Gear Friction Research Articles

Position Control of a Flexible Arm Using a Dither Signal.

In this paper, we present the feedback control of a one-link flexible arm having reduction gear friction. Tip position control was very difficult in the case of large friction treated as an equivalent viscous friction. Experiments showed that tip position. feedback control was possible by using the dither signal. We investigated the influence of the dither amplitude on linearizing the nonlinear friction and the response of feedback control. The acceleration signal from the accelometer at the arm tip, like the signal from the strain gauge at the arm root, could use feedback control for the fundamental vibration mode.

Dynamic characteristics of a flexible arm with a reduction gear in the presence of nonlinear friction.

In this paper, we investigate the system dynamics of a one-link flexible arm affected by reduction gear friction. The natural frequency of the flexible arm lessens when the friction is larger and approaches that of a cantilever beam. The system damping changes with its natural frequency. Experiments were done in cases of both small and large frictions. The friction torque was nonlinear with viscous and Coulomb damping. Nonlinear and linearized calculations were shown to be in good agreement with experimental results.

Tip Position Control of a Flexible Robot Arm Considering the Reduction Gear's Friction

The reduction gear's friction strongly affects the dynamic characteristics of a one-link flexible robot arm. Experiments of open loop response by motor torque were performed in two cases of large and small values of the reduction gear's friction, and compared with simulation. The reduction gear's friction has both viscous and Coulomb aspects and can be approximately treated as an equivalent viscous friction. However, tip position control was very difficult in the case of large friction with an equivalent viscous friction. Experiments indicated that tip position feedback control was possible by using a dither signal and linearizing the non-linear friction.

Study on friction loss of internal gear drives. (Influence of pinion surface finishing, gear speed and torque).

This paper describes the friction loss of internal gear drives. Friction loss of internal gear drives was obtained by the oil immersion formula, which measures the temperature of lubricating oil for test gears, with varying pinion surface finishing. The gear friction loss ratios were between 0.28% and 0.84%. Then, statistical analysis of the experimental data was performed. It was found that the friction loss ratio of the internal gear is influenced most largely by gear speed, next by applied torque and slightly by pinion surface finishing. Furthermore, the friction loss of internal gear drives was calculated. The calculated value agreed approximately with the experimental data.

Studies on Limiting Load for Scoring and Frictional Loss of Hypoid Gears : Mainly Effects of Surface Treatments and Lubricating Oils

The limiting loads for scoring of three kinds of hypoid gears, which have different dimensions and are produced by different methods, are tested and compared with each other. Then the effects of surface treatments on the limiting loads for scoring of hypoid gears were tested and compared with the results of spur gears and roller tests. From the test results, it was made clear that the contact conditions of the test surfaces affect the limiting load for scoring. Further the frictional losses of hypoid gears were measured. The results show that the coefficient of friction of hypoid gears does not change by the kind of hypoid gears, but it depends upon their sliding velocities, and their empirical formula was obtained.

Ester base stocks

AbstractNatural esters contained in animal fats such as sperm oil, lard oil or in vegetable oils like rapeseed and castor oil have been the main lubricants from antiquity until the early 19th century. By 1890, petroleum oils had almost completely displaced natural oils. However, fatty products were still used as ‘oiliness agents’ to reduce friction and wear in bearings and gears lubricated by petroleum products. About 1937, Dr Herman Zorn of IG Farben Industrie in Germany began an intensive search for lubricants having the lubricating properties of natural oils, such as castor oil, while eliminating the tendency of these natural products to gel at low temperatures and to form gums and lacquers when used in engine operation. This paper describes the properties, types and applications of esters, as a main group of synthetic lubricants developed during the last four decades.

Gear friction coefficients and forces

Friction coefficients used to estimate the power loss in gear trains may also indicate surface failure. The existing theory that both tooth surfaces are subjected to equal tangential forces at the point of contact is found to be incorrect. Equations are developed to estimate the surface forces in terms of instantaneous coefficients of friction and gear parameters. It is shown that the maximum coefficient of friction during the meshing cycle is about a factor of 1.5 greater than the average value. The contribution of each gear wheel to the energy loss depends upon its polar moment of inertia and the gear ratio.

