The Undercutting of Hobbed Spur Gear Teeth

1983 ◽  
Vol 105 (1) ◽  
pp. 122-128 ◽  
Author(s):  
R. G. Mitchiner ◽  
H. H. Mabie ◽  
H. Moosavi-Rad
Keyword(s):  
Spur Gear ◽  
Gear Teeth ◽  
Pressure Angle ◽  
Number Of Teeth ◽  
Minimum Number ◽  
Straight Portion ◽  
Base Circle ◽  
Tooth Flank ◽  
General Method

A general method is presented for the determination of the minimum number of teeth that can be cut in a spur gear without undercutting by a rounded-tooth tip hob. The minimum number of teeth to produce undercutting was investigated for three trochoid/tooth-profile relations: (1) trochoid tangent to the involute profile at the base circle, (2) trochoid tangent to a straight portion of the tooth flank, and (3) trochoid intersecting the involute profile at the base circle. It was found that in order to avoid undercutting, the minimum number of teeth cut into a gear occurs when the trochoid is tangent to the involute at the base circle. There is no set of hob parameters such that the trochoid intersects the involute profile at the base circle nor does the case of the trochoid being tangent to a straight flank exist. A set of figures representing the variation of the amount of undercutting versus the number of teeth, radius of hob-tooth tip, hob addendum, cutting pressure angle, and the corresponding derivatives are included for a typical gear.

Influence Gearing Parameters on the Tooth Deformation of Spur Gears

2015 ◽  
Vol 816 ◽  
pp. 27-30 ◽  
Author(s):  
Silvia Medvecká-Beňová ◽  
Peter Frankovský ◽  
Robert Grega
Keyword(s):  
Spur Gear ◽  
Spur Gears ◽  
Gear Teeth ◽  
Pressure Angle ◽  
Number Of Teeth ◽  
Basic Parameters

Gear teeth are deformed due to the load. The tooth deformation of spur gears is not constant for all examined teeth of gears. Tooth deformation is depends on the shape of the teeth, on the basic parameters of examined spur gear, such as the number of teeth, module gearing, pressure angle, gearing width, correction and modification of gearing.

The Determination of the Lewis Form Factor and the AGMA Geometry Factor J for External Spur Gear Teeth

1982 ◽  
Vol 104 (1) ◽  
pp. 148-158 ◽  
Author(s):  
R. G. Mitchiner ◽  
H. H. Mabie
Keyword(s):  
Form Factor ◽  
Spur Gear ◽  
Constant Stress ◽  
Direct Approach ◽  
Center Line ◽  
Geometry Factor ◽  
Gear Teeth ◽  
Definition Of ◽  
Line Intercept

This paper presents a simple and direct approach to the problem of the definition of the root profile for standard and nonstandard external spur gear teeth. Equations are developed for the location of the tooth center-line intercept at the constant-stress parabola. Also, the expression for the location of the point of tangency of the parabola with the root trochoid is given as well as the derivative of this expression. The AGMA Standards present charts of geometry factors, but the method by which these factors were determined is graphical and in some instances is not sufficiently accurate nor convenient to use. Although other investigators have considered this problem, their methods are either graphical or very complicated analytically. This treatment of the problem has been developed because it is not available in the open literature. Tables and charts are given for both Y and J factors for many profile variations.

Influence of Undercut on the Load Capacity for Involute Teeth With Small Pressure Angle

2003 ◽  
Author(s):  
Jose´ I. Pedrero ◽  
Mariano Arte´s ◽  
Carlos Garci´a-Masia´
Keyword(s):  
Load Capacity ◽  
Geometrical Parameters ◽  
Contact Ratio ◽  
Helical Gears ◽  
Small Pressure ◽  
Pressure Angle ◽  
Number Of Teeth ◽  
Minimum Number

The minimum number of teeth to avoid undercut on involute spur and helical gears depends on the pressure angle, among some other geometrical parameters. Higher number of teeth is required if the pressure angle becomes smaller. However, the contact ratio may be increased by reducing the pressure angle, which means the load is distributed along a longer line of contact. In many cases, even if undercut arises and teeth are weakened, both effects may result in higher load capacity for the gears. This paper presents a study on the influence of the pressure angle on the contact ratio, and through it on the length of contact and the load capacity, including a discussion on the condition to improve the load capacity by reducing the pressure angle beyond the undercut limit.

