An experiment was run to determine the optimum frequency of the rotary knif
e on a roller gin stand. Six treatment levels of rotary knife frequency, 15
0, 300, 450, 600, 750, and 900 rpm, were chosen, (The manufacturer's specif
ication for rotary knife frequency on the gin stand tested is 389 rpm.) The
factors considered in determining the optimum rate included fiber and cott
onseed quality, lint turnout bale value, and ginning rate. There were no si
gnificant differences due to treatment with respect to fiber properties. Ov
erall, fiber strength and elongation by the Stelometer averaged 27.8 g/tex
and 6.98%, respectively; fiber span length and uniformity by the Fibrograph
averaged 3.52 cm (1.38 in.) and 47.5, respectively; and fiber grade, stapl
e, and micronaire by the USDA-AMS Classing office averaged 2.17, 46.8 32nd-
in., and 38.1, respectively. These fiber properties are on samples taken fr
om the bale and included two mill-type/air-jet lint cleaners. With the exce
ption of linters content, there were no significant differences due to trea
tment on the cottonseed properties. Overall, foreign matter content of the
cottonseed averaged 2.16%, and cottonseed grade averaged 114. Linters conte
nt ranged from 1.67 to 2.88% on the 300 and 900 rpm treatment, respectively
. Lint turnout and bale value were not significantly different due to treat
ment, averaging 35.3% and $438.71 overall. Ginning rate tvas significantly
different due to treatment; the highest rate occurred on the 300 rpm treatm
ent and was 350 kg/m/h (1.90 bales/h). Using regression analysis, the optim
um rotary knife frequency occurs at 269 rpm. At rotary knife frequencies le
ss than 269 rpm, some of the ginning area on the roller is wasted, and roll
er damage is possible due to tags that cannot be cleared At rotary knife fr
equencies greater than 269 rpm, compromises are made between ginning rate,
seed cotton carryover; and choke-ups.