Abstract: A variable sprocket, particularly suitable for a bicycle transmission, comprising a drive flange and an indexing flange mounted on an axle with a pair of sprocket-segment-planets and at least two idler-planets sandwiched between said flanges forming a relatively rigid variable-sprocket, the planets adapted to expand and contract in response to a relative rotation of the flanges and thereby change the effective diameter of the variable-sprocket.

Abstract: A game racket having an elastic net and a frame molded in unison, the net comprising non-linear elements which work primarily in bending and whose cross sectional area increases toward the center of the net.

Abstract: A game racket having an elastic net and a frame molded in unison, the net comprising non-linear elements which work primarily in bending and whose cross sectional area increases toward the center of the net.

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.

Abstract: A power driven ski-bob comprising a front steerable ski and a motor driven propulsion unit which are connected to the rest of the ski-bob's structure by struts, so that the rider and motor move above the snow to minimize the drag of the snow on the ski-bob.

Abstract: A propulsion system for a snow going device comprising a tread having a roller chain carrying cleats with a resilient snow engaging portion, and an undersurface defining a groove which slidingly contains the chain, the groove also provides a longitudinal bearing for supporting the cleats through the chain.

Abstract: A propulsion system for a snow going device having a tread circulateably supported around an elongated body with skirt means on each side and extending below the elongated body for protecting the tread and improving the traction.

Abstract: A power driven ski-bob having a frame supported by a front steerable ski and a rear power driven ski sub-assembly, the rear end of which is forceably biased downwards to improve traction and steerability.

Abstract: In a tread for a power-driven ski type of device having a chain with a plurality of spaced propulsion cleats, an outwardly protruding propulsion cleat, constructed with a venting passage and with resiliency to enable it to bend and thereby withstand the dynamic forces associated with its protruding construction, and to vent snow which is continuously trapped between itself and the sprockets, when the cleat swings over and around these sprockets.

Abstract: A power driven ski with an anterior sliding portion and posterior one-way snow engaging endless belt portion, a motor for propelling the belt and control means attached to a ski pole for regulating the belt's speed.

Abstract: A power driven ski is divided by an aperture into anterior and posterior ski portions, which are held one to the other by a bridge so that their combined undersurfaces form a longitudinally smooth skiing undersurface throughout the length of the ski. A motor driven endless tread is circulateably supported around the posterior ski portion for thrusting against the snow over which the posterior ski portion slides.