The correction of gear friction coefficients for backlash

The backlash of gears changes as the centre distance between the drive shafts varies causing changes in friction losses and drive efficiency. Changes in the friction coefficient due to changes in backlash may be estimated theoretically but it was found that they require to be multiplied by a factor of about 5 to correspond to experimentally determined values.

Dynamic Behavior of Gear Systems and Variation of Coefficient of Friction and Efficiency During the Engagement Cycle

In this work, the instantaneous and average efficiency and coefficient of friction of gear drives operating at low, medium, and moderately high speeds were experimentally and analytically investigated. First, using the gear testing machine specially designed for this type of investigation, the frictional losses in gearing during the engagement period were obtained experimentally. Based upon the obtained data, the values of efficiency and coefficient of friction were evaluated. A mathematical model simulating the gear testing machine was then developed and employed for the analysis of the dynamic behavior of the gear train system and analytical evaluation of gear system efficiency. The results obtained from this model were compared to those obtained directly from experiments, and a close correlation was achieved. The influence of such factors as diametral pitch, contact ratio, magnitude of transmitted load, and speed upon the efficiency of gear drives and the coefficient of friction in gearing was investigated. This investigation showed that the suggested method may be used to predict the dynamic behavior and efficiency of gear systems if a coefficient of friction is known or assumed. This investigation also gives some promise for power gear transmission design with improved capacity when scoring is the limiting criterion for capacity.

Effects of Inclination of Contact Line on Friction and Wear of Worm Gears

The performance of worm gears is affected by the inclination of the contact line. In case of worm gears, the problem is that the contact lines of worm gears are nearly parallel to the sliding directions of the worm and the contact conditions are severe. But it has not been clear how much the inclination of the contact line affects the characteristics of friction. The authors, therefore, investigated quantitatively the relation between the performance and the contact line, and studied a method of designing and manufacturing worm gears with higher performance. First, the authors analyzed the relative motion of tooth surfaces of worm and wheel and made a test apparatus on which the contact conditions could be simulated considerably well. Next, experiments were conducted by using the apparatus which indicated pure effects of this factor. Further, the authors investigated into the performance of side worm gears, and tried to clarify the relation between the performance and the contact line.

Effects of Inclination of Contact Line on Friction and Wear of Worm Gears

Effects of Inclination of Contact Line on Friction and Wear of Worm Gears

Influence of Steel Composition on Additive Performance

Coatings formed by lubricants on rubbing surfaces are believed to control the friction, wear, and fatigue of rolling contact bearings, gears, cams and tappets, and other heavily loaded components. To investigate the influence of steel composition on the formation of these surface coatings, friction, fatigue, and static immersion studies were conducted with two case-hardened steels (1018 and 4118) and five through-hardened materials (51100, 52100, M-50, 440-C, and Stellite #3). More surface coating formed on the low alloy steels than on the high alloy steels, with the composition of the oxide layer apparently being the controlling factor. The magnitude of the steel effect depended on the additive and the oxygen available. Elemental analyses of the surface coatings obtained with representative additives indicated that all contained significant organic fractions. Decomposition of the additive in the bulk oil was a necessary prerequisite for surface coating formation. Additive decomposition was generally prom...

A Mechanical Bower for Violins

A mechanical violin bower, giving a constant and continuous tone as required for recording by a crystal analyzer and sound level recorder, was made and used for measuring the “response” from violins. The report on response measurements was given at the Pittsburgh meeting. This report deals only with the mechanical bower. The bow, as now made, is composed of fine silk strands, loosely spun, and treated with a quick hardening lacquer. This hair-like thread is wound around two grooved pulleys many times, and the two ends are fastened together to form one continuous thread. Fine-toothed guides placed in front of the pulleys keep each strand in its proper place, and form a flat belt which performs like a regular violin bow. By a proper mounting of this belt on a frame, and by having a small motor to run it, the desired results are obtained. The frame holds a violin in the same manner as held by a violinist. A spring attached to the frame and violin support hold the pressure of the bow on the string at any desired constant value. The speed of the bow is regulated by an adjustable friction gear. The silk thread bow produces tones free from scratching noises, and comparable to those produced by a horse-hair bow.