TECHNICAL TRENDS OF TRACTORS AND COMBINES (1960-1989) BASED ON ITALIAN TYPE-APPROVAL DATA

An analysis is made of the evolution of the performance of tractors an d combines according to Italian type-approval data. The following main features of engines were considered and compared: maximum power, powe r per unit displacement, rated speed, rated efficiency and stroke-to-b ore ratio. The evolution of some operational parameters of field machi nes were also considered. For combines these were power per unit mass and power versus cutting width. For tractors these were power per unit mass, maximum speed, minimum turning radius and maximum traction coef ficient. The evolution of combine and tractor engines shows an increas e in all the features examined and there are not significant differenc es between their trends. The average figures for these engines in 1989 were about 35% for the thermal efficiency at rated speed, about 2000- 2500 rev/min for rated speed, about 17 kW/dm(3) for specific power and about 1 . 1 for stroke to bore ratio. The power shows the greatest in crease in the years 1960-1989, for tractors from 28 kW in 1960 to 51 k W in 1989 and for combines from 44 to 130 kW in the same years. The in crease in power for the combines is very significant and the non-conve ntional models show the highest power requirement. The functional feat ures of tractors show an evolution which results in greater travel spe ed, manoeuvrability and power per unit mass. Only the maximum traction coefficient shows a negative trend. (C) 1996 Silsoe Research Institut e.