Determination the draft ranges at which 2WD and 4WD tractors operates at their maximum traction efficiency


This research was conducted on 2WD and 4WD tractors to determine the draft force ranges at which these tractors work at their maximum traction efficiency. Massy –Ferguson tractor of 2WD and 4WD type was used in the experiments. The total weight of the tractor is 48.85kN. The weight acting on the rear and front wheels is 34.63kN and 14.22kN respectively. The rated engine power is 95kW. The experiments were conducted using four tractor forward speeds G1(0.39), G2(0.51), G3(0.72) and G4(1.20) m/sec and six operating depths (10, 20, 30, 40, 50 and 60cm) for the plow which used to load the tractor engine. The results showed that the maximum traction efficiency of 2WD and 4WD tractors are 0.72 and 0.79 which occurred at traction wheels slip of 12% and 7% respectively. The draft force range of 4WD was wider than that of 2WD which gives 4WD tractor superiority on 2WD tractor. These draft force ranges are 15-30kN and 12.5-32.5kN and these ranges occurred at wheels slip ranges of 10-30% and 5-19% for 2WD and 4WD tractors respectively. The optimum traction efficiencies ( the optimum tractor performance) are 0.78 and 0.85 and they occurred at wheels slip of 17% and 8% and at draft force of 22kN for 2WD and 4WD tractors respectively. The maximum value of PF increased as the tractor forward speed increased for both tractors but this maximum PF provided lower draft force which means the tractor can not pull wider implements or machines working at greater depths but at lower forward speed the situation is better. For lower forward speed (0.39 m/sec) the draft force at which the maximum PF occurred at is 29 kN and 34 kN for 2WD and 4WD respectively. When the forward speed increased to 1.20 m/sec the draft force decreased to 23kN and 28kN for 2WD and 4WD respectively. The results showed clearly that 4WD surpassed in performance 2WD. it is more efficiently in using the power at the traction wheels as draft force increased with less power losses through the wheels slip and the rolling resistance and that can be seen from the difference between Pd and PF. The power at the traction wheels (Pd), the weight of the tractor (Gt) and the tractor forward speed (Va) were connected in equation for 4WD and 2WD tractors but the weight of the traction wheels (rear wheels) (Zr) was used for 2WD tractor. Both equations may be used to determine the weight required by the tractor to operate at the maximum traction efficiency.Keywords: maximum traction efficiency, optimum traction efficiency, draft force range. Draft power, power at the traction wheels