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Design and calibration of of a device to measure the pulling force of agricultural trailed implements.

(np)(place [np] (Egypt))
Publication Date
  • Agricultural Engineering
  • Measurement
  • Mechanization
  • Agricultural Science
  • Design


Draft (the horizontal component of pull in the direction of travel) and drawbar power requirements are important performance characteristics of trailed agricultural implements. These characteristics are useful in matching a proper power unit to the implement and in improving design. The common method of measuring the pull is by using a dynamometer (force transducer), which is hitched between two tractors chained to each other. The front tractor is used to pull the rear tractor and the tested trailed implement. Draft of trailed implements may be determined by a spring, hydraulic or strain gauge-type dynamometers. Drawbar dynamometers of the spring-type were difficult to read due to the undamped pointer. Hydraulic dynamometers which consist of a cylinder-piston system connected to a Bourdon tube gauge may be damped considerably by placing a restriction valve in the line to the gauge. In recent years there has been an increase use of strain gauge dynamometers of various configurations. These units, when operated with electronic readout instruments, can provide multiple ranges and avoid the oil-leakage problem inherent in hydraulic dynamometers. This paper describes the design and the calibration of a drawbar pin which could be used as a force transducer to measure the draft of trailed implements. This pin transducer consists of a pin on which are mounted a total of four strain gauges. The pin was made of mild steel and dimensioned to satisfy category II implements. This pin is used as a hitch pin and as a measuring device without changing the tractor-implement hitch configuration. Field experiments were carried out with disk harrow at different harrowing depths. The pin transducer produces a linear output dependent of pull force only.

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