Yamaha has shown a prototype of a YZM 426 WR with a two wheel drive system at Intermot show in September. The reaction of Enduro riders was great. In a questionnaire most of the respondent saw benefits in a two wheel drive for motorcycles. Of course, there were also questions about the system and it's benefits.
Öhlins, a Yamaha sister company, specialized in suspension technology and hydraulic application played a major role in the development of the 2-Trac system.
Lars Jansson, R&D manager for future projects at Öhlins AB in Stockholm answers some of the questions.
1. Why did you choose a hydraulic drive system instead of a mechanical one like a chain or shaft?
Lars: If you have a three-dimensional vehicle like a car, where you can reach the wheel hub from the side, it is very easy and efficient to fit a mechanical drive. But a motorcycle is two-dimensional. You must have a very complicated mechanical transmission to reach the front wheel. The components in the mechanical transmission are not so easy to conceal either.
In the designs we have seen so far, the front suspension members are often built around the transmission components. All this necessitates a rather complex layout of both the front suspension and the frame, together with an unorthodox styling. With our hydraulic transmission you can keep the standard layout, with the well-proven components.
2. It is known that the efficiency of a hydraulic transmission is lower than of a mechanical one. How can you justify wasting all that power?
Lars: Yes, that is true. But in a motorcycle application the front wheel can just transmit very little power. Normally 5 % and less. But what is important is, if your rear wheel starts to spin, then you loose lots of power. What we are doing is to take some of that wasted rear wheel spin and instead transmit it to the front wheel. So even if we loose some efficiency in the hydraulic transmission we are gaining lots more by reducing rear wheel spin. So if we with transmission efficiency mean "how effective can I use engine power for traction" we are improving the transmission efficiency by adding the hydraulic front wheel drive.