# Regula Pendulum Length Determination

#### MuensterMann

##### Registered User
Is there a way to determine a Regula movement's pendulum length by design? That is, if you were handed an old Regula 25 with unmarked pendulum length and you needed to order a replacement, is there a way to tell from the movement that it is 19, 23 or 28 cm pendulum length?

#### Uhralt

NAWCC Member
You could do a full tooth count and determine the theoretical pendulum length. However, this assumes that all the pendulum mass is located at the center of the bob, which is not the case for the wooden pendulum of a cuckoo clock. but it would give you a ballpark. Easier is to make a temporary pendulum and find out what you need by experiment. You could also just order the 28 cm length and shorten as needed...

Uhralt

#### Willie X

##### Registered User
You can buy one or two pendulums you like. Then buy (or make) a few 14" sticks. This way you will have all the bases covered.

Probably more than 90% will have pendulums in the 7" to 8" range.

Willie X

#### MuensterMann

##### Registered User
I was thinking more about the replacement of the movement. Which movement do you order if the present one is a mess? Most are the 19 and 23 versions, but I had a 28 not too long ago. Sometimes having the original pendulum gives a good hint - but it is often not there or cannot be trusted.

#### Willie X

##### Registered User
I've seen a chart somewhere. I think all the escape wheels are the same and the 2nd wheels are different. Someone will probably help you out on that.

Counting the train, as Uhralt mentioned, is easy enough on a cuckoo and probably the best approach. The BPH is all you need. The actual pendulum length is not a concerm. Willie X

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#### JeffG

NAWCC Member
William Bilger's Cuckoo Clock Repair Manual has a the chart you're looking for. It says for the Regula 25 a first wheel tooth count of 64/36 (wheel/pinion) would be a 19, 58/36 is a 23, and a 70/36 would be a 28. The second wheel count is 77/6, 77/6, and 77/8 respectively.
-Jeff

#### MuensterMann

##### Registered User
Thanks Jeff! That is good information. I did notice that there are places selling the first wheel and distinguishing each by giving the pendulum length. But, they don't mention how many teeth - except the 19cm one having 64.

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