A force prediction model for mouldboard ploughs incorporating the effects of soil characteristic properties, plough geometric factors and ploughing speed

A mathematical model that predicts the draught force acting on a mouldboard plough body is described. An important aspect of the model is that draught force is calculated using the geometric parameters of the plough body components, the ploughing speed and the physical properties of the soil. A spreadsheet has been developed to carry out the complex calculations required to determine the total draught force.Experimental work was conducted to examine the validity of the model using two types of plough body working in a sandy loam soil and a sandy clay soil. Ploughing depths in a range up to 225 mm were used and speeds up to a maximum of 5 m/s.Comparison of measured draught forces with those predicted by the model showed that, overall, the predicted forces were 2.8% less than the measured value and that 90% of all results were within bounds of ±20% of a line of equal magnitude.It was shown that the draught force can be expressed as a function of ploughing speed and depth. For both of these variables there was a quadratic relationship with draught force.The draught force due to the plough point and share ranged from 52% to 70% of the total force for the range of variables employed in the work. The force at the mouldboard was 12% to 29% of the total draught and frictional forces were in the range of 15% to 30%.The model enables relationships to be obtained between plough depth, number of plough bodies and speed for particular tractor and power specifications. This showed, in particular, how reducing depth can result in higher work rates by effecting an increase in ploughing speed. The work rate was shown to increase by 57%, for example, if depth was reduced from 300 to 225 mm and increasing the number of plough bodies from 4 to 6 when using a 177 kW tractor when working in a sandy clay loam. This is of particular interest to minimize the cost of cultivation techniques where the inversion of surface residues and weeds is required.