Date of this Version
The design equation for an auger to provide uniform unloading of particulate material from a container with a rectangular cross-section (Jones and Kocher, 1995) was revised to account for the minimum flighting height that could effectively unload particles with a known average smallest diameter. A minimum flighting height that was about 64% of the average smallest diameter of the particles was experimentally determined to obtain mean slopes of the top surface of the material not significantly different from zero for screened soybeans. A linear taper that best fit the square root curve for the inside diameter of the auger was determined by minimizing the integral of the squared area differences between the linear taper and the square root curve. The maximum difference between the auger radii as determined with the square root curve and linear taper functions was less than 0.3 mm, significantly less than the 4.7 mm average smallest particle diameter for the screened soybeans used. An auger constructed following this design (linear tapered inside diameter with a minimum flighting height) provided uniform unloading of particulate material from a container with a rectangular cross-section, as evidenced by mean slopes of the top surface of the material being maintained not significantly different from zero, until the top surface dropped to within 30 cm of the top of the auger flighting.