Free Drive system replaces ebike chain drives with "bike-by-wire" tech
While today's ebikes may not be identical to one another, their form factor is limited by the fact that their pedals have to be mechanically linked to the rear wheel. Schaeffler's new Free Drive system does away with that limitation, potentially allowing for unlimited new designs.
In existing ebikes – or non-electric bicycles, for that matter – the rider's pedalling power is conveyed to the rear wheel via a chain drive, a belt drive, or sometimes even a shaft drive. In all cases, though, a moving mechanical apparatus has to run between the crankset and the wheel.
By contrast, Free Drive only requires some electrical wiring to link the one to the other.
Developed in partnership with two-wheel electric drive specialist Heinzmann, it's not unlike the drive-by-wire systems utilized in some electric cars – in fact, Schaeffler even refers to it as "bike-by-wire." It consists of four main parts: a bottom-bracket-integrated generator, a 250-watt rear hub motor, a lithium battery pack, and a handlebar-mounted "human-machine-interface" (a control unit, in other words).
When the rider pedals, they spin up the generator. Doing so converts their mechanical energy into electrical energy, which is fed into the motor. That motor converts the electrical energy back into mechanical energy, which is used to turn the wheel.
The generator regulates the amount of resistance that the rider experiences while pedalling, based on the level of pedalling effort they have selected in order to maintain cruising speed. Should they pedal harder than is necessary, the excess energy is stored in the battery. That battery is also topped up by a regenerative braking system in the motor.
As an added benefit, ebikes utilizing the system should require less maintenance than their conventional counterparts. That said, in an article on the Electrek website, a Schaeffler representative did admit that Free Drive is about 5 percent less efficient than a chain drive, when it comes to converting the rider's pedalling power into forward motion.
Additionally, it's not the first bike-by-wire system we've seen. In the Mando Footloose ebike, the crankset is connected to an alternator that charges a battery, which in turn powers a rear hub motor.
Free Drive is being officially unveiled this week, at the Eurobike show in Friedrichshafen, Germany.
Source: Schaeffler via Electrek
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How much rider energy is "lost" in legacy mechanical drives owing to sub-optimal cadence and the non-linear resistance of their circular pedaling motion not correctly optimising rider muscle energy? That definitely sounds like more than 5% to me!