Metabolic cost and subjective assessment during operation of a rotary tiller with and without an operator’s seat

Abstract

he acceptance of the power tiller among the Indian farmers has not reached the level expected at the time of its introduction. This is primarily because of the drudgery involved in its operation. An operator has to walk behind the machine for a distance of 15–20 km to rotatill a hectare of land once. To overcome the problem, an operator's seat was developed as an attachment to popular Indian brands of power tiller. This study was conducted to quantify the reduction in drudgery due to provision of an operator's seat on a rotary power tiller by measuring metabolic cost and psychophysical assessment. Heart rate and oxygen consumption rate of the subjects were measured at three levels of forward speed under actual field conditions using an ambulatory metabolic measurement system. Overall discomfort rating was assessed subjectively on a 10-point visual analogue discomfort scale. Mean heart rate and oxygen consumption rate varied from 81.7 to 87.6 beats/min and 0.45 to 0.50 l/min, respectively, with increase in forward speed from 0.28 to 0.62 m/s with the operator's seat. Without the operator's seat, the heart rate and oxygen consumption rate varied from 94.9 to 108.0 beats/min and 0.54 to 0.70 l/min, respectively, with increase in forward speed from 0.29 to 0.63 m/s. Mean overall discomfort rating varied from 0.5 to 1.5 with the operator's seat and from 1.5 to 3.0 without the operator's seat. Thus, human energy expenditure during operation of the power tiller varied from 9.40 to 10.44 kJ/min with the operator's seat and from 11.28 to 14.62 kJ/min without the operator's seat. It was observed that the attachment of an operator's seat to power tiller reduced human energy expenditure by 16.7–28.6%. On the basis of physiological responses, the rotatilling operation by power tiller with and without operator's seat was classified as light and moderate work, respectively. It was concluded that the provision of an operator's seat on the power tiller reduces the drudgery of operator.