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So how does the jump hour in the 85/8900 work?

E
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And why is it so susceptible to breaking?

Let’s say you have an ordinary 3-hander with a date wheel. When the watch is in the first position, the sliding pinion in the keyless works meshes with the winding pinion so you can wind the watch. Pull the crown into the second position and the sliding pinion meshes with an intermediate wheel that turns the quick set date lever. Pull the crown all the way to the third position and the sliding pinion meshes with the gears in the motion works for changing the hour and minute.

So for a jumping hour watch like the 8900, in the second position the sliding pinion must mesh with some intermediate wheel that must mesh with some sort of gear that moves the hour wheel in one hour skips of time. What does that gear look like? I assume it doesn’t move the hour wheel by its individual teeth, one tooth at a time. It somehow flips the hour wheel over enough teeth to move it one hour. And this “jump” must be much harder on the hour wheel than the usual process by which the motion works is used to set the time in the third position?

Im just curious because I love that feature in the 85/8900. And you need it to create a true GMT movement so it’s not that crazy an idea. Does it cause problems in all watches that use it or just omega?
 
nicolamilton
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People here:s gonna say it never brakes.
Nonetheless I've seen several 8500 breaking, but I'm not aware of same issue proportion with 8900.
 
ErichPryde
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nicolamilton nicolamilton
People here:s gonna say it never brakes.
Nonetheless I've seen several 8500 breaking, but I'm not aware of same issue proportion with 8900.

Hmm... general consensus I've seen here is that it does break and is a known issue. I've seen @Archer talk about it a number of times. It comes up frequently enough. He'd definitely be able to answer the OP's question with greater specificity than I can (I couldn't find his answer I swear I've seen)

Here's a cursory google search for "omegaforums.net" "Archer" hour break 8500 & 8900.


https://omegaforums.net/threads/some-disappointment-with-a-po-i-picked-up.51304/

https://omegaforums.net/threads/seamaster-at-co-axial-8500-stem-adjusting-problems.64984/

according to this last thread from 2021, the 8900 uses identical components, so I'd assume it also can fail there.

https://omegaforums.net/threads/changing-the-date-on-8900.132147/page-2
 
nicolamilton
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spacemission spacemission
Rolex has had that kind of issues.
I don't recall that specific issue in Rolex GMTs, the most similar system you can compare to.
Amplitude and friction in seconds hand is the only recent problem with Rolex 32xx movement, and similar to what sometimes happens to Omega 3861 chronograps.
 
E
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Here’s what I’m curious about. And maybe should have put it in the watchmaker forum because it’s a nerdy question. No one ever says “be careful how much you use the 3rd crown position to change the time on your watch because you might wear out the hour wheel”. And I get that. I have a skeleton watch that does a good job displaying the motion works, and changing the hour and minute hands in the 3rd position (whether the watch hacks or not) is a very smooth and non-violent process.

But for watches where the second crown position jumps the hour hand forward and backward in one hour jumps (as opposed to a watch where the second crown position controls a quick set date) you do have watchmakers who will caution you not to overuse this action. I’m just curious how this action is accomplished in the watch and why it’s so much harder on the hour wheel than regular time setting in the 3rd crown position. Would love to see a geeky watchmaker you tube video on how this works.
 
Donn Chambers
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E Edgeworth
Here’s what I’m curious about. And maybe should have put it in the watchmaker forum because it’s a nerdy question. No one ever says “be careful how much you use the 3rd crown position to change the time on your watch because you might wear out the hour wheel”. And I get that. I have a skeleton watch that does a good job displaying the motion works, and changing the hour and minute hands in the 3rd position (whether the watch hacks or not) is a very smooth and non-violent process.

But for watches where the second crown position jumps the hour hand forward and backward in one hour jumps (as opposed to a watch where the second crown position controls a quick set date) you do have watchmakers who will caution you not to overuse this action. I’m just curious how this action is accomplished in the watch and why it’s so much harder on the hour wheel than regular time setting in the 3rd crown position. Would love to see a geeky watchmaker you tube video on how this works.

You also shouldn’t be changing the date all the time on a quickset date function for exactly the same reason. It will be less of a problem, because the gearing teeth are closer to allow 31 jumps in a 360 degrees instead of 12, but it’s the same problem.

As Archer has said in his other posts, the part should last for 5-7 years of normal use and the part should be replaced at a service. I had one of the older Seamaster GMTs based on the 1120 movement and had no problems until 7 years of continuous wear when I noticed the hour hand slipping. It was well past the time for a service, so I took it in and it came back working fine.
 
Archer
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nicolamilton nicolamilton
Amplitude and friction in seconds hand is the only recent problem with Rolex 32xx movement, and similar to what sometimes happens to Omega 3861 chronograps.

The 3230 series suffers from low amplitude, accuracy issues, prematurely worn seconds wheels, and sometimes even snapped off pallet forks. Rolex doesn’t appear to have solutions to these problems yet, many years into the life of the movement.

