The Rotating System Disc

Perhaps the design signature of the series is the Rotating System, (‘RS‘) disc used across the range. The discs replace the traditional sub-dials and are decorated elaborately with semi-circular, polished frames.

So why bother with the RS disc? It does give the Grand Carrera series a unique look, which in some cases is more legible than the reading the elapsed units from a dial (although it’s less accurate than a traditional dial as the units are in larger increments, as you can see above).

In reality the real benefit of the RS disc is that it allows designers greater flexibility on the shape and size of sub-dials- you certainly don’t need a full circle, or even a half-circle to accurately read the time. The sub-dial windows could be half the size that they are and they would still be just as legible.

But there is a downside to the RS disc system- and it’s one of perception rather than any lack of accuracy.

Some buyers are surprised that the disc does not rotate as smoothly as they expected, and wonder if something is wrong. The answer is that nothing is wrong, but what you see is the limitations of a mechanical movement amplified by the use of a disc rather than a thin hand.

If you look closely at the seconds hand on your automatic watch you’ll notice that it too doesn’t sweep around the dial smoothly. The limiting factor here is the speed at which the movement vibrates. Traditionally, a movement that beats more than 18,000 times per hour is considered to be ‘High-Beat’. The Calibre 6, 8 and 17 movements used in the models you see here all beat at 28,000 beats per hour, or 4 hz, while the Calibre 36 models beat at 36,000 beats per hour, or 5 hz. The more beats per hour, the smoother the hand or disc will rotate, but there will always be a degree of ‘jerkiness’.