The propulsion system of an agricultural machine is in charge for the delivery of the engine power to the soil and allows a vehicle travelling and performing its duties. Based on the type of this system, agricultural machines can be divided in tracked and wheeled. Although the former have their own specific applications and advantages, the latter are the most widely used. Over the time, different tyre typologies have been developed keeping into account many factors, such as tractor models, sizes and types of field/tillage operations, and wheel rims were changed accordingly. Notwithstanding an attempt of standardization by ISO, the design of these components is still conditioned by manufacturers’ previous choices and there are some interchangeability issues.
The knowledge of existing differences/dimensions is useful when there is the need for maintenance, substitution or connection of whatever device to a tractor axle. So, with the aim of developing a universal piece of experimental equipment to be used to detect the tractor performances (torque, power) at the wheels, i.e. a hub adapter, a systematic study of the different rim types has been performed. After having collected many data through direct measurements or interviews, all information has been elaborated using many statistical tools, such as scatter plots, frequency charts and clustering algorithms. Finally, four different classification keys have been applied to identify a minimum set of dimensional/functional classes of tractors using similar rims and, hence, capable of using the same hub adapters. The results of this study were then successfully used to design two optimized adapters. Their features (dimensions, number of holes) would let these two adapters connect the test equipment to the axle shafts of up to 1961 tractors of our database, corresponding to 81 % of the farm tractors below 100 kW on the Italian and European market, thus maximizing the cost-benefit ratio for these components.