The 3861 issues were solved within months of it coming up on forums, so these are not analogous situations.
 
Archer
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E Edgeworth
Here’s what I’m curious about. And maybe should have put it in the watchmaker forum because it’s a nerdy question. No one ever says “be careful how much you use the 3rd crown position to change the time on your watch because you might wear out the hour wheel”. And I get that. I have a skeleton watch that does a good job displaying the motion works, and changing the hour and minute hands in the 3rd position (whether the watch hacks or not) is a very smooth and non-violent process.

But for watches where the second crown position jumps the hour hand forward and backward in one hour jumps (as opposed to a watch where the second crown position controls a quick set date) you do have watchmakers who will caution you not to overuse this action. I’m just curious how this action is accomplished in the watch and why it’s so much harder on the hour wheel than regular time setting in the 3rd crown position. Would love to see a geeky watchmaker you tube video on how this works.

A "regular" hour wheel is a simple one piece affair that has no moving parts. It's machined from one solid piece of brass alloy, so it is unusual for it to require replacing. The hour wheel assembly on the jump hour watches is very different.

Look at this photo...



The wheel is a two piece assembly that allows one part to be stationary while another part of it rotates. One portion of the wheel must maintain contact with the minute wheel and allow the hour hand to be driven along as normal, while the other half must move separately when the hour hand is being adjusted in position 2. There are detents built into the wheel that create the 1 hour jumps. These small detents wear over time, and the wheel stops working properly. It’s nothing particularly complex, just the scale of things is quite small.

If you use this more, it will wear out faster, so I always suggest that if you are setting the date, rotate the hours in the direction that is closest to the date you want. So if the watch is set to the 5th and you want the 30th, don't adjust the hour hand forwards, go backwards.
 
spacemission
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nicolamilton nicolamilton
I don't recall that specific issue in Rolex GMTs, the most similar system you can compare to.
Amplitude and friction in seconds hand is the only recent problem with Rolex 32xx movement, and similar to what sometimes happens to Omega 3861 chronograps.

I have read that you like the calibres 31xx, la crème de la crème in your opinion. 3186, 3185 improved, had issues.
 
nicolamilton
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spacemission spacemission
I have read that you like the calibres 31xx, la crème de la crème in your opinion. 3186, 3185 improved, had issues.
So glad you follow me through time and forums
 
nicolamilton
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Archer Archer
The 3230 series suffers from low amplitude, accuracy issues, prematurely worn seconds wheels, and sometimes even snapped off pallet forks. Rolex doesn’t appear to have solutions to these problems yet, many years into the life of the movement.

The 3861 issues were solved within months of it coming up on forums, so these are not analogous situations.
So would you admit that jumping hour issue would be a more analogous situation?
Both 8500/8900 and 32xx should last for 5-7 years and the part should be replaced at a service.
 
Archer
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nicolamilton nicolamilton
So would you admit that jumping hour issue would be a more analogous situation?
Both 8500/8900 and 32xx should last for 5-7 years and the part should be replaced at a service.

No, not at all. The 32XX series has proven far less reliable than the Omegas that use the jump hour function. One is normal wear and tear, and the other is something entirely different. The Rolex fanboys will fight it tooth and nail, deny that problems exist, or say it doesn't matter, but the 32XX is a nightmare for Rolex.
 
E
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Archer Archer
A "regular" hour wheel is a simple one piece affair that has no moving parts. It's machined from one solid piece of brass alloy, so it is unusual for it to require replacing. The hour wheel assembly on the jump hour watches is very differen
Look at this photo...



The wheel is a two piece assembly that allows one part to be stationary while another part of it rotates. One portion of the wheel must maintain contact with the minute wheel and allow the hour hand to be driven along as normal, while the other half must move separately when the hour hand is being adjusted in position 2. There are detents built into the wheel that create the 1 hour jumps. These small detents wear over time, and the wheel stops working properly. It’s nothing particularly complex, just the scale of things is quite small.

If you use this more, it will wear out faster, so I always suggest that if you are setting the date, rotate the hours in the direction that is closest to the date you want. So if the watch is set to the 5th and you want the 30th, don't adjust the hour hand forwards, go backwards.

Thanks, Archer. Your explanations of watchmaking are always so clear and concise.
 
E
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One more comment. I sold my Aqua Terra 8500 in 38.5mm but I loved the jump hour. I used this watch as my daily, so I really only needed to change the dates a few times a year, for months with fewer than 31 days. But I used the jump hour all the time when flying to different time zones in the U.S. plus twice a year for daylight savings.

Once Omega went to the effort of using that jump hour wheel that Archer described, it seems to me that they weren’t that far away from a true GMT. Just need to put a second hour hand on the pipe of the hour wheel and a minimal amount of extra gearing to make this a 24 hour hand.

So it’s hard for me to understand why Omega couldn’t make an Aqua Terra GMT in 38mm with no appreciable increase in thickness.

But the only ATs that they did with GMT had a case diameter of 43mm which is crazy big
 
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