A Practical Approach to Gear Design and Lubrication: A Review

New perspectives such as harmonic mean, contact patch as translating third body, contact form factor, and service load factor are introduced in spur gear design. The harmonic mean rule characterizes the physical and geometric properties of the contact patch. The contact patch is construed as a body in translation during gear teeth engagement. The contact form factor may be used to compare the load capability of different pressure angle standards. The service load factor captures the influence of different conventional rated load modification factors. Gear design analysis is separated into design sizing and design verification tasks. Design sizing and design verification formulas are formulated and presented in simplified forms for the Hertz contact and the Lewis root bending stresses. Three design Examples are presented through which it is demonstrated that results from the contact and root bending stress capacity models compare very favorably with American Gear Manufacturers Association (AGMA) results. The worst differences in the results are 5.23% for contact stress in design Example 2 and -6.59% for root bending stress for design Example 1. In design Example 3, it is shown that using pinion teeth number higher than 17 or 18 can leads to overall size reduction of gearset. This is important because of possible manufacturing cost reduction and higher mesh efficiency. Comparison of proposed approximations for mesh overload, internal overload and service load factors for design sizing and design verification tasks yielded very close results. The highest variance in the three design examples between proposed approximated and AGMA values of these parameters is -5.32%, indicating a slightly higher or conservative value for design sizing. Due to the very favorable results in comparison with AGMA values, the design approach appears to be an acceptable one in the preliminary design of spur gears because of simplicity and transparency.

2016

The contact ratio of spur gears is a critical parameter that affects gear drive performance. The influence of this parameter on the gear drive load capacity, efficiency, and noise and vibration is well known. There are studies (Refs. 1–3) dedicated to the analytical and experimental comparison of gears with low and high contact ratios. The dynamics and efficiency of high-contactratio asymmetric tooth gears were described in (Refs. 4–5). These publications explore contact ratio using a very similar evaluation approach. The gears are designed traditionally, based on a preselected basic (or generating) rack. This makes the contact ratio dependent on the number of teeth of mating gears, basic rack addendum, and X-shifts. A contact ratio is considered nominal, as it is designed without influence of deflections under the operating load. Comparable gear sets with different contact ratios are identical in numbers of teeth, tooth size, and modules. Such comparisons might have some theoretica...

SAE Technical Paper Series, 2005

This paper presents Direct Gear Design-an alternative method of analysis and design of involute gears which separates gear geometry definition from tool selection to achieve the best possible performance for a particular product and application. This method has successfully been applied for a number of automotive applications. Some examples will be presented at the end of the paper.

Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk, and with the teeth projecting radially, and although they are not straight-sided in form, the edge of each tooth thus is straight and aligned parallel to the axis of rotation. These gears can be meshed together correctly only if they are fitted to parallel axles. In this thesis, spur gears with different contact mating teeth are modeled in 3D modeling software CATIA. The first model of spur gear has 3 contact teeth and the second model has 5 contact teeth. Structural analysis is done on both the models determine the deformation, stresses of the gear. Fatigue analysis is done on to determine life, damage and safety factor and CFD analysis is done to determine pressure, velocity, mass flow rate. The material used for gear is steel. Analysis is done in ANSYS.

Tribology International, 2009

Gears are one of the most common mechanisms for transmitting power and motion and their usage can be found in numerous applications. Studies on gear teeth contacts have been considered as one of the most complicated applications in tribology. Depending on the application, the speed and load conditions of teeth may change triggering several types of failures on teeth surface such as wear, scuffing, micro-pitting and pitting. The above-mentioned faults influence changes in vibration and acoustic signals, due to changes in operating conditions such as increase in temperature and decrease in lubricant film thickness and specific film thickness. These abnormal changes result in cumulative effects on localised or distributed faults on load bearing surfaces of gears. Such damages cause reduction in tooth stiffness and severity of damage can be assessed by evaluating the same using vibration-based signals. This paper presents the results of experimental investigations carried out to assess wear in spur gears of back-to-back gearbox under accelerated test conditions. The studies considered the estimation of operating conditions such as film thickness and their effects on the fault growth on teeth surface. Modal testing experiments have been carried out on the same gear starting from healthy to worn out conditions to quantify wear damage. The results provide a good understanding of dependent roles of gearbox operating conditions and vibration parameters as measures for effective assessment of wear in spur gears.

Volume 8: 11th International Power Transmission and Gearing Conference; 13th International Conference on Advanced Vehicle and Tire Technologies, 2011

Aerospace applications require special procedures for component design and manufacturing. Spur gears of different designs, because of their simpler geometries, are used in vital units-transmissions of helicopters and alike aerospace vehicles. In this study, performances of various profile designs of previously researched low and high contact ratio spur gears with some realistic design parameters are studied. Effects of the realistic parameters of variable tooth pair stiffness, relief shape, and adjacent pitch error on Transmission Error (TE), tooth loads and root stresses are presented; composition of these parameters determines the efficiency of the gearbox assembly. Detail of minimization of tooth root stress through optimized/proper design of relief is described. More comprehensive comparison of the gear tooth profile design cases is done to be able to guide aerospace transmission designers for practical applications with realistic parameters for each of the design cases. A preference order is done among the design cases, depending on effect of some design parameters on the results such as tooth loads, tooth root stresses, TE curves and peak-to-peak TE values. NOMENCLATURE F transmitted load per unit facewidth, N/mm F d design load per unit facewidth, N/mm f normalized transmitted load f d normalized design load fopt normalized load at which smooth TE curve is obtained f t,max normalized maximum tooth load PE adjacent pitch error PL pivotal point of the double relief (see figure 1) TEpp peak-to-peak transmission error value ε α transverse contact ratio

The analytical method of gear design is calculation-intensive and it is usually difficult to achieve optimum backlash and interference-free involute profile that are required to generate geometrical compatibility in a pair of meshing gears when design procedure is entirely based on this method. Some amount of backlash is often required in the assembly of gears but excess backlash can lead to increase vibration and wear of the gear assembly. Also, interference-risk profile can result in undercutting of gear tooth. This paper optimized a spur external involute-profile gear by developing an application for the modeling of its geometrical compatibility using Matlab®. The application uses existing models to test for interference and a proposed model to determine effective backlash in a gear. The backlash values resulting from the application are more confined and the model is applicable to a wider range of modules suggested by American Gear Manufacturers Association. Simulation of the gear-set in Solidworks® for kinematic geometry presents an interference-free tooth contour and an effective backlash.

2018

Aerospace power transmission elements and units like gears and gearboxes are critical componentswhich need to be designed, manufactured and installed for a well performing fail-safe operation. Recent development of such components has seen rather satisfying improvements regarding different subjects like materials, design, manufacturing processes, surface treatment, etc. While cleanliness of material and special alloys help increase the strength of gear material, different design methods help reduce stresses under service loads. Similarly, different manufacturing methods help reduce surface burn like defects while material surface coatings help increase the resistance to wear and pitting like failures of both gears and bearings. Different examples of recent developments in aerospace gears and gearbox designs are provided in this paper to keep readers up to date with the aerospace power transmission technology. Keywords : aerospace, development, design, gear, gearbox, performance

Problem : Design a spur gear drive as a speed reducer for a compressor running at N 1 = 400 RPM, driven by a single cylinder engine of a P = 25 kW and N 2 = 1600 RPM. The available minimum centre distance is C min = 400 mm. The pinion and gear to be made of different material.