KTM Developing Semi-automatic Transmission

[Admin]

CAD rendering of what we believe is KTM’s new semi-auto transmission that could find its way into a future 1290 model like the Super Adventure, or Super Duke GT. (KTM/)

The big 1,301cc LC8 V-twin that powers KTM’s “1290″ models including the 1290 Super Duke R Evo and Super Adventure, as well as the limited-edition Brabus 1300 R, looks set to get the option of a semi-automatic transmission in the future.

A new patent application from the Austrian firm reveals details of the system, which includes an electric actuator to shift between ratios, a centrifugal clutch to allow the bike to come to a standstill, and a built-in transmission lock to provide a “park” gear so it won’t roll away. It’s actually that last element that forms the basis of the patent application, as KTM recognizes that a bike with a centrifugal clutch that defaults to a disengaged position can’t simply be left in gear when parked on a slope.

The transmission lock itself is a fairly simple design, with a pivoting L-shaped pawl operated by the shift drum that hooks onto the teeth of one gear on the input shaft when the Park position is engaged. However, the patent document describes in detail the rest of the semi-auto box, along with clear illustrations of the transmission.

We know which transmission is depicted here, as standard KTM part numbers are clearly visible, telling us it’s from an LC8. (KTM/)

Most of the components are actually straight from the standard 1290 transmission; the patent images even include part numbers stamped onto several components that allow us to identify which gearbox this is, confirming that it’s the transmission from the big LC8-powered bikes.

The patent explains that the system uses an electronic-control unit connected to an actuator that rotates the shift drum, allowing either fully automated shifts or rider-controlled gear changes. The centrifugal clutch, similar to the type used on twist-and-go scooters, disengages drive to the transmission when revs drop to idle, allowing you to come to a halt and pull away again without manually operating the clutch. Once on the go, the combination of an electronic shifter and ride-by-wire throttle means there’s no need to use the clutch for up- or downshifts.

When in Park the electronic motor rotates the shift drum to engage the pawl. When in gear, it physically prevents Park from being engaged. (KTM/)

Of course it’s essential that the locking system doesn’t operate when the bike is moving, but having an electronic control for the shifter means it’s simple to ensure that the Park position can’t be engaged unless you’re stationary. Because the pawl is mechanically operated by the shift drum, the transmission lock is physically prevented from engaging when the bike is in gear.

In this illustration, you can clearly see the electric motor that is geared to the shift drum (#27). (KTM/)

The mechanical process of changing gear inside the transmission is identical to a conventional transmission, but there’s no foot lever. Instead, an electric motor (marked “27″ in the drawings) is geared to the shift drum, rotating it into the right position for each ratio on demand. While the patent doesn’t go into detail of how the rider would select gears, it’s likely that bar-mounted buttons will be used when operating in semi-automatic mode. The patent does mention a display that “informs a motorcyclist about the state of the gearbox, in particular whether the gearbox is locked,” and suggests this would be on the bike’s instrument panel.

KTM has been spotted recently testing a prototype that appears to be a next-generation 1290 Super Duke GT tourer, and while the bike in those pictures features a conventional clutch lever and shifter, that’s one model that might be well-suited to this transmission. The 1290 Super Adventure could also benefit, particularly since nearly half the buyers of Honda’s Africa Twin choose the DCT semi-automatic version, showing there’s an abundant market for such systems on adventure bikes.

View the full article