Abstract: A device comprising a rear adapter frame with an idle crawler track and adapted to be mounted, together with a front steering skid, in lieu of the rear and front wheels, respectively, of a motor-scooter so as to enable a quick conversion thereof, when desired, into a vehicle suitable to travel on snowy ground.

Abstract: A ground support vehicle has a rear drive track. Cleats extending transversely of the outer surface of the track are outwardly curved to facilitate leaning of the vehicle and its rider as the vehicle travels around a curve. In a preferred embodiment the vehicle includes a ski mounted on front forks so that the vehicle can be used for recreational purposes in snow or directly on unpaved ground and tracks. A wheel can be fitted in place of the ski if desired.

Abstract: A compact power driven ski bob is attained by locating the driving tracks of a rear power ski beneath the seat and pivotally mounting the front end of the power ski longitudinally forward of the seat. The rear end of the power ski is biased into engagement with the snow and is located lower than the front end of the ski to enhance driving contact with the snow. The seated operator is cushioned from impact forces and up and down movements of the power ski by a rear attachment means comprising a lost motion connection and a shock absorber. To aid in transportation of the snow bob, the front ski and the fuel tanks are detachably connected to the frame.

Abstract: A suspension system for a track driven vehicle such as a snowmobile, which has a vehicle body and a rigid frame, the suspension system pivotally interconnecting the body with the frame and comprising spaced front and rear support frames. The front support frame carries front torsion spring members having spring arms extending longitudinally along the rigid frame, each front torsion spring means having a spring arm engaging a cam surface on the rigid frame to vary the effective length of the torsion spring arm, the torsion spring arm being engageable with a cam edge of selected configuration to provide a desired progressive spring rate response to vertical displacement of the vehicle body with respect to the rigid frame.

Abstract: A power driven ski-bob with an elongated propulsion unit having preferably an anterior sliding portion, a posterior endless tread portion and an upwardly extending post means; the propulsion unit is connected to the rest of the ski-bob's structure through a pivoting connection which is substantially higher than the sliding and tread portions so that the pressure between these portions and the snow is decreased and increased respectively, in response to said tread generating thrust against the snow to secure the engagement between the tread and snow.