# Is there a formula?

#### tom427cid

##### Registered User
NAWCC Member
Hi all,
I am in the process of restoring/reconstructing a #47 Kroeber regulator. I have encountered an unusual problem. First the original movement is long gone. As near as I can tell the pendulum length is about 20" measured from the center arbor to the center of the bob. The plate configuration looks like a kitchen/parlor clock movement. I have not found any specific information regarding wheel and pinion counts. So, that being said, here's my problem. I can get an appropriately sized(length) pendulum to work, but the hands do not keep up. In other words it runs slow. Is there a formula that I can use to determine wheel count/beat rate so that the hands "keep up"? Thanks for any help.
tom
Will post photos of progress soon.

#### Vernon

##### Registered User
NAWCC Member
I believe that you multiply the teeth from each wheel starting with the hour wheel to the escape wheel. Then multiply each of the same wheels pinion teeth. Divide the wheel product by the pinion product then multiply by 2. This will be bph.

Last edited:

#### Vernon

##### Registered User
NAWCC Member
Have you thought about adding a little weight to the top of the bob?

#### Jim DuBois

##### Registered User
Gibbs Literary Award
NAWCC Member
You can use the calculator at Clockmakers Aid to complete reasonably accurate calculations on various gear trains and resultant pendulum lengths etc.

#### Bruce Alexander

##### Registered User
NAWCC Brass Member
Hi Tom,

Hope all is well with you and yours.

I'm not familiar with Jim's reference, but I'm going to check it out!

I do know that "Horology - The Index" (http://theindex.nawcc.org/) has a couple of online Calculators along with their underlying formulas.
I've found them to be helpful for Mainspring Dimensions. You can break out your own Calculator or plug values into their online forms for quick comparisons.

Here are some of the direct links to their Pendulum Length Calculators:

http://theindex.nawcc.org/CalcPendulumChange.php

http://theindex.nawcc.org/CalcPendulumLength.php

Hope that helps.

Take care.

Bruce

#### tom427cid

##### Registered User
NAWCC Member
Hi Bruce and all,
The issue that I seem to be encountering is that I can find a pendulum length and associated BPH. That is all well and good, however, I have not found any information for the specific movement how to aintain BPH. AND this is the kicker, have the hands maintain the correct speed(in other words tell time). Or is this one of those excercises where the SWAG(scientific wild a--ed guess) is necessary. It appears that the great wheel the first wheel and the center wheel are a known value as a ratio. It also appears that the second, third, and EW also are a value as a ratio although each is independent of the other because they are driven by the first wheel. Would they be the same or do I start plugging in numbers until I get the desired out come?
Thanks in advance for any input.
tom

#### Bruce Alexander

##### Registered User
NAWCC Brass Member
Hi Tom,

As I understand it, and I certainly may be wrong here, the ratios between the motion works and the gear train down to the power source are only really relevant in terms of winding cycles. The Wheel/Pinion Ratios between the Motion Works (One revolution of the Minute Hand per hour) and the Escapement will determine the necessary Beats Per Hour.

In his "Book 3, Escapements" I think that Steven Conover explains it well.
"Even with the correct type of pendulum, a clock sometimes gains or loses large amounts of time. Start your problem solving effort by determining the correct beats per hour (BPH) rate for the movement."

Do you know the correct BPH for your movement's Going Train?

Bruce

#### Dick C

##### Registered User
This may or may not be of some help as this is an original movement in a Kroeber 46 and I expect that the 47 had the same. I do not have this clock now.

#### Bruce Alexander

##### Registered User
NAWCC Brass Member
Tom,

If you have the Wheel and Pinion counts, you should be able to calculate the BPH and Pendulum Length.

If not, no problem. There's no need to take the movement apart again.

Try using the Calculate Pendulum Change calculator I provided a link to above.

Here it is again: http://theindex.nawcc.org/CalcPendulumChange.php

You just start by plugging in the current pendulum length and time-keeping error (either by hour or 24 hour period) and it produces the desired changes in BPH and associated Pendulum Length based on the error you're currently seeing.

If you decide to try it, please let us know if it works. I haven't personally used that calculator before. The Formula is given if you're so inclined to check the logic and math the calculator is based upon.

Regards,

Bruce

#### tom427cid

##### Registered User
NAWCC Member
This may or may not be of some help as this is an original movement in a Kroeber 46 and I expect that the 47 had the same. I do not have this clock now.

View attachment 614459
Hi Dick,
If memory serves the height of the #45 and the #46 is about 33" to38 or 40". The #47 is 48" and uses a longer pendulum, It is interesting to note that the #45 and the # 47 look almost identical,save the height.

