Test methodology for validating drop arm of a tractor mechanical steering system under bi-axial loading

Abstract

The drop arm is a part of tractor mechanical steering system which connects the steering gearbox to drag link. The function of the drop arm is to convert the rotary motion of the steering gear shaft into linear motion of the drag link. During vehicle testing in the field drop arm failure was observed, which was not captured in the component level testing. Typically drop arm durability test is carried out in component level with uniaxial loading. For understanding the loads acting on the drop arm, the steering system along with the drop arm were instrumented with strain gauges and data were acquired in the different agricultural field operating conditions. Data analysis revealed that apart from axial load significant bending load is also acting on the drop arm. A detailed study was carried out for finding out the parameters like kingpin torque and steering geometry which is causing the bi-axial load (axial cum bending loads) in the drop arm. A new system level test methodology was developed for simulating the bi-axial load conditions in the drop arm using a single linear actuator. Strain values measured in the newly developed test methodology were compared with the strain data measured in the field. Drop arm Durability test was carried out with the newly developed system level test methodology. The failure mode between the lab setup and the vehicle testing was found to be matching