K. Salari - Department of Agricultural Machinery Engineering, Faculty of Agriculture, Bu-Ali Sina University, P. O. Box: ۶۵۱۷۸۳۳۱۳۱, Hamedan, Islamic Republic of Iran.
R. Amiri Chayjan - Department of Agricultural Machinery Engineering, Faculty of Agriculture, Bu-Ali Sina University, P. O. Box: ۶۵۱۷۸۳۳۱۳۱, Hamedan, Islamic Republic of Iran.
J. Khazaei - Department of Agricultural Technical Engineering, College of Abouraihan, University of Tehran, Tehran, Islamic Republic of Iran.
J. Amiri Parian - Department of Agricultural Machinery Engineering, Faculty of Agriculture, Bu-Ali Sina University, P. O. Box: ۶۵۱۷۸۳۳۱۳۱, Hamedan, Islamic Republic of Iran.

Kermanshah province is the main producer of various chickpea cultivars in Iran. In this study a laboratory peg-tooth thresher was employed for chickpea threshing. The effect of cylinder speed (۹, ۱۲, ۱۵ m/s), concave clearance (۱۲, ۱۴, ۱۶ mm), feed rate (۸۰, ۱۶۰, ۲۴۰ kg/h) and material moisture content (۵, ۱۰, ۱۵% w.b.) was studied on percentage of grain damage, threshing efficiency and percentage of seed germination. The experimental plan for optimization was prepared with response surface methodology technique with composite experiment design. The effects of all independent variables on the response variables were significant. The effect of cylinder speed was the most significant and followed by the moisture content. With increasing cylinder speed in the range of ۹ to ۱۵ m/s, the grain damage increased from ۴.۹۸ to ۴۷.۹۷%, threshing efficiency increased from ۹۶.۸۱ to ۹۹.۶۹% and seed germination decreased from ۸۵.۷۵ to ۵۵.۹۸%. With increasing moisture content, grain damage and threshing efficiency decreased but seed germination increased. With increasing feed rate and concave clearance, grain damage and threshing efficiency decreased while, seed germination increased. The optimized point was determined at the cylinder speed of ۱۰.۶۳ m/s, concave clearance of ۱۳.۷۴ mm, feed rate of ۲۴۰ kg/h and moisture content of ۱۲% (w.b.). In this condition, the optimum values of grain damage, threshing efficiency and seed germination were ۳%, ۹۸.۳% and ۸۴.۲۹%, respectively.

Germination, grain damage, threshing efficiency, thresher, RSM