Variations in the Forward Motion of Farm Tractors

Abstract

ABSTRACT THE effect of a periodic drawbar pull loading on the forward velocity of a farm tractor is investi-gated through computer simulation. The relationship of the variations in forward velocity to loading frequency is found to reflect the characteristics of a system described by a linear sec-ond order differential equation. The continuing trend towards larger and more productive farm tractors has been accompanied by increased con-cern for the operator environment in terms of noise and riding comfort. In the past, the primary concern in the riding comfort area has been with the bounce (vertical) and pitch motions. Longitudinal or fore-aft vibration as well as the larger variations in forward motion due to a varying drawbar load-ing have been the subject of consider-ably less investigation. Although the level of longitudinal vibration of agricultural tractors during field operations may be considerably below that of the vertical vibration, it has been established that man's tolerance to longitudinal vibra-tion is equal to or less than his toler-ance to vertical vibration. With the definite trend to higher operating speeds and the possible future use of vibrating tillage tools, the area of longitudinal riding comfort will as-sume increased importance. The study described in this article involved the development of a math-ematical model useful for the predic-tion of the variations in forward motion of farm tractors due to a vary-ing drawbar loading. The model was then used to investigate the transla-tional frequency response characteris- tics of a tractor subjected to a periodic drawbar loading.