Initial Measurements
In order to determine how to modify the sled, we first had to take weight measurements to determine the center of gravity of the sled.
Four scales were used at each of the four "corners" of the machine to get an accurate weight distribution for front to back roll and side to side roll. The weight analysis also allowed us to find the center of gravity. To figure out the location of the center of gravity, the rear of the snowmobile was raised four inches at the location of rear scales for one trial. For the second trial the front of the snowmobile was raised ten inches at the location of the scales. The center of gravity for the stock sled was also found, and the comparison between the two centers of gravity can be seen below: |
Methods of Chassis Alteration
After taking the measurements, we sat down to determine the best way to improve the chassis design to lead to better sled handling. We determined three major modifications that we decided would be the best:
Suspension Tuning
The added weight of the tank on the back of the sled leads to a highly compressed rear suspension, and very little weight on the front. This can cause issues with the steering of the sled. Our best course of action was to increase the stiffness of the rear suspension, and to install a suspension kit that would mimic a coupled suspension and keep the front skis down.
Tank Placement
The center of gravity (CG) of the sled was much further back than the stock sled. A snowmobile is designed for the CG to be in a certain location, so to push the CG forward we will be moving the CNG tank forward. This will also require a new tunnel to be designed.
Air Silencer and CNG Fitting Modifications
Because of the need for the tank to be moved forward, the CNG fittings at the front of the tank and the air silencer need to be modified to save space.
Suspension Tuning
The added weight of the tank on the back of the sled leads to a highly compressed rear suspension, and very little weight on the front. This can cause issues with the steering of the sled. Our best course of action was to increase the stiffness of the rear suspension, and to install a suspension kit that would mimic a coupled suspension and keep the front skis down.
Tank Placement
The center of gravity (CG) of the sled was much further back than the stock sled. A snowmobile is designed for the CG to be in a certain location, so to push the CG forward we will be moving the CNG tank forward. This will also require a new tunnel to be designed.
Air Silencer and CNG Fitting Modifications
Because of the need for the tank to be moved forward, the CNG fittings at the front of the tank and the air silencer need to be modified to save space.
Suspension Tuning
To stiffen and tune the suspension we installed a Hygear Suspension Linkage Kit. Pictures of the installed kit can be seen below:
Air Silencer and CNG Fitting Modifications
To make space, the size of the air silencer was reduced. This should only impact the noise of the sled slightly, and will allow for significant handling improvements. The CNG fitting bracket was cut, and wrapped around the smaller air silencer.
New Aluminum Tube Tunnel
A new tunnel made of aluminum tubing was designed and fabricated to replace the broken extended tunnel that was on the sled.