To determine the motor power required for providing the specified machine acceleration there is a need to know the relative start time. The known formulas are obtained by numerical integration of the starting characteristics of motors provided that the acceleration process ends when the motor accelerates to nominal speed. In real terms the acceleration process ends when the rotor speed corresponds to the static moment of friction forces.

This paper provides numerical integration of the starting characteristics of asynchronous motors with the cage and wound rotor and presents curves of calculated relative start time, taking into account the static load.

When calculating the required power of the motor, which runs in the mode of frequent starts and stops in the mechanisms that have high inertia loads and small moments of static resistance it is possible to use the motors of lower power and lower the dynamic loads at start-up a by virtue of a small increase in start-up time calculated by the above formulas. It is shown that the three-stage rheostat start-up of slip-ring motors is more preferable than the two-stage startup.

The subject of research is the horizontally balanced loading platform on soft suspension.

Deviation from the horizontal direction of the platform can be caused by:

- Displacement of the gravity centre of main unit load placed on it from the vertical axis of the platform;

- Displacement of the mass centre of the load dispersed on the platform plane from its vertical axis;

- Adding a load which gravity centre does not coincide with the gravity centre of the main load.

In specific cases the use of complex and expensive tracking systems of high accuracy to balance loading platforms horizontally can be justified, e.g. when mounting the optical measuring or observation systems on a platform.

The aim is to assess the possibility to use the soft hydro-pneumatic suspension with a low power supply unit to provide horizontal balance of platform.

The paper offers a soft hydro-pneumatic suspension design of the rectangular loading platform based on four differential hydraulic cylinders to be the supports for two diagonal beams of the platform.

The head and rod ends of each pair of the beam hydro-cylinders are cross-pipe connected, and to compensate for a difference between the volumes of head and rod ends of cylinders because of their differentiality, there are hydraulic bag-type accumulators installed in the hydraulic suspension system.

The research technique involves the development of a mathematical model of the loading platform hydro-pneumatic suspension followed by its approbation using numerical methods. The paper presents algorithms of engineering analysis of parameters and structural dimensions of hydraulic suspension components.

In order to assess the adequacy of the developed mathematical model of a hydro-pneumatic suspension the paper studiesthe an effect of the following factors on the quality of the platform stabilization in the horizon:

 initial volume values of the gas chamber of hydraulic accumulators;

 pressure level of initial pressurization of hydraulic accumulators with nitrogen;

 differentiality degree of the suspension cylinders;

 value of the gravity centre displacement with respect to the vertical axis of platform;

 additional loading of the platform by the load undisplaced with respect to the vertical axis of platform.

In the context of calculating a hydro-pneumatic suspension of the platform loading diagonal beam of 2 m length, weighing 500 kg, with a load of 5,000 kg was shown that at the greatest displacement of the load gravity centre to the edge of the beam a deviation of the beam relative to the horizon is one angular degree, at most.

The work deals with creating the soft stabilized platform suspensions for stationary systems and mobile units.

As a result, a developed mathematical model allows the following:

- to show the theoretical possibility to create a soft hydro-pneumatic suspension of the loading platform based on four differential hydro-cylinders and four hydraulic accumulators to provide an acceptable accuracy of the loading platform balance in the horizon when the mass centre of the load placed on it is displaced with respect to the vertical axis of the platform;

- to find that the initial stiffness of the hydro-pneumatic suspension, defined by parameters of its hydraulic system, has little effect on the quality of the platform balance in the horizon.

