Authors: C. Peng, J.A. Lines
Addresses: School of Engineering, Oxford Brookes University, Headington, Oxford OX3 OBP, UK. ' Silsoe Research Institute, Silsoe, Bedford MK45 4HS, UK
Abstract: Whole body vibration on tractors is considered a significant long term health risk for regular drivers, since it frequently exceeds that considered acceptable by International, European and British standards. There has been little change in the vibration levels experienced on tractors over the past 20 years. Vibration levels are determined by the physical characteristics of the tractor and ground, and by the style of the driver. Reduction of vibration levels is dependent on an appreciation of both factors. This paper reviews aspects of vibration on agricultural tractors relevant to its control and reduction. Poor tyre description is the main source of error in tractor vibration simulations. Because of the linked nature of the various vibration modes, a knowledge of the vertical, lateral and longitudinal suspension characteristics of the tractor tyres is necessary. Acceptable models have been identified for the vertical and lateral characteristics of tyres, and measurements have been made of the vertical stiffness and damping characteristics of tractor tyres. Almost nothing is known about the longitudinal characteristics of tractor tyres. In many cases tractor drivers appear to respond to a reduction in vibration by increasing their driving speed. This results in vibration levels on suspended vehicles which are only a little lower than those on comparable unsuspended vehicles. It also results in increased input amplitudes of vibration which have to be accommodated by any suspension systems which may have been fitted. Suspensions must therefore be designed to accommodate vibration inputs greater than those encountered on unsuspended tractors. The introduction of suspensions can be expected to substantially reduce vibration levels only in cases where there are other limits on driving speed.
Keywords: driver-vehicle interaction; ground induced vibration; unsuspended agricultural tractors; whole body vibration; tyre characteristics; vibration measurement; tractor vibration; health hazards.
International Journal of Heavy Vehicle Systems, 1997 Vol.4 No.2/3/4, pp.166 - 182
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