Abstract: A rotor assembly for a screw pump has a light alloy rotor main body having an axially extending central bore. A steel shaft is press-fitted into the central bore. A diametrically extending fixing pin is press-fitted through the rotor main body and the shaft. Friction forces between the rotor main body and the shaft are arranged to be larger on a discharge side of the rotor assembly than on a suction side thereof. The fixing pin is disposed at substantially a central position of entire friction forces in terms of their directions and magnitudes.

Abstract: A snowmobile including a body a pair of rear wheels with tires a motor for driving the rear wheel, an axis connected to a handle originally for a front wheel, and skid member mounted on the axis. The skid member comprises a skid, extending in the longitudinal direction of the body, bent upward in its front part, support members protuberantly provided on the upper surface of the skid, and rotatably connected to the axis and at least one fin, protuberantly provided on the under surface of the skid, extending front to rear from a position beneath the above mentioned support member, located at the substantial center in its longitudinal direction of the skid, and the length of the fin is set in a range of 40 to 60% of the length of the skid.