Zero

Zero pseudo-clutch could transform electric bikes By Ben Purvis


Almost every electric motorcycle is direct drive - the motor is permanently geared to the rear wheel via a single ratio - so there's no need for a clutch or gear shifter. But American EV pioneer Zero is considering adding a false clutch lever to its electric bikes to give them an extra dimension of controllability.
While the purpose of a clutch is simply to disengage drive from an engine to the transmission, so you can come to a halt without stalling, and to shift gears smoothly, in reality, riders use that left-hand lever in a much more subtle way. It's as important as the throttle, or even more so, when it comes to deciding how fast you get off the line when the lights go green. 

It's used to moderate the amount of engine braking at the rear wheel when you downshift and can be invaluable in giving fine control during low-speed maneuvers. When an experienced rider gets on an electric bike for the first time, it's the lack of a clutch lever, more than anything else, that is initially jarring.
While electric motors offer vast torque at low revs, without a clutch you're at the mercy of a pre-programmed torque curve and throttle response map when it comes to getaways, and changing the amount of regenerative braking available often means delving into the depths of menus hidden in the dashboard's user interface.
Zero's new idea, revealed in a patent application from the company, is to use a control that looks, feels and operates like a clutch lever, but doesn't actually involve fitting a real clutch between the electric motor and transmission.
Instead, the lever will operate a rotary sensor that alters the amount of torque reaching the rear wheel, or back-torque from regenerative braking when the bike is decelerating, to mimic the response of a clutch. Pull the lever in and the power and torque to the rear wheel is cut, even when the throttle is wide open. Release it again and the torque is returned to the wheel. That means riders with years of ingrained experience of balancing throttle and clutch controls will be able to get the same response from an electric bike, using the 'pseudo-clutch' lever alongside the throttle.
It's not just useful for the sake of familiarity, though, as it gives the ability to control the throttle mapping on the fly in a natural, instinctive way, and perhaps more importantly control the amount of regenerative braking on the rear wheel without switching between modes. And with relatively few additional components - most of the changes are software driven, not hardware ones - it's a system that shouldn't add substantially to prices.