Thoughtful Engineering Is A Powerful Source Of Conversation
By
Kevin Cameron April 11, 2019
In 1973, Peter Williams brought to Daytona his evolving concept of what could be achieved in racing with the limited power of Norton’s pushrod parallel-twin 750. In conversation, what came through was his cheerful and strong belief that thoughtful engineering, as opposed to reliance upon tradition, could still improve the motorcycle significantly.
As an example, cooling air for his engine’s head and cylinders was controlled by choice of an orifice plate, installed in the wind-tunnel-developed fairing just ahead of the engine. On a high-speed track such as Daytona, the smallest orifice would be used, with larger ones for tracks on which average air velocity would be less. It is, he noted, more efficient to flow air around the motorcycle than to let it flow through it. This is why aircraft powered by piston engines had either radiator shutters for liquid-cooling or cowl flaps to adjust cooling airflow to the power being used. The old practice of leaving the whole front of the fairing open ahead of the engine turned the bike into a large drag-producing air scoop—more just a cover rather than streamlining. Peter admitted just the cooling air needed. With its sophisticated air management, Peter’s design was just as fast as our 750cc Kawasaki two-strokes.
The area of the fairing behind Peter’s front wheel was a completely non-intuitive flat surface, the veritable “barn door” perpendicular to airflow. Why? British aircraft in World War II equipped with arrays of radar dipoles would have lost a lot of top speed had a partial solution not been found; later airborne radars had steerable dish antennas inside of streamlined fiberglass fairings. The dipole arrays were therefore placed ahead of flat surfaces. Air, slowing as it piled up in front of such surfaces, generated less drag as it passed through the dipoles. The aerodynamically “nasty” exposed fork and front wheel of a racing motorcycle, looking just like a radar dipole array to oncoming airflow, was therefore treated in the same way. The flat surface behind the front wheel pushed a lump of low-velocity air ahead of itself, within which the wheel generated significantly less drag.
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