The Supercharged 1,000cc JAP with O.E.C chassis.

The O.E.C. was an unusual motorcycle, using 'duplex' steering; an OEC trademark, although not all of their bikes used this system. The advantages of this arcane steering system on these early motorcycles was great stability at speed, plus the possibility of front wheel suspension which didn't alter the steering geometry when compressed by bumps, giving totally 'neutral' steering under all conditions. In practical use, the OEC chassis was reported to be very stable indeed, although resistant to steering input! So, while potholes and broken surfaces brought no front wheel deflection, neither did a hard push on the handlebars...perfect for a speed record chassis actually.

Joe Wright had already taken the Motorcycle Land Speed Record with the OEC, back on August 31st at Arpajon, France, at 137.32mph (see top photo with news story), but Henne and his BMW had the cheek to snatch the Record by a mere .3mph, on Septermber 20th. That November day was unlucky for Wright and the team, as the Woodruff key which fixed the crankshaft sprocket sheared off, and the OEC was unable to complete the required two-direction timed runs to take the Record. As you can see in the photo below, the engine mainshaft drove the supercharger as well as the primary chain/gearbox, and was a one-off for which there was presumably no replacement, with probably no time for repair in any case.

Supercharging a v-twin motorcycle is a difficult business, as the compressor blows fuel/air mix at a constant rate into a shared inlet manifold for both cylinders, but as the cylinders aren't evenly spaced physically (as they are on a BMW, for instance), one cylinder inevitably gets a much bigger 'puff' of built-up pressure. Figuring out how to accommodate a different charge for each cylinder led to all sorts of compromises, from restricting the inlet port of one cylinder, to the use of different camshafts/compression ratios/valve sizes for each cylinder, in an effort to keep one cylinder from doing all the 'work' and overheating. It was an imperfect science, as supercharging was still relatively new to motorcycles, and only a handful of blown motorcycles were truly 'sorted out' for racing or record-breaking before WW2. Typically, these had flat-twin or four-cylinder engines, with even intake pulses! (Although, of course Moto Guzzi, typical of their genius at the time, had a lovely 250cc ohc blown single-cylinder which worked a treat).