Velocity e-bike features weight-reducing removable power system
By Ben Coxworth
March 20, 2012
For people who wouldn’t otherwise ride a bike, or who don’t want to arrive at work all hot and sweaty, electric-assist bicycles are a neat idea. Commonly referred to as pedelecs (for “pedal-electric”), they use an electric motor to augment the rider’s own body strength while pedaling, yet that motor can usually be switched off when they don’t need it. The only problem with that setup ... even when the motor isn’t being used, it and its battery are still there, weighing the bike down. For his prototype Velocity pedelec, however, Taiwanese designer Larry Chen came up with a creative solution – an easily-removable motor/battery unit. It was enough to win him a gold award at the latest International Bicycle Design Competition in Taiwan.
The “Power Core,” as it’s called, consists of a rechargeable battery pack, a control unit, two DC motors, a wireless antenna, and a drive shaft. The whole thing drops into the bike’s equivalent of a seat tube, where it is hidden from sight. Once in place, the downwards-facing drive shaft engages an internal helical gear on the bottom bracket, so the motor/pedal interface is also hidden from view and protected from the elements.
External wiring is eliminated, as a power meter built into the chain ring senses the pedaling torque being applied by the rider, and wirelessly sends that information to the control unit. That unit, in turn, determines how much extra power to send to the drivetrain.
When riders want to ride a regular non-powered bicycle, the Power Core can be pulled out, after opening the top cover and pressing the release button. Removing it reduces the bike's total weight by about six kilograms (13 lbs), leaving it at a hard-tail mountain bike-like 12 kilos (26.5 lbs).
Of course, if the rider decides to take out the Power Core once they’re already out and about, its extra weight will still be with them – it will just be in their backpack as opposed to the frame. Chen instead envisions the Power Core staying in place throughout the week, for commuting, then coming out for fitness riding on the weekends.
As the Velocity is still a design exercise, there’s no word on things like range or recharge times, or possible commercial availability.
Source: Bicycle DesignShare
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