#### tom427cid

##### Registered User
NAWCC Member
Tom,

If you have the Wheel and Pinion counts, you should be able to calculate the BPH and Pendulum Length.

If not, no problem. There's no need to take the movement apart again.

Try using the Calculate Pendulum Change calculator I provided a link to above.

Here it is again: http://theindex.nawcc.org/CalcPendulumChange.php

You just start by plugging in the current pendulum length and time-keeping error (either by hour or 24 hour period) and it produces the desired changes in BPH and associated Pendulum Length based on the error you're currently seeing.

If you decide to try it, please let us know if it works. I haven't personally used that calculator before. The Formula is given if you're so inclined to check the logic and math the calculator is based upon.

Regards,

Bruce
Hi Bruce,
The crux of the problem is that I have a Kroeber movement(of unknown origin) probably a Gingerbread or Parlor clock. About 9" center arbor to tip of the spike. I can as suggested lengthen the pendulum and I can achieve an approximate BPH for the new length 21" from center arbor to tip of the spike. However here's the issue the darn thing runs SLOW. In the process I have changed every wheel in the entire train at least once, have used Ansonia wheels(they are a direct interchange) for a different wheel count, I swear I have counted so many teeth I am starting to go cross eyed. I have counted teeth in movements of different manufacture. And trying to avoid custom cutting wheels it still runs slow. Worst about 15 minutes an hour to about 5 minutes in three hours. In this case any correction had little effect. Unfortunately I am looking for a solution going backwards-ain't this fun?
Thanks every one for your input, the fight continues.
tom

#### FDelGreco

##### Registered User
NAWCC Star Fellow
NAWCC Diamond Member
Tom:

I knew I had the formula written out from my F102 clock repair course that I took many years ago. It took me a while to find it:

Frank

#### Bruce Alexander

##### Registered User
NAWCC Brass Member
Okay, I'm lost. You have a Kroeber case, with a Kroeber Cousin Movement of unknown origin. You have swapped in Ansonia gears (Did Ansonia sell movements to Kroeber?), and your movement is still running slow. I have to assume that you've adjusted the pendulum to its maximum fast setting. So we can assume that the native case to your movement is much shorter than than the one you're working with.

If the Pendulum adjustments give no joy, you might be looking at the need to go with a different Escape Wheel/Escapement set up. Now *that* , if necessary, will be fun.

Looks like I've done all the damage I can do here.

Good luck with it Tom.

Bruce

#### tom427cid

##### Registered User
NAWCC Member
Ok guys,
Enough fun for one afternoon. This has been an almost impossible problem to wrap one's head around. I suspect that somewhere there might be a formula to work with a known pendulum length and BPH and from that determine what count is necessary to power the motion works (both hr and min hand) I think that the ratio to the escapement and the ratio to the motion works need to be the same. In the end after comparing multiple movements and looking for information regarding train counts I think I finally stumbled upon the answer. One of the things I noticed when I was swapping wheels was I had a couple of 40 tooth wheels that were slightly less in diameter. As it turned out these wound up being used with a 9 leaf pinion on the EW. Once I got to this point a couple of EW changes (tooth count) and things settled down and worked as expected. I have added a couple of photos of the case in process and the movement now running and keeping time.
Thank all who shared ideas to sort this mess out. The pendulum assy was used on the #45 but since I had to fabricate one any way I made it fit the #47.
tom

Bruce Alexander

#### Bruce Alexander

##### Registered User
NAWCC Brass Member
Glad you got it all sorted out Tom. If you have a moment or two, please share some photos of your completed project. Sounds like you kept a couple of basket cases out of the landfill.

#### tom427cid

##### Registered User
NAWCC Member
Hi all,
While the clock is not yet in its completed state, it is running, keeping time, and almost done. I have enclosed a couple of photos. The lower back panel is ready to install. I'm just waiting for a touch up to dry. Also a photo of how I spaced the movement to fit the dial. Oh, and BTW if any one has a white Kroeber beat scale plate the would part with, let me know Enjoy
tom

As a post script, to clarify the problem/formula, I think that (supposition) the final gear ratio of both the escapement and the motion works need to be the same or nearly so. The reason for this is that at the first wheel(not the great wheel) the power splits and goes in two directions. This would indicate that those two ratios would want to be the same. Since I was limiting myself to a specific pendulum length. And yes, the beat scale is mounted in original holes. Also note the beautiful Blistered Cherry behind the beat scale. It is a solid piece not veneer.

Bruce Alexander
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