I was recently asked to service a Hublot Big Bang King...interesting names these watches have. I am a bit hesitant to take on watches where I don't know what the movement is, and if I can get parts for it. This was a time and date only movement, and after doing some research it seemed that they may use some Sellita movements, namely the SW300, which is a clone of an ETA 2892.

But I could not find a movement specification for the specific model number this one was, so when I expressed my doubts, my client suggested that if I get it open and can't get parts, I can just send it back and he won't be upset. I agreed and shortly after this arrived:


44mm case made of ceramic and titanium. A dial marker had fallen off, the chapter ring had come loose, and the seconds hand was jammed on that ring. So this watch had some issues right off the bat. I removed the screws from the back of the case, and found this "HUB 21" inside:


It does not resemble and ETA 2892 or anything like that,. so at first I was a bit puzzled. I removed the rotor and then noticed a few things that looked very familiar - the click spring on the left was the first thing, then a flash later and I see the other two things:


It then dawned on me that this was a modified ETA 7750. Now it's not completely unusual to see 7750's modified for time and date only, say in a PAM 104:


This is not my watch, but I do own one of these and service them quite frequently. The chronograph parts are completely removed, but they use the seconds hand at 9 just like a normal 7750 chronograph watch does. What is interesting with this Hublot is that this is a central seconds design...so how did they do this?

Here is the movement ready to be disassembled:


Here the automatic bridge is removed, and I've added some arrows and letters:



"A" is the spring for the 2 function clutch, "B" is the two function clutch, and "C" is the chronograph wheel. They have used the chronograph wheel as the central seconds wheel, and are essentially running the chronograph all the time. The two function clutch is always pushing the oscillating pinion into contact with the chronograph wheel as you can see here before I took it apart:


They have modified the chronograph wheel to remove the finger that would trip the minute counter from the underside of the main wheel:


And they have removed the cam that would be used to reset this wheel from the top side:


It's a pretty clever solution, and this came to mind because someone again asked if it was okay to leave your chronograph running in another post on the forum today. Hublot have made it so that this part of the chronograph mechanism runs non stop whenever the watch is running. There were a few other upgrades they made, so they placed a jewel on the barrel bridge for the barrel arbor, used a ceramic ball bearing in the rotor, and used a Triovis regulator on the balance.

I did have to replace a few worn parts, but other than that, the service was pretty straightforward. as is typical, the 7750 performs very well in timing checks with a Delta of 3.2 seconds over 6 positions.

I am often surprised when I open up watches sent to me for service, and this time it was actually a pleasant surprise for a change.

Cheers, Al

 

Awesome and informative post as usual! My question is: Why? Why did Hublot (or any other brand) decide to modify a 7750 to a time only movement, when surely there are cheaper and easier options? I guess I can see why Panerai did it in that instance to allow for the running seconds at 9 o'clock.

 

Very enjoyable read - thanks for the clear diagrams and descriptions for us laypersons .

 

Panerai did it for the reasons you stated, as their manual wind watches tend to have the small seconds at 9 from using the ETS/Unitas 6497. There aren’t many automatic movements out there it’s sub-seconds at 9.

I think for Hublot they were using 7750 based movements for their chronograph watches. They were already tooled for making new bridges etc. for this movement and already have an established supply chain for the other parts of the movement, so I think it would be pretty tempting to use the same base movement here, rather than tool up for something completely different.

Glad you enjoyed the post.

Cheers, Al

 

I enjoyed reading that. Thanks for writing it and sharing with us.




Chye

 

VERY interesting. I was completely ready for you to say it was a replica. What kind of shock would it have to take to knock the chapter ring and a marker off a real Hublot. How did you re-attach?

 

Probably a Big Bang

 

Always love your informative posts, Al.

 

Well played sir

 

Hi, I am interested in how you will attach the marker and chapter ring.
Will you glue them back on?
Or punch the feet from behind the dial when attached with a stake set?

 

I agree if I were the owner, I would be pleased you found the movement so clever and intuitive to work with....I would still be a bit pissed about the dial furniture flying about. I have never had than happen in the entirety of my watch ownership

 

Excellent post, thank you.
What is your take on this Triovis regulator ? As far as I know, it's been used in Tudor's E2824 and some Nomos movements too, those are known of pretty decent accuracy.
I do not know a scheme of Triovis regulator nor how it compares (how to call it..) to an ordinary ETA balance regulator.

 

I love this stuff. Modified _____ movement is such an interesting phrase in the market. Some companies put on a custom rotor and call it good. Others really change the movement and features. I’d love to hear/see more of this from the bench perspective, as it helps us all understand with a little glimpse behind the curtain.

