# 9ft Long Pendelum on Tower Clock

#### ClockMogul

##### Registered User
Can someone explain to me what the purpose of a 9ft long pendelum on a tower clock?

Thanks, Jerry

#### doug sinclair

##### Registered User
About the only comment I could make is that not ALL tower clocks have 9-foot pendulums. Typically, a 9-foot pendulum would be on a clock that "ticks" 40 times in one minute. For example, the one in London that is commonly called "Big Ben" ticks once every TWO seconds, or 30 beats per minute if I recall correctly. The pendulum shaft on that one is likely close to 20 feet long. A clock that ticks 60 beats per minute would have a pendulum about 38 to 40 inches long, or thereabouts. Considering the proportions of a typical tower clock (some are huge), the components are also large, and the slower beat (longer pendulum shaft) is simply propotional to the size of the components. Look at the comparative length of the pendulum on a typical tall clock relative to the size of the movement. Then, look at the comparative length of the pendulum on a typical tower clock relative to the size of the movement. I think you will see a close approximaation in relative size. Hence the slower beat.

#### Les harland

##### Registered User
My local Church St Mary's Welwyn Hertfordshire UK has a twelve foot pendulum and ticks every two seconds

#### ClockMogul

##### Registered User
thanks doug for the explanation. So if i was to set a tower clock in my dining room , how much is the swing of the pendelum from left to right about. Would you think 12 inch wide cut would do it. I am planning on cutting hole in dinnng room floor and let the pendelum swing free in my basement from up above.

#### David S

##### Registered User
NAWCC Member
you may also want to check the floor loading to support the weight.

#### doug sinclair

##### Registered User
With the tower clock sitting on the floor through which you plan on cutting the hole, the amplitude of the pendulum shaft at the floor level will be a lot less than the amplitude of the pendulum at the bottom end. I think you won't be needing a foot. Hopefully the opening will be small enough that the family chihuahua won't fall through!

#### ClockMogul

##### Registered User
you may also want to check the floor loading to support the weight.
I have no problem with the load at all...Dont weigh more then 600lbs or so....

#### ClockMogul

##### Registered User
With the tower clock sitting on the floor through which you plan on cutting the hole, the amplitude of the pendulum shaft at the floor level will be a lot less than the amplitude of the pendulum at the bottom end. I think you won't be needing a foot. Hopefully the opening will be small enough that the family chihuahua won't fall through!
Does the length give it more torque having a 9ft pendelum..?

#### doug sinclair

##### Registered User
Different nine foot pendulum shafts may have pendulum weights of vastly different size. I look after two tower clocks. One is a Howard time and strike with a pendulum 9-feet in length, and the cast iron bob on that one weighs 25 pounds by actual measure. The other one is a Seth Thomas 16-A time and strike. That one has a bronze bob that weighs (my estimate) about 125 pounds! Obviously, the heavier weight requires much greater effort to cause to stop than would be the case with the lighter pendulum. Your next question might well be, " why such weight difference between the two clocks?" Maybe someone else has an answer to that one, but I don't.

#### FDelGreco

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

What are you going to do about weight drop? Are you going to cut holes in the floor as well to provide enough drop to allow the clock to run more than a couple of hours? Cutting holes in floor -- you must not be married! I'm married and have six tower clocks in my home -- all fortunately have one meter pendulums. They still don't run for more than a couple of hours because the weights - even though compounded - hit the floor in a few hours (especially the chime train). My wife views them as art. My suggestion if you don't plan to run the clock continuously (I only run mine as a demo to friends, then I stop them), is to make a short pendulum - about one meter - that doesn't need a hole in the floor. The clock will run fast, of course, but you can demo the clock when friends come over. I've relocated my half-dozen tower clocks around my home several times, so I'm glad I didn't need to cut holes.

BTW, I knew a guy who cut a hole in his floor and let the pendulum hang into the basement. He ended up hitting his head a number of times on the bob!

Best regards,
Frank

#### SamS

##### Registered User
NAWCC Member
I have a Howard "0" in my home with the standard short pendulum (about 38 inches). The weights hang from the ceiling (beam) about 8 ft above the floor, compounded. The time side runs 8 days and the strike side runs about 3 days on a full wind. I run the clock continuously. Weights are about 50 lbs each. (picture posted in other threads "tower clocks displayed in home").

