A device for retaining a bicycle chain on a sprocket includes a base plate defining a plurality of fastener openings centered on an origin. A center of each of the plurality of fastener openings is disposed at a first radial distance from the origin. The origin defines an axis extending substantially orthogonally from a plane defined by two lines extending from the origin and at least two centers of the centers of the plurality of fastener openings. A first guard is secured to the base plate and includes a first guard retaining surface including a first curved surface defined by a second radial distance from the axis that is greater than the first radial distance and a first guard guiding surface having a first end adjacent the first guard retaining surface and a second end distal from the first end. The first end is disposed at the second radial distance from the axis. The second end is disposed at a third radial distance from the axis. The third radial distance is greater than the second radial distance. A second guard is secured to the base plate and includes a second guard retaining surface including a second curved surface defined by the second radial distance from the axis. A second guard guiding surface has a first end adjacent the second guard retaining surface and a second end distal from the first end. The first end is disposed at the second radial distance from the axis. The second end is disposed at a fourth radial distance from the axis. The fourth radial distance is greater than the second radial distance.

A device for retaining a bicycle chain on a sprocket includes a base plate defining a plurality of fastener openings centered on an origin. A center of each of the plurality of fastener openings is disposed at a first radial distance from the origin. The origin defines an axis extending substantially orthogonally from a plane defined by two lines extending from the origin and at least two centers of the centers of the plurality of fastener openings. A first guard is secured to the base plate and includes a first guard retaining surface including a first curved surface defined by a second radial distance from the axis that is greater than the first radial distance and a first guard guiding surface having a first end adjacent the first guard retaining surface and a second end distal from the first end. The first end is disposed at the second radial distance from the axis. The second end is disposed at a third radial distance from the axis. The third radial distance is greater than the second radial distance. A second guard is secured to the base plate and includes a second guard retaining surface including a second curved surface defined by the second radial distance from the axis. A second guard guiding surface has a first end adjacent the second guard retaining surface and a second end distal from the first end. The first end is disposed at the second radial distance from the axis. The second end is disposed at a fourth radial distance from the axis. The fourth radial distance is greater than the second radial distance.

A bicycle sprocket comprises a sprocket body and a chain engagement structure. The sprocket body has a rotational center axis, a first side and a second side opposite to the first side in an axial direction parallel to the rotational center axis. The chain engagement structure includes a plurality of sprocket teeth. The plurality of sprocket teeth include a plurality of first teeth and a plurality of second teeth. The plurality of first teeth each include an outer-link supporting surface, an opposite surface, and a first radially outermost tooth-tip. The opposite surface is spaced part from the second outer link plate in a state where the chain engagement structure engages with the bicycle chain. The plurality of second teeth each include a second radially outermost tooth-tip that is offset from the first radially outermost tooth-tip of each of the plurality of first teeth in the axial direction.

A bicycle sprocket comprises a sprocket body and a chain engagement structure. The sprocket body has a rotational center axis, a first side and a second side opposite to the first side in an axial direction parallel to the rotational center axis. The chain engagement structure includes a plurality of sprocket teeth. The plurality of sprocket teeth include a plurality of first teeth and a plurality of second teeth. The plurality of first teeth each include an outer-link supporting surface, an opposite surface, and a first radially outermost tooth-tip. The opposite surface is spaced part from the second outer link plate in a state where the chain engagement structure engages with the bicycle chain. The plurality of second teeth each include a second radially outermost tooth-tip that is offset from the first radially outermost tooth-tip of each of the plurality of first teeth in the axial direction.

A main shaft side sprocket wheel and a countershaft side sprocket wheel are provided for relative rotation on the shafts with a chain wrapped around and extended between the sprocket wheels. One of the driven gears is a floating gear provided for relative rotation on the countershaft. The countershaft side sprocket wheel is provided for integral rotation with the floating gear. The main shaft includes a main shaft inner shaft which includes the main shaft side sprocket wheel, and an outer pipe disposed coaxially on the outer side of the main shaft inner shaft in a diametrical direction and capable of being placed into and out of integral rotation with the main shaft side sprocket wheel. A reverse transmission gear for meshing with a driven gear is provided on the outer pipe. A reduction gear ratio by the floating gear or the reverse transmission gear is set higher than 1.

A main shaft side sprocket wheel and a countershaft side sprocket wheel are provided for relative rotation on the shafts with a chain wrapped around and extended between the sprocket wheels. One of the driven gears is a floating gear provided for relative rotation on the countershaft. The countershaft side sprocket wheel is provided for integral rotation with the floating gear. The main shaft includes a main shaft inner shaft which includes the main shaft side sprocket wheel, and an outer pipe disposed coaxially on the outer side of the main shaft inner shaft in a diametrical direction and capable of being placed into and out of integral rotation with the main shaft side sprocket wheel. A reverse transmission gear for meshing with a driven gear is provided on the outer pipe. A reduction gear ratio by the floating gear or the reverse transmission gear is set higher than 1.

An electric tricycle includes a frame with a longitudinal member, a transverse axle member and a seat subframe. Front, steerable guide wheels are mounted on opposite sides of the transverse axle member and are linked to a transverse, steering handlebar linkage with handgrips. The seat subframe mounts a seat for the occupant. A hybrid drive system includes a pedal-chain-sprocket drive for driving a rear wheel and electric drive engaging the chain.

An electric tricycle includes a frame with a longitudinal member, a transverse axle member and a seat subframe. Front, steerable guide wheels are mounted on opposite sides of the transverse axle member and are linked to a transverse, steering handlebar linkage with handgrips. The seat subframe mounts a seat for the occupant. A hybrid drive system includes a pedal-chain-sprocket drive for driving a rear wheel and electric drive engaging the chain.

A chainring protection system includes a chainring having a torque input section and a torque output section. The torque output section is radially outer relative to the torque input section and has a plurality of teeth. The chainring protection system also includes a cover connected to the chainring, such that the cover at least partially covers a circumferential portion of the torque output section. The circumferential portion of the torque output section includes less than all teeth of the plurality of teeth.

A chainring protection system includes a chainring having a torque input section and a torque output section. The torque output section is radially outer relative to the torque input section and has a plurality of teeth. The chainring protection system also includes a cover connected to the chainring, such that the cover at least partially covers a circumferential portion of the torque output section. The circumferential portion of the torque output section includes less than all teeth of the plurality of teeth.