Bicycles

Free Drive system replaces ebike chain drives with "bike-by-wire" tech

Free Drive system replaces ebi...
Free Drive utilizes a pedal-driven generator that is wired to a rear hub motor
Free Drive utilizes a pedal-driven generator that is wired to a rear hub motor
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Along with ebikes, Free Drive could also be incorporated into 3- or 4-wheeled vehicles – it's built into this delivery trike
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Along with ebikes, Free Drive could also be incorporated into 3- or 4-wheeled vehicles – it's built into this delivery trike
A closer look at the Free Drive generator
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A closer look at the Free Drive generator
Free Drive utilizes a pedal-driven generator that is wired to a rear hub motor
3/3
Free Drive utilizes a pedal-driven generator that is wired to a rear hub motor
View gallery - 3 images

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.

Along with ebikes, Free Drive could also be incorporated into 3- or 4-wheeled vehicles – it's built into this delivery trike
Along with ebikes, Free Drive could also be incorporated into 3- or 4-wheeled vehicles – it's built into this delivery trike

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

View gallery - 3 images
26 comments
26 comments
Malatrope
Unless the generator and motor together are better than 95% efficient, all this notion will do is cause the rider to exert more effort. Doesn't anyone remember the tire-generators for headlights, and how much more pedaling effort they required?
Ornery Johnson
I prefer to think of it as an electric vehicle where you pedal to gain additional range, rather than a bike without a chain that is 5% less efficient. There must be a way to recharge the battery from an electrical outlet.
akarp
LOL, they should have the motor spin a friction plate that heats up water, the seam then drives a piston to raise a weight...then the weight pulls on a chain to drive the wheel. Trust me it will only be 5% less efficient. LOL
paul314
With a few software tweaks, this setup could also make for seamless pedal assist of whatever level you wanted. (Not sure what to call it: "assist"? "augmentation"? "multiplication"?)
christopher
Given that a computer will now be able to measure the rider cadence and optimally increase and decrease the resistance continually, as well as buffer energy in the battery, the perceived 5% "loss" could well be mitigated by an overall increase in transfer of energy from the rider to the wheels.

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!
Tim Read
Nice idea but why a 250W hub motor? That limits the maximum amount of power to 250W as the motor is the only means of driving the rear wheel. Most ebikes with a 250W motor would be 250W + rider which would normally be in excess of 500W total. Imagine trying to ride up an even moderate hill with this thing?
James Barson
Would this even be legal in some counties as surely this would not be considered a pedal assisted vehicle
Peter Forte
The knock on hub motors is the penalty of increased unsprung weight and its effects on ride quality and handling.
Jay
A decent cog/chain setup on a bike is 96% to 97.5% efficient. Decent 250-500 Watt motors and generators operating at optimal power levels are about 80% efficient each and perhaps 60-70% efficient each averaged over a variety of loads, so a "drive by wire" setup multiplies to 36% to 64% efficiency. The only ways this system gives up only 5% efficiency is if the motor and generator weigh 100kg each, or they are cryogenically cooled.
AndrewCooper
I question the overall efficiency, as a comment by Jay maps out. The math Jay details might be improved by factoring in regenerative braking, though I am not familiar enough with such systems to even propose what gains those could provide to overall system efficiency.
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