I also have a Howard #2 striker located in a turn of the century mill. It has the 9 ft pendulum and holes cut through the floor for weight drop and pendulum. Total weight drop is about 26 feet. Time side runs 8 days, strike side about 4 days.

I thought the reason for the long pendulum is to allow the clock to tick less frequently (ie: every 2 seconds or so), thus reducing the weight drop on each tick allowing for a longer run time for a specific weight drop length. The less frequent tick also reduces wear on all components simply due to less total start / stop "motions".

#### doug sinclair

##### Registered User
A clock with a seconds beat pendulum (60 bpm) requires a pendulum approximately one meter long. A clock with a 40 bpm pendulum requires a pendulum 9 feet long (or approx 2.78 meters by my calculation). To try to produce a tower clock of any size that would have a 60 bpm pendulum would require some peculiar gear train configurations for a tower clock (IMHO). I still contend that a 2.78 meter (9 foot long) pendulum is proportional in length on a timekeeper the size of a tower clock when compared to a one meter pendulum as compared to a timekeeper the size of a tall clock movement. Smaller tower clock movements would reasonably use a shorter pendulum with quicker beat. Consider the more rapid bpm rate of a post (or street) clock, for example. The movements in these quite resemble a tower clock but are much smaller.

#### ClockMogul

##### Registered User
A clock with a seconds beat pendulum (60 bpm) requires a pendulum approximately one meter long. A clock with a 40 bpm pendulum requires a pendulum 9 feet long (or approx 2.78 meters by my calculation). To try to produce a tower clock of any size that would have a 60 bpm pendulum would require some peculiar gear train configurations for a tower clock (IMHO). I still contend that a 2.78 meter (9 foot long) pendulum is proportional in length on a timekeeper the size of a tower clock when compared to a one meter pendulum as compared to a timekeeper the size of a tall clock movement. Smaller tower clock movements would reasonably use a shorter pendulum with quicker beat. Consider the more rapid bpm rate of a post (or street) clock, for example. The movements in these quite resemble a tower clock but are much smaller.
I have finally bought the clock with the 9ft pendelum.. It is a E Howard No2 with 4 50 inch dials and complete drive train..

#### ClockMogul

##### Registered User
Since the pendelum rod is over 9ft long i am going to have to cut a hole in my floor to allow the pedelum to swing. Could someone give me an approx size rectangular size hole to cut in my lovely living room floor..? I was htinking mabe like 4inches wide by 12 inches long..Any suggestions anyone...

#### gvasale

##### Registered User
NAWCC Member
That size opening sounds appropriate. Two weeks ago I could have measured one for the clock in question & have provided the size the original installers woiuld have made.

#### tom kerr

##### Registered User
Re: E Howard Tower Clock Serial Numbers

Found a great paper with a detailed analysis of the mechanics of the Howard #1 tower clock prepared by the folks at Johns Hopkins (paper at Princeton):
http://www.princeton.edu/~timeteam/mechanics.htm . Speaks to several of the points discussed above. Great photos.

#### gvasale

##### Registered User
NAWCC Member
Re: E Howard Tower Clock Serial Numbers

The author apparently does not recognize that the tooth shape of wheels in the time train are not involute. So much for J.H. ...

#### stevett

##### New Member
Comments made are right - pendulum length determines the time of one arc or swing . I use the following rule of thumb re pendulum length: 10 inches= half a second per swing, 39 inches= 1 second per swing, 5 feet= 1 and a quarter seconds swing, 7 ft= 1 and a half seconds and 13 feet= 2 seconds swing ( swing is from one extreme to the other)
Clocks with longer pendulums tend also to have heavier bobs, Joyce clocks with 5 ft pendulums tend to have a gravity escapement and a bob weighing 2 cwt - very heavy - this gives mass to the operation which can then withstand any additional forces acting on it .
The actual arc of swing is determined by the weight on the time side, plus the efficiency of the train - what you know is the the time of he beat will be constant - either a narrow and slow swing, or wider but faster swing - so be careful before cutting into floors
Good luck

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