The Effect of threshing units’ design on performance of Teff [Eragrostistef (Zucc.)Trotter] threshers

Teff (Eragrostistef (Zucc.)Trotter) is a typical crop growing in most areas of Ethiopia, with the first area coverage. Threshing of teff can be performed indifferent ways; by hand beating, animal trampling and use of stationary threshers. In all cases of teff threshing, separation and cleaning are the most tedious and time consuming activities. In this research, the design effect of a newly developed type threshing unit was compared against SG-2000 stationary thresher. The comparison was focused on two independent variables: feed rate and drum speed, with three levels 275, 325 and 400kg.hr-1; and 900, 1000 and 1200 rpm respectively. The result revealed mean values of the threshing capacity, cleaning efficiency and separation efficiency are 42.30 and 45.81 kg.hr-1; 24.85% and 35.92%; and 85.66% and 93.34% for SG-2000 and the newly developed threshing units respectively. The newly developed threshing unit (closed type concave) showed significant difference in separation and cleaning efficiency of teff over SG-2000 (the open concave type). To perform closer to 100 % cleaning efficiency, it is recommended to adopt other mechanism or use of  additional sieves under the concave