3861 initial thoughts...

Archer

So I have been looking into the new 3861 movement and have some initial thoughts...

The movement has generally been thought of as an 861/1861 with a co-axial escapement, but that isn’t the case at all. There are very few parts in the 3861 that originate from the 321/861/1861 calibers, and most of the parts are specific to the 3861. Even parts that visually appear the same as the 1861, are specific to this caliber. In some cases these may be finishing differences, but I can’t say for sure just looking at the list.

There are some specific design changes that have been made, and the most obvious one is the co-axial escapement – the co-axial wheel and pallet fork are from the Cal. 8800. Of course the movement now uses a silicon balance spring and a new balance that is free sprung, rather than using a regulator (the balance assembly is specific to the 3861). But there are also changes made for the hacking mechanism, and a few other things. The dial side has a different look than the previous designs due to an oversized spacer called the dial support, and the new design covers a much larger area than it does on any of the previous movements, and also includes a section that restrains the hour wheel (this used to be held by the dial itself along with a dial washer).

There is a big positive that I see in that both ends of the barrel arbor are now supported by jewels. Previously the barrel arbor just ran in a hole that was drilled directly into the brass “barrel and wheel train bridge”, and in a similar hole in the “hour recorder bridge”. This leads to wear and elongation of the hole over time, and when it gets bad enough it will allow tipping of the barrel inside the movement and loss of power. This often required the parts to be replaced (what Omega does at service) or for the holes to be repaired using bushings. In fact bushing the hole in the barrel and wheel train bridge is the most common repair I do on these watches, and I even see 1861’s with wear that requires repair, so it’s not just the really old watches that suffer from this. Here is an example of the wear often seen in the 861/1861 bridge:



And after being repaired with a bushing:



So this accounts for of a couple ....

For anyone who has one of the watches that house this movement, and didn’t immediately flip it for a profit, I would be interested in hearing how the watch is performing so far."

Cheers, Al

Saad

I've been obsessed with watches for a while and have read many threads on this forum and finally decided to give input after your post. I've had the moon watch (ref xx.005) but just recently bought the 50th anniversary with the new movement. I've worn it for 2 weeks straight so far, and absolutely love it. As far as comparing the 2, it is more accurate as we all know. The only negative so far I would say, it's tighter/a bit harder to wind. Anything specific you wanted input on?

abrod520

I didn't notice it hacking, but I'll check and confirm when I get home later

Archer

So I have been looking into the new 3861 movement and have some initial thoughts...

The movement has generally been thought of as an 861/1861 with a co-axial escapement, but that isn’t the case at all. There are very few parts in the 3861 that originate from the 321/861/1861 calibers, and most of the parts are specific to the 3861. Even parts that visually appear the same as the 1861, are specific to this caliber. In some cases these may be finishing differences, but I can’t say for sure just looking at the list.

There are some specific design changes that have been made, and the most obvious one is the co-axial escapement – the co-axial wheel and pallet fork are from the Cal. 8800. Of course the movement now uses a silicon balance spring and a new balance that is free sprung, rather than using a regulator (the balance assembly is specific to the 3861). But there are also changes made for the hacking mechanism, and a few other things. The dial side has a different look than the previous designs due to an oversized spacer called the dial support, and the new design covers a much larger area than it does on any of the previous movements, and also includes a section that restrains the hour wheel (this used to be held by the dial itself along with a dial washer).

There is a big positive that I see in that both ends of the barrel arbor are now supported by jewels. Previously the barrel arbor just ran in a hole that was drilled directly into the brass “barrel and wheel train bridge”, and in a similar hole in the “hour recorder bridge”. This leads to wear and elongation of the hole over time, and when it gets bad enough it will allow tipping of the barrel inside the movement and loss of power. This often required the parts to be replaced (what Omega does at service) or for the holes to be repaired using bushings. In fact bushing the hole in the barrel and wheel train bridge is the most common repair I do on these watches, and I even see 1861’s with wear that requires repair, so it’s not just the really old watches that suffer from this. Here is an example of the wear often seen in the 861/1861 bridge:



And after being repaired with a bushing:



So this accounts for of a couple of the jewels that raise the jewel count from the 18 found in the 1861, to the 26 jewels in the 3861. There are 2 more added for the co-axial wheel, and then 2 more on the pallet fork. All these serve a specific purpose that makes sense from a watchmaking point of view, but that leaves us 2 jewels short of the 26. So where are those?

The last two are very puzzling to me, and they are added for the minute counting intermediate wheel – one on the “barrel and wheel train bridge” and one on the “chronograph bridge” and these were formerly just bushings. When the chronograph is running, the wheel that the seconds recording hand is on turns once per minute, and it has a small finger on it that flips the minute counting intermediate wheel, and that wheel in turn flips the minute counting wheel that the hand for that is attached to (located at 9 o’clock sub-dial).

Here is where the bushing is in the barrel and wheel train bridge:



And here is where it is in the chronograph bridge:



So why would Omega add jewels to a wheel that only turns when the chronograph is running, and only turns 18 degrees (1/20th of a rotation) every minute? Well it’s certainly not because of wear, because in servicing hundreds of Speedmasters I’ve never had to replace the bushings that are in these locations because they were worn out (have replaced some because of damage due to ham fisted watchmakers). So that one is a mystery to me...

