Traction performance of a model 4wd tractor

A model tractor, based upon approximately 1/4 length scale of the John Deere 8640 four-wheel drive tractor, was designed and fabricated for traction studies in a soil bin. The tractor was powered by a 2.25 kW electric motor and was capable of either two-wheel-drive or four-wheeldrive modes. Various components were instrumented to measure individual axle torque, axle speed, and drawbar pull. Data were col lected with a HP2240A data logger connected to a HP 1000 mainframe computer. Tests were conducted in front-wheel-drive, rear-wheel-drive and four-wheel-drive modes to investigate the traction characteristics with different drive modes. Test results showed the four-wheel-drive mode produced a drawbar pull about three times of that produced by the rear- or front-wheel-drive mode. The rear-wheel-drive mode was found more favorable than the front-wheel-drive mode. The motion resistance of the four-wheel mode was greater than that of the frontor rear-wheel-drive mode. A theoretical analysis and model tractor tests were conducted to find the optimum traction ratio. The results showed the optimum traction ratio ranged from 0.3 to 0.4.