Abstract: An automobile tire having retractable tread studs for increasing traction of the tire on slippery surfaces which are actuated by air pressure that is controlled by the automobile driver from the driver's seat.

Abstract: An internal combustion engine wherein a rotor is turnable within a housing while having an outer periphery which defines a circular channel with an inner periphery of the housing, the rotor having a pair of diametrically opposed projections end surfaces of which fluid-tightly and slidably engage the inner periphery of the housing. At least a pair of rotary members are connected with the housing while having a sealed, fluid-tight engagement therewith, these rotary members extending into the channel between the inner periphery of the housing and the outer periphery of the rotor and having a fluid-tight engagement with the outer periphery of the rotor. The rotary members are respectively formed with pockets which receive the projections as each projection moves past each rotary member.