pushing ahead

AmSnow.com is now SnoWest.com

Simply put, racers have been responsible for most advances in snowmobile chassis technology. Progress usually has been the result of an intense effort to stay ahead of the competition on the track.

At Arctic Cat, Roger Skime and his crew leap-frogged the competition and put Arctic way ahead with its slide-rail suspension back in the 1970s. Skime is still vice president of sled engineering at Arctic Cat, and racing has a high priority as a testing ground for advances in chassis and suspension design.

It's no surprise then that Arctic's new Slide Action rear suspension is the direct result of years of testing and brainstorming in a continuing quest to improve chassis performance. This time the brainstorming took place back in 2004 on a long drive back to Montana, where Arctic racing veterans Kirk Hibbert and Russ Ebert tried to solve a particular problem with the long-travel "coupled" suspension used in racing.

Long travel woes
The problem with long-travel suspensions has been their tendency to generate too much ski lift as the suspension is compressed in back. This reduced ski pressure, when exiting corners under hard acceleration, results in the front end washing out.

If you stiffened the rear to reduce ski lift, you also negated some of the long-travel suspension's advantage of soaking up bumps. It's this compromise that kept travel relatively short until the advent of a coupled suspension.

A regular slide-rail suspension consists of a front link to transfer power and a "floating" rear link to allow the slide rail to "articulate" over moguls. As long as the rear link was free to float, all power was transferred through the front link, which then would lift the skis until the front strap stopped the movement. However, a coupled suspension only allows the rear link to "float" a certain amount, and then it hits a stop that "couples" it to the slide rail.

You now have two solid links in a parallelogram; the result is that the front arm pulls the slide rail up, rather than pushing it down, and pressure is then put back on the skis. The coupled suspension solved many problems and allowed suspension travel to grow longer and soak up bigger bumps.

However, there was one nagging problem, and this is what Kirk and Russ were brainstorming on their trip back to Montana.

When the coupled suspension is "locked" and the front arm is pulled up with it, the whole suspension stiffens. When the front of the slide rail then hits the next mogul, the jolt is a lot harder, and this shows up fast in rough mogul sections on a Snocross track. This was the problem the two racers were trying to solve.

Both had a lot of experience from Snocross and Cross-Country racing, and both had sons in their prime, racing the Snocross circuit. Tucker Hibbert is a proven champion, and Ben Ebert is busy proving himself in the tough environment of professional Snocross.

In engineering, there's a saying that first you have to identify the problem, and then you are 50% closer to a solution. Once you know the problem it's easier to focus on possible solutions.

Kirk and Russ determined that they wanted to "uncouple" the front link when the rear link was locked. This would allow the front of the rail to unload and move down to soak up the next mogul. It also would allow more track to remain on the ground for better grip.

Somehow they had to let the front link grow longer under coupling to prevent the front of the rail from pulling up and stiffening the front of the suspension.

Theory testing
By the time the two racers got to Montana, they had a good idea of what they wanted. They wanted a front link that would float and become longer when the rear link was locked in coupling. Fabricating parts was second nature to these racers, and they soon had suspension parts made.

Once testing began, it didn't take long before they got the proportions right, and a good working prototype was mounted on Ben Ebert's Snocross racer. Ben reported more traction on takeoff, and when exiting corners from the apex out, he had both better traction and improved steering.

Eager to test the new invention in battle, the racers headed to the Detroit Lakes race in the spring of '04, where Ben proved the concept with a class win first time out.

The new invention was then tested in the toughest possible environment, on the factory Snocross sleds during both the '05 and '06 racing seasons. At the end of the '06 campaign, Arctic again earned championships in the Pro Stock and Open classes.

From racing to production
Now the invention is patented by Arctic, naming both Kirk Hibbert and Russ Ebert as originators. The new system also is in production on Arctic's F-Series models and the 4-stroke Jaguar.

If you look closely under an F-Series machine, you'll see that the front link is not welded to the cross shaft. Instead, each arm has a fork that slides over the crossbar. These forks allow the front suspension arms to move back and plant the front of the suspension on the ground, ready to soak up the next bump. The arms will not move unless the rear arm is "coupled" solid to the rail, so there is always power being transferred either through the front or rear link.

Instead of the suspension going "solid" on both arms when coupled, there is now always a solid arm and a floating arm, shifting the action between the front and rear arms. This increases the slide-rail's articulation and softens the coupling action.

Both Kirk and Russ are excited about this new step forward, and so is Arctic Cat. Kirk's son, Tucker, has returned to the Snocross circuit with an Arctic factory ride.

Oh, and we suppose Ben Ebert also can expect some good factory equipment this season, as father Russ has be-come Arctic Cat's new race manager.