Every winter, Snocross fans flock to Michigan, Wisconsin and other snowy states to watch snowmobiler racers battle the elements and the laws of gravity to perform amazing feats—including long distance jumps and double back flips. What the fans don’t see is the ongoing battle between fasteners and vibration within every bolted joint of the snowmobile.
Polaris Industries Inc. is a leading manufacturer of snowmobiles, and it sponsors the Polaris Racing team that participates on the snocross racing circuit. The team’s members win a lot of medals at snowcross events. Polaris’ design engineers always specify the use of Loctite threadlockers on fasteners to keep them secure.
“We apply threadlockers [to fasteners] in all of our engines,” says Jason Miller, snowmobile product manager for Polaris Industries. “A very critical interface is the mount between the engine and chassis, where there is extreme vibration and temperature variation.”
Loctite 242 threadlocker is applied with a hand pump onto the mounts. The pump ensures that assemblers use the correct amount of product. Loctite 243 is applied to the snowmobile’s drive clutch jam nut, as well as the clutch’s spider assembly.
Interference fits between cylindrical parts are equally important in snowmobiles. Here, retaining compounds enable engineers to design robust, lightweight interference-fit joints at a lower cost than traditional interference fits by reducing dimensional precision requirements. Additional benefits of retaining compounds include their potential to seal an assembly to prevent corrosion, as well as fill surface irregularities and clearance gaps between metal parts.
Loctite adhesives are also used to bond the clutch cover bearings and the moveable sheave bearings. Here, the clutch has to operate reliably in an environment where temperatures range from -40 to 90 C. In this case, Polaris engineers use Loctite 648 to ensure that the bearings are fully seated and retain their position throughout the life of the machine.
In an engine application example, where operating temperatures can reach 230 C, Loctite 620 retaining compound is used for retaining crown shaft bearings as it is formulated to survive higher temperatures than the engine is likely to achieve.