Increased efficiency of eccentric cycloidal engagement

Gears with eccentric cycloidal engagement have large gear ratios, small overall dimensions, low noise and vibration levels. A relatively low efficiency factor limits their use in transmissions mechanisms, where involute gearing with gear ratios up to 10 and high efficiency (over 0.98) are in demand. The power losses of the eccentric cycloidal engagement are caused by friction in the jointly working kinematic pairs, which are formed by the gear with at least half of the pins, and the latter form the pairs with axles or sockets in the housing. It is possible to reduce the power loss by reducing the number of jointly working kinematic gear-pin pairs, which is done by modifying the theoretical profile of the gear. The modified profile is obtained from the theoretical one by removing the tops of the protrusions so that the remaining parts of the profile provide a smooth transfer of the load to a given number of pins. The study introduces a method for calculating power losses and the efficiency of eccentric cycloidal gearing for theoretical and modified gear profiles. Findings of research show that the modification of the cycloidal gear makes it possible to reduce the power loss in the engagement by more than 60% and to increase the efficiency by 0.03 ... 0.04 without a significant decrease in the strength of the working surfaces. The obtained result confirmed the possibility of increasing the efficiency of eccentric cycloidal gearing for it to be used in transmissions of transport vehicles.

SYNTHESIS OF A LEVER-CAM MOTION TRANSDUCER FOR A ROTARY VANE PUMP

The article solves problem of synthesizing a lever-cam motion transducer that converts rotary motion of input shaft of a rotary pump into motion of its vanes required for volumetric pumping of gases and liquids. Analytical expressions for theoretical profile of cam of lever-cam transducer of the movement of rotary vane pump are obtained. The cam profile was built according to analytical expressions.

The Improvement of the Precision of the Archimedean Spiral Toothline Gear Cutting Mill

The precision of gears has a major influence on the quality of the transmission. If the gear cannot be finished by grinding, the precision of the generating tool becomes essential. Archimedean spiral toothline cylindrical gears are obtained by reciprocate meshing using a milling cutter built up by individual cutters, organized in groups. The profiles of edges must be realized with a minimal profile error. In order to ensure the quality and the precision of the meshed tooth surface, and also the profile constancy after re-sharpening, relief faces must be realized by a grinding relieving operation. A secondary effect of the kinematics of relieving end the spatial extent of the grinding wheel a post undercut results and this produces an inevitable profile error. The present paper discusses a possible grinding wheel setting that produces a maximum theoretical profile error under 1μm along the whole re-sharpening reserve of the cutter. The proposed setting can be realized on a classical relieving lathe.

The Numerical Evaluation Errors of the Geometric Model of the Straight Teethed Shaper Cutter

It is well known that straight teethed shaper cutters present a theoretical profile error. The side edges are situated on a common conical rack face with the result that they and their projection in the generating plane can’t be involute curves. The optimization of the cutter requires such a correlation of the edge defining parameters that the potential theoretical profile error is kept to the minimum possible. Thus the relevance of the edge equations is of great importance. This paper deals with the analysis of the edge equations, presenting two different forms of it. The comparison between the two different forms is realized by applying the numerical evaluation, by substitution of the edge point coordinates in the implicit equations of the originating surfaces. The obtained results present a difference of magnitude 10-E3. Finally, it can be concluded that the two forms of the edge equations cannot be used randomly but only in correlation with the goal proposed by the running application.

Controlling a demographic wave in defined contribution pension systems

In several developed countries, the baby boomers will come to retire in the next decades. This problem will threaten the sustainability and the intergenerational equity of mandatory pay-as-you-go pension systems because they will have to drain the “demographic wave” of retirees with a relatively small number of contributors. In this paper, we give the operating method developed on the basis of a general principle, which a defined contribution pension system, in a state of stable sustainability, should adopt to control these issues in the presence of a demographic wave. In the theoretical profile, our approach breaks and overcomes the classical juxtaposition between funded and pay-as-you-go pension schemes, carrying out the integration of the two financial methods.

Solution of the problem of the theoretical profile of non-dimensional speed on the thickness of the boundary layer at the turbulent flow in the boundary layer based on the solution of the differential equation of Abel of the second generation with the application of the Lambert function

В статье было найдено точное аналитическое решение дифференциального уравнения для касательных напряжений в турбулентном пограничном слое, являющихся частным случаем т.н. дифференциального уравнения Абеля второго рода, полученное с помощью специальной функции Ламберта, в то время как ранее считалось, что оно не разрешимо в квадратурах. Кроме этого, были получены ещё несколько важных решённых частных случаев этого уравнения. Полученные в статье аналитические решения преимущественно отличаются от имеющихся ранее либо численных, либо приближённых решений задачи. Полученное решение в безразмерном виде представляет собой теоретический профиль безразмерной скорости по толщине пограничного слоя при турбулентном течении в пограничном слое. An exact analytical solution of the differential equation for tangential stresses in a turbulent boundary layer, which is a special case of the so-called " of the Abel differential equation of the second kind, obtained with the help of the special Lambert function, whereas previously it was assumed that it is not solvable in quadratures. In addition, several more important solved special cases of this equation were obtained. The analytic solutions obtained in the paper are predominantly different from the previously available either numerical or approximate solutions of the problem. The solution obtained in dimensionless form is the theoretical profile of the dimensionless velocity along the thickness of the boundary layer for turbulent flow in the boundary layer.

Perfil Geomorfológico de Maturidade da Bacia do Rio Paracatu (Geomorphological maturity profile of the Paracatu river basin )

Apresenta-se uma avaliação da maturidade do perfil geomorfológico da Bacia do Rio Parcatu, afluente do Rio São Francisco. As relações entre comprimento e queda média dos seguimentos de rios para cada ordem pelo método de Strahler são analizados por leis empíricas para comparação com um perfil teórico de máximo equilíbrio. Os resultados demonstram que a Bacia do Rio Paracatu está próxima de seu estágio máximo de maturidade, embora ainda não o tenha alcançado completamente. A partir do estudo aplicado, são tecidas reflexões sobre as possibilidades de investigação de bacias hidrográficas com base em abordagens de entropia, meta-estabilidade, geovulnerabilidade e evolução geomorfológica. A B S T R A C T An assessment of the maturity of the geomorphological profile of the Paracatu River Basin, a tributary of the São Francisco River, is presented. The relationship between length and average stream fall for each order using the Strahler method is analysed using empirical laws for a comparison to a theoretical profile of maximum equilibrium. The results show that the Paracatu River Basin is close to its maximum stage of maturity, though it has not achieved it completely. Based on this study, reflections are made about the possibilities to study this watershed based on entropy approaches, metastability, geological vulnerability and geomorphological evolution. Keywords: Equilibrium profile, entropy, metastability, geovulnerability, geomorphological evolution, Paracatu.

The detection of reverse accumulation effect in the positron annihilation profile of stack of aluminum and silver foils

The implantation profile of positrons emitted from 22Na into a stack of aluminum and silver foils is the subject of the presented report. The characteristic dimple in the profile behind the Ag foil was detected. This effect arises from the differences in the linear absorption coefficient of aluminum and silver. The good agreement between the theoretical profile obtained within the multiscattering model and experimental one was achieved. The observed phenomenon can affect the positron annihilation characteristics measured for the inhomogeneous samples.