Design and Performance Parameters of Vibrating Potato Diggers

The performance of three similar types of vibrating potato digger blades was estimated by observing the potato separation and material flow on the bottom plate. Each machine was tested with different drive amplitudes, frequencies, and travel speeds. Blade performances were observed in three categories: (1) success by acceptable digging and soil/potato separation, (2) partial success by good material flow but poor soil/potato separation, and (3) failure by bulldozing or stalling. Three parameters, λ, the ratio of the vibrating blade speed to travel speed, ρ, the ratio of blade acceleration to travel speed, and K, the ratio of blade acceleration to gravitational acceleration, were compared to see which best predicted the interface between acceptable and marginal digging and separation. K was the most consistent predictor and a value of K ≥ 2.0 is suggested as an absolute minimum design criterion of a vibrating digger.¹