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ITR 13-7

Mike Walker

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Nov 5, 2020
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Looking for information on the pendulum for an ITR 13-7 master clock which I recently aquired.
There is a suspension spring fitted but I don't have the pendulum or bob.

dial_closeup.jpg
 

Toughtool

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If I recall correctly, your pendulum is about 39 inches. I have seen one for sale recently so there are available occasionally. Looks like your logic was mounted in a separate cabinet. You may want to look at the last several pages of this forum that refers to IBM master clocks for helpful information. Joe
 

Toughtool

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I'm sure we can find a photo. If not I'll take a photo of mine and include measurements. If you are going to build one, you need to buy a rod of Invar steel, which is 64 percent Iron (Fe) and 36 percent Nickel (Ni). See Wiki at: Invar - Wikipedia. I will measure mine so you can order it. I believe my pendulum weight is around fifteen pounds, of mercury and glass. I have the compensating mercury pendulum. I think the cylinder versions are closer to ten pounds. You will need a "Tap and Die", with a very fine thread count to make the rod threads and adjusting nut.

This pendulum weight just sold on Ebay that has dimensions listed, except for weight, @ ORIGINAL IBM/ITR (/???) PENDULUM BOB FOR MASTER CLOCK | eBay
"ORIGINAL IBM/ITR (/:???:) PENDULUM BOB FOR MASTER CLOCK
2.9/16 inch diam x 7.1/8 inches long with a 5/16 inch diam hole through.
It has been a chromed bob which has started peeling and is now rusty, the chrome wants removing, then grinding to remove rust."

The terminals on top of your clock's case will be important as these are the connections to your logic components.
 

Mike Walker

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Excellent - many thanks for that Joe.
I would like to make a mercury compensating pendulum if possible so any info on that would be much appreciated.
I do have some mercury from an old project - I'll weigh it and see if there's enough.
I've got a selection of taps and dies so no problem with thread cutting.
Look forward to hearing from you.
All the best
Mike W.
 

Toughtool

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I would like to make a mercury compensating pendulum if possible...
That is going to be a challenge. Pendulums are very complicated. I would look for one first. All things have a temperature coefficient, usually expanding when warmer. The glass jars of an IBM mercury compensating pendulum are graduated, meaning the inside bottom is smaller than the inside top. This means when the ambient temperature gets warmer, the mercury as it expands, will raise the center of gravity [of the mercury] more than if the jars had straight sides. This will tend to speed the clock up. Even an Invar steel pendulum rod, as it expands will get longer which tends to slow the clock down. They figured out the correct balance to make it work. Hence the compensating mercury pendulum. Wood has a better expansion coefficient than steel, and is also cheaper, so it was often used in clocks until Invar steel was discovered.They also did some neat tricks with multiple rods, some dropping down to hold rods going up to cancel the expansion problem.

I will work on some photos and measurements of my pendulum tomorrow. I finally found the correct dial for may clock and wanted to mount it anyway. When I bought my clock in 1966, the face had been altered. I tried to buy a new one but the only ones available from IBM were the square face dials of the 1950's. Of which I used for about 35 years. I found a reproduction someone was selling (new) on the bay but it had "IBM" instead of the correct "International Time Recording" logo. Now is a good time to change it.

See also: Elemental Mercury Releases Attributed to Antiques --- New York, 2000--2006
 
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Toughtool

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My master is a 1930 ITR model, and looking at the bracket that holds the impulse contact, I guess my contact assembly will be an earlier version than I always thought. I have posted the reproduction dial with the IBM International logo and the one I bought recently with the correct International Time Recording Co. ,of New York, Endicott, N. Y. logo. I notice the numbers are slightly larger. Cool!.

The Pendulum:
The Invar steel pendulum rod's diameter is 0.280”, and mine is 44-1/4 inches long, from tip (bottom) to top. The brass “head” is 0.375” diameter and the cutout ends 0.184” from the top. I have posted a rear view and a side view to show how it is cut. I just realized I forgot to measure the slot but is near 0.100”. This slot should be the width if your suspension spring pin pads that are on each side of your spring. Sorry. The brass head is 1.180” long with a rounded top. I don't think it matters that it is round. It appears to be pressed onto the Invar rod and looks to have a pin through the head and rod (near the bottom) to insure the head does not come off. The Invar steel pendulum rod's diameter is 0.280”.

The glass jars are 7-1/4 inches tall, and fit inside the cups with an inside diameter is 0.180”.

P Head.jpg P1 Head.jpg mercury Weight.jpg Frame.jpg Correct dial.jpg Repro Dial.jpg 1930 master.jpg
 

Toughtool

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Aug 12, 2016
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"
The glass jars are 7-1/4 inches tall, and fit inside the cups with an inside diameter is 0.180”.
Opps, my mistake, the inside diameter is 1.800 inches, not 0.180 inches. The thickness of my suspension spring and pad is 0.088" so a slot between .088" to .100" should be fine. The pendulum should easily drop over the pin. Joe
 

Scot Traffis

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one other thing about the pendulum. It matters what crutch is on the verge, a mercury pendulum has a forked crutch and the stick has a single post
 

Jim Hartog

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Jan 6, 2010
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Hello Mike,

That UK eBay listing is NOT correct for your clock. Both of my cylindrical bobs measure 2.5" in diameter and are 9.0" long. There is also a micro adjustment feature at the bottom. The entire bob rotates on the rod for coarse adjustment and a small "nut" at the bottom rotates separately for fine adjustment. There will be nothing about making a correct cylinder bob that is easy either. Better to keep an eye out for one or advertise to buy one.

After mercury vials and cylinder, there was a lenticular style bob available, too, which was usually found on the older clocks. The lenticular bob on a wooden rod is 8.0" in diameter.

Check IBM"s Clock Corner for lots of good information on these clocks.

Jim

P1020044.JPG P1020307.JPG
 

Toughtool

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I knew the bay listing was not correct and the rod looks like it was cut off. Mike wanted to make a mercury pendulum and I though the frame may work, at least to give him a model to work with. The listed glass jars certainly are not correct. I see mercury is about $150.00 per pound. May be cheaper to buy a master and make one from two. Just saying. Joe