Vibrational characteristics of tractor seat cushion materials and ride comfort

Tractor seat design can be used as a means to modify loads on body structures to reduce operator's discomfort. The overall comfort and performance of the tractor seating system consist oi fi-ame. cushion. covers. suspension and damping mechanisms. Vibration attenuation in a tractor seat is achieved by selecting the proper suspension and damping mechanism. The vibration characteristics of cushion materials are often overlooked. This paper describes a method of vibration characterisation of tractor seat cushion materials to improve operator's comfort. Nine commercially available seat cushion materials of different density, thickness and composition were randomly selected for this study. Transmissibility data were obtained by measuring input acceleration values on the base plate and output acceleration values at mass at different frequencies from 1 to 7 Hz. It was observed that vibration transmissibilities at resonance and the resonance frequency were significantly affected by the thickness of cushion materials. In the frequency range above the resonance, especially at frequencies higher than 5 Hz, the thinner sample had a higher transmissibility than the thicker sample. In contrast, over the frequency range below the resonance, especially at frequencies lower than 4 Hz, thicker samples had a higher transmissibility than the thinner samples. The synthetic rubber foam cushion materials 1.9D (thickness of 101 mm, density of 69.72 kg/m(3)) and D (thickness of 54 mm, density of 68.70 kg/m(3)) may be recommended for tractor seat pan and backrest cushion materials, respectively on the basis of vibration characteristics.