Based on XT600 Enduro motorcycle from Yamaha (Version 2KF from 1988 y.), the goal was not to create a powerful motorcycle, but rather to provide a functional system with a variable caster angle during riding, in manual mode and in automatic mode indexed on the motorcycle speed.
The idea was to pre-feel effects on motorcycle's stability and maneuverability while changing caster angle:
- With a large caster angle, the bike is stable, but not very maneuverable.
- With a small caster angle, the bike is maneuverable, but not stable.
Caster angle variation of this prototype goes from 22 degrees to 29 degrees. The original bike has a fixed 28-degree caster angle.
Never introduced before, this solution is a worldwide innovation. Ever since the motorcycle was created in 1890, no big or small motorcycle manufacturer has dared to experiment with the caster angle variation during riding. The Research & Development (R&D) created about this prototype was that much more difficult because no one really had any constructive opinion or idea about motorcycle behavior during the variation:
- Will the bike be dangerous to drive?
- Will the driver fall because of changes in the functional parameters of the bike (caster angle, gyroscopic effect of the front wheel ...)?
- How will the motorcycle behave during an emergency braking, with its variable caster angle?
No one was really able to provide us with a clear and qualitative explanation, including people of the professional pilot community.
Throughout the mechanical design, additional technical difficulties appeared for having chosen an Enduro-based bike: the huge frontal suspension displacement (200 mm) and the handlebar right-left rotation (+/- 30 degrees) complicated the position and design of various mechanical elements.
The frontal cycle part of this prototype was entirely redrawn starting from a ‘White page’. Only the engine and rear suspension of the original motorcycle were preserved.
Quite surprisingly during testing, the bike was very sound, very stable, eliminating in large part vibrations and sways. Unlike the original motorcycle XT 600, which is unstable above 95 Km/h, this prototype was tested at 130 km/h keeping its complete safety.
During emergency braking, frontal suspension of this prototype collapses only by 2 cm, in contrast to the 12 cm of the original motorcycle. With this, the pilot can maintain his driving position and his arms are not overloaded by the load transfer, thus ensuring double security for handling and road behavior.