|
From YourSITE.com Miscellaneous Features It’s no surprise, most Audi owners and enthusiasts understand and value of all-wheel drive. When quattro burst onto the scene in the early eighties, it took the world by storm and allowed the cars fitted with it to seemingly break the laws of physics. Since then, all-wheel drive in automobiles has become a “must have” option on many high-performance cars. Still, when thinking of all-wheel drive, most don’t think of the bicycle or motorcycle. That’s not so with Steve Christini.
The young engineering student actually built a prototype mountain bike, which still hangs on the wall of the downtown Philadelphia loft office of his company, the sign on the door reading “Christini Technologies”. Of course, that one prototype is not the only all-wheel drive vehicle in the office. Steve’s company has grown, and with it the scope of their offerings. In racks and on the walls, Christini-branded mountain bikes can be found in various levels of build.
A bit more refined than that prototype on the wall, today’s Christini mountain bikes feature an all-wheel drive system that can be controlled via a “shift on the fly” clutch located within the rear spiral gear and controlled by a lever located on the handlebars. With the clutch engaged, the gear locks with the rear hub and transfers power to a forward spiral gear via shafts that run within the bike’s aluminum tube frame. A gear set in the head tube, viewable through a service opening when the bars are turned fully to one side, channels the power down through a telescoping multi-spline driveshaft where it drives a free hub. Even with the clutch engaged, the front wheel of the bike is not powered under normal non-slip conditions due to gearing differential. Noticeable power transfer to the front happens either when the rear wheel slips or if the speed of the front wheel decelerates faster than the rear such as a front tire slipping out in a corner.
We didn’t have a chance to test a Christini bike on trails, but the practical applications that Christini suggests seem to make sense. In a climbing situation when the rear wheel slips, the front helps pull the bike up the hill. When encountering a slippery rock or root, the front tire tracks in the direction it’s pointed. Much like all-wheel drive in those early Audi rally cars, we’d expect the system in these bikes would totally change the benchmark in regards to how much is capable and under what conditions. We inquired with Steve about durability, and he suggested it’s very good. The company has been testing these bikes for over five years and they’ve found the all-wheel drive components, designed for optimal corrosion and wear resistance, outlast a bike’s chain drive considerably. Even better, for those hardcore muck-riders who are quick to point out they’ve changed out their chain drive system several times over, Christini adds that the all-wheel drive system has been designed for easy service. Steve boasts that the entire internal drive system can be disassembled for a complete overhaul in about 10 minutes by someone who knows what they’re doing.
The company also warranty’s the bikes for 2-years on the entire all-wheel drive system and 5-years on the frame. Even better, there’s a one year crash replacement warranty on the drive system parts. All Christini bikes feature 6061 aluminum frames and full suspension with either 100mm or 100mm/150mm adjustable travel setups. Is there a downside to the Christini all-wheel drive bikes? Well, Steve will admit they’re higher in price than the competitors. In a day when truly capable full-suspension mountain bikes can be had for about $1000, the Christini bikes are significantly more.
Another thing working against their mountain bike efforts is market demand. Five years ago, the relative newness of then-trendy Mountain bikes kept the segment outselling road bikes ten to one. Today, with the market somewhat saturated and the much-lauded successes of Lance Armstrong on roads of France, road bikes have now flip-flopped with mountain bikes and now outsell their off-road counterparts ten to one. Still, the specialized nature of this technology would lead us to believe there are several automotive companies who sell bikes under their own brand who’d benefit from such a unique approach – emphasizing all-wheel drive. Noticing a Jeep-branded frame on a rack and hung next to a Cross Pro frame from Audi Design, we asked some questions along these lines. Here’s what we learned.
