Determination of the Braking Period Duration in Case of an Electric Motor Driving Mechanism with a Hydrodynamic Coupling

Hydrodynamic coupling is a power-transmitting device with no stiff kinematic relation between the shafts of its basic parts (pump and turbine impellers) and no torque transformation. It has been used in various driving mechanisms due to its certain advantages, especially in transient working regimes of machines. Nevertheless, no sufficient attention has been devoted to the study of a braking period of such driving mechanisms, either in research papers or in practice. The existing few papers analyse only the experimental results concerning the braking period. The paper outlines a combined graphical and numerical method which enables the survey a of driving system operation in either steady-state or transient working regimes. The method is based on mechanical characteristics of all relevant driving system components defined either experimentally or in manufacturers’ catalogues. The method is explained through defining the braking period duration on an example of a typical belt conveyor driving mechanism with a hydrodynamic coupling. The importance of the proposed method for the practice, and certain limitations of its application are pointed out

Determination of the strength performance of table frames

The objective of this study was to investigate relation of diameter of pilot hole and screw, and machining accuracy on withdrawal strengths of the screws and durability of the dining tables. For this purpose, fasteners and material types on the failure loads of dining table corner joints have been analyzed experimentally and statistically. Double ended thread bolts with different drilling regimes have been used as fastener types. Parallel investigation of rigidity and durability of tables, according to the current EN norms, and withdrawal capacities in accordance with the procedures described in ISO 9087 was performed. According to the results, it is concluded that the diameter of the drilled hole significantly influences the value of the withdrawal strengths of the screws. By analyzing the effect of drilling diameter on rigidity of tables, a statistically significant difference was determined. As the drilling diameter increases, the rigidity of the examined dining tables decrease

The analysis of influential parameters on calibration and feeding accuracy of belt feeders

Continual material feeding represents a process of great importance for process industries. Feeding with belt feeders represents one of the most common methods. Belt feeders are devices that require little space, they are not expensive and, most importantly, they do not interrupt material flow while feeding. Calibration of belt feeders, as well as other measuring devices, is a prerequisite for measuring and achieving a defined level of measurement accuracy. On the other hand, the defined level of measurement accuracy is often difficult to achieve in practice due to the multitude of factors that affect the operation of belt feeders. Existing mathematical models indicate a number of influential factors on measurement accuracy. The paper presents the measurement procedure performed on a belt feeder in laboratory conditions, with variable speeds and belt tensions and the known raised position of the measuring idler. Based on the obtained results, appropriate conclusions were made about the influences on calibration and measurement accuracy

Analiza dinamičkih parametara liftova sa rešenjem zbirne akvizicije podataka tokom eksperimentalnih istraživanja

Modelling of the dynamic behaviour of elevators with high lifting velocities (contemporary elevators in building construction and mine elevators) is a complex task and an important step in the design process and creating conditions for safe and reliable exploitation of these machines. Due to high heights and lifting velocities, the standard procedures for dynamic exploitation are not adequate. With the purpose of identifying the basic parameters of the dynamic model (stiffness and damping), a unique method was applied, based on experimental measures for a concrete elevator. Due to the verification of this procedure, the experiment was conducted on a mine elevator in RTB Bor, Serbia. Simulations of the dynamic behaviour of an empty and loaded cage are presented using the obtained computational-experimental results.Publishe