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

The background to the development of a two-wheel drive agricultural ga ntry system, its assessment and evolution into a commercial machine ar e described. Details of the main frame, transmission, implement attach ment linkages and vehicle control systems are discussed and their perf ormance assessed. Soil and crop responses to gantry systems are presen ted. A minimum power-to-weight ratio of 15 kW/t is recommended for ade quate performance. To maintain vehicle stability, the ratio of the wei ght on the drive wheels to that on the undriven castor wheels should n ot exceed 75:25. Up to 70% tillage energy savings can be made by remov ing all traffic from the cultivated area and plough resistance may be reduced by up to 50%. Conventional traffic on the soil increases aggre gate size and reduces porosity compared with zero traffic operations. The yield of spring barley in 1991 on a clay soil was increased by aro und 0.75 t/ha under zero compared with conventional traffic, confirmin g 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 tracto r systems in many aspects of their operation. The effect of improved b oom stability on chemical applications needs to be quantified as well as the precise bout matching made possible by gantry systems.