The Method of Determination of Properties of Air Springs with Two Pressure Stages and Counterpressure

BACKGROUND: The issues of choosing reasonable properties for suspension system of wheeled vehicles, including vehicles for agricultural purposes, still remain relevant, especially for the vehicles, which load capacity is comparable to their curb mass. Significant difference between static loads, acting in suspension under the curb and total masses of a vehicle, is a consequence of high load capacity. Two or three times difference is possible (depending on axles load distribution), whereas 70% to 80% of mass of trailing load is on rear axles. Use of convenient suspension systems with metal springs is not able to ensure demanded nonlinearity of properties, where non-zero static wheel travel under the curb mass is kept with reasonable value of period of vertical eigenmodes for curb-massed and total-massed vehicle as well as with dynamic factor value. Air springs with two pressure stages are more advanced solution, as they allow choosing stiffness for small and large wheel travel by means of operation of different pressure stages, which volumes are conditioned by differents stiffnesses in area of static displacement. AIMS: The aim of the study, which results are given in this paper, is to develop the method of determination of main design parameters and characteristics of air springs with two pressure stages (stiffnesses) and counterpressure, applicable for ensuring non-zero static wheel travel of curb-massed vehicles with keeping the given value of dynamic factor. METHODS: The analytical analysis methods are used. RESULTS: An example of implementation of the developed method for the KamAZ-53215 Selhoznik truck is given as the study result. CONCLUSIONS: The dependencies, presented in the paper, make possible to determine main design parameters of uncontrolled air suspensions with two pressure stages (and stiffnesses) and counterpressure for wheeled vehicles, which give an opportunity to ensure given values of static wheel travel and dynamic factor and, in addition, provide insignificant increase of stiffness in comparison to air suspensions without counterpressure.