A review is made of investigations on the vibrations to which drivers of heavy vehicles, e.g. bulldozers and tractor are subjected. These vibrations are of great amplitude and low frequency (up to 10 c-s, and in this range it appears that the human body does not react as an entity, but as a complex whole system, each part having it own reactions, and subject to certain interactions, mainly in the resonance frequency range of 3-8-s. The system: vehicle-seat-men was examined first by means of a simplified model, and then in reality on an agricultural tractor on a test track. Accelerations in vertical movements were measured at the fact, the pelvis the breast and the head, with drivers of widely varying posture, and at different speeds. It appears that there is a considerable amplification in the longitudinal component of the vibration from the foot to the head of driver, and there is also amplification in the transversal movements. It is concluded that the present seating arrangement in heavy commercial vehicles is insuitable from the viewpoint of transmission of vibrations. Further it is shown that a mechanical model of the human body can be satisfactorily used in the testing of vehicle vibrations.
Samenvatting