A Mathematical Model of the Kinematics of a Rotating Disc for Inter- and Intra-row Hoeing

The paper describes a mathematical model, which analyses the kinematics of a rotating disc which moves along a path parallel to a crop row. The disc has a cut-out section with peripheral bevels which enable it to avoid the plant stems but to act as a hoe between plants to achieve intra-row weed control. Each plant has a no-till circle surrounding it and the model enables the disc to be designed so that no part of it enters the no-till zone during its passage parallel to the row. The model is used to optimise the effects of the distance of the disc centre from the crop row, the disc radius, the plant spacing within the row and the no-till circle radius. It was found that a disc with a cut-out sector angle of 130°, a radius of 87·5 mm and angled bevels of 25° cut back at 70 mm along the sector edge was a suitable design when moving at 50 mm from a crop with a 300 mm spacing and a 40 mm radius for the no-till circle. A design modification to the disc is required if spacings of 250 mm are encountered in practice. In such a case a cut-out sector angle of 150° is required with a sector length of 61·25 mm with an angled bevel of 35° to the sector cut-out edge. The model has wide applicability for the interactive design of discs for a range of crops.