Breakthrough Shimano Magnetic
Wheel Bearings Unlikely
Bearing manufacturers and application engineers have recently been paying close attention to the bicycle industry.
Widespread news reports had Shimano (Japan) out of the laboratory and road-testing true magnetic bearings in bicycle wheels, specifically testing by the world's top rider, Lance Armstrong.
If Shimano has managed to build the almost frictionless magnetic bearing units small and light enough for racing bicycles, it would revolutionize the sport -- regardless of cost.
However, magnetic bearing experts interviewed by eBearing all said the reports must be mistaken, or more likely, a misunderstanding of the technology being used.
True magnetic air gap bearings capable of carrying the wide variety of loads on a bicycle wheel would be exceptionally large and heavy, agreed the experts. The weight and size would more than offset any rolling efficiency gains.
As a former bicycle racer myself, this author has to agree that any additional weight and/or size in the wheel hubs quickly renders a racing bicycle uncontrollable. The extra hub weight, at each end of the bicycle, increases its polar moment and therefore its tendency to fly out from under the rider, especially in a sprint. Weight is also the enemy of acceleration and handling. As one engineer put it, "Even Lance Armstrong can't win races on a 75-pound bike."
A fellow cyclist and representative from SKF's Revolve Magnetic Bearings, world leader in magnetic bearing technology, offered another explanation for the reports. While, "A bicycle is the last place I would expect to see a magnetic bearing," he said there might in fact be a magnetic bearing technology at work -- just not a true magnetic bearing.
He suggested instead that Shimano could be magnetically separating the balls within a "conventional" bearing. This approach eliminates the retainer and its associated drag, without resorting to a full-complement bearing which has its own friction and weight issues.