Development of compact tractor hitch testing unit

摘要

The development of a low-cost hitch testing facility that complies with relevant international standards is described. A simulation model of the actual hitch forces encountered by a large 150 kW agricultural tractor, operating under actual field conditions, was developed. These indicated a maximum pulling force of 81.36 kN which is just above the ISO Standard value of 80 kN. It was found that, for cost effectiveness, the maximum feasible frequency of application of the testing force is 6 Hz. The resultant unit is compact (4 m X 2 m) and applies a maximum loading of 90 kN at a maximum cycle frequency of 6 Hz and complies with international standards. Additional features were added in order to meet the more stringent Dromone Standard. These include lifting (maximum lifting force 100 kN) and destructive (increasing load to failure - maximum 500 kN) tests. A fatigue test was carried out on a Renault Ceres 95 pick-up hitch. Deflection of the hook was less than 10 mm and no cracking was observed. The hitch was deemed to conform with the ISO and EU Standards. It is envisaged that this unit will be integrated into a computer-based design and testing facility that will minimize the number of destructive tests required.