Jeep has worked with Christini to make an all-wheel drive mountain bike, something that was expected to be packaged as an option with a special edition of the Wrangler Rubicon model. Regarding the Audi frame, Steve would only say that Audi had been evaluating the technology. The frame had been sent to Christini to see how difficult it would be to add the system to the Audi design. The answer was that the frame was suitable, and it could be done relatively easily. Will there be an all-wheel drive Audi mountain bike? Christini wasn’t sure. Talks on the project had stalled from what we could tell from his response. In addition to these tie-ins, Christini is also working on a downhill racer. Downhill seems to be the only form of off-road biking still getting airtime, and the benefits all-wheel drive would bestow on such a bike would be significant. The company is excited about the potential such competition promises. On to Motorcycles
Expected to have even more potential, Christini also has several all-wheel drive off-road motorcycle development mules that he’s been working on. Performance conditions at the greater speed of a motorcycle are more extreme, making the need for such a system even more obvious. However, adapting the system for motorcycle use required some changes to the design. Where Christini has gone is essentially a positraction drive system that transfers power to the front wheel only in situations slip or great difference in rotation between front and rear wheels. The motorcycle’s all-wheel drive system is run off the main transmission at the countershaft sprocket, utilizing a chain drive to a right angle gearbox located under the seat where a drive shaft transfers power to the head tube like the company’s mountain bike designs. Different from the mountain bike though, the motorcycle system employs two counter-rotating shafts, each telescoping like that of the mountain bike, but going down each side of the fork. This two-sided design eliminates torque steer and actually aids in stability for this more extreme application. Better yet, Christini claims that the system is efficient enough that there’s no noticeable loss of power. Early versions of the motorcycle, unlike the mountain bike, could not be disgengaged, making rolling the bike backwards very difficult – something you might not be appreciative of while trying to get the bike off the truck. With that in mind, the latest mules from Christini also have a switch where they can be engaged or disengaged, making the concept much more user friendly.
Under normal conditions, the front of the motorcycle freewheels. Under slip, power is matched at the front. What ratio runs to the front wheels? Christini suggests 60% is pretty good, and going much higher makes the bike hard to steer. That said, changing out the ratio is relatively easy and he’s considering selling replacement gear sets for riders to change out with relative ease. Stopping is also easier. Where a front wheel might begin to skid under braking on a conventional rear-wheel drive motorcycle, the system shifts power forward and keeping stopping power more even. Such a quality certainly helps control the bike, making novice riders better and creating an exploitable advantage for experienced ones.
The most obvious motorsport type to benefit from such a system is off-road endurance. Being acknowledged and successful here is important to Steve and he was quick to point out they’d just scored a 2nd place win in their first-ever competition event. Steve sites Audi’s rally efforts during the 1980’s as the effect he expects this technology to have on motocross and off-road endurance races. He wouldn’t be surprised to see the technology get banned, then maybe let back in as it spawns a new class. Consider it “Unfair Advantage”, the sequel. It’s important to note, Christini isn’t the only company working an all-wheel drive systems for motorcycles. Yamaha currently offers a hydraulically based system sourced from Ohlins for limited European availability, but it’s not attainable here in North America unless you import it yourself and it is inherently not as efficient a system from what we’re told. Christini is unique in their gear-driven design, of which the company holds a patent (US Patent #6505699) on the setup.
Still, all-wheel drive on motorcycles is extremely far from mainstream. Christini is talking to OEMS like Honda and others about the potential of installation of his system on new bikes. He’s also working on some retrofit kits for folks wishing to convert their bikes – in that case, expect a short application list. When the technology finally breaks in the market, off-road bikes are expected to be the most likely candidates for the system as the environments encountered are more extreme. However, the physics of the system are something that would undeniably help road bikes too. Thus far, no prototypes of a sport bike or any road bike for that matter have been built, but one of the all-wheel drive Yamahas with street tires was tested by journalists in Europe. Whether it’s the Yamaha or Christini’s Honda-based prototypes, the motorcycling press who’ve sampled it have overwhelmingly suggested that all-wheel drive will be the next big thing , at least in the off-road market. Related Links: www.Christini.com Fourtitude Bike Week Links Bike Week Main Page Part I: A 2 Wheeled History of the 4 Rings Part II: Audi Moto Concept Part III: Bicycles from quattro GmbH Part IV: Unfair Advantage, the Sequel by Christini J.J. Lehto, Choppers and Cross-Country Cruising with Frank Biela
© Copyright 2004 by YourSITE.com |
