Abstract: A speed change device for a bicycle comprises a carrier jointed to a crank arm and a plurality of planet gears rotatably supported on a plurality of shafts arranged in a circle on said carrier. Each of the planet gears includes a plurality of planet gear elements different in number of teeth. The device further comprises an internal gear in mesh with ones of the planet gear elements of the planet gears and formed in an outer circumference with a sprocket to form a driven rotary body, one-way clutches for connecting the driven rotary body to the carrier, a plurality of sun gears provided on a crankshaft and in mesh with the planet gear elements of the planet gears, respectively, and one-way clutches provided between inner circumferences of the sun gears and a fixed bearing enclosing the crankshaft. One of the one-way clutches last mentioned is able to connect selectively.

Abstract: A bicycle frame comprises tubes closed at their ends and lugs for connecting the tubes to form the frame, which lugs are formed by die casting in dies in which the tubes are arranged so as to integrally surround the closed ends of the tubes by the die-cast lugs. The tubes are previously formed at their ends with tapered portions each extending from that corresponding to an extreme end of a boss of the lug surrounding the end of the tube toward an extreme end of the tube. The outer surfaces of the bosses of the die-cast lugs are in substantially constant outer diameter or slightly tapered, thereby, in conjunction with the tapered portions of the tube, eliminating stress concentrations at the extreme ends of the bosses of the lugs, and saving the amount of the die-cast metal resulting in light weight bicycles which can save driving power and cost of manufacture.