A sprocket assembly defining a sprocket assembly width. The assembly has at least eleven sprockets and the sprocket assembly mounts to a bicycle freewheel hub that rotates about a rotation axis which defines a predetermined axial distance on the hub between a plane that is substantially perpendicular to the rotation axis. At least one point of the attachment seats for spokes closest to the freewheel body and a plane is substantially perpendicular to the rotation axis and defined in the fastening portion to the frame. The sprocket assembly width is lower than or equal to the predetermined axial distance. A chain that engages the sprockets has a maximum thickness in the direction of the rotation axis between and including 4.6 mm and 5.8 mm.

A sprocket assembly defining a sprocket assembly width. The assembly has at least eleven sprockets and the sprocket assembly mounts to a bicycle freewheel hub that rotates about a rotation axis which defines a predetermined axial distance on the hub between a plane that is substantially perpendicular to the rotation axis. At least one point of the attachment seats for spokes closest to the freewheel body and a plane is substantially perpendicular to the rotation axis and defined in the fastening portion to the frame. The sprocket assembly width is lower than or equal to the predetermined axial distance. A chain that engages the sprockets has a maximum thickness in the direction of the rotation axis between and including 4.6 mm and 5.8 mm.

A drill press has variable speed drive via belts on stepped pulleys that transfer rotational force from the motor to the drill press spindle. Three stepped pulleys connected by two belts are provided in the example. A belt tension roller is bears against one of the belts to provide tension for effective power transfer from the motor to the spindle. The belt tension roller is adjustable along an arcuate slot in an anchor plate and is fastenable in position by an adjustment knob on the belt tension roller. The middle pulley is mounted to vary its position so that tension adjustments on one belt by the belt tension roller result in tension adjustments on the second belt as well.

A bicycle freewheel body and sprocket assembly is provided. The freewheel body has a predetermined axial width. The sprocket assembly has at least eleven sprockets of various diameters that are arranged on the freewheel body with a largest diameter sprocket and a smallest diameter sprocket forming end sprockets of the sprocket assembly. Each of the end sprockets has an outer face and the respective outer face of each end sprocket faces in an opposite directions and the outer faces are spaced from each other along the freewheel body predetermined axial width. An assembly of at least eleven sprockets has an overall axial width measured between respective outer faces of end sprockets in the assembly that is no greater than 40.5 mm. A chain is comprised of an alternating succession of inner and outer links, connected to each other at respective connection ends.

A bicycle rear wheel sprocket assembly has twelve sprockets in a twelve sprocket assembly. The twelve sprocket assembly is configured to be mounted to a bicycle freewheel hub. The freewheel hub rotates about a rotation axis and has a spoke attachment portion and a frame fastening portion which are spaced apart by an axial distance. End sprockets of the twelve sprocket assembly are positioned within the axial distance.

An electromechanical front gear changer for a bicycle is provided, the bicycle having a chain, including a base member attachable to the bicycle. A linkage is movably coupled to the base member. A chain guide is movably coupled to the linkage for contacting the chain. A motor is supported by the base member. A gear transmission is driven by the motor to move the linkage. A CPU is provided for controlling the motor and a power supply is supported by the base member to power the motor and the CPU. A manually operated device is disposed on the electromechanical front gear changer.

An electromechanical front gear changer for a bicycle is provided, the bicycle having a chain, including a base member attachable to the bicycle. A linkage is movably coupled to the base member. A chain guide is movably coupled to the linkage for contacting the chain. A motor is supported by the base member. A gear transmission is driven by the motor to move the linkage. A CPU is provided for controlling the motor and a power supply is supported by the base member to power the motor and the CPU. A manually operated device is disposed on the electromechanical front gear changer.

An electromechanical front gear changer for a bicycle is provided, the bicycle having a chain, including a base member attachable to the bicycle. A linkage is movably coupled to the base member. A chain guide is movably coupled to the linkage for contacting the chain. A motor is supported by the base member. A gear transmission is driven by the motor to move the linkage. A CPU is provided for controlling the motor and a power supply is supported by the base member to power the motor and the CPU. A manually operated device is disposed on the electromechanical front gear changer.

An electromechanical front gear changer for a bicycle is provided, the bicycle having a chain, including a base member attachable to the bicycle. A linkage is movably coupled to the base member. A chain guide is movably coupled to the linkage for contacting the chain. A motor is supported by the base member. A gear transmission is driven by the motor to move the linkage. A CPU is provided for controlling the motor and a power supply is supported by the base member to power the motor and the CPU. A manually operated device is disposed on the electromechanical front gear changer.