Ski Technology: New Solutions to Old Problems

When it comes to ski technology, consumer development may sometimes actually benefit racing!
Back in the 1980s I tried a flat bottom ski with twin runners and I was not impressed. The sled, Ski-Doo's early MX, was more impressive overall than the skis. At that time, the MX was considered radical, to say the least. It featured one of the first attempts at making a truly long-travel suspension. The rear suspension worked great in large moguls, but since coupling was not yet invented, there was a tendency to lift the skis on acceleration due to the large angle the suspension arms had to travel through.

Lifting the ski was not all together an easy job. These were large welded steel contraptions with flat bottoms and two runners- placed one on each outside edge. Each ski weighed 40 pounds!

The engine in the MXZ was the trusty 500cc fan-cooled Ski-Doo mill. Although a great engine, it was not exactly a hot performer. With all this new technology, the machine was heavy and had an unfortunate tendency to "push" in the corners.

One nice winter day, my test rider, Jimmy the Greek and I took the sled out for a shakedown cruise. Jimmy is a long- time friend and master technician. His last name, Anagnostopolous, created a considerable problem when he tried to put the name on his race helmet. The name wrapped all the way around the helmet, so Jimmy simply became known as "The Greek." A name he is well known by yet today. I first met Jimmy when he was a test driver at Evinrude. He was the only factory sponsored race driver. Because of his profession, he was very agile on a machine and never got hurt in all his days of racing and testing prototype machines. Testing the MX, however, was a close call.

The twin runner skis did not turn as well as the conventional keel designs, so Jimmy was forced to improvise his riding style and adapt to the new machine. His new "style" consisted of banking off the snow banks to compensate for the lack of positive steering.
Unfortunately, one of the snow banks ended too early and Jimmy came flying by me in the air while doing a perfect somersault. He landed in a huge snowdrift totally undamaged. The left ski had caught a tree and Jimmy decided to jump off. So, how did he manage to perform a somersault? When you jump, you don't let go of the handlebars right away and that pivots your legs up, was his explanation. That way you don't catch your knees on the bars and break something. I thought it was some kind of test driver trick developed through years of breaking prototype sleds, but later found out he is a black belt in Judo and knew how to get thrown. Fortunately, the damage to the left ski was not bad and we could continue our trip. The incident, however, did leave me skeptical about twin runner skis.

That brings us forward from that early MX to Ski-Doo's REV MXZ. Last winter I rode a Ski-Doo REV with twin runner skis and was positively impressed. The REV handled great in all the trail conditions we encountered at our new machine tests. Twenty years have gone by and sleds are a lot different now.

With the new driver forward position, there is more weight on the skis. An aggressive single keel ski is harder to steer and gives too much handlebar feedback in regular trail conditions, although single keels still are used on Ski-Doo racers. The second large difference is the new "coupled" suspension, which reduces front-end lift and keeps the skis planted on the ground. The REV had such excellent handling and steering; I had to double-check and see if it really had twin runner skis. With typical 20/20 hindsight, I've re-thought the MX we rode in the 1980s and feel it was actually way ahead of its time. It may only have lacked "coupling" of its long travel rear suspension to make it acceptable.

Ski Doo claims that twin runner skis reduce "darting" on the trail and therefore are safer and easier to run. With a single runner, the carbide will fall into a groove made by a previous carbide runner. This will force your ski to follow the groove and dart your front end around accordingly. With two runners, the other runner will hold the first one up off the groove and prevent it from forcing your steering into the darting mode. Unless of course, both runners fall into equally spaced grooves.

The probability of falling into two grooves at the same time is fairly small, while one runner by itself usually will find a groove to follow. If the twin runners prevent darting, how about mounting them on conventional single keel skis? One of the first to grab this concept was Woody's, the after-market traction and control manufacturer. They introduced twin runners mounted on a plate, which in turn could be installed on a conventional single keel ski.
The result from this modification has been excellent. When you use two carbide runners next to each other, each runner ends up shorter than a single runner. This makes turning easier, keeps just as much carbide on the ground and reduces the tendency to "dart".
Polaris is now introducing a plastic ski with a wider keel and two short runners mounted one-inch apart. As usual, it does not take long for a good idea to catch on in the snowmobile market. A single keel ski with two runners seems to be a good idea. It would reduce the darting on hard ice, while also providing a keel for steering in deep loose snow. No wonder then that one of the first models from Polaris with this design is their new "Switchback" mountain sled.

"Darting" has long been a severe problem in oval racing ever since the first IFS sleds appeared on the track. This problem was so troublesome that several race teams were skeptical of the new IFS technology and decided to stick with leaf spring skis. It is frequently forgotten that Polaris ran leaf sprung versions of its famed "Indy-pendent" IFS-styled sled back in the 1970s when it introduced IFS models in the first races. As soon as the darting problems were cured, the leaf spring models where gone. On a leaf spring sled there was less "darting" because it lacked the change in ski stance common with the IFS models. Leaf springs also could bend sideways, while IFS skis were held firmly in place by their radius rods. When the aggressive carbide hit a groove, the ski would get into a shaking motion. This could be so severe that the handlebars where ripped out of the driver's hand and he would part company with the sled. The first year of serious factory IFS development saw some strange sled behavior and many drivers where scared of driving the "ill handling" monsters.

As usual in racing, someone found an answer to the problem. In this case, it was Bob Eastman and his Polaris race team. They quickly discovered that a long flat carbide runner was not the ideal shape to turn with; the carbide should follow a radius in any given turn, but the skis were straight. This meant that the front and back portions of the runners would have to skip over the ice, but this created a strong vibration in the ski. Broken ski-loops where a common occurrence and racers needed strong arms to hold on.

The solution was simple, but remained a racing secret for many years. Something called a "rocker" was introduced to the carbide. This meant the carbide runner by itself was bowed in the middle and the center of the runner could be as much as a quarter-inch lower than the ends. If you grabbed a ski with "rocker" built into it, you could move it up and down like the rails on a "rocking chair."
With this modification, "darting" and ski vibration were reduced and the race sleds handled much better in the turns. Racers could now drive harder with confidence without the fear of suddenly having the handlebars ripped out of their hand. The shape of the carbide bar was so critical to handling that on a Sno Pro race day, scores of high paid factory drivers could be seen by their factory rigs grinding their own carbides. While they gladly left other mechanical work to the factory mechanics, each had their own exact preference when it came to the amount of "rocker" they wanted on ski carbides.

Regular snowmobiles seldom approach even 25 percent of the grip an oval sled sees on glare ice. "Rocker" has until now not been a large issue on consumer skis. With the new twin carbide design, each one of the carbides can be half the length and you would still have as much carbide on the ground. This in fact brings the twin carbide design closer to a "rocker" configuration. Since most of the carbide is concentrated in the center, there is no runner sticking out in front or back to feed vibration or "darting" motions into the ski.

We are presently witnessing a revolution in ski and carbide designs that may in fact improve handling on race sleds.
At the present time, only single runners are allowed in oval racing, but officials are looking into changing the rules if this would improve handling and make racing safer. We would then be in the unique position for once that consumer development benefits racing!

This story ran in the January 2004 issue of American Snowmobiler magazine
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