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# Thread: Make a Pendulum Replacement?

1. ## Make a Pendulum Replacement?

I found this clock in a local shop but it has no Pendulum.
Can anyone identify the clock and/or movement please?
Can anyone help me make a replacement Pendulum please?
Andrew.

2. ## Re: Make a Pendulum Replacement?

Moving to clock repair for better coverage.

3. ## Re: Make a Pendulum Replacement? (By: leeinv66)

I think the pendulum specs are stamped on the back plate. Give us a closer pic of the stampings.

4. ## Re: Make a Pendulum Replacement? (By: fixit9660)

Look up German box clocks. That will show you what the clock that once held your movement/dial once looked like. There is not an exact answer for the length. The length will have to be determined by experiment.
Willie X

5. ## Re: Make a Pendulum Replacement? (By: Willie X)

The movement says 42 cm

6. ## Re: Make a Pendulum Replacement? (By: shutterbug)

I think it would be 42x10x.03937= 16.5354 inches This is a good place to start. Bob would be about 4 1/2 inches. approxiately

7. ## Re: Make a Pendulum Replacement? (By: R&A)

Based on the beat, it calculates to a 12 inch pendulum
but I'd go with the 16.5 for the starting length.
Do note that is usually from the top of the post for the suspension
spring to the rating nut end.
The calculated is from about the center of the suspension spring
to the center of the bob for a simple pendulum. It is longer if
the pendulum is a lyre type.
When buying a pendulum you need subtract the end of the leader
to the top of post.
Always buy a slightly longer one. It is easier to remove some
Tinker Dwight

8. ## Re: Make a Pendulum Replacement? (By: Tinker Dwight)

Tinker - for my continuing education from your excellent posts - can you explain - "based on the beat, it calculates to a 12 inch pendulum." That implies about 6240 BPH. Which is related to the 42 / 108. The 108 is beats per minute which would mean 6240 BPH which matches the 12 inch pendulum you suggest. But the rest of the explanation puzzles me a bit. You suggest going all the way to 16.5 to start with and I didn't understand the "subtract the end of the leader to the top of post". ( I am trying to construct a pendulum for a movement that came with no pendulum or suspension spring and has no info stamped on the plate, but also calculates to 6240 bph - covered in another post)
thanks

Originally Posted by Tinker Dwight
Based on the beat, it calculates to a 12 inch pendulum
but I'd go with the 16.5 for the starting length.
Do note that is usually from the top of the post for the suspension
spring to the rating nut end.
The calculated is from about the center of the suspension spring
to the center of the bob for a simple pendulum. It is longer if
the pendulum is a lyre type.
When buying a pendulum you need subtract the end of the leader
to the top of post.
Always buy a slightly longer one. It is easier to remove some
Tinker Dwight

9. ## Re: Make a Pendulum Replacement? (By: fixit9660)

From working on these type clocks, I would guess that the pendulum (as a stand alone part) will be a good bit shorter than 16 1/2". However that would be a good place to start the already mentioned experimentation.
If you have the case, I don't think I've ever seen one where the pendulum went below the bottom of the door glass.
Most have a simple disk pendulum about 3 1/2" to
4 1/2" in diameter, with a 3/4" oval wood stick. A length of wire with a 2 ounce lead fishing weight will work just as well as any pendulum (temporarly).
Willie X

10. ## Re: Make a Pendulum Replacement? (By: Willie X)

It's easy to shorten a pendulum. Not so easy to lengthen one

11. ## Re: Make a Pendulum Replacement? (By: shutterbug)

Yes - I understand - am puzzling over what needs to be subtracted. On mine, I think I need the usual little rectangular, two spring, two block suspension spring that is about an inch long - not unlike the one in the photo here. I guess I will start with about 16 and work it shorter.

Originally Posted by shutterbug
It's easy to shorten a pendulum. Not so easy to lengthen one

12. ## Re: Make a Pendulum Replacement?

If the movement is stamped "47", why would the actual length be less? We still haven't seen a clear picture of the stampings, and haven't heard back from the OP.

13. ## Re: Make a Pendulum Replacement? (By: bangster)

Here is a blow up of the 42/108 stampings

Originally Posted by bangster
If the movement is stamped "47", why would the actual length be less? We still haven't seen a clear picture of the stampings, and haven't heard back from the OP.

14. ## Re: Make a Pendulum Replacement? (By: THTanner)

When you buy a pendulum from a supplier, They have no idea
how long the suspension spring is or how long the leader is
They sell it by the length of the part they have. Rod, bob and adjuster.
The number on the clock
is for case construction. Different manufactures use different locations
on the movement for the top of this measurement. It could be the center
shaft or even the bottom of the movement. It would be specified
with the movement drawing, usually sent with the movement from
the movement manufacture to the case manufacture.
It is more useful to know the rate of the pendulum. At least then, one can
calculate the simple pendulum length. The beat number is usually quite
close that is stamped on the back of the clock (often rounded to the nearest
hole number ).
Lyre pendulums have a different weight distribution and without knowing the
position and mass of each component it is difficult to predict what the
desired size should be.
I use inches because I can remember 39.1 inches better than the metric length
of something close to a meter.
( 60/108 )^2 = x/39.1
x = 12.07 inches.
To buy a new pendulum you take the estimated total length and subtract
the parts you know. That would be the leader and suspension spring.
Tinker Dwight

15. ## Re: Make a Pendulum Replacement? (By: fixit9660)

What Tink said, plus add on a few inches for good measure.
As stated many times in the past, the number stamped on the clock plate doesn't mean that much.
Now, if you have the engineering drawing that shows a stick pendulum and where the actual measurements are taken, that can be helpful. But you would still be making a big mistake to assume your length would be within an inch or so of the published drawings, using the same size and style pendulum bob.
Willie X

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