Research of braking peculiarities of used cars

This paper briefly describes some analysis of a car braking process - the peculiarities of car wheel-to-road adhesion, the influence of distribution of braking forces on car stability between front and rear axles. The requirements of EU Directive 71/320/EEC to braking force coefficients of car front and rear axles are exposed. Structural designs of braking systems are analyzed with respect to their meeting the EU standards. Experimental measurements of braking force coefficients for some models of cars which are used in Lithuania, are presented with the analysis how these coefficients meet the EU standards. The analysis of test results, suggestions for the ratio of braking forces of car front and rear axles are presented

Comparative research of a motor car motion in the case of the loss of contact with the road surface

The paper describes the car motion when the contact between its wheels and the road surface is lost. A simulation of such car motion was carried out using a mathematical package "Maple 6" for the two cases: 1) The car flies off a horizontal surface; 2) The car runs over a springboard. The dependencies of the main parameters of motion (velocity and distance) upon the height of the horizontal road step or upon the springboard height and its inclination angle (in the second case) were found. The work presents the graphs of these motion parameters and evaluates the influence of air resistance in both cases

Analysis of calculation methods used for accuracy evaluation of the results of road accident examination

For examination of road accidents often calculations are being performed according to mathematical equations having many variables, real values of which are of stochastic nature and they depend on many accident factors. Therefore it is important to know limits of determination of final values of every being analysed parameter of car movement and their probabilistic characteristics. This paper presents some cases of simulation of some road situations by mathematical methods of calculations, which now are widely used for evaluation of accuracy of values of the calculated parameter (in this paper – the braking distance). Also here is presented some analysis of these methods. The paper presents the following cases of car braking: braking with making attempts to prevent a collision with another car, braking through impact-to-pedestrian prevention and conventional (rectilinear) car braking. The main attention in the analysis of the mentioned road situations is paid to veracity of the car braking distance, i.e. to limits of variation of values of this parameter and also to influence of accidental factors on the final result which is being looked for. Some conclusions on the expediency of application of the described methods of calculations to analysis of road accidents are present

Evaluation of veracity of car braking parameters used for the analysis of road accidents

During the road accident analysis speed of the examined vehicle often is being established in accordance with the length of the trace remained by the vehicle tires. Usually in such case there are values of braking deceleration used for calculations, which are selected from the corresponding references. The real experiment, establishing the braking parameters of the given vehicle, is performed more seldom. In both cases it is important to calculate the vehicle speed in accordance with the received or found values of deceleration as well to estimate the possible limits of the vehicle speed, i. e. to evaluate the veracity of such calculations. This paper presents the results of evaluation of car braking parameters, which are treated as random values in the known probabilistic characteristics

Modelowanie i ocena amortyzatora i jego zaworu talerzowego oparte na zasadach metody sił

W danej publikacji został opisany model matematyczny zaworu talerzowego jednorurowego amortyzatora, wyprowadzenia którego zastosowano metodę sił. Metoda ta wyraża związki pomiędzy przemieszczeniami i siłami działającymi na elementy amortyzatora. Stosowanie metody sił w praktycznej sferze modyfikacji amortyzatorów samochodowych pozwala efektywnie analizować wpływ różnych parametrów, w tym ilość, wzajemne położenie i właściwości materiałów talerzy zaworu, na generowaną amortyzatorem wielkość siły tłumienia. Tłumienie, które generuje amortyzator, wywiera znaczący wpływ na komfort jazdy samochodem oraz jego dynamikę. W publikacji również został stworzony kompletny model jednorurowego amortyzatora. Walidacja modelu matematycznego oraz możliwość zastosowania jego w praktyce zostały ocenione na podstawie eksperymentalnych pomiarów charakterystyk amortyzatorów na specjalnym stanowisku.In this paper, a mathematical model of a monotube shock absorber’s shim valve, which is developed by applying the force (flexibility) method, is described. This method expresses the relationship between displacements and the forces existing in the shock absorber structure. An application of the force method in the field of practical modification of vehicle shock absorbers enables to effectively analyse the influence of a wide range of parameters, including the number of shims in the valve, their disposition and the properties of the material on the level of the damping force. The damping of the shock absorber considerably impacts comfort and road holding characteristics of the vehicle. In addition, a whole model of a monotube shock absorber is designed in this paper. The validation and practical application of the mathematical model were evaluated by carrying out experimental measuring of the characteristics of the shock absorber using a special stand