Snowmobile Chassis: From AWS to Formula 2000

In the early years of the snowmobile, different people had different ideas of what the proper chassis design should be.

For example, Carl Eliason of Sayner, Wisconsin, one of the pioneers of snowmobiling, placed the engine behind the rider and on top of the track/drive assembly, on his “power toboggan.” Flotation of the machine was actually handled by skis that ran the length of the machine. The track was only used to transfer power to the surface of the snow, not to provide floatation.

Eliason eventually sold his patents and concepts to the FWD Corporation. FWD produced a few sleds utilizing Eliason’s concepts, but more noteworthy than those machines was the fact that they became the roots of both Polaris and Arctic Cat when Allen and Edgar Hetteen founded the two snowmobile manufacturers.

The early Polaris Sno-Traveler and the original Arctic Cat Model 500 both used the engine in the rear concept. However, Arctic Cat abandoned the long skis and utilized the track for floatation as well as propulsion.

J. Armand Bombardier of Valcourt, Quebec, Canada, interpreted the snowmobile chassis design quite differently from Eliason and the Hetteens. His original concepts can be seen almost exactly as he originally conceived them in today’s Ski-Doo Elan. The engine is mounted in front of the rider, on top of the track tunnel. The rubber track provided virtually all the floatation as well as the propulsion. This chassis design provided excellent floatation in snow, was lightweight and offered acceptable handling. Bombardier’s chassis design became the concept that almost all snowmobile manufacturers utilized until the mid 1960s.

Along with these more conventional chassis designs, there have been some strange incarnations as well, such as the Larven and the American Eagle, both of which didn’t have skis and the operator, more or less, sat on top of the engine, motorcycle style. The Larven was a single track affair while the American Eagle was equipped with two tracks and steered like a caterpillar tractor.

These variations of ski-less snowmobiles are still around, too. There is a ski-less sled being produced in Europe called the Flex- Track. Without skis and with no bellypan, the entire surface of the machine in contact with the snow is track. The flexible track design allows the track to be bent to either side to allow the machine to turn. No, you’ll never see one on a race track!

You old timers will all recall the Huskee and later, the Bolens Diablo-Rouge. These designs looked like garden tractors pulling ironing boards on skis. They were both totally different chassis design concepts from the other manufacturers. The problem is they didn’t work very well and whenever you took a ride on one, everyone who saw you fell to the ground laughing hysterically.

A more successful, unique chassis design was found in the Raider and later the Manta. These twin tracked vehicles allowed the operator to sit in the vehicle with the engine behind.

Arctic Cat defined what was to become “the” chassis design for snowmobiles when it introduced the 1966 Arctic Cat Panther. The engine was taken off the top of the tunnel and moved forward into the belly- pan. The stamped, aluminum tunnel was equipped with a slide rail suspension system and the machine even had a hinged hood that allowed easy access to the engine compartment!

This basic chassis layout is the design used by all manufacturers today with the exception of a few specialty sleds such as Ski-Doo’s Alpine and the good old Elan. The evolution of snowmobile chassis design has all worked off that original, 1966 Panther.

Within the last two seasons, three of the manufacturers have introduced new chassis designs and Polaris will introduce the first major change of the Indy chassis for the 1994 model year. Here’s a look at each of these new chassis designs is and what the manufacturers are trying to accomplish with the designs.

Arctic Cat’s AWS III: Arctic Cat introduced its newest chassis design last season on the supremely successful 580 and 440 ZRs. The ZRs were obviously aimed at the race track. Development started with interviews with race drivers and mechanics. A stronger front wishbone design was needed along with a wider stance and improved geometry. What grew out of the study of the front suspension is what became the AWS III design. It is the third version of Arctic’s A-arm suspension, which made its debut in 1985 on the El Tigre.

A fourth version, AWS P1, will be used on the ZRs this season.

Arctic Cat Wishbone Suspension (AWS) III features a shock mounting location on the outside of the bellypan. This provides more space under the hood for exhaust systems and a mounting location, which is 2 inches further forward, for the rigidly mounted engine. The steel ski spindles mount with a 40-inch stance and along with narrow skis, bring the overall width to the legal limit of 45 inches. The A arms themselves are made of 4130 chromemoly steel.

