Self adjusting controlled acceleration sheet stacking offsetting system

A sheet stacking offsetting system with a stacking tray offsetting movement system with which printed sheets from a reproduction apparatus are stacked offset relative to one another, with a simple rotary drive of an eccentrically rotated extending pin cam which reciprocally drives a simple two part cam follower providing a variable width cam follower slot positively engaging the eccentrically rotated cam to smoothly reciprocate the sheet stacking tray. The slot width is automatically reduced by spring loading movement of one of the two parts of the cam follower so that both sides of said slot directly engage the eccentrically rotated cam at all times. The cam follower slot is also open ended and beveled to easily assemble the pin cam into that open end.