Electric Motor Enables Chain-Free Bike-by-Wire

New pedal-powered drive moves hybrid, cargo e-bike

4 min read

Schaeffler's chain-free bike parked in grass.

Generator by Schaeffler, hub motor and system integration by Heinzmann, hardware by Bayk—in all, a bike-by-wire cargo vehicle with no chain


An increasingly-seen sight in Berlin and other German cities is the oversized electric cargo delivery bike, hissing along (and sometimes in bike lanes) like parcel-laden sailboats on appointed Amazon rounds. German manufacturer Schaeffler sees an opportunity: it is introducing a new generator at the heart of a smart drivetrain concept that some observers are calling bike-by-wire.

It's a bike with no chain.

Schaeffler's e-motor assembly was among the more out-of-the-ordinary items on display at the recent IAA Mobility show in Munich, which used to be the Frankfurt Motor Show, and more accustomed to roaring supercars and sleek news Benzes (and a thronging public, in pre-Covid times). But in some ways Schaeffler's pedal-cranked generator looked familiar; it's the world around it that's changing. That just might include reimagining the 130-year-old chain-driven bicycle.

Schaeffler is working with German electric drive maker and systems integrator Heinzmann to develop a complete bike-by-wire drivetrain. The partners had a prototype on display in Munich (and the previous week at Eurobike) with a robust cargo three-wheel e-bike made by Bayk. Production models could come out as soon as first-quarter 2022, says Marc Hector, an engineer in Schaeffler's actuator systems unit and one of the developers on the pedal generator project.

It's a hard thing to beat pedal-turns-sprocket. But maybe conditions are changing.

Bike by wire physically de-links two kinetic systems: the turning pedals and the powering wheel on a bike. They are instead linked by a controller, an electronic brain, which directs power to either battery or hub motor. It also sends a resistance signal to the pedal, so the rider feels that he or she is pushing against something. Instead of producing motion, pedaling is producing current. Taking the chain out of the mix—if done successfully—would fly open the cramped world of cycle design to new shapes and configurations. Remove the electronic brain, however, and you're left with a stationary exercise bike bolted to a wheeled frame powered by rear electric motors.

No wonder industrial designers and engineers have toiled for years on the concept: it's a hard thing to beat pedal-turns-sprocket. But maybe conditions are changing.

Schaeffler\u2019s pedal-powered generator, chainless e-bike designSchaeffler's pedal-powered generator enables new, chainless e-bike designsSchaeffler

Schaeffler is an auto parts and industrial manufacturer which made its name as a ball-bearing and clutch maker. It's developed electro-mobility products for 20 years, but has been on a buying spree: snapping up an engineering specialist firm in e-drives and another in the winding technologies used, among other things, to superefficiently wrap copper wire inside electric motors. It launched a new e-mobility business division that, reportsAutomotive News Europe, includes 48-volt auto powertrains as well as subsystems for plug-ins and full-electric vehicles.

Here it's a different scale of electrics: Schaeffler's pedal generator is a self-contained four-kilo crank-driven e-machine in a cylindrical housing the shape of an oversized soup can placed in the bottom bracket of a cargo bike. The pedals turn the crank running through a standard brushless DC machine inside: fixed coil copper windings around an iron core are arranged within the cylinder as the generator stator. Magnets in the turning rotor create the current. Temperature sensors and a controller are housed along with the generator.

The bike-by-wire controllers direct that current where needed: to the onboard battery for charging, to the interface display, to the rear hub traction motors that propel the bike, and back to the rider's feet in the form of counter-torque, giving the feeling of resistance when pedaling. The trick will be by synching it all up via Controller Area Network (CAN) bus, a 500 kbits/sec messaging standard which simplifies the amount of cabling needed. It should move the bike on one hand, and independently send the "chain feeling" back to the rider. Move pedal, move bike.

“Pedal by wire has huge potential. Micromobility is coming."

"The feeling should be the same as when there is a chain there," says Thorsten Weyer, a Schaeffler system architect. "But there is no chain."

Propelling the bike will be the two Heinzmann hub motors, which the controller can get rolling set at European Union specs at 125 watts of power each, 250 total (500 watts in mountainous Switzerland, 600 in Austria). Each hub can each generate 113 newton-meters of torque on the axle, powering it ahead. "With the hub motor you have power where you need it," says Heinzmann electric drives managing director Peter Mérimèche. The controller's programmed with nine gear settings: the countercurrent controlling torque on the axle is reduced or increased automatically based on the grade the bike is traveling on.

Designers have dreamed of chainless bikes for more than a century—in analogue form—and at least 25 years for e-bikes, as Andreas Fuchs, a Swiss physicist and engineer, developed his first chainless working models in the mid-90s. Challenges remain. Han Goes, a Dutch consultant and bicycle designer, worked with a Korean auto supplier a decade ago on a personal portable chainless folding bike. Pedaling parameters proved a struggle. "The man and the machine, the cyclist and the generator, the motor: nothing should feel disruptive," he says. If so, the rider feels out of step. "It is like you are pedaling somewhere into empty space."

Goes is still at it, working with design partners on a new chainless cargo bike. Our parcels keep needing delivery, and the city is changing. "Pedal by wire has huge potential. Micromobility is coming," he says. Dutch and Danish and other developers are at it, too. "It offers design and engineering freedom. Simplicity. Less parts and maintenance. Traditional chain drives can never offer that."

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