Reinventing the (front) wheel

(continued from previous page)

Christini came up with his idea in the mid-'90s during some time off. A friend had a model helicopter and he studied how the engine spun the two separate rotors in two different directions at the same time. He was also an avid mountain biker and wondered how he could improve his ride.

The Christini system essentially involves taking a helicopter drivetrain and adapting it to the fork of a motorcycle or bike. In a helicopter, the engine turns a gear. Instead of turning a chain (and a wheel) directly, that gear is attached to two other gears, which turn separate chains that then power the two rotors.

In Christini's drivetrains, a chain runs between the main cog (the big gear that's also attached by a chain to gears on the rear wheel) and gear inside the head tube. The head tube then transfers power to two separate drivetrains on the left and right of the fork. Like on a helicopter, the drivetrains spin in opposite directions, but both work to turn the wheel forward. It's the same principle that allows boats with two propellers to go forward without swirling in circles.

"By having counter rotating shafts, it allows the motorcycle to steer straight. (The gears) are both spinning the wheel forward but they are spinning in opposite directions," he said. "We essentially put a helicopter drive system in a motorcycle."

In ordinary motorcycles and bikes, steering is accomplished by a central bar inside the head tube. The steerer effectively connects the fork to the handlebars. Since the gears are in the head tube in the Christini system, the steerer is attached to the forks.

Christini points out that the system gives riders all-wheel drive, rather than permanent two-wheel drive. The drivetrain kicks in when the front wheel and the back wheel are spinning at different speeds. When that occurs, the system begins to power the front wheel and then shuts off again after equilibrium hits.

"Because you're not powering the front wheel all the time, you're not sucking power all the time," he said.

Bergman said that the steering can occasionally feel a little heavy, but that it's not a huge difference. "You really have to pay attention to notice it," Bergman said.

The company initially marketed the front-wheel drivetrain for mountain bikes and signed a deal with Jeep in 1998 to put it on that company's mountain bikes. Sales though, were never huge.

Although it still sells all-wheel drive bikes, the company began to emphasize developing a product for motorcycles in 2002. It finally began to sell a product, for three types of Hondas, this year.

Adding the system takes some work. The entire frame on the motorcycle has to be swapped. Riders bring their motorcycles to a dealer, who then performs the swap (which takes about four to six hours). It costs $5,995 and riders have to turn in their old frames.

That's steep, he admits. However, the price could drop to $1,500 to $2,000 if manufacturers decide to insert all-wheel drive at the factory.

"Everything new is more expensive when it first comes out. It's a volume issue," he said. "We don't have a single person who doesn't get on this who isn't giddy when they get off of it."

"And let's face it," he added. "There are a lot of people in this country and overseas with plenty of money who want to be first movers."

[mssoot]

similar has been done before

Ronkin actually produced a similar function with a torque converter setup back in the 70's

[Phillep_H]

ROKON

Yup. Along with maybe 3 others, though I might be counting one twice.

At least one had a drive shaft on the front.

[ArtInvent]

Complicated answer to a question no one asked

Number one, what on earth does this mean?

"In ordinary motorcycles and bikes, steering is accomplished by a central bar inside the head tube. The steerer effectively connects the fork to the handlebars. Since the gears are in the head tube in the Christini system, the steerer is attached to the forks."

There are no good photos or diagrams of the mechanism in question, and the above baffling description helps not in the least.


Secondly, front wheel drive of any kind is only marginally useful on two wheels. Think about it - since an off road motorcycle or mountain bike (or street bike for that matter) is so very top-heavy relative to a very short wheelbase, they can easily be made to lift the front or rear wheel under many circumstances. Under heavy acceleration and especially uphill nearly all the weight is transferred to the rear wheel, and the difficulty is to keep the front wheel planted with enough weight just to maintain the ability to steer. Adding drive power to the front wheel is only liable to make it loose traction. Very bad news on two wheels.

Such a system would only be mildly useful maybe in snow or ice, and on the road would probably have to have anti-lock thrown in to keep the front wheel from sliding. A rather expensive and complicated and probably heavy system, for very little in return.

[mikeburek]

What a thinker

You sure can analyze how a motorcycle handles and the physics of it in many different situations for someone who can't figure out what the fork, handlebar, and head tube are without a picture.

"Adding drive power to the front wheel is only liable to make it loose traction." - I guess all those off-roading people are just suckers wasting money when they get 4x4 or all-wheel drive on their vehicles.

Think about this:
Sit on a bike/bicycle and turn the wheel 90 degrees either way and try peddling. You'll fall. But if that front wheel was powered, you'd move in the direction you turned.

When you're moving a heavy object, like furniture, sometimes it's easier to push and sometimes easier to pull. Same thing with front and back powered tires.

Why are/did so many cars move to front-wheel drive? Because of better handling. Same with the bike.

Also, since the bike's tires are narrow, it's much easier for it to get stuck in a rut. Great if that rut is going the same direction, but if not, then the front drive can help pull the tire out of the rut. Otherwise, you may have to stop and pickup the front tire yourself.

[ayteebee]

Actually, the reason that the front wheel lifts off the ground

when you're going up a hill is because the power is being transferred via the rear wheel. If the front wheel was used to drive, then the bike would actually stick to the road better.

If you still don't understand, consider it this way: There is a bike travelling uphill from left to right as you look at it. Torque is transferred to the rear wheel, making it move in a clockwise direction, therefore pushing the bike up the hill. The equal and opposite reaction of this however, is that torque is added to the *frame*, causing it to turn in an anticlockwise direction about the rear axle. Ergo, the front wheel lifts off the floor.

If you put the drive in the front wheel then the frame still tends to rotate anticlockwise, but this merely forces the rear wheel into the ground.

In a nutshell, you can't do a wheelie on a front wheel drive bike. But come to think of it, it could have interesting implications for engine braking...

[Jim Hubbard]

Maybe CNET should hire adult writers...

You know....someone with the common sense to attach pictures that actually show the product being discussed in a meaningful way.

My favorite useless phot in this series if photo 3. The only thing that could have made it any worse would have been to have the bike actually facing away from the camera.

[ira_davis]

Front wheel drive MC

I guess none of the people writing this article never road a motorcycle because if they had they would know that 70% of your braking on a motorcycle comes form the front wheel brake.

[angelfast]

That was nice...

Indeed that was a cool reinvention...
Anyway,here are some tips on how you can buy and have a quality used car, so as you would not be replacing unnecessary parts along the way...Hope, this might help...
Tips & Warning
? As a final precaution, take the car to a mechanic, who should charge a reasonable fee to check over a used car. The seller should agree to this, but may require that you leave a deposit. If the seller won't let you take the car, offer to meet him or her at a mutually convenient garage.
? If you give the seller a deposit in order to take the car to have it checked, make sure to write out an agreement stating that the deposit will be returned immediately if you decide not to buy the car.
If the vehicle's mileage appears unusually low, have a mechanic determine whether someone has tampered with the odometer. If so, the seller must refund any money you have paid and may be liable for punitive damages under federal and state odometer laws?
This is how I acquire my car; I inspected all its auto parts from exterior and interior aspect down to its mitsubishi performance exhaust and other accessories. By doing so, you could be sure of the quality of vehicle you are getting?=)

[mc_rog46_sd1]

Photo Link

I came to this article through this link. It has some pics of the mechanics, enough to give you a rough idea.
http://www.news.com/2300-11389_3-6205157-1.html?tag=ne.gall.pg