I had mentioned in one of the threads on the 50th watch that the sub-dial hands are all the same hand. This is very different from the traditional Speedmaster movements where all the sub-dial hands are different, because the posts they mount to are all different sizes as you can see here:



In the previous versions, the hour recorder post was the largest diameter, the minute counter a bit smaller, and the constant seconds the smallest. These are all now one size.

One other thing of note is that the movement is shown in two finishes – one in Moonshine gold, and the other is what they are calling a “standard” finish, and that is rhodium plated and resembles the 1863. Normally when the finish changes Omega would give the movement a new designation (there are some exceptions) but in this case they are still both called the 3861. I think the fact this is in a “standard” finish indicates this will likely be the caliber used in Speedmasters in the future.

So as often happens when movements are initially released, the makers find that changes need to be made, and the 3861 already has had some changes made to it that are found in another document. These are so far minor issues related to parts sometimes rubbing on each other that shouldn’t, so the upgraded parts are not considered mandatory replacements.

For anyone who has one of the watches that house this movement, and didn’t immediately flip it for a profit, I would be interested in hearing how the watch is performing so far.

Cheers, Al

Archer

So I have been looking into the new 3861 movement and have some initial thoughts...

The movement has generally been thought of as an 861/1861 with a co-axial escapement, but that isn’t the case at all. There are very few parts in the 3861 that originate from the 321/861/1861 calibers, and most of the parts are specific to the 3861. Even parts that visually appear the same as the 1861, are specific to this caliber. In some cases these may be finishing differences, but I can’t say for sure just looking at the list.

There are some specific design changes that have been made, and the most obvious one is the co-axial escapement – the co-axial wheel and pallet fork are from the Cal. 8800. Of course the movement now uses a silicon balance spring and a new balance that is free sprung, rather than using a regulator (the balance assembly is specific to the 3861). But there are also changes made for the hacking mechanism, and a few other things. The dial side has a different look than the previous designs due to an oversized spacer called the dial support, and the new design covers a much larger area than it does on any of the previous movements, and also includes a section that restrains the hour wheel (this used to be held by the dial itself along with a dial washer).

There is a big positive that I see in that both ends of the barrel arbor are now supported by jewels. Previously the barrel arbor just ran in a hole that was drilled directly into the brass “barrel and wheel train bridge”, and in a similar hole in the “hour recorder bridge”. This leads to wear and elongation of the hole over time, and when it gets bad enough it will allow tipping of the barrel inside the movement and loss of power. This often required the parts to be replaced (what Omega does at service) or for the holes to be repaired using bushings. In fact bushing the hole in the barrel and wheel train bridge is the most common repair I do on these watches, and I even see 1861’s with wear that requires repair, so it’s not just the really old watches that suffer from this. Here is an example of the wear often seen in the 861/1861 bridge:



And after being repaired with a bushing:



So this accounts for of a couple of the jewels that raise the jewel count from the 18 found in the 1861, to the 26 jewels in the 3861. There are 2 more added for the co-axial wheel, and then 2 more on the pallet fork. All these serve a specific purpose that makes sense from a watchmaking point of view, but that leaves us 2 jewels short of the 26. So where are those?

The last two are very puzzling to me, and they are added for the minute counting intermediate wheel – one on the “barrel and wheel train bridge” and one on the “chronograph bridge” and these were formerly just bushings. When the chronograph is running, the wheel that the seconds recording hand is on turns once per minute, and it has a small finger on it that flips the minute counting intermediate wheel, and that wheel in turn flips the minute counting wheel that the hand for that is attached to (located at 9 o’clock sub-dial).

Here is where the bushing is in the barrel and wheel train bridge:



And here is where it is in the chronograph bridge:



So why would Omega add jewels to a wheel that only turns when the chronograph is running, and only turns 18 degrees (1/20th of a rotation) every minute? Well it’s certainly not because of wear, because in servicing hundreds of Speedmasters I’ve never had to replace the bushings that are in these locations because they were worn out (have replaced some because of damage due to ham fisted watchmakers). So that one is a mystery to me...

I had mentioned in one of the threads on the 50th watch that the sub-dial hands are all the same hand. This is very different from the traditional Speedmaster movements where all the sub-dial hands are different, because the posts they mount to are all different sizes as you can see here:



In the previous versions, the hour recorder post was the largest diameter, the minute counter a bit smaller, and the constant seconds the smallest. These are all now one size.

One other thing of note is that the movement is shown in two finishes – one in Moonshine gold, and the other is what they are calling a “standard” finish, and that is rhodium plated and resembles the 1863. Normally when the finish changes Omega would give the movement a new designation (there are some exceptions) but in this case they are still both called the 3861. I think the fact this is in a “standard” finish indicates this will likely be the caliber used in Speedmasters in the future.

So as often happens when movements are initially released, the makers find that changes need to be made, and the 3861 already has had some changes made to it that are found in another document. These are so far minor issues related to parts sometimes rubbing on each other that shouldn’t, so the upgraded parts are not considered mandatory replacements.

For anyone who has one of the watches that house this movement, and didn’t immediately flip it for a profit, I would be interested in hearing how the watch is performing so far.

Cheers, Al

Archer

There have been a few issues with lubrication of the centre wheel, and new lubrication instructions were published to watchmakers by Omega.

But nothing else that I have seen.

Archer

The modification of the lubrication instructions was made in Sept. of 2020.

Archer

The modification of the lubrication instructions was made in Sept. of 2020.