to the integral shaft 88 the cylinder 73 may be equipped with a linear positioning device providing exact piston location within the cylinder and a control panel on the gin 50 configured to provide an adjustment range similar to the range available using the manual lever 96 another potential method of moving the seed roll retaining member 60 during ginning operations would be the use of a ball screw actuator equipped with a rotary encoder other means common in the art are also within the contemplation of this invention but are not as favored as the cam shaft assembly 89 due to increased costs in one preferred embodiment the seed roll retaining member 60 is configured such that it can only be moved into the fully extended position by the retainer pneumatic cylinder 73 but not cam shaft assembly allowing the positioning of the seed roll retaining member 60 into the fully extended position using the manual lever 96 of the cam shaft assembly or other means may be potentially disadvantageous because as shown in fig4 with the breast 18 in the operative ginning position fully extending the seed roll retaining member 60 would substantially close off or restrict the unobstructed portion of the seed discharge shaft 31 not occupied by the blades 13 of the saw 12 said open span being referred to herein as the open shaft span 93 substantially restricting or closing off the open shaft span 93 of the seed discharge shaft.