Conditions of wheeled machine motion on horizontal surface evaluation on coasting deceleration

Abstract

In everyday usage and in the testing of transport and technological wheeled machines, it becomes necessary to quantify the actual driving conditions of this particular machine: the wind direction and speed vw, the coefficient of air resistance Cd and coefficient of rolling resistance Crr. The values obtained in the wind tunnel, on a tire stand with a large diameter drum, at the nearest meteorological station, may be far from the particular case under investigation or simply inaccessible. Therefore, in this study, the task is to justify the methodology for determining these indices from the machine output, preferably without expensive equipment and excessive labor, time and money. In the article, it is suggested to evaluate the joint impact of weather conditions and resistance to motion on the data of the wheeled machine coasting in two opposite directions. The method of calculating the required indices is justified. A real example is presented – a coasting of a Daewoo Lanos sedan (notchback) with Belshin tires Artmotion 185/60 R14 82H on a horizontal road, two adjacent sections of which are located at an angle of 53°. When processing the experimental data, the dependence of the rolling resistance on speed is described by the second degree polynomial, the air resistance is described by the conventional quadratic function, and the transmission idling losses – by the linear function. The solution of the system of two equations with two unknowns gave an average value of Cd = 0.38 (according to unofficial manufacturer's data – 0.375), the average value of Crr = 0.0117 (there is no data for comparison, but judging from the literature data such a value is possible). The average estimated wind speed at the height of the pressure center at the beginning of the experiment was 1.9 m/s, after 80 minutes – 3.56 m/s. Measurement with anemometer at an altitude of 0.9 m showed at the same time's intervals 2.19 ± 1.2 m/s and 3.97 ± 0.86 m/s. Thus, the described method yields results linked to a specific object under specific conditions and comparable to data from specialized measuring means, but does not require the use of expensive equipment, highly qualified experts and excessive time, labor and finance.