Drawbar performance of high-powered farm tractors with rear-wheel and four-wheel drive

Abstract

Having evolved equations for the drawbar performance and the travel speeds possible for tractors with rear-wheel and four-wheel drive, these were evaluated using experimental constants. The effects of the traction coefficient, weight transfer factor and weight per unit of horsepower were determined as a result and were applied to tractors of 60 and 90 h.p. The drawbar pulls which can be achieved by these tractors are compared with usually encountered draughts. As an example, the number of plough bodies and the working speed which can be achieved were determined for a furrow depth of 20 cm and a workin width per body of 32 cm and, using these data, the theoretical area worked per unit of time (without turning and other unproductive time) was calculated. It was found that on light to medium soil a tractor horsepower of 60–70 h.p. was hardly utilized for ploughing in view of the limit applied at present with respect to the number of bodies on the plough and the vibration to be sustained by the driver at higher travel speeds, furthermore that on medium to heavy soils, four-wheel drive was required to overcome the draught of multi-furrow ploughs, especially when the coil conditions were unfavourable for traction, if the consideration are confirmed to wheel tractions.