The article “Systems of the heat balance maintenance in modern test benches for centrifugal pumps” makes the case to include cooling systems of a working fluid (heat setting) in test bench for impeller pumps. It briefly summarizes an experience of bench building to test centrifugal pumps, developed at the BMSTU Department E-10 over the last 10 years. The article gives the formulas and the algorithm to calculate the heat capacity of different types of impeller pumps when tested at the bench as ell as to determine the heating time of the liquid in the bench without external cooling. Based on analysis of the power balance of a centrifugal pump, it is shown that about 90% of the pump unit-consumed electric power in terminals is used for heating up the working fluid in the loop of the test bench. The article gives examples of elementary heat calculation of the pump operation within the test bench. It presents the main types of systems to maintain thermal balance, their advantages, disadvantages and possible applications. The cooling system schemes for open and closed version of the benches both with built-in and with an independent cooling circuit are analysed. The paper separately considers options of such systems for large benches using the cooling tower as a cooling device in the loop, and to test the pumps using the hydraulic fluids other than water, including those at high temperatures of working fluids; in the latter case a diagram of dual-circuit cooling system "liquid-liquid-air" is shown. The paper depicts a necessity to use ethylene glycol coolant in the two-loop cooling bench. It provides an example of combining the functions of cooling and filtration in a single cooling circuit. Criteria for effectiveness of these systems are stated. Possible ways for developing systems to maintain a thermal balance, modern methods of regulation and control are described. In particular, the paper shows the efficiency of frequency control of the circulation pump in the autonomous cooling circuit of the bench, as well as the feasibility of automated control of this circuit.

The accuracy of positioning surfaces to be processed on automatic lines with pallet-fixtures essentially depends on the setting error of the pallet-fixtures with work-pieces in ready-to-work position.

The applied methods for calculating the setting error do not give a complete picture of the possible coordinates of the point when in the pallet is displaced in different directions.

The aim of the work was to determine an accuracy of the setting work-pieces on automatic lines with pallets-fixtures, using a computational and analytical method, to improve a manufacturing precision of parts.

The currently used methods to calculate the setting error do not give a complete picture of the possible coordinates of the point of the pallet displacement in different directions. The paper offers a method of equivalent mechanism to determine all the variety of options for displacements in the horizontal plane with a diverse combination of angular and plane-parallel displacements.

Using a four-bar linkage, as an equivalent mechanism, allows us to define a zone of the possible positions of any point of the work-piece pallet platform, as the zone bounded by the coupler curve. In case the gaps in the nodes of the two fixtures are equal the zone of possible positions of the point in the parallel displacement of the platform is determined by the circumference and at an angular displacement by the ellipse.

The obtained analytical dependences allow us to determine the error at the stage of design with the certain gaps in the fixture nodes.

The above method of calculation makes it possible to define a zone of the appropriate placement of the work-piece on its platform for the specified parameters of the pallet to meet conditions for ensuring the coordinate accuracy of the processed axes of holes.

Features of manufacturing process and use of carbon fibre-reinforced plastics (CFRP) define specific types of only their defects. Furthermore, the CFRP structure material and its properties considerably differ from those of the metal materials. Therefore, a relevant task is to conduct research to justify the selection of the ultrasonic testing parameters of these materials.

Optimal parameters and recommendations on quality control of such materials were grounded in the course of experimental studies on samples made from the UTR1000-12-400P carbon fabric, based on the T700GC-12K yarn and the T-31 epoxy binder, filled with artificial defects to imitate the bundles of different size and the impact damage.

It is shown that with increasing frequency of the ultrasonic oscillation propagating in the samples there is an increase both in damping and in SNR for artificial defects. In other words, on the one hand, the lower is the oscillation frequency, the less is a damping effect, but, on the other one, the higher is the frequency, the higher is the sensitivity control. It was found that the optimum frequencies for the ultrasonic test of CFRP are those in the vicinity of 5 MHz.

Furthermore, to detect the small-sized defects it is advised to use an ultrasonic beam focus, which can be achieved using phased arrays.

The most optimal method of ultrasonic testing to search for impact damage is a mirrorshadow method, which is based on the measurement of the amplitude of the bottom echo signal. It is shown that the amplitude of the bottom echo signal in defect-free zone is, in average, 14 dB higher than in the area with shock damage.