Below: that trickledown effect in action. The new Ker 56 Varuna VI, built at Knierim Yachts in Germany, features finger operated paddle shift controls on her Stayinphase pedestals to select winches. Far right: the same objective achieved using two different types of customised assemblies. On the Maxi 72 Momo (top) the hydraulic pump clutch is carefully detailed and positioned within the system to minimise friction. On Rán 6 (below) one of the boat’s primary structural bulkheads is designed to also directly support the front pedestal, incorporate the hydraulic pump and resolve loads transmitted by drive belt compression
Of devils and details –
Engineer Jon Williams addresses the not insignificant challenge of achieving small boat levels of friction while designing for Maxi 72 loads…
28 SEAHORSE Live transmission
In mid-2013 the brief from Rán Racing was to give them a maxi yacht winch system that felt as free running as their fully tuned and sorted TP52. So it was logical that we would focus again on gearboxes, second in line behind the pedestal mechan- ics as the biggest source of efficiency losses and added friction across the many systems found on the modern pure racing yacht. The M-Class series of gearboxes comes out of a collaboration with key figures from within the European helicopter industry’s transmission and high-precision machining sectors. We set out to achieve a range of carefully engineered gearboxes
that the best race crews can dependably load up to their maximum with minimal power losses.
The project began with identification and assumptions on load cases and config- urations. Gear teeth are then sized appro- priately, while bearings are matched and then encased in aggressively optimised housings. These casings, machined on DMG Mori five-axis machines, feature lubrication galleries and the very best rotary shaft seals that are currently available. During assembly a great deal of care is also taken in tuning the unloaded contact patch position on gears made from very high-specification stainless steels.
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