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<x-charset iso-8859-1>A while back Pat wrote: > The late model solid state type III clock usually fails in the plastic gears, > not the electronics. There is one small bevel gear that cracks and then free > spins on the shaft. If you find one that starts and runs for a bit with the > hands moving and then stops... it is due to dirt. Then Jim wrote: >I've seen this gear that slips on the shaft, but there are very positive stops on >its travel. It appears to me that it is intended to move. Even when my eyes >were better, I was never able to see any crack there, and I spent a lot of time >looking. That part certainly has me puzzled. Well, I just scored a couple of late clocks cheap on Ebay- cheap because they didn't work. Today I had a clock day and I think I may have a solution, or at least some further insight into the late clock problem! Both of these clocks now work (for now anyway) and I've put one in my fasty so I'll let you know for how long. I'm not sure if Jim was talking about the same thing as Pat, but I couldn't see any bevel gear in these clocks. The gear that Jim talks about IS meant to be free, but limited, on the shaft. It is the little pink coloured nylon, strangely shaped, drive gear that kicks the even stranger shaped gear, with long axially aligned teeth, around one tooth for every cycle of the swing of the "pendulum". I'd call it the escapement mechanism except it isn't! The escapement in a wind up clock controls the escape of the stored energy of the spring, and in turn imparts enough energy into the pendulum to keep it swinging. In this case the mechanism is driven by the electro-magnetic pendulum drive, to push the clock hands round. Anyway this pink gear is free on the steel drive shaft but has tiny (read TINY) pins which locate in larger holes in the smaller bluish nylon part fixed next to it on the shaft. As Jim said, this allows the gear to rotate freely but with very positive stops. There is a logical reason for this, though this is my theory. The pendulum has two phases when it is at its weakest, and most likely to be stalled by the mechanism it drives- when it changes direction and momentarily is stationary. This mechanism is a very simple and clever way of insuring that the pendulum is always moving , and therefore has the required momentum, when it drives the clock. Each time it changes direction, it can freely turn the small amount allowed by the holes in the blue nylon part to gain velocity, until it re-engages with the mechy and drives the gears that drive the hands. Now I suppose that its possible that these tiny pins could break off allowing the pink gear to spin freely- this would be a fried clock. I've only seen 3 of these clocks so I don't have enough experience to say if this is a common failure mode. However I think that the problem with the clocks that I've seen is the strange, axially toothed, driven gear. If you look at one of these clocks you will see that this gear has a thin metal spring bearing down on one of its bearing spigots. I believe this to be intended to damp the motion of this wheel so that it doesn't bounce back once its been kicked by the pink drive gear, and stopped on the other side of that gear. At the other end of its shaft, on one of my clocks, there was a tiny plastic thrust washer- less than 1/10mm thick, between it and the brass carriage of the clock. On the other clock there was just the remnants of this washer in the form of strands of plastic wrapped around the shaft. By carefully lifting this gear against its spring, I cleared out these remnants so there was now a clean bearing surface for it to run on. On the clock with the washer, after relieving the spring pressure, I could see that it was showing signs of breaking up and becoming "furry". I think that it is this washer breaking up which increases the friction of the mechanism to the point at which it stalls the pendulum, stopping the clock. Both of these clocks showed signs of life, but still stopped occasionally. My solution was to very, very gently pry the little spring up with a scalpel to reduce its pressure on the gear. I tried this with the clock powered and sure enough it started to run much freer. After a few attempts I was happy that the clocks were running OK and I left them for a few hours and they were still keeping good time. If I'm right about the function of this spring, it should only impart the very slightest of dampening force on the gear, yet it was really quite tight. I relieved it so it was barely acting on the gear at all- only just, and I hope that it will keep working for a good time. Only time will tell. I'm sure there must be several ways that these clocks fail, but in the three I've seen, a good clean and lube of the steel shaft bearings, and this easing of the mechanism seem to work. Anyway, just thought I'd share my thoughts on this and hope this may save a few of these condemned clocks from mineralisation! Its nice to have the original working the way it should. By the way, if you clean the mechanism with solvent, which I think I will stop, at least for the nylon gears, be very careful not to let any anywhere near the clear plastic part of the dial (with the numbers painted on its back). I managed to get some isopropyl alcohol, which is usually fairly gentle with plastics, into the clock body and a few minutes later the dial had cracked, emanating from the injection moulding sprue stump on its edge- ruined a perfect dial on a now working clock- bummer! Mark Seaton '73 TA London ------------------------------------------------------------------- Search old messages on the Web! 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