The illustration represents a highly efficient apparatus more especially designed to serve the convenience of bicycle manufacturers for inflating pneumatic tires, and for which a patent has recently been granted to Frank N. Stevens, of the Davis & Stevens Manufacturing Company, Seneca Falls, N. Y. The pump is double acting and has two oscillating brass cylinders, each two by eight and onehalf inches and each screwing at its lower end into a head with trunnions turning in bearings on the base, there being in the bottom of each head a packing ring which makes a very tight joint to prevent leakage. The piston rods, extending through the open ends of each cylinder, connect with THE STEVENS POWER "CYCLONE" PUMP. crank disks on a driving shaft on which are tight and loose pulleys eighteen inches in diameter, the disks having their wrist pillS set opposite each other, so that the pistons compress the air alternately to insure a continuous operation of the pump, which is aiso adapted to be operated by hand power. Each piston is formed with a cup of leather or rubber, into which fits an expansible disk or spreader with slotted flaring sides, in which washers are held by a nut screwing on the lower threaded end of the piston rod, so that the sides of the cup are made to form a close contact with the inner surface of the cylinder. The valve casing at the bottom of each tube has an outlet valve communicating with a tube which is connected near its middle with a tank or reservoir in which the compressed air is stored, this tank being made of different capacities and being provided with pressure gage, safety valve and stopcock. The construction of the pump is such that any part may be readily repaired in case of wear or injury.