IBM IBM 35-7 cable drum servicing

[Jim Hartog]

Hello,

My IBM 35-7 stopped running because it had no power to the escape wheel. Since the movement has been recently lubed, I suspected the cable drum.

I locked the drum, removed the weights, removed the electrical peripherals from the movement and then removed the movement. After unlocking the drum, I tugged on the weight cables and noted a "tight" spot. The tight spot disappeared and then the cables pulled down easily.

I had previously (last week) put some oil in the hole at the screw at 2 o'clock on the front iron bracket. It looks like an oil hole. Today, I dropped some oil on some of the gears in front of the actual cable drum. Everything has been re-assembled and is now running fine.

I see three screws in the iron bracket on the front of the drum assembly. If I want to service the cable drum, what happens when I remove those three screws? No doubt, there are bearings in there. Does anyone know what to do to dis-assemble the drum?

Jim

 

[Kevin W.]

Jim i have heard there are ball bearings in the drum. Wish i knew more to suggest more about properly lubricating the winding drum.

 

[paradise]

There is a good short on you tube by Dave Dietrich on the disassembly of the pulley on that clock.

 

[Kevin W.]

I searched by the name on Youtube but could not find it.

 

[Jim Hartog]

Hello Paradise,

Found it. Thanks. Not a lot of detail on servicing the actual drum but good stuff on how to remove it. Lots of other good stuff, too.

Title is : ITR weight driven master clock - operations and service Dave Dietrich

Mine is now running but I see the amplitude of the pendulum swing changing with a delta of about a centimetre.

Jim

 

[Kevin W.]

Thanks Jim i will have a look .

 

[Kevin W.]

Thanks Jim, great video, learned some new things.

 

[paradise]

Did anybody look at any other of Dietrich shorts? What do you think of his lighting effects?

 

[Jim Hartog]

Hello Paradise,

Yes, neat use of the LED strips. Probably enough power in the case he could tap off that so that he did not need more holes. The end of the "operations and service" video shows clocks in, what appears to be, a restaurant or bar. Pretty interesting props for a business, I'd say. Check out his website for the business end of the master clocks. I hope he does some more videos.

Jim

 

[Jim Hartog]

Hello,

My IBM 35-7 stopped again after a couple of weeks of operation with an inconsistent pendulum swing amplitude. According to the beat scale, it was around 4 inches, sometimes more, sometimes less, so I took the plunge and serviced the suspect cable drum assembly with no instructions. I will post the process in two parts, the first, removal of the assembly, the second, dis-assembly of the cable drum assembly itself. I am sure some of you would do this differently. The clock is now up and running with a 5 inch pendulum amplitude.

IBM 35-7 Master Clock Cable Drum Assembly Removal

remove the weights (2, 1/2" nuts)
remove any electrical peripherals from the movement
remove the movement (4 screws)
remove the base of the drive shaft (3 screws, the motor coupling tube will be freed)
lower the weight cables to where the weights would bottom out
note the position of the fan gear poking out to the right (I taped it in position), the limit switch will be closed
note that the right cable comes off the back of the cable drum
note that the left cable comes off of the middle of the cable drum
cut off the knots below the weight nuts (the nut will not go through the pulley brackets)
remove the cable drum assembly (3 screws)
note where the single tooth pinion gear engages the "teeth" (notches) of the fan gear (on re-assembly the pinion tooth should be in the 1 o'clock position)

Jim

 

[Jim Hartog]

Hello,

No ball bearings will fall out on you. There are a bunch of washers you need to keep track of (I didn't do well, here). This thing is well built.

IBM 35-7 Master Clock Cable Drum Assembly Dis-assembly

pull the cable drum off the drum assembly axle
mark the position of the rear flange on the drum so that on re-assembly the flange and the drum cable holes will be in the same position
remove the rear flange off the drum (2 screws, one screw probably holds the rear cable end)
remove the rear cable from the drum
remove the front flange off the drum (2 screws, one screw may hold the middle cable end but there is a cable set screw there, too)
remove the middle cable
note that the cable drum has four holes, use two holes for one flange and the other two for the other flange
slide the gears off the axle (both must come off together, they will dis-engage when off the axle, remember this for re-assembly)
note the 3 steel washers in front, between, and behind the gears
the satelite gears can be removed by unscrewing the screw between them
remove the axle from the front casting (set screw at the 2 o'clock position)
remove the cable drum lock assembly (screw in front)
note the thick, brass washer/collet for the back of the lock assembly on the axle

