Effect of geometry and operating conditions on spur gear system power loss

The results of an analysis of the effects of spur gear size, pitch, width, and ratio on total mesh power loss for a wide range of speeds, torques, and oil viscosities are presented. The analysis uses simple algebraic expressions to determine gear sliding, rolling, and windage losses and also incorporates an approximate ball bearing power loss expression. The analysis shows good agreement with published data. Large diameter and fine pitched gears had higher peak efficiencies but low part load efficiency. Gear efficiencies were generally greater than 98 percent except at very low torque levels. Tare (no-load) losses are generally a significant percentage of the full load loss except at low speeds

Efficiency of nonstandard and high contact ratio involute spur gears

A power loss prediction was extended to include involute spur gears of nonstandard proportions. The method is used to analyze the effects of modified addendum, tooth thickness, and gear center distance in addition to the parameters previously considered which included gear diameter, pitch, pressure angle, face width, oil viscosity, speed, and torque. Particular emphasis was placed on high contact ratio gearing (contact ratios greater than two). Despite their higher sliding velocities, high contact ratio gears are designed to levels of efficiency comparable to those of conventional gears while retaining their advantages through proper selection of gear geometry

Spur-Gear-System Efficiency at Part and Full Load

A simple method for predicting the part- and full-load power loss of a steel spur gearset of arbitrary geometry supported by ball bearings is described. The analysis algebraically accounts for losses due to gear sliding, rolling traction, and windage in addition to support-ball-bearing losses. The analysis compares favorably with test data. A theoretical comparison of the component losses indicates that losses due to gear rolling traction, windage, and support bearings are significant and should be included along with gear sliding loss in a calculation of gear-system power loss

Comparison of spur gear efficiency prediction methods

The predictions of five spur-gear efficiency calculation methods were compared with three sets of test data using different gear geometries. The data and the analysis methods were limited to jet lubricated, ground, spur gears. The data covered a range in pitch line velocity to 1 to 20 m/sec (200 to 4000 ft/min) and K-load factor range of 17 to 1600

Design of Spur Gears for Improved Efficiency

A method to calculate spur gear system loss for a wide range of gear geometries and operating conditions was used to determine design requirements for an efficient gearset. The effects of spur gear size, pitch, ratio, pitch line velocity and load on efficiency were determined. Peak efficiencies were found to be greater for large diameter and fine pitched gears and tare (no-load) losses were found to be significant

Does International Trade Synchronize Business Cycles?

This paper studies the relationship between international trade and output fluctuations. The authors find evidence that the business cycles of countries that are more open to international trade are more likely to by synchronized with the business cycles of their major trading partners. A detailed study of the South Korean case shows that while business cycles are related to openness, the diversification of export destinations seems to weaken these links. The authors find no relationship between openness and output volatility.Coherence; Volatility; Business Cycles; Time Series

CO adsorption on (111) and (100) surfaces of the Pt sub 3 Ti alloy. Evidence for parallel binding and strong activation of CO

The CO adsorption on a 40 atom cluster model of the (111) surface and a 36 atom cluster model of the (100) surface of the Pt3Ti alloy was studied. Parallel binding to high coordinate sites associated with Ti and low CO bond scission barriers are predicted for both surfaces. The binding of CO to Pt sites occurs in an upright orientation. These orientations are a consequence of the nature of the CO pi donation interactions with the surface. On the Ti sites the orbitals donate to the nearly empty Ti 3d band and the antibonding counterpart orbitals are empty. On the Pt sites, however, they are in the filled Pt 5d region of the alloy band, which causes CO to bond in a vertical orientation by 5 delta donation from the carbon end

Evaluation of a high performance, fixed-ratio, traction drive

A test program was initiated to evaluate the key operational and performance factors associated with the Nasvytis multiroller concept. Two sets of Nasvytis drives, each of slightly geometry, were parametrically tested on a back to back test stand. Initial results from these tests are reported. One of these units was later retrofitted to the power turbine of an automotive gas turbine engine and dynamometer tested