The Secrets of the Honda MotoGP Gearbox

One of the heavily guarded secrets in motorsport is MotoGP technology. And Honda's super mysterious Slickshift gearbox on the Honda RC212 MotoGP race bike is one of the biggest secrets.

Although Honda have never officially disclosed the secret of their transmission, MotoGP wizards have a fair idea about it. As a matter of fact, so secretive was the whole Honda MotoGP gearbox affair that Mike Webb, technical director of FIM, had to be convinced about its legality behind closed doors. And not just that, HIRC has just one mechanic to adjust the gear cluster cassette to change gear ratios for the Honda RC212 riders!

Exhaustive search of the patents registered on Google and the US Patents Office led exports to believe that thr transmission was developed by the British gearbox firm, Zeroshift. Devised by Bill Martin, the Zeroshift technology combines the efficiency of manual transmission and the operational ease of an automatic into a masterpiece of seamless transmission.

In a synchromesh manual gearbox, the gears on the output shaft are free to rotate and the dog clutches or synchronizers lock the gear selected to the output shaft, which finally propel the motorcycle via the chain. Structurally speaking, the Zeroshift transmission is a manual gearbox, but one without the dog clutches. The dog clutches are replaced by a pair of bullet rings complete with three bullets each. The bullets form a cam-and-pawl arrangement between the Zeroshift ring and the gears. This ensures that each set of bullets is unidirectional in motion.
  As the shift lever is slotted in the first gear, the first locking ring gets engaged by the first gear, which is followed by the second ring. Backlash is ruled out by the action of the second bullet ring. The smart part about this movement is that although the second ring is slotted with the first gear, it is not under any load due to its pawl profile. On the other hand, the first ring continues to be engaged with the gear on account of its retention angle. Now that the first gear is completely engaged, the second bullet ring moves in readiness for the second gear. The point to be noted here is that even though the second bullet ring moved towards the second gear, the drive continues to be driven through the first gear. Now when the shift lever is slotted to the second gear, the Zeroshift ring skips the neutral gear (very much unlike the conventional gearbox) and the first bullet ring is disengaged from the first gear. Since the second gear is running faster than the first, the second bullet ring instantaneously picks up the drive in zero seconds, thus making it a perfect Zeroshift!

So how does this Zeroshift and bullet ring stuff translate to the riding experience?

To put it simple, you don't need to chop off the throttle while shifting gears... While the clutch needs to be pulled in, you can do a powershift (change gears without chopping off acceleration) without facing the violence of releasing the clutch. And all this time you still have the throttle fully open. That fractional loss of acceleration might not make much difference while you are speeding to work; it is a huge edge for the prospective MotoGP champion.

This gearbox apparently saves 0.3 to 0.5 second per lap. And with the slipper clutch working in tandem, late braking and downshifting while approaching corners becomes a smoother affair and the motorcycle stays planted on the track instead of fishtailing sideways. Also, upshifting while exiting corners keeps the motorcycle stable and allows for super-dynamic inputs from the rider. What's more, Zeroshift has confirmed homologation for production motorcycles so soon we can see this on our road bikes. If you want to know more about the new Honda Dual Clutch (DCT) gearbox on Honda's road bikes.
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