(DE19633345-C2)      This bicycle includes a novel auxiliary drive. Two pressure rollers swing into contact with the sides of the tyre (20), and are coupled both together and to an electric drive motor through gearing. A battery and motor speed control are included. A lever actuator working through a Bowden cable, is fixed to the handlebar and swings the rollers in, against a retraction spring, preferably to drive the front tyre. In a novel arrangement, the pressure rollers (17, 18) have freewheel connections to their shafts (15, 16). The shafts connect to driven wheels (9, 11). During engagement, these orbit their drive wheels (10, 39) through an arc, carried on links swinging under cable actuation. The drive wheels mesh both with each other and a shaft wheel, which is separately geared-down from the drive motor.    Preferably the wheels (9-11, 39) and swinging arms (21, 22) are arranged in plastic upper and lower sections (2, 3), enclosed dust-tight by a casing, all attached to the frame, and bringing the rollers to a position on either side of the tyre. The frame of the unit is a front or rear wheel pack carrier. The upper section (2) has an opening for the motor reduction wheel (8) and the transmission wheel (10). The drive trains, yokes ball bearings for shafts and connections to the Bowden cables are further detailed. A curved leaf spring biases the drive rollers away from the tyre. The knurled pressure rollers and the toothed wheels are made of polyoxymethylene. There is a central rubber drive layer on the drive rollers. Battery and speed control are fastened to the frame.    USE -   An auxiliary drive for a bicycle, using a battery-powered electric motor.    ADVANTAGE -   This drive applies mechanical power to both sides of the tyre in balanced arrangement. It is compact. Energy consumption is reduced over prior art. Safety is increased. The freewheel couplings are claimed to limit speed to about 20 km/h. The drive rollers retract as soon as the control lever is released. High transmission efficiency should allow the battery size to be reduced, for very compact construction. The drive is said to be more robust.