Friction wheel 5 rotates about fixed axis B-B and contacts friction wheel 6 which rotates about axis C-C of frame 1. Rigidly attached to wheel 6 are two friction wheels, 2 and 3, of equal diameter. Frame 1 with wheels 2, 3 and 6 can be swivelled about fixed axis A to bring either wheel 2 or 3 into contact with bevel friction wheel 4 which rotates about fixed axis D. Wheel 4 rotates in either direction depending upon which wheel, 2 or 3, it is in contact with.
$3372$SmF,ML$