A crank assembly comprises a crank arm, a front sprocket unit, and at least one chain-drop control protrusion. The at least one chain-drop control protrusion is configured to inhibit a drive chain from getting into a space provided radially inwardly from the at least one control protrusion and between the crank arm and the front sprocket unit in the axial direction. The at least one chain-drop control protrusion is configured to be provided to at least one of an axially inwardly facing crank-surface of the crank arm and an axially outwardly facing sprocket-surface of the front sprocket unit. The at least one chain-drop control protrusion has a through bore.

A sprocket for engagement with a drive chain has a plurality of teeth extending radially from a periphery of the sprocket, including a first and a second group of teeth; the teeth of the first group and the second group are alternately arranged so that each tooth of the first group is followed by a tooth of the second group, and vice versa; each tooth of the first group having a first maximum width, each tooth of the second group having a second maximum width which is larger than the first maximum width; each tooth of the second group has a protrusion on at least one lateral face of the tooth; the outer lateral face of the protrusion extends over a first portion of the lateral face of each tooth of the second group, the length being 50% of the length of the respective tooth or less.

The invention discloses an automatic downshifting and variable speed transmission bicycle, comprising a bicycle stand, wherein the bicycle stand is installed with a bottom bracket; the bottom bracket is installed with a bottom bracket sprocket set, and the bottom bracket sprocket set is composed of three chain discs of different sizes; a rear axle of the bicycle is provided with a tower footing, and the tower footing is fixedly installed with a sun gear; one side of the sun gear is provided with a planet carrier, and the planet carrier is installed with planetary twin gears. The invention is easy to start, can run at high speed, has multiple functions, and is reliable in operation, with convenient maintenance and low cost, and is energy saving and environmental-friendly; it has a good market prospect and brings great convenience to cyclists.

A sprocket for engagement with a drive chain has a first and a second group of teeth, wherein the teeth of the first group and the second group are alternately arranged and each tooth of the second group is wider than each tooth of the first group. The profile of each tooth of the second group has a first protrusion in the front half of the tooth on a first lateral surface and a second protrusion in the rear half of the tooth on a second, opposite lateral surface of the tooth. In particular, the portion of each tooth of the second group engaging the chain may have a center plane that is rotated or twisted during forming about the radial center line of the tooth with respect to the central plane of the sprocket.

A single sprocket for mounting on a pedal crank of a bicycle is provided. The sprocket h is mounted rotatably about an axis of rotation of a bicycle, and for engaging in a bicycle chain with chain inner link plate pairs and chain outer link plate pairs. The sprocket includes an axial outer side, an axial inner side, a hub region, a tooth region and a connecting region. A tooth center plane of the sprocket is offset inwards in the axial direction with respect to a hub center plane.

A wide range of existing bicycles can be converted into electric power assisted bicycles with ease. The bicycle electric power assist device comprises a housing (52) configured to be attached to a frame (18) of a bicycle (10), an electric motor (54) attached to the housing (52), a battery (102) configured to be mounted to the frame and serves as a power source for the electric motor, an annular rotational output member (81) rotationally driven by the electric motor (54), the rotational output member being rotatably mounted on the housing and positioned around a crank axis line which is a rotational center line A of a crankshaft (24) and a crank arm (26) for a pedal of the bicycle, and a connecting member (90) connecting the rotational output member (81) to the crankshaft (24) or the crank arm (26) in a torque transmitting relationship.

A slide member is provided with a base material, a plated slide layer and an intermediate plated layer. The plated slide layer contains a solid lubricant. The intermediate plated layer is disposed between the base material and the plated slide layer, the intermediate plated layer increasing cohesion of the base material and the plated slide layer. The plated slide layer has a content of the solid lubricant in a range from 30 to 70 vol %, inclusive.

An individual chain wheel for a bicycle front crank arrangement for engaging in a drive chain includes a plurality of teeth formed on a circumference of the chain wheel and having a first and a second group of teeth. The teeth of the second group of teeth are arranged in an alternating manner between the teeth of the first group of teeth. Each tooth has a load flank via which force is transmitted between an adjacent roller of the drive chain and the respective tooth. Each tooth of the first group may also have at least one profile with an opening in the vicinity of the flank, in which a portion of an inner link plate of the drive chain, which portion protrudes beyond the roller, engages.

Chain-rings set, for a power transmission system, which includes a chain, a first chain-ring, a second chain-ring where the first chain-ring is formed by a support part of the teeth and a teeth part, where the second chain-ring is formed by segments each formed by a support part of the teeth and a teeth part, which includes axial displacement means of the segments, where an up-shift segment of the segments has a first tooth which is the first which is engaged with the chain in the rotation movement, and where the displacement means are configured for moving the up-shift segment to an engaging position such that the first tooth can engage with an engaging link of the up-shift section of the chain, when the chain is engaged in the small chain-ring, and without the support part of the up-shift segment reaching the same plane than the support part of the first chain-ring, and to successively displace the other independent segments to an engaging position with the chain without the support parts of the independent segments reaching the same plane than the support part of the first chain-ring.

A bicycle sprocket comprises a sprocket body, a plurality of sprocket teeth, a mounting member, at least one fastening member, and a cover member. The sprocket body has at least one first threaded portion. The mounting member has at least one fastening hole configured to be aligned with the at least one first threaded portion in the assembled state. The at least one fastening member has a fastening shaft portion, a fastening head portion, and a second threaded portion. The second threaded portion is configured to threadedly engage with the at least one first threaded portion of the sprocket body in the assembled state. The cover member is configured to at least cover the fastening shaft portion of the at least one fastening member when viewed from an axial direction with respect to the rotational center axis in the assembled state.