Its true that 4*4 cars/jeeps have an edge when it comes to hardcore offroading and dirt bike racing is still predominantly fought out on single-wheel-drive vehicles that spin up, fishtail and slide wildly across rough terrain. But now the All Wheel Drive (AWD) revolution is coming to the motorcycle world too with Yamaha and KTM having done significant work with hydraulic front-wheel-drive systems, and when new ideas like this successful all-mechanical AWD kit from Christini hit the mainstream, dirt bike riding will never be the same again.
While the hydraulic system on the Yamaha received high praise for its handling, climbing and traction advantages, it sapped significant power from the rest of the bike, leading to lukewarm reviews. And here is where Market minnow Christini comes in : a new system that suffers virtually none of the power loss of the Yamaha and KTM’s hydraulic systems. Using a set of gears and drive shafts mounted through the frame, triple clamps and forks, Christini claims they have developed a system that saps less than a tenth of one horsepower from the engine as it works.
Christini's patented mechanical All Wheel Drive system delivers power from the motorcycle transmission to the front wheel through a series of chains and shafts. There is no energy-robbing hydraulics involved. The lightweight all-mechanical system works similar to that of AWD systems found on four wheeled vehicles. The AWD system (powering the front wheel) is driven at a slightly lower rate than the rear wheel (approximately 80%). Under optimum traction conditions, the rear wheel is actually driving faster than the front AWD system. One-way clutches within the front hub allow the front wheel to freewheel under these conditions. At this point, the AWD system is effectively passive. Though the front AWD system is turning, it is not actually transferring power to the front wheel. When the rear wheel loses traction, the drive ratio, relative to your forward speed, changes. The AWD system engages, transferring power to the front wheel until traction is reestablished at the rear wheel.
The way the front system works is like pedaling a bicycle down hill. You are pedaling, but because of gravity (acting like the rear drive) the bike is traveling faster than you are delivering power. When you get to the bottom of the hill and slow down (similar to what happens when the rear wheel spins), you will begin to power the bike again.
An added benefit of AWD is that the front wheel does not want to wash out. When a front end tucks, the wheel stalls, stops turning, and begins to push. With the AWD system, as soon as the wheel begins to stall, power is delivered to the front wheel, forcing it to turn. With the front wheel under power, it is nearly impossible to wash out the front end.
Here are pictures which will help you understand the system better
Power runs via chain from the secondary countershaft sprocket up to a gearbox located on the frame.
Power is converted to a drive shaft running under the tank to the modified steering head
Counter rotating bevel gears located within the head tube transfer power to the lower triple clamp.
The lower triple clamp contains a small chain and sprocket system that drives two counter-rotating drive shafts.
The specially coated drive shafts are telescopic and incorporate linear ball spline bearings. They are counter rotating to eliminate torque effect. They run the length of the fork to the front hub.
The Christini AWD front hub is equipped with one-way clutches allowing the wheel to transfer power when needed, and freewheel when not in use.
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