The forward placement of the engine also allows for a longer drive belt, which helps reduce the operating temperature of the belt. The engine is placed as low in the new chassis as possible and still allows for changing the drive belt. Rider position on the ZR chassis was also given a lot of thought. The deep tunnel places the rider’s feet 2 inches lower than they are on Arctic’s other chassis designs. The seat is extra soft and easily removable while the handlebars can be adjusted fore and aft as well as up and down.

The race drivers also demanded sturdy bumpers front and rear that you can easily wrap a gloved hand around and muscle the machine around when the need arises. A race driver doesn’t have to carry around 11 gallons of fuel so the ZR is equipped with a 9-gallon tank. The rear suspension includes a lot of adjustability for any riding style and type of competition. The torque arm, front arm, can be relocated 2 inches to the rear and there are two separate positions for the rear suspension arm. If you can’t find the amount of weight transfer you want with this setup, you’ll never find it!

The 1993 ZRs were equipped with a single piston, Wilwood hydraulic brake. The system was extremely powerful but did lack driver “feel.” It often seemed to be on or off. For 1994, a dual piston caliper is employed. It is equally powerful but more progressive in its application. The ZR’s excellent handling is further enhanced with an adjustable stabilizer bar that has been raised and moved a bit further forward for 1994. Throw on a set of well calibrated, Fox gas shocks and Arctic’s latest chassis design is simply sensational.


A 700cc version of the ZR will be available for 1994 and slightly altered versions of the ZR chassis such as the one found on the 580 EXT prove that the effort poured into Arctic’s latest chassis will permeate through most of its line. The success of the ZR should be a lesson for all involved in snowmobile development talk with those who will ride it!

Polaris’ Indy Chassis: Polaris’ newest chassis is pretty much the same one we’ve known since the 1980 TX-L Indy. The rest of the industry has been trying to one up the Indy chassis from the day it first hit the snow. Over a decade of fine tuning has been poured into the Indy chassis and it should be noted that the basic design was first employed for racing on the original RXLs.

Polaris' Indy chassis offered removeable side panels.
The Indy chassis design attacked the problems of weight, handling, ride and production cost from the very start. Its original focus on racing defined the need for excellent handling and strength and it’s got it. The location of major components such as the engine, drive axle, jack shaft, handlebars and bulk head have always provided the Indys with the ability to fly level, handle extremely well and run hard in the rough.

For 1993, Polaris had reworked its rear suspension in an effort to improve weight transfer. The setup did transfer harder, but it was too much for the hard trail rider. When you got on the throttle hard, the skis lifted enough to lose traction in the turns. The system for 1994, called the XC-100, mounts the suspension 1-inch further back in the tunnel than the former ITS system and uses a longer front torque arm. The rear shock can be located in one of two positions to allow for different damping characteristics. The XC-l00 system provides reduced ski lift for more positive handling in the corners, improved steering and ride quality, and great acceleration. The ITS system, still installed on many Indy models for 1994, has been modified with new shock calibration, higher spring preload and new limiter strap hole locations.

The suspension system changes on the Indys during the last couple of seasons is an indication of how good the Indy chassis design really is. It’s just plain difficult to improve on it. The Indy didn’t take Polaris to No. 1 in new unit sales for no good reason. Certainly shock absorber design and calibration, spring rates, stabilizer bar adjustments and other nuances will continue to be fine tuned for particular applications, hot the Indy chassis still has the best weight distribution, neutral handling characteristics and basic geometry in the business.

Over the years, Polaris has taken some heat about “not making enough changes.” When it was rumored that Polaris would introduce a new chassis for 1994, we wondered what they could build that would so out-perform the Indy design that new tooling could be justified. With the unveiling of the 1994 Indy 500 EFI Classics and Indy 440s, we were impressed by the wisdom of the Roseau crew. The Indy chassis and all its superb characteristics were preserved, but it was fitted with a new bellypan and hood along with some other comfort, convenience and aesthetic changes. Removable side panels allow for easier servicing in the more compact engine compartment of the new design and the tapered bellypan will likely improve performance in deep snow. Those who said Polaris needs some change should be happy. Polaris certainly has a new look in these models, one that incorporates some nice features, but under the new skin lies that incomparable Indy chassis. Who says racing doesn’t breed a better trail sled?!

