the rotor of a rotary position sensor mounts directly upon the rotary shaft to be sensed . the rotor prior to installation is retained in position by a pair of small protrusions extending from the rotor that cooperatively engage a pair of small indentations formed in a pair of supporting arms . during the installation process , the rotor is slipped onto the shaft and the protrusions are released from the engaged position . during operation of the position sensor , the rotor is free from direct contact with either the supporting arms or any other stationary part of the position sensor . only the contactors engage the stationary components . this design eliminates the need for bearings and return springs prevalent in the prior art .