Abstract: A coast brake of the type having a screw cone provided with a tapered part to be screwed into an internal end part of a male screw cylinder to which a chain gear is fixed, the screw cone being removed by means of the rotation of the male screw cylinder. A brake shoe is in mesh with a fixed brake cone which is provided outwardly of the screw cone to engage with a hub body by pressing the brake shoe being expanded. The coaster brake further includes: a cylindrical part smaller in diameter than a top end part of the brake cone being provided on one end part of the brake cone; a clutch spring with a projection being fitted on an outer periphery of the cylindrical part to exert a force in a direction of fastening itself when a negative rotational force works upon the projection around the cylindrical part; and an axial notch part provided on the screw cone, the projection of the clutch spring being in mesh with this notch part.

Abstract: A stepless transmission device for a bicycle which has sufficient durability and smooth operation characteristics for practical use is provided. The transmission device can steplessly change the rotational ratio of a wheel to a drive sprocket by changing the oscillation angle of rachet arms which are radially disposed on the periphery of a disk fixed to a shaft for said sprocket. The transmission device is characterized in that said rachet arms incorporated with respective crank arms are pivoted to said sprocket in positions equally distributed on a coaxial circle, and one end of each crank arm constitutes a guide pin, said guide pin being engaged in an annular groove which is coaxially provided in a rotatable bearing race the eccentricity of which can be changed.