Forces on a Model ‘Spot Plough’

The draught and the side force exerted on each working component of the model spot plough are discussed. The 150 mm wide model was composed of, principally, the share, main mouldboard, tilted disc coulter, and sub-mouldboard arranged in sequence. The vertical beams supporting each component were equipped with strain gauges and calibrated as force transducers. Soil bin experiments were conducted in wet plastic, dry compact, and dry loose soils at speeds of 0·2–1·3 m s–1 and at working depths of 50–70 mm. The force exerted on the share was the largest in the dry compact soil and significantly increased with speed. The effect of speed on the force on the main mouldboard and tilted disc coulter was mostly insignificant, suggesting the adaptability of the spot plough to high-speed applications. The side force was mostly compensated for between the main mouldboard and tilted disc coulter in wet plastic and dry compact soils, but the redesign of the share or relocation of the tilted disc coulter was suggested for completely balancing the side forces. The force on the sub-mouldboard was negligible as to imply its exclusion from the design.