Abstract: An opener of the door of a gravity flow vehicle which allows a mechanical advantage in initially raising the door. After the material within the vehicle begins to flow and decrease the effort required to raise the door, the mechanical advantage is bypassed so that the door may be quickly raised and lowered.

Abstract: A stabilizing support assembly for movably mounting a horizontally extended boom to one end of a portable frame. The support assembly has a pair of spaced apart parallel link systems each of which interconnect the portable frame and the boom, a spring member interconnected with each of the link systems to resiliently support the boom from the frame, shock absorbing members interconnected with each of the link systems to dampen up and down oscillatory movement of the boom, and torsion members fixed to and extended between the link systems for restricting horizontal tilting movement of the boom.