Bicycles Are Revolutionizing The EV Transmission

Technology / Comments

Inmotive's brilliant two-speed transmission is perfect for EV applications.

Of all the volume-production EVs ever made, the majority have foregone a typical transmission, shipping with just a single-speed reduction gear. It's the rare EV that features more than one forward gear, and even then, cars like the Porsche Taycan and Rimac C_Two feature just a pair of ratios - one for lower speeds, and one for the Autobahn.

The reason for this is simple: your average electric drive motor has a nice, fat torque curve and exceptional efficiency starting from near-rest, giving it a far more broad "optimal" operating band than an internal combustion engine. As soon as you start adding gears, you begin accumulating excess rotating mass, friction, and pumping losses that can quickly erase whatever slim benefit you might otherwise have added. But one Canadian company is reinventing the transmission, and has taken influence from an unlikely source: bicycles.

Inmotive
Inmotive
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Based on the aforementioned factors, two speeds is about the limit for an EV's transmission. While that's not likely to change anytime soon, the design of the transmission could, courtesy of Inmotive.

The Inmotive Ingear started off as CTO Anthony Wong's idea for how to redesign a bicycle drivetrain. Conventional bike drivetrains use derailleurs - one at the crankset, and one at the rear sprocket "cassette" - that apply lateral force to the chain to "throw" it up a gear or down a gear. Wong's concept was to have the chain stationary, while the gears do all the lateral movement.

The design that resulted from that sort of thinking - well, you can see it for yourself in the video above. It's ingenious.

Inmotive
Inmotive
Inmotive

There are two drive gears, the larger of which is broken into five segments that slide out of the way, one by one, each time an upshift is requested. Those gear segments wait until they are within the open space between the chain to move, so they're not creating friction against the chain. As the last of the five segments slides away, the chain engages with the smaller gear located beneath.

The benefits of this system are many, and Inmotive specifically cites up to 15 percent more range than a single-speed reducer, with up to 20 percent better acceleration and top speed.

Inmotive
Inmotive
Inmotive

Furthermore, since the chain and gears use straight teeth rather than helical - or "slash-cut" - teeth, there's no axial load against the case, meaning less friction and lower cooling requirements than existing two-speed EV gearboxes. That, coupled with the fact that it requires no high-pressure pump, makes it more efficient.

As for the cost, Inmotive says the Ingear should only be about $150 more expensive than a typical single-speed reducer.

So far, Inmotive has development contracts with two global OEMs and is in discussion with several others. The company hopes to bring Ingear to market within three years. But that might not be the only place where Ingear is implemented; the company says its design is scalable, meaning it could be adapted to everything from bicycles to wind turbines.

Inmotive
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