The mechanical clock pendulum length
The mechanical clock pendulum length
A pendulum clock without a pendulum is a shame for sure. Hence, getting the mechanical clock pendulum length correct does take some diving into the clock world.
If there is no idea what pendulum it would take, this is a basic guide. Of course, this is a basic guide to narrow it down to the best pendulum for the clock. This will cover most situations, without special equipment to figure out the length.
The movement CM or PL stamp
On the back plate of the clock movement usually, there are some numbers and or letters for identification. Likewise, there may be an indication of how long the pendulum should be in the mix of these numbers.
It may say CM or PL and this stands for centimeter or pendulum length. Subsequently, this would be the length where it should keep approximate time. Generally, there are a few different ways to measure this depending on the country of origin.
Mechanical Clock Pendulum Length for German made movements
Most mechanical German made clock movements are easy to figure out the pendulum length. In essence, the numbers will let us know or the stamp will clearly state the CM or PL number. If it is German, keep in mind the CM length is not the actual pendulum length.
Altogether, German units measure this length from the top of the clock movement, and this includes the three components of the pendulum all in one length, in centimeters.
This length will include the pendulum itself, the leader that it hooks to, and the suspension spring on the top that the leader hooks on to, all in one CM measurement. To clarify, CM stands for centimeter and PL stands for pendulum length.
If no stamp try to convert
When there is no stamp with the CM on the movement, there are some additional steps that need to happen. You will need to cross reference The numbers on the back plate to the pendulum length that you need. The first step is to identify the manufacturer of the clock movement by using the movement numbers.
The movement numbers indicate who the actually manufacturer is of the movement. Various clock retailers may have a stamp of their name on it, but the numbers are always true to the manufacturer.
Converting numbers to CM length
Moreover, some movements do not have an indication of the pendulum length on the back plate. The unit will have a number that would need to be found on this website first to find out what the correct CM length is for it.
Conversion number example
Generally speaking, let's say that the movement has no CM stamp on the movement and only shows the Urgos number UW32319.
Go to the identification page to look at the movement number examples. In this example, we see that it is a Urgos. Now it is possible to go to the Urgos page and find the number to see what the pendulum length is.
In this example, the pendulum length would be 80cm, representing the full length with the size including the size of the bob.
German grandfather movements
Almost all grandfather clock movements are going to be German if made after 1950. The first thing we need to do is get the numbers off of the back plate of the movement. This is the only way, and we can't cheat by looking at the paperwork or clock case.
It has to come right off the back of the clockworks. The manual and the sticker on the case is of no use to get the pendulum.
American clocks
The American mechanical clock movement manufacturers refer to the pendulum length as a "drop". The drop is the length of the pendulum from the hand shaft all the way down to the bottom of the pendulum rating nut threads.
It is a different way of measuring the pendulum length then the German made way. The basis for both ways are on the smallest bob diameter. If the bob is larger or heavier, the length would be longer than what the stamp indicates.
No luck
If everything fails for one reason or another, the best chance for a pendulum is the wood stick style. This is the only style of pendulum that can be easily modified because it can be cut down.
These types of clocks are usually antiques, or of Asian origin, and information such as pendulum length is simply not available. Sometimes it takes a good guess on where the manufacturer meant to have the bob sit. To do it this way, you only need a pendulum with a stick that is way too long to begin with.
Chop it, try it, chop it, try it. Each time slowly cut an inch and half off of the sticks length and hang it back on. It will only take a couple of times, and if starting way too long it can always go shorter.
Clock makers method for Mechanical Clock Pendulum Lengths
There is another way, which is known as setting the beat rate. This is a more complex way and is usually just done by clock makers. It involves a beat detecting device that counts out the beats per hour, or the beats per minute. To do this, first figure out what the beat rate is suppose to be for that particular movement.
Then keep adjusting the pendulum length until it keeps time. There are cell phone apps out there these days that will tell the beat rate and the cell phone will listen and say if the clock will keep time with that pendulum. Go longer or shorter until the phone says the beat rate is set.
