Encontrei a explicação abaixo:
""
This is from WatchTime Omega-specific magazine, page 15 (about caliber 8500):
"The organ that's often described as the "motor" or "engine" of a watch movement - the barrel - is doubled in Caliber 8500: two series mounted barrels provide power for at least 60 hours of uninterrupted running. The barrels are "fueled" either manually, by turning the crown, or automatically, by the automatic winding mechanism. Sixty manual rotations of the crown are needed to rotate the barrels 18 times and thus completely "fill the tank." The so-called "hand-wound barrel" without slip clutch is wound first: when fully wound, it amasses a torque of 6,450 micro Newton meters or 3.19 microwatts. Soon afterwards, the winding engergy is also conveyed to the so-called, "automatic barrel" with slipping spring. When fully wound, this barrel accumulates a torque of 6,330 micro Newton meters or 3.13 microwatts.
In the opposite direction, the automatic barrel first discharges its stockpile of energy directly to the center wheel. When its energy supply has become equal to the amount stored in the hand-wound barrel (which occrs in a short time), both "engines" begin simultaneously discharging their remaining store of power. The barrels are coated with DLC (diamond-like carbon), so they work with little loss due to friction and with nearly no wear; a test simulating long-term behavior over a 10-year period showed no traces of premature aging or wear."
""
Fonte:
http://forums.watchuseek.com/f20/dual-barrel-torque-delivery-371905.htmlPelo que entendi o tambor com brida fixa é o primeiro a ser carregando (quando a carga é pela coroa) e sem seguida o de brida deslizante........ já o consumo ocorre inversamente, o primeiro que começa a funcionar é o de brida deslizante e só quando esse perde força e se iguala ao de brida fixa é que os 2, ao mesmo tempo, começam a funcionar conjuntamente...
Agora, segundo o texto acima, o tambor com a brida deslizante acumula
menos energia que o de brida fixa.....o que torna a explicação meio contra intuitiva...
Encontrei em outro site a mesma explicação, sem a apresentação dos valores de força do tambor.
http://www.speedywatches.com/articles/caliber-9300-explained/de toda forma me parece que os 2 tambores são utilizados simultaneamente pra manter o torque mais alto por mais tempo.....ao dividir o trabalho, eles demoram mais a chegar na parte final da corda, que pelo que já aprendi aqui, piora a precisão.
Abraços.