1981 Ski-Doo Twin Track: The Snowmobile that Forever Changed Oval Racing 1981 Ski-Doo Twin Track: The Snowmobile that Forever Changed Oval Racing
By Hal Armstrong The snowmobile that would change and dominate oval racing for nearly two decades was an evolution of the Gilles Villeneuve 1974... 1981 Ski-Doo Twin Track: The Snowmobile that Forever Changed Oval Racing

By Hal Armstrong

The snowmobile that would change and dominate oval racing for nearly two decades was an evolution of the Gilles Villeneuve 1974 twin track Alouette race sled and the Jimmy Shampine ‘Offset” super modified race car that was dominating the Oswego, NY speedway in the late 70’s. Three key individuals would bring the concept to life and Jacques (Jocko) Villeneuve would be the factory driver that piloted the sled on the SnoPro race circuit in 1981.

1974 Allouette

Times Were Changing
The ‘76 race season had seen another Gilles Villeneuve designed race sled beat the factory Ski-Doo machines that had superior engine power. The secret was Villeneuve’s Skiroule race sled could corner faster. The trick? An IFS ski suspension designed by Gilles that kept both skis on the ice to improve cornering control.

The Designer
Rejean Beauregard was the designer of the SnoPro race sleds at the time and he had seen the writing on the wall. The ‘77 oval race sleds came to the track with his version of an IFS, based on the Ford Twin I-Beam suspension used in their pick-up trucks at the time. The ‘77 season was not one for the record books for Ski-Doo but it provided valuable lessons for Rejean and the race team to improve the ‘78 race sled and ultimately win the SnoPro High Point title with Allen Decker in 1979.

Rejean had designed the new ‘78 race sled with a tubular chassis to improve torsional rigidity and reduce weight. The new independent front suspensions had changed the dynamics of snowmobile setup and the increased spring pressure used on the skis to corner hard required a chassis that would not flex. This chassis design was unique to the Ski-Doo race sleds and would later be exploited further with the yet-to-be designed “off-set “race sleds.

1981 Ski-Doo Twin Track

The Mechanic
Gaetan (Chester) Duval joined the race team as a mechanic in 1977. He also had been working with Rejean on the design and fabrication of the new race sleds each year and had taken an interest in improving the aerodynamics of the sleds. His work at the National Research Council wind tunnel in Ottawa was instrumental in reducing drag. The new SnoPro race sleds starting in ‘78 all featured aero windshields for the driver to duck behind, which up to that point had been eliminated on all manufacturer race sleds. In addition, for 1980 a large “NACA” duct was designed to improve airflow to the radiator for engine cooling.

The Boss
Peter Hill was the VP of Marketing for Ski-Doo with the race team reporting to him. Prior to working at Ski-Doo he ran Skiroule and knew the importance that racing had on snowmobile sales. He had become good friends with Gilles Villeneuve and convinced the owner of Skiroule to hire Gilles to race for them and also provide some sponsorship money for his Formula Atlantic race car. Gilles told Peter he had an idea for a radical new race sled that would turn out to be the ‘76 IFS race sled. Gilles had calculated that to win the world championship he needed to run 2-3 seconds faster per lap. He would achieve this with a new race sled with IFS that would make up the advantage in the corners. His design worked and was later copied by all the other race teams. Peter hired Gilles and brother Jacques because of their “will to win”. This alliance with Gilles and brother Jacques would later prove valuable at Ski-Doo. Jacques was hired when Peter returned to Ski-Doo.

Peter stated, “Having a Villeneuve on the race team brought two advantages; a fearless driver and the Villeneuve name which brought race fans by the droves to the track.”

The pieces were now in place for the 1980 race season. All that was left was a fateful trip to the Oswego Speedway

Oswego Speedway
Rejean and Chester made a trip down to the Oswego Speedway in the spring of ‘78 to watch the Super Modified (auto) racing on the 5/8 mile paved oval track. On that night they watched a race car driven by Jimmy Shampine dominate racing all night. The car was unique as the driver and engine were “offset” to the left side of the car.

