Horological Meandering

jfsuperior
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further technical observations

John,

As a watchmaker I appreciate your technical input and I raise similar concerns though I would like to see the Bucherer movement in my hands to reach any definitive conclusions.

But, I've attached a photo I stitched together of three different automatic rotor systems for comparison and discussion. One is the PP calibre 350 you already mentioned, another is the Longines calibre 340 with its outer geared track, and the Perrelet company celebrated double-rotor movement. All three have one criteria in common which differ in construction from the new Bucherer system. That is they are all primarily supported at the top center with screws or through a ball bearing unit. The logic was that the added smoother traction on the peripheral enhances the rotation of the weights.

Perrelet uses a double rotor winding system with one rotor at each end of a common shaft. The theoretical advantage is that it places a balanced stress on the shaft as opposed to having a weight at one end only applying forces at right angles to the axis of the shaft. Rotor shafts and mounts used to break because of these forces. With contemporary ball bearing rotor mounts the issue is moot.

But even standard oscilating weights in today's modern watches experience stress and wear on their ball bearings. I have seen all too many watches, which received severe shocks, come in for repairs because the rotor wobbles (has too much play) on the tiny ball bearings. Either the ball bearing unit or the complete rotor needs to be replaced under those circumstances.

The Perrelet automatic winding system represents a considerable improvement on existing technology as it draws its energy from two rotors revolving around a common shaft meshing with a pinion that is mounted on a special support. This patented technical innovation has earned a dozen international awards.

In principle, at least, twin rotors turning in unison would reduce the one-sided weight and distribute it evenly between the two interdependent rotors. As Perrelet is a small company with a limited production, I know of no extensive research or tests done by anyone to determine the efficiency of their double rotor system in comparison to single rotors found on the same caliber movements.

Your point of concern that the outer weight on the peripheral in the Bucherer reduces the mass inertia of the weight is well taken.

Regards,
Jack Freedman

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