The tricky part of re-assembly is getting the rear pinion gear, the fan gear and the cable turns on the drum correct. A mercury pendulum or a cylinder pendulum uses longer cables and the weights can drop to the bottom of the case when the power is off. The lens style bob is too wide for the weights to drop to the bottom of the case so the cables will be shorter and the weights will not drop as far when the power is off. Changing the number of turns on the drum has the same effect as changing the mesh of the pinion/fan gear. One cable turn equals one tooth? See page 16 of Service Instructions: IBM Archives: Clock Corner Reference Room for the IBM version of this.

I did not replace the two, skinny washers seen in the pictures. I wanted a little more end play.

I cleaned stuff, put Singer sewing machine oil on bearings and sliding surfaces and put grease on the gear teeth and worm gear. There was some anxiety on the test run.

Jim

 

[Jim Hartog]

Hello,

Correction to post #10. I had assumed that the beat scale units were inches. They are not. So my 4 inch swing did not become a 5 inch swing. My 3 1/4" swing became a 4 1/4" swing. On the beat scale the swing went from the second big increment to the ends of the beat scale. The new swing almost covers the whole beat scale.

Jim

 

[Kevin W.]

Thats great Jim, great posting, very descriptive. I am amazed how much swing you now have on your clock, i would think that would help in the time keeping of the clock.

 

[Alan]

Hi Jim, Kevin and others,

The older design winding drum does have loose ball bearings. I know because I had to take one apart to fix a loose one tooth wheel that moves the fan gear. My clock is from 1927. There are 4 places where loose ball bearings are placed. There are 15 11 11 & 15 bearings. Thank goodness IBM kept improving. I also found out the old and new winding drum are not interchangeable. The shafts are different sizes.

 

[Kevin W.]

Thanks Alan, thats a good posting and also good to know about the older IBM clocks. I find it difficult to find out repair info on these clocks and i am grateful to those hat do post about these clocks.

 

[Jim Hartog]

Hello Alan,

Thanks for your posting with photos. I have a 16-7 which is older than my 35-7 and I was going to service the cable drum in the 16-7 because of the very positive results I got from the servicing of the 35-7, but, now I may reconsider that idea. Those are scary looking loose bearings!!! From your information, I should be able to determine if I have the older or newer style in my 16-7 by measuring the size of the shaft at the front where it is visible. Doing that today.

Jim

 

[Jim Hartog]

Hello,

Just measured the cable drum shaft on my 35-7 and my 16-7. Both are approximately 6.3 mm in diameter measured from the little part visible from the front using digital calipers. My 16-7 is an earlier, oak cased, round dial (wooden edge) model but it likely has the later cable drum assembly, I hope. Both my clocks are of Toronto manufacture and apparently there are no serial number/date records to accurately date these clocks.

Jim

 

[Alan]

Hi Jim,

I may have good news for you. Just measured both cable drum shafts. The one with loose bearings measures 7.8 mm. The one with sealed bearings measures 6.4 mm. I say go for it.

Alan

 

[Jim Hartog]

Hello Alan,

Great!!!! Thanks again for the information. My 16-7's cable drum assembly is going to get serviced next week, but I will be cautious with disassembly, just in case.

Jim

 

[Jim Hartog]

Hello,

The cable drum assembly on my 16-7 was just serviced today. It was not causing problems and was not as dirty as my 35-7. There were some differences in the two that I have noted below.

1. in the 16-7, the 3 spacing washers were not steel, they were brass, sort of a two level washer.

2. the left cable, that attaches at the middle of the drum, was attached to the drum by the little set screw only, no crimped/soldered lug. the right cable at the back did have a crimped/soldered lug.

3. there was a skinny, steel washer between the front brass washer and the brass collet at the cable drum lock.

After servicing, there was no radical improvement in the pendulum swing of the 16-7, probably because the drum assembly was not that dirty and was not causing a problem. The rating assembly reaches the second large increment on both sides of the beat scale after letting it settle down for an hour. On the other hand, the 35-7 still has a consistent pendulum amplitude of two small increments past the second large increment on both sides of the beat scale. There is, therefore, a considerable difference between the serviced 35-7 and the 16-7 for which I cannot surmise a reason. Both movements had been recently lubricated.

Jim