Wheelie into the future
E-bike firm Zero develop ‘pseudoclutch’ to offer riders extra control and pull the odd stunt too…
On the face of it the clutch of | a conventional combustion engine motorcycle does a simple job: it disconnects the running engine from the transmission when you want to interrupt drive to the rear wheel and reconnects it when you want to move. But in practice the clutch is a subtle instrument that we control with just as much finesse as throttle or brakes – and electric motorcycle makers Zero have realised that by adding a simulated clutch to their bikes they can introduce a whole new layer of controllability.
Far from simply an on/off control to connect or disconnect drive, riders use the clutch to modulate the torque reaching the rear wheel while pulling away. How you release that left-hand lever has just as much influence on your initial getaway as how wide you open the throttle. We also use the clutch during deceleration as a means to vary levels of engine braking, or to get an extra layer of control during low-speed manoeuvres. Not to mention tricks like dipping the clutch briefly while adding power to get a thump of torque that lifts the front wheel (professional rider on a closed road, and all that).
With a conventional, direct-drive electric bike, all those subtleties are gone. Software controls how throttle openings relate to torque at the rear wheel, and how much simulated engine braking there is, and even when there’s an ability to alter that response it often means digging into menus and switching between riding modes.
But that could all be about to change, as designs from Zero illustrate how a ‘pseudoclutch’ lever – familiarly placed on the left-hand bar – could be added to its machines to bring back all of the control that a conventional bike’s clutch allows.
In a new patent application the company’s engineers describe how the fake clutch lever will be designed to emulate the mechanical feeling of a real one, with a similar initial resistance followed by a plateau of opposing force and then a drop-off as the lever comes back to the bar, but instead of controlling a clutch it will operate a rotary sensor that alters the throttle’s relationship with the torque at the back wheel.
Pull the pseudoclutch in entirely and opening the throttle won’t send any torque to the wheel, and regenerative braking will also be disabled to let the bike freewheel. Let the lever out slowly and you’ll be able to blend throttle and ‘clutch’ to control precisely how much torque reaches the rear wheel and how fast it ramps-up.
Fine tune the control
You’ll be able to open the throttle wide and dump the clutch for fast getaways or use the clutch to make tiny changes to torque when riding
‘You can open the throttle and dump the clutch’
at walking pace. But, unlike a petrol bike, if you don’t want to use the clutch and prefer the simple twist-and-go control of a normal electric bike, that’s still possible, too. It turns out you can have your cake and eat it.
Better still, all this extra functionality comes without substantial changes to the bike. Zero’s patent illustrates the pseudoclutch on an SR/F, but apart from the bar-mounted lever, its integrated rotary sensor and a couple of wires to the bike’s ECU, all the changes relate to the programming of the control electronics. This means that Zero’s pseudoclutch could easily be adopted across its whole range and might even be able to be fitted to existing bikes if their programming can be updated to suit it.
The rotational sensor essentially works in reverse to the throttle, cancelling out its operation. With 100% throttle applied along with 100% clutch, you’ll go nowhere until the clutch starts to get released.
The control mapping also works on the regenerative braking when the throttle is closed, allowing the clutch to modulate the back-torque at the rear wheel during deceleration.