The mobility of small and medium sized combine harvesters in muddy conditions

Abstract

The objective of this study was to investigate the factors which have an effect on the mobility of wheeled combine harvesters in difficult harvesting conditions. Test areas included wet clay soils, high organic matter soils and slippery clay soil slopes. In the experimental combine harvester, it was possible to change the wheel gauge in the rear, wheel sizes and the weight distribution. Radial, cross-ply and dual tyres were compared. In addition, a hydrostatic rear wheel drive system was included in the research programme. In most cases the high motion resistance of the rear tyres caused high slippage values at the front tyres. The most obvious improvements in the mobility of combines can be made through improvements to the rear axles. The wheel gauge in the rear axle should be exactly the same as in the front. Rear tyres with large diameter should be about half as wide as the front tyres and even the rear tyres should have a “V”-tread. By changing the rear axle construction and the tyre size, it was found possible to reduce resistance to motion by 30%. Large diameter tyres provide the most effective means of improving mobility of combines in soft conditions. Wide tyres with a wide contact area are likely to cause bulldozing effects when the bearing capacity of the topsoil is small.