War of the Gyros
WAR OF THE GYROS
IT IS A WELL-KNOWN FACT of motorcycling that the faster you ride, the more strongly the spinning front wheel—which is a great big gyroscope—resists your efforts to steer it. Lighter tires, wheels and brake discs have eased the steering task, but we humans always want more of anything desirable.
Soon, any desired reduction in steering effort will become possible if Robby Kasten (www.reverserotatingroors.com) has his way. Kasten’s concept employs gears to spin the front brake discs backward at greater than wheel speed. Because of their opposite rotation, the gyro reaction of the discs will be subtracted from that of the wheel itself. Disc speed is increased to make up for their small diameter as compared with that of the wheel. With the discs rotating backward at 2.7 times wheel-forward rpm in his prototype device, Kasten calculates that 80 percent of the gyro resistance to rider steering input will be eliminated.
Sound crazy? Thirty-five years ago, English physicist David E.H. Jones, writing in Physics Today, described his efforts to construct an unrideable bicycle. Because so many people claimed (and some continue to claim today) that twowheelers steer as a result of front-wheel gyro reaction, Jones built a front wheel with zero gyro reaction. This consisted of the normal front wheel, plus a second rotor spinning in the opposite direction. Of this nongyroscopic bicycle, Jones said, “It could easily be ridden.”
In the mid-1970s, a similar counter-rotating brake disc concept was tried by Aermacchi on its 500cc two-stroke Twin roadracers. Not much was written about the setup at the time, and it seems to have passed into history with little fanfare. Certainly, no current race team has felt a need to revive the concept.
Kasten comments that his version will reduce steer torque “to a fraction of what it is even on a MotoGP bike.” He also expects it to increase resistance to wobble.
Most of the response he has had to his concept has been positive, but some have pointed out that the gears and other extra parts required will increase front unsprung weight V and add complexi ty. His reply is that, "Every part of a motorcycle has a costbenefit ratio. Think of the transmission as an example. Yes, it adds mechanical complexity. Yes, it adds weight. But it greatly increases efficiency-we can’t do without it.”
He went on to point out that because people grow accustomed to limitations like heavy steering effort, they usually don’t question such things or seek a way around them. They just accept them.
When I spoke with Kasten, his prototype was in final assembly and about to be tested. He anticipates that reduced steering effort may change the whole setup compromise of motorcycles, allowing novel combinations to work and opening up fresh possibilities.
Let us hope so. Too many people today seem to regard the motorcycle’s evolution as complete except for details. What a bore that would be!
Kevin Cameron
