The aerodynamics of motorcycles have entered a completely new era in recent years, with MotoGP teams developing increasingly complex and effective solutions to increase speed. But the latest innovation comes from a company that is not involved in the MotoGP world championship, BMW.
While most aerodynamic innovations in motorcycling aim to increase downforce, or at least counteract lift, to push the tires onto the asphalt, BMW is taking a different path and trying to use airflow to counteract centrifugal forces, reducing the workload of the tires and increasing speed in corners.
The Bavarian company has filed a patent application for a duct system that collects air from one side of the motorcycle and directs it to the opposite side, where it is expelled through jet-shaped outlets. The only image accompanying the patent shows a simplified view of the underside of a motorcycle equipped with the system and demonstrates the path that the air takes. The motorcycle in the illustration is moving from right to left, so the wider section of the fairing is facing forward.
You may be thinking that the two air ducts and their corresponding jets must surely cancel each other out? The patent explains that when the motorcycle is traveling in a straight line, that is true: the air on each side of the motorcycle moves at the same speed, so the two ducts cancel each other out. But all of this changes when the motorcycle leans into a curve.
This is the clever part. When you are making a turn (for example, turning left), the airflow on the opposite side (the right) can separate from the fairing, reducing the pressure on that side. Meanwhile, the pressure on the side closest to the ground (the left in our example) increases. Essentially, it’s as if the road surface and the side of the fairing work together to become a wider and broader channel for the duct on that side, compressing the air towards the intake. As the ducts cross each other, this means that the “jet” outlet on the opposite side releases more air, at a higher pressure, pushing the tire towards the ground and the motorcycle into the curve.
The BMW patent continues to explain that by making the inlet larger than the outlet and giving the outlet a nozzle-like design, it is possible to increase the speed of the air exiting the “jet”. The document provides an example of an inlet of 5,000 mm2 (7.75 square inches) and an outlet of 1,000-2,000 mm2 (1.55 to 3.1 square inches).
Since BMW does not compete in MotoGP, where an idea like this could be applied to a purely prototype machine, it is possible that the company is considering using the technology in a road sport motorcycle. The M 1000 RR would be the logical machine to adopt it, as it is a track-oriented motorcycle that competes in WSBK.
