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ETA 2893-2 with stuck GMT hand in a self made 24h watch

Ascanio

By Ascanio
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Ascanio Member

Ascanio

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Hi again!

I really love the idea of a 24h watch and I wanted to build it. I know it's not the proper way, "pure" as it is referred to, but I used an ETA 2893-2 movement using the GMT hand as my hour hand, it's a bit tricky to set properly but the final result is actually good I think. I had to broach the hour hand hole from 1.5mm to 1.8mm, I think I did it good enough and I think i placed the hands properly.

The movement was brand new and purchased from reliable source.

Problem: My GMT/Hour hand stops! I notice it remains stuck at some position, but if I place the crown in first stop and rotate to adjust the GMT, it jumps forward. Also if I pull it to 2nd stop and adjust time, the GTM/Hour rotates following the minute hand properly until it stops at some places and then I can rotate minutes full circle many rounds and GMT remains stopped... if then I gently move minute hand back and forward (!) a few times it starts moving again for a while then stops again...

I will double check if GMT hand is well fixed, but I think so, and I don't think it conflicts with minute hand. I am afraid of other troubles with the movement. Possibly I made some damages in pushing the hands or something... or the GMT wheel does not gear properly... I did not study how 2893-2 internally works yet to find possible explanation for this sad behaviour, but I am very concern about the watch running with one gear stopped.

Also if there is any trick about using standard hour wheel for 24h operation instead of using GMT, it's welcome: I know some 24h watches use this movement using regular hour hands instead of GMT, but most likely they have modified wheel train which can not be purchased as standard pieces.

Thank you!!

Ascanio

 

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Ascanio Member

Ascanio

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Hi!
I made a video about what happens when I try to set the time, which I think it's more meaningful. During normal operation it just happens that the GMT/Hour hand remains stopeed while minute and second hands keeps running keeping good time.

Please don't get mad at me as I have build such thing with parts sourced on the Internet, I am going to love this watch and I build it just for my personal enjoyment, not to resale or stuff.

Thanks!

 

 

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Ascanio Member

Ascanio

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Uhm... I have given a second look and deeper thought to the movement tech sheet.

The movement came with the 24H wheel (251) in a plastic bag. I did just place the wheel on top of the hour wheel 2558 without oiling the sides of 2558! Could this be the reason? Should I now expect the 251 being damaged with many broken teeth? And maybe even the mating gear which I cannot understand from the drawing what it is? :(

Stupid me! :wacko:

Now I cannot service/open the watch for one week or so. I assume to reduce damages, as it is still geared up, I can keep it in 2nd stem out position so it's hacked and nothing is supposed to move inside, am I right?

 

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Ascanio Member

Ascanio

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Well, as an update on the subject, after disassembly and a few trials, it seems just the hour hand broached from 1.5 to 1.8 mm is not really stable as the pipe basically disappears (it's too thin to make a real grip).

As 1.8mm watch hands are very rare, now the plan is purchase one pocket watch 1.8mm hand, and "innest" (cut and glue) on it my original hour hand. If I can do a decent job, it should be it.

I hate mentioning "glue" but i would not solder due to discolouration from heat.

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Ascanio

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Job done and turned out quite ok, not perfect but ok. 

Transplant of hour hand over a GMT hand was successful. Yes I used Loctite which is very clean and precise, but drawback is zero repositioning chance. Since I don't need Loctite strength on such operation, in case I would ave to do it again I think I will try a more gentle glue. It would have been better to reposition the hand 1/2 mm and having some black paint to fix the GMT round part which is chrome instead of matt black.

I had to sandpaper the height of the tube part of the GMT hand which was quite long, like 1.5 mm to 1 mm (it came from Rolex replacement hand set with 1,8mm exact width). That part went well and easy.

Actually I finally found the real issue: the dial center hole was too tight to take into account the 24H wheel of the ETA 2893-2 movement so I had to broach it to more than 2 mm diameter.

Clearly it was not designed to use the 24H wheel, so for sure the original watch movement would have been a modified ETA 2893-2 to use the regular hour wheel. In case anybody has any information on this modification with standard (not custom build) parts, I would be interested to hear.

However at the end the watch is running smooth since a few days and I am very happy with it! :)

Have a great day!

Ascanio

 

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