Ducati Developing Seamless Shift for Streetbikes

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Ducati has developed a simple seamless-shift gearbox for use on streetbikes. (Ducati /)

When MotoGP’s rulemakers decided to make the switch from two-stroke to four-stroke 20 years ago, they hoped the result would be bikes that were more relevant to production models. The sheer amount of GP-derived innovation that’s reached showrooms since then must have surpassed their wildest dreams. Traction control, quickshifters, inertial measurement units, aerodynamic winglets, and 200-hp-plus engines have all come to the street directly from MotoGP. Ducati, the manufacturer in the technological vanguard, wasn’t even involved in GP racing until after the four-stroke switchover. Now the same firm is working on bringing another MotoGP technology from the racing series to the street in the form of a seamless-shift transmission.

The system works like Honda’s DCT, but uses a clever combination of lockable roller bearings rather than twin clutches. (Ducati /)

MotoGP actually resisted the introduction of seamless gearboxes, which allow riders to change gears up or down without even a momentary lapse in the transmission of torque to the rear wheel. The series banned dual-clutch transmissions like Honda’s DCT before anyone even tried to introduce one, but the result was a development race to create alternative systems that could achieve seamless shifting with just one clutch. Honda got there first with a gearbox so expensive and so secret it had its own security man in the GP paddock. But rivals have caught up; now every bike on the grid has some sort of seamless-shift transmission.

Ducati’s system uses a single clutch on an input hub that acts on two lockable bearings, one on each shaft. (Ducati /)

Thus far, the high cost of MotoGP seamless-shift boxes has prevented implementation of the systems to road bikes. Sure, Honda’s dual-clutch transmission has been around for a decade on the VFR1200, NC750, and now the Africa Twin, but it’s a relatively heavy setup with semi-automatic operation, more suited to touring convenience than high-performance riding.

Now Ducati has developed a seamless shift box that’s cheaper and simpler, with a conventional foot-operated control and the ability to simply swap cogs with no need to disengage the clutch or interrupt the power delivery. The new box, seen here in photos from Ducati’s own patent application, works very much like Honda’s DCT, but replaces the twin clutches of Honda’s system with a clever system of lockable roller bearings.

The input shaft has two parts, with first, third, and fifth gears on the farthest end from the clutch. (Ducati /)

As with the DCT box, Ducati uses an input shaft split into two parts. The odd-numbered gears—first, third, fifth—are on the end farthest from the clutch, while the even-numbered (second, fourth, and sixth) are fitted to a sleeve that fits over the end near the clutch. However, where Honda’s DCT has a separate computer-controlled clutch for each half of the input shaft, Ducati’s system uses a single clutch, mounted on an input hub and acting on two lockable bearings, one for each shaft.

DCT allows two gears to be engaged simultaneously, with computer-controlled operation to decide which ratio you’ll want next and to modulate the pressure on the two clutches during shifts. Ducati’s system, in contrast, is all-mechanical, with a conventionally operated clutch that’s only used when coming to a halt.

Pressure is applied to one bearing to lock its rollers to the input shaft while the other runs free, thus transferring drive from one to the other. (Ducati /)

As with the Honda DCT system, Ducati’s box engages two gears at the same time, but on the Ducati it’s only for a brief moment.

Because Ducati’s seamless gearbox idea could be integrated into traditional applications, mass production would be viable. (Ducati /)

A conventional selector drum acts on fairly normal shift forks to engage the gears, but the drum is configured to put a slight delay in disengaging the previous gear when the next is selected. That’s where the lockable bearings in the input hub come into play; during the fraction of a second when both ratios are selected, drive transfers from one bearing to the other. The shape of the input hub’s inner surface applies pressure to one bearing or the other, locking its rollers against the input shaft while releasing the other’s rollers so it runs free. It’s a clever system, and significantly, it’s not dissimilar to a conventional gearbox. This makes mass production relatively affordable.

The mechanical simplicity of Ducati’s system also makes further development and eventual production more likely. (Ducati /)

According to Ducati’s own patent, the idea means “it is possible to realize a seamless gearbox mechanism integrated into a traditional gearbox, suitable both for mass production and racing.” The fact that the patent includes photographs of the box’s internals shows that this isn’t just a wild idea; it’s really been built and tested, so a production version may not be far away.

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