DESIGN, OPERATION AND PERFORMANCE OF A GANTRY SYSTEM - EXPERIENCE IN ARABLE CROPPING

The background to the development of a two-wheel drive agricultural gantry system, its assessment and evolution into a commercial machine are described. Details of the main frame, transmission, implement attachment linkages and vehicle control systems are discussed and their performance assessed. Soil and crop responses to gantry systems are presented. A minimum power-to-weight ratio of 15 kW/t is recommended for adequate performance. To maintain vehicle stability, the ratio of the weight on the drive wheels to that on the undriven castor wheels should not exceed 75:25. Up to 70% tillage energy savings can be made by removing all traffic from the cultivated area and plough resistance may be reduced by up to 50%. Conventional traffic on the soil increases aggregate size and reduces porosity compared with zero traffic operations. The yield of spring barley in 1991 on a clay soil was increased by around 0.75 t/ha under zero compared with conventional traffic, confirming a similar winter wheat yield response in 1990. It is concluded that suitably engineered gantries are able to carry out most operations on a farm and that they offer significant advantages over existing tractor systems in many aspects of their operation. The effect of improved boom stability on chemical applications needs to be quantified as well as the precise bout matching made possible by gantry systems.