Propulsion world could turn on Axis Drive

Dispensing with the problematical aspects of stern drives in the form of CV joints and rubber bellows, whilst combining the benefits of conventional stern drives/outboards, Beachyhead and his engineers (ex Cosworth F1), have over the past nine years created the first drive system that is fully trimable and steerable (through 32 degrees), yet is connected directly to the engine through a constant mesh gear system. The engine/leg unit is mounted to the transom at 45 degrees, thus taking up far less internal space than a conventional sterndrive and no more than a fully tilted equivalent outboard. The engine and leg are effectively one unit, with the XTrac helical geared constant mesh gearbox mounted at the top of the cast stainless steel leg section (all stainless is surgical grade) with power delivered to the propeller via a stainless steel drive shaft to a bevel gear/prop shaft.

Because the package comes as a one piece unit, during installation it can be lowered into the craft complete, as there is no separate leg to fit. The complete installation from packing crate to being fully operational takes less than an hour, including the fitting of the NMEA 2000 modular C.A.N system fly by wire ‘intelligent gear selection’ remote controls. With finger tip lightness and positive gear selection feel though the ergonomically designed gear/throttle lever, combined with the actuator cone clutch constant mesh gear selection set up, there is no thump or noise accompanying gear selection, just a linear movement from forward through neutral to reverse.

As an electronically managed package, everything from throttle response to gear change is monitored by the engine’s ‘brain’, if a clumsy operator throws the gear lever from reverse to forward, straight through neutral (potentially catastrophic for any sterndrive/outboard motor), the brain will only allow the gear to engage once it has calculated that it is safe to do so. The ‘brain’ works in fractions of a second and when testing this particular aspect of the Axis drive/craft at sea last month, there was only a second’s delay whilst the computer worked things out. The ‘brain’ also provides RPM hold (cruise control) and dual engine RPM synchronisation.

There are full electronically managed petrol and diesel options, all with dry sump oil bath lubrication and the unique Caudwell Axis drive. The three petrol units are Nissan Infinity based; a 3.5 V6 300hp, a 4.5 V8 350hp naturally aspirated, plus a 450hp supercharged version available in 2010, all with DOHC VVT technology. The latest Ford/Jaguar/Range Rover diesel based engine is a 3 litre V6 variable nozzle turbocharged DOHC 24V unit developing either 270 or 300hp depending on application. Both weigh in at a low 400kg.

Caudwell are currently evaluating a technically similar Ford based V8 diesel with up to 450hp and 600NM torque. Once tests are concluded, this unit could be available, along with digital docking control, by late 2010.

Initial tests have shown diesel units to be up 20% more efficient than comparable stern drives and petrol units up to 30% moreso, but when testing two identical craft, one with the Caudwell drive, the other with a popular alternative, it was the exceptionally smooth power delivery and sharp, precise steering of the Caudwell that stood out. Unlike a conventional drive, the Axis leg cleverly follows the craft’s keel angle, which provides tighter, safer turning.

With the emphasis on clinically sound engineering and efficiency, the Caudwell Axis drive offers a genuine alternative to conventional existing drive units. The first chance to see and try one will be at this year’s Southampton Boat Show, where European importers, Golden Arrow Marine will be demonstrating the petrol 300hp version in a Ballistic 7.8m RIB.

By Paul Lemmer