Improvement of mathematical models of the interaction of vehicle wheels with a roller traction stand.

Abstract

As is known, currently the most widespread are stands with running drums (roller stands). When testing on them, each wheel rests on two parallel rollers of small diameter. They are quite simple in design, compact, create high adhesion forces in contact between the tire and the roller, ensure a stable position of the car during traction tests, and allow testing in stable or dynamic modes, at different speeds.

In most cases, both wheels of one axle are tested simultaneously on the stand. Such stands are called single-axle. The stand layout is called symmetrical if the front and rear rollers are located at the same height, asymmetrical – otherwise. Often the front and rear rollers of each pair are connected to each other using a mechanical power transmission – chain or V-belt.

The design of the roller block must ensure the implementation of the specified traction force on the drive wheels during testing; a stable position of the car on the stand during testing; the ability of the car to leave independently after the end of the tests; and prevent increased tire wear during testing.

The article considers the conditions for the implementation of traction force, which are determined by the roller arrangement schemes (symmetrical and asymmetric) taking into account the angles between the vertical and the line connecting the centers of the wheel and rollers – , as well as taking into account the adhesion coefficient . The dependence of the load utilization coefficient q on the angle α for different roller arrangement schemes is analyzed.

The interaction of the car with the stand in the running-in and loading modes was analyzed and mathematical models were developed to calculate the forces acting in the "wheel-roller" system. The analysis of the forces of interaction of the car with the stand was performed for roller arrangement schemes that do not have a mechanical transmission between the rollers and for a scheme with a mechanical transmission.

The values of the normal reactions  and  are necessary to determine the design parameters of the roller unit (calculations for the strength of the rollers, their shafts, selection of bearing supports, etc.). In addition, knowledge of the reactions  and  helps to optimally distribute the inertial masses between the rollers of the stand. To eliminate slipping of the wheels relative to the rollers, the total inertial mass must be distributed between the rollers of the stand in accordance with the distribution of the normal reactions.