Measurement of the loads applied to a steering system – Tie rod and steering column

Currently in the automotive industry it is indispensable the evolution of technology applied in the design and manufacturing of components, either for a specific performance improvement or even as part of a cost reduction plan. For these main reasons, it has been constantly invested in methods that may help engineers to understand the dynamic efforts to which the components are submitted. In order to determine the loads suffered by the steering system of a vehicle in motion, the Group of Automotive Technology from the Lutheran University of Brazil (also known as “GTA”) conducted tests using a front-wheel drive road vehicle with a 1.4L transverse engine. The steering column (which joins the steering wheel to the steering gearbox ) and the tie rod (which connects the steering rack to the steering knuckle) were used as elastic elements to form load cells by the attachment of resistive strain gages in a full Wheatstone bridge. The steering column was used to measure the applied torque and the tie rod to measure the resultant force. The calibration of the load cell formed by the tie rod presented linearity with R² of 0.98 and the one formed by the steering column a R² of 0,99. Analyzing the obtained results it is possible to infer that under standard driving conditions the highest loads occurred during hard braking combined with steering wheel maneuvers (cornering). In this condition the measured force in the tie rod achieved 300 N whilst the torque reading for the steering column was at 0.6 Nm. In a straight line the maximum resultant loads remained under 80 N and 0.3 Nm, respectively. When the vehicle is stationary and without the hydraulic assistance the torque applied to the steering column is about eight times higher in comparison to a moving vehicle (4.55 Nm and 0.55 Nm, respectively).