Contacting us for help with Mechanical Clock Pendulum Lengths
Please email the movement numbers from the back plate, and explain what part you need. The email address to send this information to is [email protected]. We always welcome pictures but they are not a necessity. If emailing pictures please include the back side of the clock movement where the markings are.
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I have a Hermle clock that I need to replace the pendulum and bob. I know the pendulum needs to be 94cm but I am not sure how to determine the bob size. I read one place that you measure the inside of the clock waist and subtract 4 inches. My clock waist is 9 1/2″. Based on this I would need a 5 1/2″ bob. Is that right or is there a better formula?
Here are the numbers on the movement. 81 Hermle 451-050H 94cm/66. (what does the 66 mean)? Thanks for any help you can offer.
Please order either a wood stick pendulum, or a metal lyre pendulum from the below links. The bob diameter is to be 4inches less than the interior width of the clock case, or less. This way it has some room to swing.
Please order a pendulum for a Hermle 94cm movement by clicking one of the below links
For a wood stick style pendulum, here is the link
https://www.clockworks.com/product/wood-stick-pendulum-for-hermle-clocks
Lyre pendulums are at this link
https://www.clockworks.com/product/hermle-lyre-pendulum
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
Would be there be any problem in ordering the 4.5 inch instead of the 5.5 inch bob? It is mainly a cost issue, but I want to make sure the clock works properly.
Will work the same either way
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
I have a Herman Miller grandfather clock that I bought without a pendulum. The works are German and have 93cm stamped on the plate. I now know that I have to measure this distance from the top of the suspension spring. But where is the end of the 93cm? Is it at the bottom of the bob or its middle or the rod itself or some other distance?
93cm is from the top of the movement, down to the very bottom of the rating nut threads, with the lightest possible pendulum and the smallest bob diameter.
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
I will put up the other working parts to clock No 1 sorry not a very good photo.
Kind regards Mr Simon carter
Whatever it is it is required in parts for that clock movement is no longer made or available.
Something custom would be made or modification to that what does exist. Or we would need to match it up to one of our own parts units.
If you would like to send it in for restoration, we could figure it all out here, along with the restoration process.
Are you interested in sending the movement only?
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
Good afternoon Sir/madam, I have two clocks with no Pendulums I have the numbers in which there is no PL or CM. Can you please help with pendulums and the weight required please? If you can help I would be very grateful I would like of sent more photos but would only let me send one if you would like the rest ie the clock faces of both clocks and the other clock workings please send me an e-mail and I return by attachments.
Clock 1 (2373 48)
Clock 2 (3209 46)
Thank you for any help Kind regards Mr Simon Carter
I replaced the Regula 34 movement in my cuckoo clock with the exact movement. The original pendulum (19.5 cm) that came with the clock is not long enough to adjust the time correctly. The clock runs fast. How is the best way to correct the problem. Would additional weight on the pendulum work or a longer pendulum?
Thank you
Robert
No to the added weight
Cuckoo pendulum lengths such as 19.5 is from the TOP of the movement and down. If pendulum is 19.5cm by itself it will need a movement with a longer drop
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
Hi,
I’m trying to find the correct movement for an Ansonia Ledger no. 1. The clock i have is just the box and dial, and I need a time only movement. I think it would be one of two that I’ve found online. One is stamped with an “A” and the other is stamped with a “12”. I think the number/letter may tell if it is a long drop or short drop but I’m really not sure. Either would work, but a long drop would look much better. Any information would be appreciated. Thank you!
Not available new. Short drop is usually 13 inches from the hand shaft down, long drop is usually 18 inches.
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
Hi, I am trying to find a pendulum for a smiths grandaughter clock. stamped on the back of the movement is the smiths logo and K6P 575. Your help would be much appreciated. Kind regards Brian
Whatever it is it is required in parts for that clock movement is no longer made or available.
Something custom would be made or modification to that what does exist. Or we would need to match it up to one of our own parts units.
If you would like to send it in for restoration, we could figure it all out here, along with the restoration process.
