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New Asian copy of the ETA 7750 |
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Articles -
Watchmasters Corner
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Written by Ziggy Zumba
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Page 6 of 7
I put the movement on the watch analyzer and re adjusted the beat and rate (the load changed them both), but the change was nowhere near what it was the first time with all the extra friction. So far it seems to have corrected the problem, all the gears were installed, and the movement has been running for 2 days. How it will perform in the long run is beyond me, but the Swiss ones are not doing that well (the ones I have seen anyway). It works, but just barely, the load is too great from these extra gears.
I did speak with the owner and he decided to remove the running seconds gears, and freeze the sub-dial as this will improve the functioning of the watch and the reliability. I think this was a good decision.
Anyone who has asked my opinion on a Daytona model has gotten the same answer; don’t get one with running seconds at 6, everyone I have seen is problematic, it’s asking too much for the movement to deal with the extra load of 11 gears. The lowly movement was not designed to take this load, it’s like taking a 4 cylinder car engine and putting it in a large dump truck, it will work, but the engine will fail eventually – sooner than later…
Now this is only my opinion, based on what I see.
Why did they not oil the movement?
Remember I said that the movement was not oiled? Why would someone make such a nice movement, and not oil it except for the balance cap jewels? What does oil do in the pivots and jewels? Sure it reduces wear by allowing the pivot to rotate on a film of oil and not touch the jewel. It also adds a small amount of friction to the pivots - a very small amount mind you - but friction is increased when you oil a watch. A dry pivot on a jewel will require less power to turn than one with a film of oil between the pivot and the jewel, at least in the initial stages of the usage of the watch. It is possible to over-oil a movement, so much so that it doesn’t run at all…what is my point with all this?
Have you figured out yet why they did not oil the movement?
Take a movement, add 11 extra gears, causing the movement to be on the verge of not working, and to make it all work, reduce the friction in the movement to the least amount you can. How ? by not oiling any of the pivots…make sense doesn’t it, it does to me…this is pure speculation on my part, but the only reason I can come up with.
Taking the extra 11 gears out of the picture, you have an excellent copy of a 7750, no question a vast improvement over the existing ones. I wish I could buy a dozen of these and replace the ones in my watches.
Even better is the fact that this movement is running at 28,800 BPH, so the seconds chrono hand is nice and smooth, identical to the OEM model.
If this was my watch, I would just take the running seconds gears out of the watch, freeze the 6-counter, and use the watch like this. Reason I say this is simple, the addition of these 5 gears for the running seconds, is too much for the movement to handle. I can’t correct design problems, and with the running seconds in place and loading down the movement, there is no question that the watch is going to have problems, and probably stop intermittently and maybe stop running at all. I rather have a reliable watch than a non reliable one, even if it means loosing a function.
Summary
Overhaul was straight forward, only snag was the fact that once I oiled the watch, (correctly I might add – not over oiled) the limit of the available power from the movement was noticeable. As soon as I added the last bridge with the extra gear, the movement came to a grinding halt. So I ended up spending a couple of hours on the extra transfer gears, and finally took the pressed gears off, cleaned them really well, and oiled with my lightest oil and reassembled. Then I took extra care to make sure the pins were pressed just right so there was as little clearance as possible and as little friction as well. My efforts were rewarded since the movement will now run with all the gears in place…but I have my doubts that it will be reliable in the long run.
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Last Updated ( Tuesday, 14 August 2007 )
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