1981 Ski-Doo Twin Track

This new car was also built on an all tubular chassis which Rejean had already began to exploit with his race sled designs. It was obvious that the offset design reduced the effect of centrifugal force trying to force the car to the outside of the corners. The design intrigued Rejean and he could not wait to get back to Valcourt and start sketching a design for a sled chassis. The idea just made too much sense to ignore. The problem of inside ski lift was still an issue with the race sleds of the day. Moving the inside ski closer beneath the driver and extending the right ski further away from the chassis centerline would improve stability in the corners.

The original tubular Blizzard race sleds (‘78 and ‘79) were built from small diameter thick wall 4130 chrome moly tubing. The tubular frame was lighter and more torsionally rigid than a conventional chassis but for the new offset race sled, Rejean wanted to take the design one step further.

He recalls, “In ‘80 we went to larger diameter thin wall 4130 chrome moly tubing to further improve torsional resistance. When the suspension spring rates were changed, the stiffer chassis was more sensitive to changes than the previous design. The new sled was also lighter because less material was used. After the chassis was fabricated the entire structure was put in an annealing furnace to stress relieve the chassis. We benefited from Bombardiers mass transit division which had metallurgists on staff to assist us with the annealing process (temperature and time).

The offset chassis allowed Jacques Villeneuve to win the world championship for Ski-Doo after a 10 year hiatus. The results were good, but Rejean Beauregard still had more unfinished business to fully exploit the offset chassis design.

1981 Ski-Doo Twin Track

The Twin Track
Rejean wanted to further the design of the offset chassis for ’81, but how? Chester Duvall recalls, “We always admired Gilles ‘74 twin tracker. We liked that idea of the twin track but we wanted a design that looked like a snowmobile and we also wanted the driver to still have the ability to shift his weight to compensate for loss of traction.”

Rejean explains, “Jacques Villeneuve and I were talking one day about the twin track his brother had built. He reminded me that Gilles had used a motorcycle clutch to disengage the inside track when the steering was turned to go left. The inside track is allowed to free wheel and all the power is transferred to the outside track to force the sled to turn left.”

Rejean had also recently seen a couple of drivers killed because of loss of control in the corners. Rejean started work on a new twin track design based on the offset race car chassis. The driver in his design would sit above the left tunnel which would offset the driver’s weight from the chassis centerline. This change combined with four points on the ground would make for a faster more stable race sled. Rejean pushed the idea to his boss and with the support of Peter Hill the funds were made available to build the first prototype.

1981 Ski-Doo Twin Track

Testing in Quebec – Spring 1980
The development of the twin tracker continued under Chester Duvall who was promoted to Race Team Manager for the ‘81 season. Rejean had left the company after drawing up the new sled but Chester still had a strong group to work with to further refine the sled over the summer and fall. The group consisted of Marc Dandurand and Claude Desrosiers who had worked and raced out of the race shop. Chester spent time again that summer at the wind tunnel in Ottawa at the National Research Council refining a moveable rear wing and small fixed wings on the front of the sled to create more down force on the chassis to improve traction in the corners. The external wings would later prove to be more of a detriment than an advantage.

Chester explained, “That first year we built 4 sleds. We tested the prototype in Northern Quebec that spring. We were happy with the machine on the cornering but the top speed was down more than we expected from the single track sled. Top speed was down because of the extra power required to now turn two rotating tracks. We tried a shorter 90” long track and located it further back in the tunnel to improve straight line stability. We thought with the shorter track (less rotating mass) the straight line speed would increase. We were wrong and settled on the 103” long track from the ‘80 sled. Believe it or not we cut the 15” track in half to make the two tracks at the race shop so we met the race rules. The tracks were built by Goodyear and were nylon reinforced. Cutting the tracks in hindsight was a mistake but there was no supplier for a 7- 1/2” wide track that year.

1981 Ski-Doo Twin Track

On the Race Track
“The 1st year we did not win one race”, recalls Chester. “We got a few seconds and thirds that year and continued to plug away at solving all the technical challenges this sled developed at every race”. Peter Hill stated;” We never thought of abandoning the design. We were confident we had a good machine to work with but we knew we had more work to do. The wins would come eventually.”

