Adventure and touring bikes are currently the big growth market for motorcycle manufacturers, especially in the US and Europe and just about every company is looking to replicate BMW’s success with their GS series of adventure bikes. For some, any consideration of a bike other than the 1200 GS necessitates a shaft-drive transmission and new patents from Aprilia indicate they may very well be planning on doing just that.
The majority of the patent, titled ‘Homokinetic Motorcycle Transmission and Motorcycle Comprising Said Transmission’ is in Japanese, but the limited amount of the document which is in English is as follows:
A motorcycle transmission (4) comprising a swingarm (8) which extends from one hinging end (12) to a motorcycle chassis, defining an oscillation axis (X-X), at one connection end (16) to a wheel (20), a homokinetic joint (36) arranged on the side of the hinging end (12), and a a geared coupling (40) positioned on the side of the connection end (16), wherein the homokinetic joint (36) kinematically reciprocally connects a first end (44) of an input shaft (48), connected to a power take-off, and a second end (52) of an output shaft (56) mechanically connected to the geared coupling (40), and wherein the geared coupling (40) transmits the motion to the wheel (20). The homokinetic joint (36) performs an instantaneously constant transmission ratio between the first and the second end (44, 52), the homokinetic joint (36) is offset to the hinging end (12) of the swingarm (8), in a vertical direction (Y-Y) perpendicular to the support surface (P) of the wheel (20) and permits an oscillation of the output shaft (56) between a stroke start and a stroke end, parallel to the oscillation axis (X-X).
Now, we’re not overly literate when it comes to the mechanical side of shaft drives, nor are we all that good at comprehending the wording used in patents (which makes legal documents comprehensible by comparison), so if anyone out there decipher whether this is a fairly run of the mill shaft-drive system or something else, we’d greatly appreciate it.
Regardless, perhaps Aprilia feels like they need to do more to boost sales, given how sales of their Caponord range of bikes really don’t reflect how good they are.