"World’s most efficient" bicycle drivetrain unveiled at Eurobike
Of all the items currently on display at this year's Eurobike show in Germany, one of the most attention-getting is CeramicSpeed's DrivEn pinion-style shaft-drive system. According to its designers, it creates 49 percent less friction than the high-end Shimano Dura Ace chain-and-derailleur setup.
At the heart of the prototype drivetrain is a cylindrical carbon fiber shaft, that reaches from the single chainring in front to a flat 13-speed cassette on the rear wheel.
Mounted on either end of that shaft are sets of very-low-friction ceramic bearings (there are a total of 21 of them), which engage the teeth on the chainring and the cassette cogs. As the rider pedals, the bearings transfer torque from the chainring through the shaft and into the rear wheel, turning it.
In its current form, DrivEn can't shift between gears, although BikeRadar reports that this could conceivably be managed using a wireless servo to move the rear bearing mechanism fore and aft relative to the cassette.
"CeramicSpeed has proudly accomplished what many have said couldn't be done," says company CTO Jason Smith. "We achieved a 99-percent efficient multi-speed drivetrain while eliminating the chain and complex rear derailleur."
That efficiency is reportedly achieved due to the fact that the system does away with the eight points of sliding friction that are present in a regular drivetrain, where the chain articulates while passing through the chainring, cassette and derailleur.
DrivEn was developed in partnership with the Mechanical Engineering Department at the University of Colorado, and has just received the 2018 Eurobike Award. There's currently no word on commercialization.
And for another take on the shaft-drive bicycle idea, check out the Alpha Bike concept.