Workshop Hints
"Current Notes"
By Mike Frost
CN# 14: Comments On Telechron Rotor Repair
Many times the professional clock repairman will be asked to look at an electric clock that has a Telechron rotor as the power mechanism, so a basic understanding of these units is necessary. This is not a CN on how to completely repair these rotors.
Telechron started making sealed capsule rotors around 1910 and has continued until the present to produce some of the styles. Over the years, there were hundreds of types, but only a few styles that the repairman will have occasion to see. These are: "B", "H", "S", and "C". All styles had many different output pinion options as well as RPM and torque requirements.
The "B" rotors themselves had several styles, most notably the standard and most common "B", the "BF" which had a shorter tail, and the "BMX" which had a longer tail. The "H" rotors were mostly the same except a few were 14.4 rpm rather than the standard 3.6 rpm. The "S" rotors were basically the same at 3.6 rpm for clock and timer uses, and the "C", which was used in tower clocks, were also pretty much the same.
Case material was generally copper, but brass was used during the war years due to copper scarcity. Much later, most cases were stamped aluminum. ALL copper or brass case rotors were oil-filled, although this is a misleading statement. Actual oil amounts was in the range of 1 to 1.5 cc's of a special oil. The later aluminum units have grease inside and no oil. All copper and brass units have the word "TOP" printed on the shell and this word should be facing UP when installed to allow for oil dispersal. The aluminum rotors have no oil so placement is not critical.
The movements inside are just that. They are a small gear reduction movement with all the attendant problems one would expect. There are different materials that were used for the movement plates starting with beryllium copper, brass, phenolic resin, plastic, and some type of fiber board used in most of the recent rotors. These plates had a capillary plate in place to keep the oil on the shaft ends. Wheels in the movements were mostly brass and phenolic resin, with layered stainless steel pinions for oil retention and all were just pressed on to the shafts. Shafts were all polished stainless steel, and most drive pinions inside were steel and brass. Output bearings were hard brass or bronze.
Now, when the repairman is faced with an electric clock with one of these types of rotors, it is imperative that first the rotor and coil assembly be in good working order. After all, how can one repair the movement correctly if one cannot run the movement? How can one even try to run the movement just to ascertain just what is wrong with the clock? That being said, and you have a bad rotor, what now? The following will help those in this situation understand what is going on with the rotor and possible repair options.
CAUTION: NEVER USE PLIERS TO TRY AND TURN THE OUTPUT PINION. Using your fingers lightly will give some idea as to some of the problems you may encounter. Trying to force the pinion is like trying to wind a clock mainspring back through the train by moving the hands backwards.
First, assuming the coil is good, does the rotor work at all? Is is frozen? Does it feel loose or skip when the output pinion is run? Does it make noise? Does it work by itself, but not under load? All these possible problems are ones needing attention. I should say right here that very few rotors 'just need oil'. Noise is due to worn wheels and/or plates, or possibly higher torque requirements than the rotor was designed for. Frozen or lock up is due to broken wheels, badly worn pivot holes, or gummed up lubrication. Looseness or skipping is due to wheels or pinions slipping on the shafts or completely broken. Rotors unable to handle the load desired means that you have the wrong rotor or any combination of the above. Quite possible you may have a coil that doesn't provide the required magnetic field for the particular rotor.
Now, drilling and oiling these rotors is certainly an option, but any good repairman can understand that this will not solve most of the abovementioned problems. At best, it is a short term solution. Certainly putting oil in a greased rotor will not work.
Opening the rotor can be tricky. It can be turned on a lathe to remove the solder (never use heat), but the design of the rotor will make it difficult to remove the shell. Particularly on the "B" rotors, there is a small groove cut into the base and the shell is rolled/crimped into this groove. It is difficult to use a graver to cut into the copper as copper doesn't cut easily. Even when cut, the short overlap of the shell on the base leaves little room for re-sealing. THERE IS NO EASY WAY TO OPEN COPPER OR BRASS ROTORS! If you are able to get it open, the movement is held in place by three dimples and the movement must be pressed out the get past them.
If you can get this far, the two movement plates are separated by three pillars. Separating the plates will allow for bushing of the plates and wheel replacement. The last two wheels are usually the ones which have the most wear as well as the pivot holes. When placing everything back together, the oil is placed inside first, and epoxy can be used to seal.
From the above information, it can be seen that repairing these rotors can be as much work as repairing a small clock. Each repairman must decide whether their time is better spent in other areas. While the cost of new rotors ranges from $25 to $50 and cost of repair around $40, one must also remember that the new aluminum units do not provide enough torque to run anything more complex than a time only clock.
A few notes on new rotors: Telechron is no longer making ANY rotors. Most parts houses no longer have a decent supply or any 60 rpm rotors. There are plenty of "S" rotors available for around $4 each and a limited number of "H" and "B" rotors. When they are gone, repair will be the only option, so don't destroy the old rotor. Save them or send them to a repair company for availability in the future.
Mike Frost
TIME GUARD, INC.
9655 RICHMOND STREET
MANASSAS, VA 20110
1-800-390-5540
"HELPING YOU SET THE CURRENT TIME.
