Vibration Characteristics of Walking and Riding Type Power Tillers

The power tiller is a multi-purpose hand tractor designed primarily for rotary tilling and other farm operations. Of late, it has become a main or the sole mechanical resource in small and medium size farms in India owing to the development of a variety of matching equipment. In the event of such wide and constant use, their ergonomic characteristics assume a great importance. This paper deals with machine vibration, hand transmitted vibration (HTV) and whole-body vibration (WBV) of walking and riding type power tillers during rototilling in untilled and tilled fields and in transport mode on farm and bitumen roads. The HTV was measured and analysed as per the guidelines of International Standards ISO 5349 (1986) and the WBV was investigated in accordance with the stipulations of ISO 2631/1(1985). Vibration was measured using the portable four-channel multi-analyser system (Bruel and Kjaer Type 3560 C). The results indicate that machine vibration increased with increase in engine speed and major excitation of the vibration of the power tiller was the unbalanced inertial force of the engine. The walking type power tiller showed higher HTV than the riding type during rototilling, whereas the riding type power tiller exhibited higher hand transmitted and whole body vibrations during the transport mode. Rototilling in the untilled field resulted in 20% more HTV than rototilling in the tilled field. Vibration during transport of the power tiller attached to an empty trailer was significantly higher on the farm road than on the bitumen road, the increase being 32% for HTV and 8% for WBV. Vibration intensity was a maximum in rototilling compared with transportation. Continuous use of the power tiller can involve the risk of vascular disorders of the hands after relatively shorter periods. It was observed that, if the power tiller is used at least 4 h per day at the forward speed of 2·4 km h−1, these disorders would appear in 4 yr, for 10% of the operators, under usual working conditions. The results suggest that it is necessary to reduce the vibration transmitted to the user's hands by providing adequate insulating systems. Exposure time for the power tiller operator should not exceed 4 h during rototilling and 8 h during transport. Increasing exposure time may cause severe discomfort, pain and injury.