ShiftFX develops second-generation semi-auto By Ben Purvis
Semi-automatic transmissions are finally coming of age with manufacturers including KTM, BMW and Yamaha adding them for 2025. Now a company that was a pioneer in the field is developing a simplified design that could make semi-autos cheaper for manufacturers to adopt.
Canada's ShiftFX has been working on the idea of automated manual transmissions for the best part of two decades. It has created a system similar in concept to those being adopted today by BMW and Yamaha - with electro-mechanical actuators for the clutch and shift drum, operated by its own control unit - as far back as 2017.
To do so, the company developed a unique, fast-acting, high-force linear actuator for the clutch that has been adopted in other industries, leading to the creation of a subsidiary company, Kinitics Automation, to supply them. It also developed an advanced system to monitor the feedback from the motor operating the shift drum, allowing ShiftFX to accurately position the drum without the need for the ratcheting system used in a conventional manual transmission.
Now the company has patented a new version of the idea that eliminates the need for a clutch actuator entirely, adopting a centrifugal clutch and modifying the gearshift to provide a 'neutral' position between every gear, to allow for perfect rev matching before the next ratio is engaged.
"simplified transmission from a pioneer in the field"
While KTM's new AMT transmission also does away with the clutch actuator and uses a centrifugal clutch, its system appears to act more like a conventional up/down quickshifter - interrupting the ignition and modulating the throttle to help slip between ratios.
ShiftFX's new design makes that happen more easily and smoothly. A normal gearbox uses a star indexer cam, which has a detent for each gear position and a peak between them to prevent the gearbox hitting false neutrals between ratios. ShiftFX's new design modifies this star indexer to have an additional detent between every gear to intentionally allow the box to briefly stop in a neutral halfway through each gear shift.
Combined with the company's clever monitoring of the DC shift motor's position, it means the box can stop in a neutral for exactly the time needed for the input and output speeds of the next ratio to be matched, letting the transmission slide into the next gear more smoothly.
ShiftFX isn't intending to sell the system to individuals, but to act as supplier to manufacturers, and it's possible we'll see the system adopted on a production bike in the not-too-distant future.
