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By-Tor
10-16-2007, 01:17 AM
http://i.imgur.com/4tRnH6l.jpg

G.M.T = Greenwich Mean Time


I decided to write this quick guide, because there still seems to be lots of confusion about the GMT movements. Besides the real GMT movement, like ETA 2893-2, there are three kinds of "faux" GMT movements in replicas, 2 based on ETA 2836-2, one based on Asian 21J movement.

The first one is the "correct hand stack" modification, which mimics the genuine GMT movement, i.e the "hour hand adjustable" watch. This modification has the GMT hand placed above the hour hand on the stack. The factories have developed this modification specifically for Rolexes, GMT Master II & Explorer II.

On this modification the date change follows the GMT hand, unlike the "wrong" hand stack modification, which makes the date change to follow the hour hand. (Technically the "wrong" hand stack version is just a standard ETA movement where the GMT hand has been attached to the main hour hand with a double sized rotor (that makes the full turn 2x slower.))

The "correct hand stack" modification acts like the real GMT movement, and it allows you to set the hour hand independently without stopping the seconds hand. When you set the crown into the 2nd position, only the hour hand moves in one hour jumps, while the GMT stays immobile. Like I said, there is no hack signal in the hour hand setup position, and the seconds hand keeps running.

Good example of a replica like this is the Explorer II ("correct hand stack model"), which I have reviewed HERE (http://www.repgeek.com/showthread.php?t=8016) and HERE. (http://www.repgeek.com/showthread.php?t=654)

Below is a picture of the correct hand stack on my Explorer II:


http://i.imgur.com/QLnlTTb.jpg

However this modification might be unreliable, which is why I don't recommend it. Ziggy explains the potential technical problems with this modification in his movement review section. The link is HERE. (http://www.rwg.cc/members/index.php?showtopic=78321)


There is also another "faux" GMT movement, which is widely used on replicas. It's the "wrong hand stack" 2836-2 version.

Replica snobs look this movement down their noses, because it doesn't act like the "real" GMT movement. In this modification it's not possible to set the hour hand independently at all, but you set the GMT hand instead. This happens when you unscrew the crown into date set position, and turn the crown anti-clockwise.


http://i.imgur.com/epn735s.jpg

The problem with the GMT hand setup is that the GMT hand turns freely and smoothly over the dial, which (supposedly) makes it difficult to set the GMT hand "in sync" with the local time.

In my opinion, this is absolute nonsense. There's nothing difficult to make it sync with the hour hand. Just wait until time is say, 9'o'clock sharp (or before setting the local time, set all the hands at say, '12 sharp manually), and move the GMT hand exactly into the desired xx:00 2nd timezone position.


http://i.imgur.com/ZUngzdB.jpg

When you have once set the GMT hand in sync, you don't necessarily have to touch it anymore, ever again (assuming you have a watch like Rolex GMT Master, which has rotating bezel with 2nd timezone hour markers). When you set the time (in the crown position 3) the GMT hand follows along perfectly (and stays in sync). If you want to set your GMT hand to follow some other timezone, you just turn the bezel into the desired position.

If you have a watch like "wrong hand stack" Rolex Explorer II (Exp II has a fixed bezel) or "Bond" Seamaster GMT, you have to manually make it "sync" again with the local time if you want to change the watch to follow another 2nd timezone.


It's also important to understand that the GMT hand takes 24 hours to make "full circle" on the dial. All GMT watches have separate markers for the GMT hand. For example on Rolex GMT Master, Black Omega Seamaster and Explorer II the hour markers for the GMT hand are on the bezel. These 24h markers are probably more natural to use for the Europeans, because it's the European way to tell time (24h system, not AM/PM 12h system).

The Asian 21J version of the "faux" GMT acts exactly the same way.

