The Yamaha Twin-Clutch Transmission
Seamless gearshifts are the current cutting edge of MotoGP technology. As with everything which helps Valentino Rossi and Jorge Lorenzo go faster on the track, the technology is being targeted to make the leap into production motorcycles in the not-too-distant future.But while the systems in a MotoGP motorcycle only need to last a race weekend before they can be stripped, checked and rebuilt, components in a production motorcycle will need to endure almost endless kilometers. The challenge for manufacturers is how to offer it road legal motorcycle customers a durable system which can mimic those fitted to a MotoGP race bike.
A recent Yamaha patent reveals the company is well on the way to developing a road-going seamless transmission, using technology that's arguably more advanced than the race motorcycles, allowing even the clumsiest gearshift to be perfect.
At the moment there's no official word on when the Yamaha seamless gearbox will be ready for production, but it's been under development for several tears and now can't be far from readiness.
Yamaha has been developing its twin-clutch, road-going gearbox to give seamless changes to production motorcycles. It's unlike the MotoGP transmission, which uses a single clutch because twin clutches are banned. The Yamaha design is more like Honda's DCT, but where Honda uses two clutches on one side of the transmission, the Yamaha design puts one clutch on either end, each taking its drive directly from the crankshaft and attached to its own half-length input shaft. One clutch is responsible for first, third and fifth gear, while the other looks after second, fourth and sixth. This allows two gears to be engaged at once and shifting gear is simply a case of disengaging one clutch and engaging the other.
The trick to making a seamless gearbox system, is the dual clutch system needs to be able to determine which gear you'll be shifting to next. This is done using a combination of throttle and brake position sensors, speed sensors and clever pre-programming to make the calculation. This allows it to always have the appropriate next gear pre-engaged, ready when you decide to shift. Or, if you're feeling lazy, it could do this shifting itself.How Yamaha's system differs from Honda's is that it adds a hybrid electronic element to the design to make the shift even smoother.
The system is being developed to work with either push-buttons os the handlebars or a conventional foot-operated gear lever.
As well as the smart transmission, Yamaha's system also features and electronic motor and generator attached to the motorcycle's crankshaft and wired into its gearshift management brain. The electronic motor work with the gear shift system to alter the speed of the engine crankshaft during gearshifts.
On up changes, instead of reducing revs and slipping the two clutches to suit the next gear, the generator will add extra load to the crank to sharply slow it down to exactly the right speed for the next gear. Conversely , on downshifts the electronic motor will boost the crankshaft's speed, upping the revs to match the transmission and helping to control engine braking.
