Development and performance evaluation of thresher for onion umbels

The post‐harvest unit operations of onion umbels are being carried out manually. To mechanize this process, the present study was carried out to develop an onion umbels thresher. The developed machine works on the principle of abrasive and impact actions from rasp bars. Thresher performance was evaluated at different numbers of rasp bars (2, 3, 4, and 8 numbers), feed rates (25 ± 1, 30 ± 1, and 35 ± 1 kg/h), concave clearance (6.5 and 7.5 mm), and peripheral speeds (2.5 and 3.3 m/s). At 35 ± 1 kg/h feed rate, 2 numbers of rasp bars, 7.5 mm concave clearance, and 2.5 m/s peripheral speed recorded higher threshing efficiency (97.82%) and lower seed damage (2.08%). The parameters such as the number of rasp bars on the threshing cylinder, peripheral speeds, concave clearances, and feed rates recorded significant effect (p < 0.01) on threshing efficiency and seed damage. Practical Applications The manual onion seed extraction process such as beating with sticks, cleaning of threshed onion umbels by manual sieving than further cleaning by dipping in water, sun drying, and packaging is tedious and requires 6–8 days for completing all associated unit operations. Onion umbels are subjected to impact force leading to damage of the seeds, which affects the germination rate and lower vigor index. In this context, mechanization of the onion umbels threshing process is imperative to maintain the quality of the seed.