I have owned several "wrong hand stack" GMT's, and they have been bullet proof and reliable. There's absolutely no reason to avoid this movement. While it's not technically like the real GMT movement, it serves the exact same purpose perfectly and is completely functional as a "GMT watch". The purpose of a GMT watch is to follow the 2nd timezone, and this "poor man's modification" does it perfectly.


http://i.imgur.com/WfpNRRb.jpg

Guest1
10-16-2007, 01:27 AM
Dayumm. Well writen By Tor. Thanks for taking the time to do this for all of our members. This is very informative.

I usually set the GMT hand independantly for CN time so I konw what time it is when I am bothering the dealers out there. :)

By-Tor
10-16-2007, 01:28 AM
I usually set the GMT hand independantly for CN time so I konw what time it is when I am bothering the dealers out there. :)

You are a true addict & rep geek. :D

DaveF
10-16-2007, 01:35 AM
Yes, thank you. I appreciate you sharing your knowledge.

By-Tor
10-16-2007, 01:42 AM
Thanks Pizza. :hi:

No big deal actually, it only took me an hour to compose. It's easier to answer GMT-related questions in the future... I only have to post a link into this thread. ;)

mauiman
10-16-2007, 02:31 AM
Outstanding write up as always. I really enjoy reading your tutorials. Very informative. I guess I am going to try that the next time I wear my GMT. I usually keep it the same as the local time and just move the bezel over to the 2nd time zone that I want to track.

J-C
10-16-2007, 03:27 AM
Well done BT.

Stellar, as is the norm w all your works.

By-Tor
10-16-2007, 03:34 AM
Thanks guys. ;)

I actually like this "ghetto" GMT modification a lot, and consider it extremely clever. However, the functionality isn't quite as handy on watches that don't have rotating bezels like the Master or black Seamaster GMT.

bklm1234
10-16-2007, 04:04 AM
Nice writeup, By-Tor.
One nice about the incorrect hand stack (aka GMT hand adjustable) is the date change follows the hour hand, unlike on the correct hand stack it follows the GMT hand. Most people set the hour hand to where they travel to. It makes sense to have the date on the watch indicate the date at where you are.

-bk

By-Tor
10-16-2007, 04:12 AM
Nice writeup, By-Tor.
One nice about the incorrect hand stack (aka GMT hand adjustable) is the date change follows the hour hand, unlike on the correct hand stack it follows the GMT hand.


Excellent point, which I forgot to mention. Added, thanks.

jocelyn
10-16-2007, 09:13 AM
Shoudn't be time for another award? :cheesy:

bambax
04-23-2011, 12:25 PM
love reading your write up . very informative especially for new members
keep up the good work
thanks by-tor and repgeek for the excellent data base :cool:

Fruggy
05-22-2011, 08:13 PM
Good analysis, the only problem with the IHS is that is sort of defeats the purpose of the GMT... to be able to quickly and easily change the time zone that the watch is in, in hour hops, without changing the GMT hand and without stopping the seconds, when you're traveling frequently between time zones.

Of course how many people actually use it for that? Not many. But the original functionality is there for that very reason and is what makes the GMT so unique.

And Ziggy's link in the OP is gone.

sneed12
05-22-2011, 11:38 PM
Good analysis, the only problem with the IHS is that is sort of defeats the purpose of the GMT... to be able to quickly and easily change the time zone that the watch is in, in hour hops, without changing the GMT hand and without stopping the seconds, when you're traveling frequently between time zones.

This functionality exists on only a few GMT movements.


Of course how many people actually use it for that? Not many. But the original functionality is there for that very reason and is what makes the GMT so unique.

The "original" GMT didn't have that functionality. In fact it wasn't added until the 16710.


And Ziggy's link in the OP is gone.

Thread is 4+ years old...

alou
01-13-2012, 09:59 AM
Great analysis !

Rolex0815
05-26-2013, 05:40 PM
thans for this infos!

umaz662
06-18-2013, 11:06 PM
need to buy this

marblegranite
11-19-2013, 12:54 AM
Great post! Very helpful for those that purchased the latest version of the Explorer II.

Cabbyking
11-19-2013, 01:30 AM
Thank you...

mysfit
12-26-2013, 08:38 PM
Nice post

Berlin
05-30-2014, 10:41 PM
Thank you

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