Thursday, July 27, 2006

Rolex Oyster Perpetual Cosmograph Daytona 4130 Chronograph Gear Train

Briefly, I already touched on the Rolex 4130 here. I hoped to return to peform a little bit of analysis of the gear train strategy sooner, but got waylaid by other matters. Anyway, I finally got to sit down and review the details and have some comments. You can read a magazine overview of the movement here. Very useful, but it's a bit lacking in technical detail and left me wanting to know a lot more about the novel layout as this movement is promoted on the basis of robustness and ease of maintenance founded on a minimum parts count and simplicity of the chronograph gear train.

To go deeper we need to pull the patents out, and with the following figures, let me give you a fly through the gear train. It's best to sit down with the document of US patent 5793708 as I will refer to gear train numbers, but I have included the figures from these below. My particular concern is that any meshing gear pair is an efficiency loss, so I was intrigued to read Rolex's claims. Let's follow the drive of the chronograph. Ready, here we go:

Figure 2 is effectively Section II from Fig1.
Figure 3 is Section III from Fig1.

Start at the centre wheel and we go to '14' and then '15'. '15' gives the running seconds of the watch. Now '15' meshes '17' meshes '18' to give the chrono seconds. Ok, now go back to '17' and on the same shaft is '27' a finger for driving the minutes and hours counters. So we go '27' meshes '35' meshes '37' meshes '38' the 30 min counter. Go back to '35' and mesh to '40' meshes to '41' the hour counter.

There are actually a total of seven mesh steps to display hrs, mins, seconds on the chronograph if we take it from the running seconds. Now to me, that seems no simpler than any classic chrono form be it the gear paths of any intermediate wheel chronograph, modular chronograph, etc.

What is more interesting though is the transition (sic) fit of the wheels 38 and 41 and their respective shafts. This allows for the reset hammers to operate on the zero cams and respective indicator needles resetting to zero with the chronograph geartrain locked. In addition, reset adjustment is apparently provided by a simple eccentric post ('77') rather than several eccentric stops. Clever stuff Rolex!

But, I'm not sure I buy the claim that "Periodic driving of the hours and minutes..... allows reduction of the power provided by this gear train to drive the chronograph..." as you have to turn the wheels in the end and compared to other chronos with intermittent drive where's the advantage? Also, there are seven meshing steps to overcome. However, the novel packaging approach does lead to a slim movement with good space for spring barrel, balance wheel and winder.

No comments: