Investigation of the maize ear threshing process

Abstract

Wet maize ears of the ‘Benicia’ variety with a moisture content of 32.5% and medium dry maize ears of ‘Attribut’ variety with a moisture content of 18.5% were fed in parallel and perpendicular to the drum shaft of a conventional threshing drum. Maize ears fed in parallel with the drum shaft in the concave clearance moved twice as fast (4–5 m s −1 ), received twice as few (5–7) rasp bar impacts, and 10–20% of the threshed grain passed through the concave when compared to threshing with the maize ears fed perpendicular to the drum shaft. Threshing losses of wet ‘Benicia’ maize ears did not exceed the permissible range of 0.5% when drum rasp bars moved at the speed of 16 m s −1 and the concave clearance was in the front 21 mm and at the end 6 mm (21–6 mm). When medium dry ‘Attribut’ maize ears were threshed, the concave clearance was in the front 27 mm and at the end 15 mm. When maize ears were fed perpendicular to the drum shaft, the clearance could be increased by 2 mm as the maize ears moved through the concave at an approximately 1.8 m s −1 slower speed, and received 8 additional rasp bar impacts. During the threshing of wet ‘Benicia’ maize ears the threshing damage was 30% greater as compared with the threshing damage of medium dry maize ears of ‘Attribut’ variety. Wet maize should be immediately crushed and preserved as silage.