design, development and evaluation of a single wheel tester

the single wheel tester is an experimental device used to measure wheel forces when studying the relation of soil and wheel in a soil bin or in the field. in the model under development, a special frame holding the test wheel is connected to a loading carriage by two pairs of vertical rails and four rollers to provide a floating connection. by applying a driving torque to the test wheel shaft, the tester frame and loading carriage moved along the soil bin and the net traction force developed by the test wheel is measured using a pair of force transducers (load cells). the driving unit consists of a 3-phase, 1.1 kw ac motor and a reduction gear unit (gear ratio 1:48). the drive unit is mounted on an independent frame which is mounted on the tester frame by a pivot shaft running through the center of mass of the drive assembly. a chain drive system transmits the output rotation of the drive unit to the test wheel axis. the torque transmitted to the test wheel was calculated by measuring the tension force of the chain using a load cell to measure the reaction force sensed by the pivotal frame during transmission. rotary and linear encoders equipped with infrared sensors were used to measure angular and linear velocities of the test wheel and tester frame, respectively. the sensor output was sent to a data acquisition board to digitalize the data before being sent to a computer for further processing. the single wheel tester was capable of measuring net traction, linear and angular velocities, slippage and driving torque of test wheels as large as 25 cm in width, 70 cm in diameter and with a maximum net traction of 600 n and maximum torque of 170 n-m. during the evaluation tests, the traction parameters of an agricultural tire with an inflation pressure of 140 kpa, intended for a walking tractor, were measured. the evaluation results were recorded in diagrams of net traction force, driving torque, angular velocity; travel speed and wheel slip along a 2.5 m test track in a laboratory soil bin.