“When we brought it to the first race of the year in Winnipeg the guys from Arctic, Scorpion and Polaris told us that it looked like we did a lot of home work over the summer. We had a lot of eyes on our sleds all winter long as we refined the design.”

The biggest challenge that winter was keeping tracks on the sled and refining the track differential. So how did the power get delivered to the track? Gaetan explains; “We used the same clutch used on the Can-Am motorcycles that Bombardier had been building. We thought since a car differential runs in an oil bath we should do the same. The clutch was integrated into the chain case and ran in an oil bath as we thought we were going to be generating excessive heat causing clutch slippage. We were wrong. The wet clutch slipped too much. We quickly learned that the oil bath clutch was killing us on the hole shots and down the straights. When the sled was under development we did not have the money to develop a differential for the drive. We discovered that the increased traction from a studded track was causing the clutch to slip. We could not put enough pressure on the clutch to prevent the slippage. So we switched to a dry disc so we did not have to put so much spring tension on the clutch pressure plate. The dry clutch solved the hole shot problems and improved top speed.”

This simple differential was cable operated from the handlebars. As the driver turned the handlebars to enter a left hand turn the clutch was disengaged allowing all the power to be transferred to the right hand track. Straighten the bars out for the back straight away and the power is shared 50/50 between both tracks. Sounds simple, but when that clutch did not disengage entering a corner the sled would go straight. That first year, Jacques Villeneuve made a few extra trips into the hay bales.

Work on the new sled did not stop at the chassis or drive. The Rotax engines used were the same 340cc from the 1987 sled except they were doing development work. The 340 back at that time was putting out 85 hp. They had a high torque engine running around 9000, as well as a high rev option that ran at 10,500 rpm putting out a few more hp.

1981 Ski-Doo Twin Track
The 1981 Twin Track race sled had the wing on the rear and the two small wings on the front. Ski-doo only built three or four sleds that year. Jacques Villeneuve rode the entire SnoPro circuit that winter with the Ski-doo colors. Only “Jocko” raced the sled that year; except for the 1981 TT Moto-Ski (shown here).
The Moto-Ski colors and graphics were done specially for (brother) Gilles Villeneuve. Gilles was part of Bombardier’s advertising campaign for Moto-Ski, and raced the sled at the Montreal SnoPro in the winter of ‘81. When Enzo Ferrari found out his F1 driver had raced a snowmobile that weekend he was not amused. That was the last snowmobile race Gilles ran before being killed during practice for the Belgium Grand Prix at Zolder in May of 1982.
This was the sled that Gilles raced at Montreal and it sits today at the Snowmobile Hall of Fame in St. Germain, Wisconsin. The sled is now owned by Brad Warning.

Did the Twin Track Kill Interest in Oval Racing?
The question always posed by race fans was whether the twin track sled killed interest in oval racing. The’ 81 sled did not set the racing world on fire but the redesigned ‘82 version claimed the world championship and for many years to follow. The sled came at a time when the other manufacturers could not afford to continue to compete. Ski-Doo continued to refine the sled and used it as a proving ground for future engine designs (RAVE engine). It was also a time when independents like the Wahl Brothers, Deckers, Vessairs, Dale Loritz and Bobby Donahue (among others) continued oval racing well into the 90s. These sleds were truly Formula 1 machines built for the snow.

1981 Ski-Doo Twin Track

I asked Chester if he thought the twin track killed oval racing. “Of course not. The best years of racing were the Export series in the mid 80’s”.
Does he miss all the action? ”Being a race team manager helping 50 riders and building 20-25 new sleds each year was a lot of work. It took 8 months to build 25 sleds and we raced the other 4 months. It was lot of work and a lot of fun!”

The Ski-Doo twin track sled was a marvel of engineering and provided lots of entertainment for the racing fan. The spin-off for the consumer was minimal. Ski-Doo at the time was losing market share and when the Twin track program was cancelled, renewed effort was spent on the new challenge – SnoCross – which Ski-Doo would dominate years later with their next chassis innovation, the REV!

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