From Page 31 of this thread:
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"Here are my thoughts and observations as I try and put this movement and its accuracy into context through my years of experience gleaned at the bench.
As previously mentioned in my article on the ETA 2892,
accuracy and reliability are the result of intelligent design with well thought out compromises, executed as superbly as possible. Examining the movements that fit into this category does highlight a few important areas that seem common to most of them.
First off,
almost all of them are high beat (28,800 BPH) movements. I know that some manufacturers prefer a slower beat (usually 21,600 BPH) in order to reduce wear on the pivots. I know that many will disagree with me, but I honestly don't believe that the gains justify the losses in going with a slower beat.
The most important gains are
more torque, which usually results in a smoother and more even transmission of power. Greater moment of inertia. So that the
balance wheel is disturbed less and recovers faster from shocks and bumps. Also, the fact that the balance is moving faster, means that it's spends
less time in contact with the escapement. These things contribute greatly to increased accuracy and reliability.
The two main negatives from a higher beat are theoretically more wear of the pivots, because of higher friction due to the higher torque. Secondly, the automatic winding will need to be more carefully designed and implemented. Both to take into account the increased pressure on the driving wheels and pivots, and also the gear ratios in order to more efficiently wind up the >stronger mainspring. A perfect example of a poorly designed automatic system is the old Patek Philippe Cal. 310. The gear ratios were poorly chosen for the strength of the mainspring used. This not only resulted in poor winding efficiency, but also in the steel ratchet wheel deforming the teeth of the ratchet driving wheel within a short time.
The only reason that I say 'theoretically more wear' is because in all my years at the bench, I honestly
don't see any difference in wear on the pivots from an old 18,000 BPH watch to the Zenith Cal. 400 chrono, which is the fastest beating mechanical movement currently in production. The one thing that seems to destroy pivots in short order, is moisture in the movement and then leaving it running for an extended period of time before its next service. Poor servicing (i.e. inadequate cleaning, which leaves dirt and dried out oils on the pivots) and careless lubrication is also responsible for worn out pivots.
Smooth and even transmission of power also helps considerably in the accuracy department. Easier said than done. But obviously a good understanding of the mechanical principles involved, together with the knowledge gained from decades, if not centuries of experiments. The older watches relied on the fusee, maltese cross in the barrel etc to achieve that aim.
Modern watches rely on specially shaped teeth (such as the ETA microgear toothing), correct shape and material of the mainspring, modern lubricants, careful lay-out of the drive train and the smooth rolling of the Glucydur teeth on the steel pinions.
Variations in amplitude on my timing machine are consistently the least with the modern Rolex calibers and the chronometer grade ETA 2892 and its variants. With the Valjoux 7750 and JLC 889 being not too far behind.
A well designed and accurately set up escapement is a given. This, together with a
modern Glucydur balance that has been dynamically poised by computer and used in conjunction with an excellent hairspring are just some of the 'secrets' of an accurate movement. And what I mean by 'excellent hairspring' is both it's shape and material.
Rolex and ETA (in their chronometer versions) both use the highest quality Anachron for their hairsprings. Rolex having refined and perfected the
Breguet hairspring, and ETA having refined and perfected the flat hairspring with dog-ear bend to achieve virtually identical results.
The fit and finish of important parts -- escapement, balance wheel and hairspring etc -- is exemplary. While the decoration of the basic plates is really quite crude where visible, and virtually non-existent when it's out of sight. This might bother some people, but
Rolex obviously spare no expense concentrating on those parts that affect precision and reliability while just giving a basic nod to bare-bones decoration of their movements.
I know that some people might attribute this movement's extraordinary precision to its Breguet hairspring, but I'm not one of them. Putting this movement on a timing machine shows
its very smooth and exceptionally stable transmission of power from the barrel to the escapement, and putting it through its paces in the various positions shows its absolutely astonishing isochronism. This is the same type of performance that I see in the better adjusted Omega watches fitted out with their Daniels escapements -- and the latter do not have Breguet hairsprings.
All in all, I'm very impressed with Rolex's new movement. I really take my hat off to them for not sitting on their laurels, because there really was no pressing need for them to update their already accurate and reliable Cal. 2135. While other movements do match it, both in terms of precision and reliability,
none do it with the volume and consistency of Rolex. A tribute not only to both their movement designers and precision engineering, but also to their
amazing quality control."
But, this movement (caliber 9001) is just so damn interesting!
