Study of Arc-Shape Designed Shallow Digger for Onion Harvest

Abstract

This study aims to design a shallow digger for onion harvest to adapt the onion bulb growing altitude position and result in the same cutting length below the onion bulbs.For the need of design consideration, the field investigation was firstly conducted to survey the types of planting onions, the width of full bed, the actual plant bed width and the growing altitude variations of onions ready for harvest. This information is important for the design of the onion digger (Chen et al., 2010). According to the field survey results, the incident angle of digger into the ground is about 14-20°, so 18° is chosen. In order to be suitable for five or six rows planting and steel specifications etc., the shallow digger designed is arc in shape, whose cutting edge is at the inner side of the arc. The radius of the arc shallow digger is 800 mm; the chord length is 1100 mm; the distance between the chord and curve is 220 mm; the cutter width is 75 mm; the thickness is 12 mm; and the cutting edge is 25°. By the field testing results show that adopting the designed arc-shape shallow digger can harvest a full bed of onions for each digging, and the residual root length of onion bulbs among 93.3% in normal distribution are less and equal to 2.5 cm and fitting the market demand. The harvested onions by adopting the designed digger in harvest do not require further labor work in trimming roots. The designed digger can accommodate the growing altitude of onion bulbs and maintain the constant cutting length of onion roots accordingly. The arc-shape designed shallow digger can be applied to the onion combined harvester in this study.