Abstract

                                A portable paddy thresher was tested for its performance in terms of threshing efficiency and grain damage for nylon rasp bar threshing cylinder at different levels of factors namely concave clearance (15, 20 and 25 mm), cylinder peripheral speed (11.7, 14.1 and 16.5 ms-1), grain moisture (13.5, 16.5 and 19.5 per cent) and feed rate (200,400 and 600 kg h-1). The experiments were statistically designed and executed. The effect of individual factor and combined effect of different combination of factors on threshing efficiency and grain damage were statistically analyzed. Comparing the minimum grain damage in different combinations the minimum loss was achieved at a combination of 25 mm concave clearance, 11.7 m s-1 cylinder speed, 19.5 per cent moisture content and at a feed rate of 600 kg h-1. The grain damage occurred at this combination was 0.475 and 1.16 per cent, respectively for nylon rasp bar threshing cylinder and cast iron rasp bar threshing cylinder. The threshing efficiency occurred at this combination was 98.22 per cent for nylon rasp bar threshing cylinder. It is concluded that the nylon rasp bar threshing cylinder has comparatively better performance over the existing cast iron rasp bar threshing cylinder.

Key words : Paddy, Thresher, Nylon rasp bar, Threshing efficiency, Grain damage.