Vibratory diggers for harvesting sweet potatoes in cloddy soils

Abstract

A vibratory digger blade for proposed use on a sweet potato harvester was designed and tested. Investigations were conducted to evaluate the effect of peak acceleration of vibration and the combined effect of three operating variables (forward velocity, amplitude and frequency of vibration) on the geometric mean diameter (g.m.d.) of clod size and on percent reduction in soil bulk density after treatment. A dimensionless velocity ratio was formed to express the combined effect of the operating variables. A mechanical rotary soil sieve was built and used for separation and measurement of the clod sizes. Vibratory and non-vibratory operations of the digger blade were compared. Low and high-density soil conditions in a silt loam soil (1·16 g/cm 3 and 1·28 g/cm 3 ) and two levels of each of the operating variables were tested. It was found that the vibratory digger, as compared with the non-vibratory one, produced smaller soil clods and a greater reduction in the soil bulk density. Peak acceleration values greater than 3 g produced approximately the same clod break-up and reduction in soil bulk density. Peak accelerations below 1 g resulted in poorer clod break-up. Dimensionless velocity ratios greater than 3 improved the performance of the vibratory digger blade. Design specifications of the vibratory digger and the rotary soil sieve are given.