Abstract: A preload release mechanism comprising a preload spring assembly (26) adapted to apply a preload to a first connector member (16) which is mounted on a support structure (14) and adapted for connection with a second connector member on an object (10). The assembly (26) comprises telescoped bushings (28,29) and a preload spring (25). A tubular shaft (41) extends through the spring assembly (26) and openings in the first connector member and support structure (14), on which it is clamped. A plunger rod (51) in the shaft (41) is provided with a tip end (52) and a recess in the rod near the other end thereof. A retainer (55) precludes passage of the rod (51) through the shaft in one direction and an end cap (62) closes the bore of the shaft at the other end and provides a shoulder which extends radially of the shaft.