful info. Just what I needed to move forward!

Tom H

 

[Willie X]

Best to not pay to much attention to the measurements. Just find a Hermle pendulum that you like and adjust it up or down until it keeps time. A good place to start is with the pendulum below where you think it would have been. You can usually see scratch marks on the glass, or back of the case, where the old pendulum bounced around. If the pendulum shows, start with the pendulum at or near the bottom of the view area. Shorten as necessary, never removing more than 1/2 the adjustment range at a time.

Willie X