Design of a Motorised Maize Sheller and Optimisation of its Operating Parameters

Abstract

Maize shelling is an important post-harvest operation to separate the grains from its cob. Traditional methods involve rubbing maize cobs against each other, rubbing on stones, or hand method. These methods are labour-intensive, time-consuming, and drudgery-prone. Migration from rural population to cities for better livelihoods has creates labour shortage in rural areas during the peak period of maize shelling. A study was undertaken to design, develop, and evaluate the performance of an electric motor powered maize sheller. It consisted of a frame, feeding chute, cylinder, outer cover, rotor shaft, electric motor, belt, and outlet. The developed maize sheller was operated at three cylinder speeds (150, 200, 300 rpm) and three cob moisture contents [12, 14, 16% (w. b.)]. Highest and lowest shelling rates were 96.9 kg.h-1and 90.92 kg.h-1at cylinder speed and moisture content of 300 rpm, 12% (w. b.) and 150 rpm, 16% (w. b.). Shelling efficiency was 98.60% at 300 rpm, 12% (w. b.) and 89.00% at 150 rpm, 16% (w. b.). Grain damage was 8.37% at 300 rpm, 16% (w. b.) and 3.1% at 150 rpm, 12% (w. b.). Shelling rate and shelling efficiency decreased with increase in moisture content, but grain damage increased. Shelling rate, shelling efficiency, and grain damage also increased with increase in cylinder speed from 150 rpm to 300 rpm. Sheller cylinder speed of 150 rpm and grain moisture content of 12% (w. b.) gave the best shelling rate, shelling efficiency, and minimum grain damage of 92.07 kg.h-1, 91.40%, and 3.10 per cent. The payback period of the maize sheller was 1.13 year, while the benefit-cost ratio was 1.01.