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Uncovered Gear Train Wheels, Strange?


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Recently a customer came to us with a rather old and inexpensive Avia watch that had a rather peculiar ETA movement in it, 455.111 (maybe a 450.111) I believe was its serial, but I may have miss-remembered that. 

I took a picture with what I had to hand, so it's a bit blurry, but take a look. 

eSFmKl8.jpg
Perhaps the gasket should have been cleaned before the picture instead of after, hmn.

Anyway, as you can see a couple of the gear train wheels are not covered by any bridge or cock. 
At first I thought perhaps it had been cowboy'd and I was in for a little problem but then i could see no fixtures to hold a bridge, and could see no pivots, so it had to be by design, sure enough it worked okay once I carefully changed the battery. (you can see the wheels are unnervingly close to the battery.)

But I couldn't think of a time when I'd seen anything like this, is this as unusual as i think?, or is this an established way of configuring the gear train that I just by fluke hadn't seen til now? any thoughts or insights?
 

Edited by Ishima
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    • As I was typing this, @HectorLooi expressed the same idea. It's possible that when a wheel is pushed in the opposite direction it cants a little, or lifts up in its setting. I'd check end shake on everything first, since it's already assembled--I had a Seiko 6139 where one of the upper bridge jewels was pushed up a bit and caused it to behave unpredictably. Then I'd probably take all the wheels out and reinstall one at a time until I found the noise. Also look very closely at the bridge and flat parts of the wheels for wear marks. Look for shiny spots.
    • This sounds like one of the pivot holes has worn and become elliptical. Can you post some photos of the plates?
    • Even after thorough cleaning unfortunately the issue persists. I have made sure that all wheels are perfectly clean, no teeth are chipped, no gunk is left built up on them etc. yet the issue is not gone. When reassembling the movement I of course checked if the wheel train moves freely as that was the suspected cause of the issue before. And the intersting thing is - it does - but only in the "wrong" direction. Driving the wheeltrain by turning the mainspring barrel in the opposite direction as it would turn in normal operation, all wheels spin freely, and continue spinning for a few moments even after I stop providing power by hand. They behave the way I'm used to and have seen with other wheels before. However: When I apply torque in the opposite direction, the power delivery througout the train is not smooth or continuous. While it does turn, there are stages of increased resistance in the train. In addition to this, you can hear a slight "rubbing" sound whenever the trian passes by this point of increased resistance. The sound, to me, is more indicative of a surface rubbing on another surface, rather than the teeth of two wheels getting stuck within each other. Installing the click and putting a wind in the mainspring confirms this same issue, it does unwind and all wheels are powered, yet when the power reserve approaches depletion, it doesn't have enough power to push the wheeltrain past this point of friction. The slightest bump on any of the wheels will free the train, make it spin for however many rotations and then get stuck in the same way. You can do this several times before the power is actually completely depleted. This has really left me dumbfounded. I have inspected all of the wheels, pivots, teeth etc. on the entire wheel train and can't find any traces of dirt, any bent teeth or any warped or out of plane wheels. Besides: If one of the wheels was bent and rubbing up against some other part of the movement during a rotation, shouldn't it be doing this regardless of the direction of the rotation? This is supremely confusing to me and I can't figure out for the life of me why there is increased friction in only ONE direction and not the other. Installing the balance yielded the same result as before the disassembly: the watch runs great for about 50 seconds and then get's stuck when the wheel train get's bogged down. I mentioned earlier that there is a periodic scraping noise that can be heard when the gear train turns fast, this noise is not present when turning the train the opposiste direction. Does anyone have any ideas about which parts of the movement I can check for rubbing? I found no signs of wear or scraping on any of the bridges etc. so what would cause this periodic friction in one direction but not the other? I am very much a novice and have never dealt with such an issue before so I would love to hear what you people think about this. Thanks.
    • For me the second site has been hacked. 
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