Balanced harmonic drive with output shaft disconnect

A harmonic drive, comprising:

• a housing;
• an output shaft within the housing;
• an input shaft within the housing, the input shaft is configured for being in a first position in which rotation of the input shaft rotates the output shaft, and a second position that is axially offset from the first position, in which rotation of the input shaft does not rotate the output shaft;
• a solenoid coil within the housing that, when energized, moves the input shaft to the second position;
• and
• a spring within the housing that, when the solenoid coil is not energized, moves the input shaft to the first position;
• wherein:
• the housing is hollow and extends axially from a first outer end to a second outer end;
• the input shaft extends axially from a first side to a second side, the first side faces the first outer end of the housing and the second side faces the second outer end of the housing;
• the solenoid coil is disposed at the second outer end of the housing and the defines a center aperture;
• the housing includes a radially extending perimeter wall that extends within the housing at the first outer end of the housing, and a radially extending partition wall that extends within the housing between the first and second outer ends to define a first cavity between the partition wall and the first outer end, and a second cavity between the partition wall and the second outer end, wherein the perimeter wall defines a first input shaft aperture and the partition wall defines a second input shaft aperture;
• and
• the input shaft is within the first cavity and the solenoid is in the second cavity, wherein the input shaft has a raised shoulder having a first side that faces the first outer end of the housing and a second side that faces the second outer end of the housing, and the spring extends between the partition wall to the shoulder of the input shaft.