Are you interested in sending the movement only? Only then we can match up a pendulum
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
any idea on pendulum length of a Colonial Clock Company movement 64
Hi,
What are the numbers off of the back plate of the clock movement itself? If it is hard to get to, usually you can stick a cell phone up behind the movement and get a picture of the numbers. Or through the side access panel if there is one.
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
The movement says Jauch 96
It would be between 32 inch and 36 inch tip to tip when off the clock, depending on the weight of the pendulum and how wide the bob is.
Please order a pendulum for a Hermle 94 cm movement from this link
https://www.clockworks.com/product/wood-stick-pendulum-for-hermle-clocks
Please order a top hook for a Jauch movement to go on above pendulum from this link
https://www.clockworks.com/product/jauch-clock-pendulum-top-hook
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
Can I shorten the length of a pendulum and still keep the correct time
No, not with out swapping the movement with a different CM stamp
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
I need time chain ratchet wheel for cuckoo clock German made .It is Regula 25-v ,64 teeth (ccw) if you see the brass wheel
Out of stock, please check back in 6 months
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
I need to know the size of the pendulon for a Barkwick clock/howard miller model 475884
Hi,
For that we need the movement numbers off of the back plate of the movement itself please. Right off of the brass back plate
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
I was trying to find a Pendulum for a Howard Miller 625-409 clock
What are the numbers stamped on the back plate of the brass on the movement itself ?
James Stoudenmire
30yr Clockmaker
Author of Clockworks.com
hi I have an 1939 haller grandmother clock that was a gift to my grandmother and grandfather on their wedding day it does not have a pendulum and im wondering if you could help
Hi,
Whatever it is it is required in parts for that clock movement is no longer made or available.
Something custom would be made or modification to that what does exist. Or we would need to match it up to one of our own parts units.
If you would like to send it in for restoration, we could figure it all out here, along with the restoration process.
Are you interested in sending the movement only?
James
Hello, I need a pendulum for a movement I obtained. It is a Hermle 1161-853 but it was made for Sligh and does not have the CM stamped on it. It actually says Made in the USA 8710 A-415-015 but for sure it is a Hermle 1161-853 I also need weights for it, but not sure the specs for that either…
I do not know how long that pendulum is to be.
ST number conversions do not provide this information in all instances, such as the number provided.
The weights are easy =
That clock takes 1 weight at 7.7LBS and two weights at 9.9LBS from this link if the pendulum bob diameter is 8 1/2 inches wide or more
https://www.clockworks.com/clock-parts/clock-weights.html
Or it takes 2 weights at 7.7LBS and 1 weight at 9.9LBS from this link if the pendulum bob is less than 8 1/2 inches wide
https://www.clockworks.com/clock-parts/clock-weights.html
The heaviest weight would go on your right as you face the clock.
The lightest weight will go on your left as you face the clock.
The middle is light or heavy depending on the bob diameter.
(The larger bob diameters require more weight in the center.)
James
Hello,
I have a Sligh clock, model 2071-850. I am trying to find a pendulum for it. The stamp in the back says 114cm/60.
Could you help me find the proper pendulum to order?
Thank you
Please order the 1171-850 114cm from this link
https://www.clockworks.com/product/new-1171-850-clock-movement-by-hermle
It is the same unit for replacement purposes
James
I have a Franze Hermle 151-080 Clock Movement. I need to replace the pendulum. According to the stamp on the movement, it is a 21cm length pendulum. Can you provide a replacement? It is a brass pendulum.
Hi
Please order a brass rod pendulum for a Hermle 21cm clock movement, from this link https://www.clockworks.com/product/hermle-brass-rod-clock-pendulum
James
Thank you !
I have a 1906 Ingraham Landua wall clock with a Gilbert Clock company mechanism. Can you help determine the correct pendulum and bob? There are no markings on the front or back of the mechanism.
Dan
Hi
Can you email some pics of this clock to clockworks@clockworks.com
Ill need to see this one to get an idea of what pendulum should go with it
James