Bombardier Inc.

Raymond Cote

Roger Rioux

Berthold Fecteau

Willy Bostelmann

Jean-Guy Talbot

Yvon Gagne

Gilles Pesant

This invention relates to an improved snowmobile drive train configuration arrangement that incorporates a fixed ratio speed reduction mechanism directly coupled to the engine crankshaft. This mechanism is in turn coupled to the driving pulley of a variable ratio belt drive system, the driven pulley of which is mounted on the axle of the sprocket wheels that drive the snowmobile track. Interposing the reduction drive between the engine and the belt drive system reduces the operational speed of both the pulleys and the belt, which proves beneficial from several aspects: the mechanical efficiency of the global system is increased, the dynamic response of the transmission to throttle modulation is improved; aerodynamic losses are reduced; the bending vibrations of the crankshaft are no longer transmitted to the drive clutch; and the engine can be run at higher RPM without decreasing the efficiency of the belt drive system.

Snowmobile reduction drive

In a snowmobile drive train the variable ratio belt drive is not directly coupled to the engine crankshaft as in the prior art, but rather the driving pulley of the variable ratio belt drive is carried on one end of a jackshaft and the engine power is applied to the opposite end of the jackshaft. The jackshaft is supported in a fixed bearing in the vehicle frame, this bearing being immediately adjacent to the driving pulley so that the influence on the belt drive of vibrations generated by the engine is vastly diminished. Therefore the engine mounts can be arranged to fully absorb vibrations of the engine. Previously, when the driving pulley was directly coupled to the engine crankshaft it was necessary to include a tie restraint to limit movements of the engine housing in the direction of separation between the axes of the driving and driven pulleys.

Snowmobile transmission jackshaft

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Richmond, Canada

Raymond Cote