Development and evaluation of vibration isolators for reducing hand transmitted vibration of walking and riding type power tillers

The presence of a large number of small holdings in India has rendered the power tiller to be the most suitable farm equipment, in view of its compact size and versatility. Continuous use of the power tiller can involve the risk of vascular disorders of the hands even after relatively short periods under usual working conditions and the results suggest that it is necessary to reduce the vibration transmitted to the userʹs hands by providing adequate insulating systems. In this study, new types of vibration isolators for engine, handle bar and handle were developed to increase the safe exposure level of operators by reducing the vibration transmitted to the hands. Combined effect of the three stages of reduction in vibration was measured and analysed to know the reduction of machine vibration in walking and riding type power tillers at stationary condition. The results indicated that provision of vibration isolators reduced handle vibration by 50–60%. The effectiveness of vibration isolators in reducing the hand transmitted vibration (HTV) was also investigated during rototilling in untilled as well as tilled fields and in transport mode on farm and bitumen roads based on ISO standard (). HTV was reduced from 4.55 m s−2 to 3.18 m s−2 for walking type whereas for riding type, it was reduced from 4.24 m s−2 to 2.85 m s−2 after incorporating vibration isolators during rototilling. Vibration transmitted to the hand was significantly reduced from 3.96 m s−2 to 2.67 m s−2 at 5 km h−1 in the transport mode of power tiller. The risk of vibration-induced white finger was prolonged from 5 years to 9 years in the case of rototilling at the forward speed of 2.4 km h−1, 7 years to 11 years during transport at the forward speed of 5.0 km h−1 respectively for the 10% of operators if the power tiller is used 8 h day−1. On mounting the vibration isolators, daily exposure limit was increased from <0.5 h to 2 h during rototilling and from 1 h to 2 h during transport respectively. The vibration isolators developed were of simple structure and could be easily installed in the existing power tillers. The installation of these dampers would not lead to variation of the geometry characteristics of the guide system of the power tillers.