Project Overview
The use of compressed-natural gas as a reliable automotive fuel source is becoming more common. Although its use is spreading through a number of large vehicles, it remains largely absent in the small engine field.
Due to the increased weight and size of a CNG tank needed, several issues come about on a smaller vehicle that would otherwise be nominal for a larger vehicle such as a car or bus. The snowmobile conversion to compressed natural gas seeks to show that CNG is an effective fuel source that is both cost effective and cleaner burning while also keeping the same, or higher, level of performance and handling.
For a smaller vehicle like a snowmobile, weight distribution is critical to the handling and performance of the machine. A large, heavy CNG tank is needed to keep the same travel length requirements of the stock machine, which severely hurts the handling when using the stock suspension and chassis setup.
The Chassis team is working to improve the handling and weight distribution of the sled with the additional CNG equipment to approach that of the stock sled. The handling of the sled has been improved by working with the rear suspension skid. Since the snowmobile is designed to ride in deeper snow, it features a 141-inch long track and uncoupled rear suspension – meaning that the front and rear shock of the suspension skid work separate from each other. (In a coupled suspension, the two shocks work together.) While the 141-inch long track was a benefit to the conversion, the uncoupled suspension hurt the overall handing because it is designed to cause the front of the snowmobile to lift up and have a “light” handling feel (a great benefit for deep snow, but a hindrance for trail riding). Combining the uncoupled suspension and CNG tank, the front suspension feels extremely light, meaning that turning was difficult with CNG modifications, but no other changes. Using a linkage kit to change the linkage rate of the rear shock, the suspension is significantly improved. The number of pivot points is reduced from four to three which causes the rear spring to act stiffer than in stock form. The improved suspension design also raises the rear of the sled which brings the center of gravity forward to where it should be. A second modification will be made to the tunnel for strength and to move the center of gravity. To do this, the tunnel will rebuilt using much thicker aluminum than stock and a flat tunnel design as suggested by Arctic Cat. The original tunnel design was not created to be weight bearing, but a similar design for a tunnel designed specifically to hold large amounts of weight will be followed to support the weight of the CNG tank.
Later modifications to the chassis include moving the CNG tank closer to the front of the sled to move the center of gravity closer to the front of the sled where it would be in stock form. Additional bogie wheels will be added to the rear suspension to reduce the noise of the rotating track and help create a more efficient drive system.
Representative Image:
Due to the increased weight and size of a CNG tank needed, several issues come about on a smaller vehicle that would otherwise be nominal for a larger vehicle such as a car or bus. The snowmobile conversion to compressed natural gas seeks to show that CNG is an effective fuel source that is both cost effective and cleaner burning while also keeping the same, or higher, level of performance and handling.
For a smaller vehicle like a snowmobile, weight distribution is critical to the handling and performance of the machine. A large, heavy CNG tank is needed to keep the same travel length requirements of the stock machine, which severely hurts the handling when using the stock suspension and chassis setup.
The Chassis team is working to improve the handling and weight distribution of the sled with the additional CNG equipment to approach that of the stock sled. The handling of the sled has been improved by working with the rear suspension skid. Since the snowmobile is designed to ride in deeper snow, it features a 141-inch long track and uncoupled rear suspension – meaning that the front and rear shock of the suspension skid work separate from each other. (In a coupled suspension, the two shocks work together.) While the 141-inch long track was a benefit to the conversion, the uncoupled suspension hurt the overall handing because it is designed to cause the front of the snowmobile to lift up and have a “light” handling feel (a great benefit for deep snow, but a hindrance for trail riding). Combining the uncoupled suspension and CNG tank, the front suspension feels extremely light, meaning that turning was difficult with CNG modifications, but no other changes. Using a linkage kit to change the linkage rate of the rear shock, the suspension is significantly improved. The number of pivot points is reduced from four to three which causes the rear spring to act stiffer than in stock form. The improved suspension design also raises the rear of the sled which brings the center of gravity forward to where it should be. A second modification will be made to the tunnel for strength and to move the center of gravity. To do this, the tunnel will rebuilt using much thicker aluminum than stock and a flat tunnel design as suggested by Arctic Cat. The original tunnel design was not created to be weight bearing, but a similar design for a tunnel designed specifically to hold large amounts of weight will be followed to support the weight of the CNG tank.
Later modifications to the chassis include moving the CNG tank closer to the front of the sled to move the center of gravity closer to the front of the sled where it would be in stock form. Additional bogie wheels will be added to the rear suspension to reduce the noise of the rotating track and help create a more efficient drive system.
Representative Image:
The picture above shows a comparison of the location of the center of gravity (red dot) for the CNG snowmobile at the start of the year and the center of gravity of the sled in stock form. The center of gravity for the CNG snowmobile is 8.5 inches closer to the rear of the sled than it is for the stock center of gravity, but the goal of the team is to get the difference as close to zero as possible. Also note the suspension for each (circled in red). The ride height of the stock sled is very high but the suspension, again stock, for the CNG sled is very compressed with the added weight. The addition of the added suspension kit will help to bring the ride height back to that of the stock sled. After modification, the center of gravity is only 5 inches from the stock location.