 

Well, the current owner bought it in this state, and I'm sure paid appropriately because of the damage. I don't think he's all that disappointed, but the original owner might be.

I know it's common to think that if something doesn't happen to you, then it rarely or never happens, but markers coming off is not exactly an unheard of thing, no matter what the brand is.

 

This is true. I guess I have seen a few Omega’s in the world with missing indicies- and even the king with crooked coronets!
As always, thanks for the interesting and informative write-up.

 

This is the back of the dial:


You will see that when the items are attached to the dial, the feet stick through the dial and then are ground off. The act of doing this sort of "smears" the material together and keeps the item attached to the dial...mostly.

Here is the front of the dial:



I've already attached the missing marker, but you can see that there are 4 holes around the perimeter of the dial for the chapter ring, and you can see that in addition to the feet, they used some type of adhesive to hold this ring on as there is obvious residue from that present. I also used adhesive to attach the parts back.

Adhesive use in watches is as old as watchmaking itself. The most obvious example is shellac, which is still used to hold the roller jewel in place on the roller, and still used to adhere the pallet jewel in place in the pallet fork. But other instances are also common, such as the modern practice of gluing the balance spring into the stud, instead of pinning it:



The specific adhesive I used remains flexible to a degree, so it has less chance of failing over time.

Cheers, Al

 

The old Valjoux versions of these movements just used standard regulating pins, and a pointer style regulator - I just happen to have one of those in the shop right now, so here is what that balance looks like:



Note that this is sort of rare - most of the 7750's I get in are ETA's, not Valjoux's. You can see the normal regulating pins, the balance spring stud held in by a screw, and the rather distinctive 7750 pointer regulator. The ETA versions use the ETACHRON system, that uses specific tool for adjusting the centering of the balance spring, for opening and closing the regulating pins, and another for removing the stud from the balance cock. Here is what that looks like - note the rectangular pieces on the stud and regulator - one of the tools fits over these so they can be turned:



You can see it also uses the same regulator as the Valjoux version.

The Triovis uses the standard old regulating pins that the original Valjoux version uses, and the stud is held in place using a screw. But the way the regulator works is quite different. It uses a small screw on the side of the stud carrier that operates a small worm gear type arrangement, so the fine adjustment of the regulator can be quite accurate. Here is what it looks like:



This in itself doesn't make the watch more accurate, as all that is due to other things, but once you get good Deltas then this system makes is easy to adjust the final average rate. The only thing is you have to be a little careful when turning the screw, since pressing hard with the screwdriver will move the stud carrier and throw the watch out of beat. It's just a very clean looking way to fine regulate the rates.

Cheers, Al

 

Superb thread, so so so informative, thanks Archer

 

There are varying degrees of modified movements out there. As you say, some slap a rotor on and call it modified, but others do much more.

Sticking with the 7750 for a minute, another brand that used the modified 7750 without chronograph parts is the old Anonimo watches. This is the same sort of thing that Panerai did, but instead of having the seconds at 9, they turned the whole movement in the case:



The crown ends up at 6, and the sub-seconds is under the 12 marker. This watch was unusual from another perspective - it had a date magnifier that was attached to the dial, rather than the crystal, and that is something you don't run into very often.

Another example is from a company that typically was only painting the rotor red, and calling it modified - Oris. Here is a Carlos Coste dive watch - note the position of the sub-seconds:



So what movement would this be? An ETA 2826-2 modified to remove the day, and relocate the seconds hand. Here you can see the train side of the movement, and it has an extra pinion at the red arrow:



With the bridges removed, you can more clearly see the pinion being driven off the third wheel, and the friction spring for it:



In order to make this work, they shortened the seconds wheel in the middle of the movement that would normally carry the seconds hannd, added the extra pinion and friction spring, and had to machine the main plate to accept these parts, plus added one extra jewel:



Oris did further modifications to the ETA 2826-2 in the "Der Meistertaucher" model. The same offset sub-seconds, but in addition to this they made it into a regulator model, so the minutes are on the central axis, and the hours are shown on a sub-dial:



So in addition to the same mods for the Carlos Coste model, they made some changes to the dial side of the movement:



This again required more changes to the main plate, but on the dial side this time.

So some modifications are not much more than superficial decoration, but others can be quiote a bit more involved.

Cheers, Al

 

Thanks for posting the Oris Al. It's fun to see the work and design that can go into a movement to make it unique or different.