Daytona Seconds @ 6

[japanic]

I have a question regarding the problems surrounding the Daytona models with the seconds at six.

If I were to replace the asian 7750, which automatic movement would be best suited for this "transplant"

My first thought would be the Valjoux 7753, but on further reading, the seconds run at 3 for that particular movement.

Could any of the Daytona pros help shed some light on this dilemma?

[ubiquitous]

There's not much in the way of options for movement transplants into the A7750 seconds at 6:00 Daytona (116520 replication) as the movement's subdial positions are slightly different than the standard tri-compax layout like the 7753. If you'll notice, the 9:00 and 3:00 subdials sit slightly above the center of the dial on the modified seconds at 6:00 A7750 (i.e. if you drew a line from the 9:00 to 3:00 hour markers, the hour and minute counter sub dials sit slightly higher, closer to 10:00 and 2:00). This is unique to this specific watch.

The genuine 116520/4130 has the subdials in the same positions, so the replica factories took the time to emulate this change when reconfiguring the subdial functions.

[japanic]

Thanks Ubi, what actually causes this movement to be so problematic?

I've read the thread where the movement was stripped down, but my I was out of my depth; my engineering knowledge is limited.

Would one be alright if one does not use the chronograph function?

[ubiquitous]

Keep in mind that to achieve the look and function of the genuine 4130/116520 Daytona, the A7750 movement is fitted with a number of new gears that relocate the functions of the subdials. The biggest concern is the running seconds, which is a constant running subdial and the fact that the pivot is not sitting in a jeweled bearing means that failure is likely.

You could have a jewel installed for the pivot, though others have had their movement plates either augmented with graphite powder or treated to a DLC coating to help with longevity.

[sneed12]

The 7753 has seconds at 9, not 3.

[szvwj]

Well, this is an eye-opener. I never noticed that the layout of this particular movement was different from the others.

So, this means that there are at least 3 distinctly different (not all parts are interchangeable) A7750 versions (are there more?).

- Low beat (21,000bpm) A7750

- High beat (28,800bpm) A7750

- Daytona Seconds-at-6 A7750

This may explain why, even though I've replaced parts in my daytona movement (with parts from a High bt A7750), it's not working (the escape wheel won't engage properly).

Thanks for the info.

[sneed12]

Well, this is an eye-opener. I never noticed that the layout of this particular movement was different from the others.

So, this means that there are at least 3 distinctly different (not all parts are interchangeable) A7750 versions (are there more?).

- Low beat (21,000bpm) A7750

- High beat (28,800bpm) A7750

- Daytona Seconds-at-6 A7750

This may explain why, even though I've replaced parts in my daytona movement (with parts from a High bt A7750), it's not working (the escape wheel won't engage properly).

Thanks for the info.

I think you misunderstood what ubi said.

In a very real sense, there is only one configuration of the venerable 7750 movement. All 7750s have exactly the same subdial spacing and layout.

Reps which have different configurations of the subdials use a plate installed on top of the movement, which use transfer gears to move the subdials into different positions. Depending on how much movement is needed, this can end up being quite complex.

However, all movements derived from the 7750--movements like the ETA/Valjoux 7753--use this same idea. The 7753 has transfer gears which move the output shafts to a different place, but unlike the rep makers' transfer plates, the movements are designed and built with this modification in mind, and the transfer gears go underneath the calendar plate. In other words, it's the exact same idea, but a different (higher quality) execution.

The Rolex Daytona uses a movement that's entirely different from any flavor of 7750. It's a Rolex in house movement. Therefore, all three subdials need to be moved (which involves a lot of gearing) including the seconds subdial (which sees the most wear, since it's running all the time). Also, the transfer plate installed on the front of the movement makes the overall thickness even greater (which is bad, b/c the 7750 is too thick to begin with) and increases the stem height (which is bad, for the same reason). That's why all rep Daytona cases have serious flaws--they HAVE to be bigger than a gen case, or the movement won't fit inside.

The actual base movement without the transfer plates, though, should be a standard A7750. You should in principle be able to swap any A7750 into any seconds-at-6 Daytona, pretty much, as long as you match low beat/high beat.

[PPN]

I think you misunderstood what ubi said.

In a very real sense, there is only one configuration of the venerable 7750 movement. All 7750s have exactly the same subdial spacing and layout.

Reps which have different configurations of the subdials use a plate installed on top of the movement, which use transfer gears to move the subdials into different positions. Depending on how much movement is needed, this can end up being quite complex.

However, all movements derived from the 7750--movements like the ETA/Valjoux 7753--use this same idea. The 7753 has transfer gears which move the output shafts to a different place, but unlike the rep makers' transfer plates, the movements are designed and built with this modification in mind, and the transfer gears go underneath the calendar plate. In other words, it's the exact same idea, but a different (higher quality) execution.

The Rolex Daytona uses a movement that's entirely different from any flavor of 7750. It's a Rolex in house movement. Therefore, all three subdials need to be moved (which involves a lot of gearing) including the seconds subdial (which sees the most wear, since it's running all the time). Also, the transfer plate installed on the front of the movement makes the overall thickness even greater (which is bad, b/c the 7750 is too thick to begin with) and increases the stem height (which is bad, for the same reason). That's why all rep Daytona cases have serious flaws--they HAVE to be bigger than a gen case, or the movement won't fit inside.

The actual base movement without the transfer plates, though, should be a standard A7750. You should in principle be able to swap any A7750 into any seconds-at-6 Daytona, pretty much, as long as you match low beat/high beat.

This is very informative, thank you. I did not realize so much was involved with the Daytona rep.

[paulvillo]

Found this while digging out Daytona info as the PVD versions sort of started to appeal to me

This is some precious info to anyone looking for a Daytona, thanks guys!