conversion of rice common thresher to an axial - flow thresher and its performance evaluation

there are different methods used for threshing of grain crops. usual threshers operate based on the impact force (in threshing unit) that may damage the grains. in another method named axial-flow, grain damage is less so these types of the harvesting machines are being used more than before. in this study one of the common rice threshers (model t30) locally made in ashtad company was modified to an axial flow thresher. for converting the cross flow unit to an axial flow, the cover of t30 thresher was replaced by irri axial flow thresher cover design. the thresher feature has also been changed. then the machine was tested and evaluated on two rice varieties. the numbers of treatments were twenty and each experiment was carried out in four replications. independent factors were grain moisture contents (two levels), varieties (khazar and hashemi) and drum speeds (five levels). depended factors were the percentage of damaged grain, unthreshed grain and straw/grain ratio. the trials carried out in split plot based on randomized completely block design (rcbd) and duncan’s multiple range test (dmrt) was used for mean comparison of samples. the results revealed that drum speeds had significant effect (p<0.01) on percentage of damaged grain. the varieties had no significant effect on threshing loss. its valve was zero for khazar but remarkable for hashemi. the moisture contents had no significant effect on depended variables in all experiments.