Tef Separator And Cleaning In Ethiopia Case Study

Available evidence suggests that tef grain separating and cleaning, in the rural area of Ethiopia, is very much traditional and makes use of wind as winnower to effect separation manually operated set of flat sieve to accomplish the cleaning. This method is time and labor consuming, and often lead to contamination of the tef grain with dust, dirt, small sands or silt on the threshing ground. In an effort to alleviate the above stated problems, a small engine driven tef grain and chaff separator and cleaning machine was designed and manufactured.

Key words: belt, design, fan, moment, power, pulley shaft.

1. INTRODUCTION
One of the economical cereal crops in Ethiopia is tef. It is indigenous to the country, and is a fundamental part of the
Materials and method
2.1. Design Considerations
The tef separator and cleaner was designed and developed based on the following considerations.
I. The availability of materials locally to reduce cost of production and maintenance.
II. The materials for the construction of the various component parts were selected on the basis of the force that would be acting on them, the work they are expected to perform and the environmental condition in which they would function.
III. Due to small size of tef grains and their low terminal velocity, separation of grains from chaff and straw and complete cleaning was thought to be practically impossible. Hence, it was decided to use combination of fan (pneumatic) and mechanical (sieves) methods to effect the separating and cleaning.
2.2. Description of the Machine
Figure 1 gives details of machine designed and constructed and used in the experiment.

Figure 1. Details of the Experimental Tef Chaff Separating and Grain Cleaning Machine (all dimensions are in
The sieving unit consisted of three sieves for separating and cleaning simultaneously. The three sieves had length of 60 cm and width of 40 cm. The top sieve had round holes, 3 mm in diameter, the middle sieve had round holes 2 mm in diameter while the bottom sieve had 1 mm slotted holes. The vertical intervals between sieves were 10 cm (Fig. 4). The oscillating or the rocking legs were made from sheet metal having a thickness of 4 mm, a width of 4 cm and height of 50 cm. The bottom side of separating and cleaning unit was connected to connecting rod. The other end of the connecting rod was connected to a wrist pin eccentric to the wheel centre that produced a reciprocating motion on the separating and cleaning