David Garside

David Garside was a project engineer at BSA's Umberslade Hall research facility. He is notable for having developed an air-cooled twin-rotor Wankel motorcycle engine which powered the Norton Classic road bike. Although the Classic was not the first production rotary-engined bike, it was significantly lighter, smoother and more powerful than the contemporary Suzuki RE5.

Garside, who had been impressed by the Fichtel & Sachs engine in the DKW Hercules bike, installed a bought-in F&S air-cooled single-rotor engine into a BSA B25 'Starfire' frame as a "proof of concept". This proved reliable and smooth, but under-powered. Garside then created a prototype twin-rotor engine (with F&S rotors) which doubled the capacity of the earlier test "mule". This twin-rotor engine was installed in a BSA A65 frame.

Wankel engines run very hot, so Garside gave this air-cooled motor additional interior air-cooling. Air was drawn through a forward-facing filter situated to provide a ram air effect. This air was channelled initially to the rotating 'crankshaft', through the interior of the two rotors, then entered a large pressed-steel plenum before entering the combustion chambers via twin carburettors. The plenum (which doubled as the bike's semi-monocoque frame) enabled the transfer of much of the heat to the surrounding atmosphere. The carburation process further reduced temperatures via the heat of evaporation.

Even so, at 50 °C the fuel-air mixture was still hotter than ideal, and the engine's volumetric efficiency remained somewhat impaired The eccentric shaft's main bearings and the inlet manifolds were fed by oil-injection lubrication, and the fuel-air mix also carried residual mist of oil from the interior of the rotors, which helped to lubricate the rotor tips.

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