Ski-Doo’s Formula 200 Chassis: Have you heard about the Formula 2000? That was the project name given to the program at Ski-Doo to develop an all new, high-peiformance chassis some years ago. The plan was to develop a design that could carry Ski-Doo into the year 2000 without major changes. The chassis had to be light, strong, cost less to produce than the earlier Formula chassis’, allow for easier servicing and be flexible enough to be produced in several engine, track and feature configurations. Bombardier introduced the design last season as the MX Z and Mach Z.

The “Z” chassis met its design objectives and provided Ski-Doo fans with the best riding machine Bombardier has ever produced. There’s no company in the business that will invest more in research and development of its products than Bombardier. It has developed and produced models with A-arm front suspensions, trailing link designs, twin I-beam designs, telescopic strut designs, the PRS design still used on several Formula models and now the DSA (Direct Shock Action) design. Bombardier first used the DSA front suspension design on its 1978 Blizzard, production race sleds. Several chassis/suspension designs were developed and produced between then and now, but the Formula 2000 chassis embodies evetything that Bombardier has learned about chassis design. Does Bombardier’s front suspension look like Polaris’? Yes, it does. Both companies have worked with the design for years and it offers many advantages over other front suspension designs.

The Z chassis utilizes an all-aluminum frame to reduce weight, has a 40-inch ski stance which puts the overall width at the racing limit of 45 inches and mounts a 15- by 121- inch track. The Formula Z for 1994 weighs 57 pounds less than the previous Plus X model. You can see how effective the design objective of weight reduction was!

The MX and Mach Zs of last season were aimed at the trail rider. For 1994, the MX Z and the Formula Z are aimed at the production iacer with lowered engine mounting locations, HPG (high-pressure gas) racing shocks and tons of horsepower from BombardierRotax. Ski-Doo’s new chassis is already a hit and more involvement in competition will fine tune it even further.

Yamaha’s Vmax Chassis: Yamaha’s latest chassis was introduced on the 1992 Vmax-4. For 1994, the whole fleet of 500 and 600cc Vmaxs ride on somewhat longer and wider versions of that original chassis. From the back of the hood to the tail of the new Vmaxs, the chassis is identical to the original Vmax-4. The dimensional changes in the latest chassis are all forward of the track tunnel. Yamaha uses a 17-inch wide tunnel that allows for increased fuel tank capacity without having the tank high in the air, raising the machine’s center of gravity. The chassis is all aluminum and extremely light.

Yamaha has stayed with their telescopic strut suspension and has refined it every year since its introduction. The newest Yamaha chassis now mounts the struts on 40-inch centers for stability. One of the major advantages of the strut suspension is that it allows a chassis design that has a “clean” bellypan. The pan is perfectly smooth and offers little resistance when running in deep snow. Without the slots and openings in the pan for suspension components and the components themselves hanging out all over, the Yamaha design is superb in deep snow. The sides of the pan are also radiused to allow for cornering in deep snow with less drag. When it comes to ability in deep snow, the Yamaha chassis design is the best of the lot.

Yamaha's Vmax chassis for '94 models featured a longer wheelbase and extra-wide ski stance for more stability.
Yamaha has provided lots of room in the tunnel with the placement of its heat exchangers for the installation of studs. This is an important consideration for racers and most riders who run on the trail systems. Yamaha also kept ease of service in mind in its chassis design. Yamaha was first with removable panels to ease servicing, but earlier chassis designs had incredibly compact engine compartments and even with the removable panels, some service procedures were tough. The new chassis has met the design objective of easy serviceability.

The design of Yamaha’s chassis was certainly inspired by the requirement to keep weight down. Every bracket on the machine is beautifully made with lightening holes wherever possible. The TSS suspension design is light and simple. The liberal use of aluminum and plastics has allowed the Yamahas to be as light or lighter than anything on the market while offering all the comfort and features of any snowmobile.

Down The Read – Each manufacturer has a little different twist to their design, but the basic configurations are the same. The big four will hone their designs and provide more interesting features, comfort and convenience items but we don’t see any radical changes in basic chassis design in the near future. Yes, the Diablo Rouge is dead!

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