In mathematical modeling of dynamic and vibration protection systems of operators of construction and road machines, it is necessary to take into account the damping properties of the mechanisms. Accounting for the friction force in mathematical models is often performed using a coefficient, according to the viscous friction model. In more complex models, it is common to use a well-known expression in which the functions of the exponent and hyperbolic tangent are present, and the independent parameters are the Coulomb and separation friction forces, the separation friction rate, and the coefficient of viscous friction. This expression is used in a well-known mathematical package. However, the well-known expression does not accurately approximate the experimental friction curves. In the present work, an alternative expression for the total friction force has been supplemented. The refinement made it possible to apply a new formula for the entire range of change in the velocity argument and more accurately reproduce the characteristic shape of the experimental friction characteristics. For the new expression, complementary formulas were obtained that establish the relationship between the input parameters and a number of others that have a clear and simple physical meaning of the parameters. A comparison was made of the generally accepted and proposed expressions according to experimental data, graphs of the relative error were constructed. Also, a comparison of two expressions of the total friction force was made, as an example, on a dynamic model of forced oscillations of a concentrated mass on a moving base. The comparison results showed a significant discrepancy between the generally accepted expression in comparison with the proposed one, in terms of the total friction force, as well as a discrepancy in the amplitudes of relative displacements and absolute mass accelerations obtained on the dynamic model. The proposed expression can be used to approximate the total friction force in mathematical models of dynamic vibration protection systems for operator seats.

During the operation of aerial ropeways, the system of carrying and carrying-traction ropes, which provides the possibility of moving passengers or transported goods between the terminal points of the route, experiences a high level of loading from a variety of operational loads and environmental influences. These loads and influences form the tension of the ropeway system variable along the length of the ropeway route, which has a decisive impact on the main technical and economic indicators of mobile ropeways, and thereby determines specific areas of their effective and inappropriate or unacceptable use. This article presents an engineering technique for constructing tension diagrams of carrying-traction ropes in stationary and non-stationary modes of operation of a mobile ropeway. Calculated dependences are given to determine the tension forces of ropes at characteristic points along their length, as well as calculated dependences for determining the resistance forces to the movement of ropes on characteristic sections of the mobile ropeway route. This technique can be used both for calculating the loading of the rope system based on taking into account a large number of factors characterizing operational loads, terrain parameters and transported cargo, and for analyzing the direction and significance of the variation of these factors and the main design parameters of the main technological equipment of mobile transport and reloading rope complexes. The results of the analysis of the influence of the variation of a number of significant quantitative parameters on the change in the tension forces of the carrying-traction ropes are also presented.

Among the existing variety the problem of comparison of several samples of automotive equipment capable of performing their functions under certain conditions and under the specified operating conditions often arises, and, consequently, the problem of choice of the optimal design solution. This entails the need to develop a methodology for assessing the quality, which would make it possible for each sample under consideration to match a quantitative indicator displaying its operational properties and functionality. In this study, the authors set themselves the following goal — developing a universal methodic that allows to calculate the mobility index of automotive equipment considering only the structural features, that is, in the conditions of their operation on a solid road surface without taking into account the conditions of rough terrain. Based on analytical data displaying the technical characteristics of the machines, such as speed, braking and traction properties, controllability and maneuverability, stability, smoothness, patency, etc. empirical criteria are constructed, then the simplest indicators are aggregated into integral one, taking into account the weight of their contribution to the mobility indicator. Using the obtained methodology, the mobility indicators for a number of models of wheeled all-terrain vehicles were calculated, the ranked vehicle series are given according to this indicator.

The paper deals with the problem of vibroimpact screen operating regimes selection for the regime of anti-phase oscillations of its elements. The criteria of effective screen operation accepted are impact impulse transferred to sieve from vibroimpact lattice and sieve double amplitude, which provide effective regimes of sieve cleaning from clogging particles and maintenance of preset sieve oscillations regime for support of technological parameters of material screening. Using the developed mathematical model and program the computational experiment was conducted for operating oscillation frequency range from 105 rad/s to 160 rad/s and adjustment gap between vibroimpact lattice and sieve for operating range from 0 to 5,5 mm. Influences of oscillation frequency and adjustment gap on impact impulse transferred to sieve and sieve double amplitude are obtained in the form of regression equations. On its base the recommendations for determining effective operating regimes of vibroimpact screen are offered. Obtained regularities explain nonlinear behavior of two-mass vibroimpulse oscillating system according to its operating parameters changing and show principal opportunities of system control. Also obtained results could find an application in screen operating regimes adjustment during commissioning and start-up operation and screen operation period, and could decrease labor costs and fasten the procedure of rational screen operating parameters searching.

The article is devoted to the actual problem of improving the quality of cleaning roads and sidewalks by communal machines with brush working equipment. One of the main parameters of the working process of a communal machine with brush working equipment, which determines the cleaning efficiency and brush life, is the brush pressing force against the surface to be cleaned. In order to ensure the highest efficiency of the cleaning process during the operation of the communal machine, it is required to maintain a certain value of the brush pressing force. During the operation of a communal machine equipped with brush implements with track rollers, the pressing force can vary significantly. To maintain the required value of the brush pressing force against the surface to be cleaned, a device for controlling the position of the brush working equipment using a hydropneumatic accumulator connected to the rod end of a standard hydraulic cylinder is proposed. The pressure of the working fluid created by the hydropneumatic accumulator and acting on the piston of the hydraulic cylinder creates a force acting on the brush working equipment, which makes it possible to provide the necessary force for pressing the brush to the surface to be cleaned. The performance indicators of the device for controlling the position of the brush working equipment depend on the selected values of the design parameters of its elements, including the parameters of the hydropneumatic accumulator. The dependences of the deviation of the brush pressing force from the required value during the vertical movement of the brush working equipment on the useful volume, the initial charging pressure and the maximum pressure of the hydropneumatic accumulator are obtained. A method is considered to reduce the deviation of the brush pressing force from the required value by connecting an additional volume to the gas cavity of the hydropneumatic accumulator.

This article discusses the dynamic behavior of a spool plunger with a modernized drive. Modernization of the drive consists in replacing the electromagnet with a stepper motor with the transformation of rotational motion, — with the help of a screw pair, — into a rectilinear one. The contact between the ends of the screw and the plunger is provided by a spring. The value of the preliminary compression of the plunger to the end of the screw is assigned on the basis of guaranteed operation without loss of contact, due to which the plunger practically does not respond to disturbances and is devoid of an oscillatory component during the transient process. The mathematical model includes the influence of fluid friction and hydrodynamic force arising from pressure loss on the distributor 4 MPa. The study of the dynamics of the plunger consists in the accelerated retraction of the screw — which is in force contact with the end face of the spool — and the determination of the limit values of acceleration as a function of the preload force.