August 29, 2007 12:06 PM PDT

Reinventing the (front) wheel

What happens when you breed a helicopter with a two-wheeler? You get a motorcycle with all-wheel drive.

Philadelphia-based Christini has begun to market a drivetrain that can apply power from the engine to the front wheel of motorcycles. A second chain turns the front wheel so that riders can get through sand, snow, mud or uneven terrain more easily.

"I love it. It is a total advantage," said Mike Bergman, a professional motocross racer who's raced twice on motorcycles equipped with Christini's drivetrain. "Let's say you come into a rough corner with deep ruts, it will pull you right around it."

Christini recently released a version of its drivetrain for some Honda dirt bikes and will soon have a unit that works with off-road motorcycles from KLM. Over the next few years, it hopes to move from selling its system as an aftermarket device to something that is integrated into a motorcycle at a much lower cost at the factory.

Eventually it will also come to street bikes because it can increase safety and handling, according to founder Steve Christini.

"The average rider gets the most benefit out of this," he said. "The benefit of all-wheel drive is control, stability, safety and cornering. It keeps the front end from washing out."

Photos: All-wheel-drive motorcycle

The company has all-wheel mountain bikes, too. With bicycles, all-wheel drive allows riders to get up steep slopes without having to stand up and pedal, or down slippery surfaces with less fishtailing.

Although they don't get near the attention that cars do, inventors actively tinker with the technology behind bikes and motorcycles. Shimano recently came out with an automatic transmission for bikes, and Zero Motorcycles and Vectrix have come out with electric motorcycles.

The all-wheel drive concept sounds simple, but it's difficult to execute. Large, established manufacturers have tried out different ideas for putting a second chain on the front wheel, but ultimately backed away from coming out with products.

The difficulty was in how to deliver power to the front wheel without disrupting steering and handling. If you attach the chain to one side of the hub, it will pull the front wheel, and hence the rider, in that direction. One manufacturer spent years on a system that would drive the wheel through pressure hydraulics. Hydraulic systems, though, consume lots of power.

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11 comments

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similar has been done before
Ronkin actually produced a similar function with a torque converter setup back in the 70's
Posted by mssoot (169 comments )
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ROKON
Yup. Along with maybe 3 others, though I might be counting one twice.

At least one had a drive shaft on the front.
Posted by Phillep_H (497 comments )
Link Flag
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.
Posted by ArtInvent (374 comments )
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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.
Posted by mikeburek (418 comments )
Link Flag
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...
Posted by ayteebee (32 comments )
Link Flag
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.
Posted by Jim Hubbard (326 comments )
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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.
Posted by ira_davis (12 comments )
Reply Link Flag
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 <a class="jive-link-external" href="http://www.aftermarketperformanceparts.com/mitsubishi-performance-exhaust.html" target="_newWindow">mitsubishi performance exhaust</a> and other accessories. By doing so, you could be sure of the quality of vehicle you are getting?=)
Posted by angelfast (21 comments )
Reply Link Flag
Photo Link
I came to this article through this link. It has some pics of the mechanics, enough to give you a rough idea.
<a class="jive-link-external" href="http://www.news.com/2300-11389_3-6205157-1.html?tag=ne.gall.pg" target="_newWindow">http://www.news.com/2300-11389_3-6205157-1.html?tag=ne.gall.pg</a>
Posted by mc_rog46_sd1 (11 comments )
Reply Link Flag
 

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