GEAR DESIGN

Engevista ◽  
2014 ◽  
Vol 16 (4) ◽  
pp. 313
Author(s):  
Florian Ion Petrescu ◽  
Relly Victoria Petrescu
Keyword(s):  
Inclination Angle ◽  
Normal Pressure ◽  
Original Method ◽  
Gear Design ◽  
Pressure Angle ◽  
Number Of Teeth ◽  
Minimum Number ◽  
Gear Efficiency ◽  
Driving Wheel ◽  
Tooth Inclination

The paper presents an original method to determine the efficiency of the gear, the forces of the gearing, the velocities and the powers. The originality of this method relies on the eliminated friction modulus. The first chapters are analyzing the influence of a few parameters concerning gear efficiency.  These parameters are:  z1   - the number of teeth for the primary wheel of gear; z2   - the number of teeth of the secondary wheel of gear; alpha0 - the normal pressure angle on the divided circle; beta - the inclination angle. With the relations presented in this paper, it can synthesize the gear’s mechanisms. Today, the gears are present everywhere, in the mechanical’s world (In vehicle’s industries, in electronics and electro-technique equipments, in energetically industries, etc.). Optimizing this mechanism (the gears mechanism), we can improve the functionality of the transmissions with gears. At the gear mechanisms an important problem is the interference of the teeth. To avoid the interference between teeth, we must know the minimum number of teeth of the driving wheel, in function of the pressure angle (normal on the pitch circle, alpha0), in function of the tooth inclination angle (beta), and in function transmission ratio (i). The last chapter presents an original method to make the geometric synthesis of the gear, having in view the minimum number of teeth of the driving wheel. The classical methods use many different relations to determine the minimum number of teeth of the driving wheel. By this paper we want to give a unitary method to determine the minimum number of teeth of the driving wheel 1, to avoid the interference between the teeth of the two wheels (of the gear).

Influence of Pressure Angle on Load Sharing Based Stresses in Asymmetric Normal Contact Ratio Spur Gear Drives

2013 ◽  
Vol 465-466 ◽  
pp. 1229-1233 ◽  
Author(s):  
P. Marimuthu ◽  
G. Muthuveerappan
Keyword(s):  
Parametric Design ◽  
Load Sharing ◽  
Spur Gear ◽  
Contact Model ◽  
Contact Ratio ◽  
Element Analysis ◽  
Normal Contact ◽  
Gear Teeth ◽  
Pressure Angle ◽  
Gear Drives

The aim of this paper is to investigate the influence of pressure angle on drive and coast sides in conventional design asymmetric normal contact ratio spur gear, considering the load sharing between the gear teeth pair. The multi pair contact model in finite element analysis is used to find the load sharing ratio and respective stresses. It has been found out that the predictions through multipoint contact model are in good agreement with the available literature. A unique Ansys parametric design language code is developed for this study. It is found that, the maximum fillet stress decreases up to the threshold point for drive side (35o) and coast side (25o) pressure angles, beyond this point it increases. The load share based maximum fillet and contact stresses are lower in the high pressure angle side than that of the low pressure angle side, when it is loaded at the critical loading points.

An Approach to the Determination of Spur Gear Tooth Root Fillet

2004 ◽  
Vol 126 (2) ◽  
pp. 336-340 ◽  
Author(s):  
V. B. Math ◽  
Satish Chand
Keyword(s):  
Gear Tooth ◽  
Spur Gear ◽  
Tooth Root ◽  
Base Circle ◽  
Point Of Intersection

The purpose of this paper is to present an approach for the determination of geometry of spur gear tooth root fillet. An equation is developed to determine the point of tangency of involute profile and root fillet on the base circle for a spur gear without undercutting and the point of intersection of root fillet and involute profile above the base circle for an undercut gear. Generation using a hob or rack type cutter with protuberance (increase in tooth thickness at the tip of the hob tooth) is also discussed.

An Evaluation of Stresses and Deflection of Spur Gear Teeth Under Strain

1974 ◽  
Vol 96 (1) ◽  
pp. 85-93 ◽  
Author(s):  
G. Chabert ◽  
T. Dang Tran ◽  
R. Mathis
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Static Load ◽  
Simple Calculation ◽  
Spur Gear ◽  
Spur Gears ◽  
The Finite Element Method ◽  
Gear Teeth ◽  
Pressure Angle ◽  
Maximum Stresses

This paper aims at an evaluation of the stresses induced by a static load applied to gear teeth. For spur gears of different ratios with 20-deg pressure angle and standard addendum proportions, the stresses and deflections are computed by the finite element method. Formulas are drawn allowing a simple calculation of the maximum stresses, and the results are compared with what is given by ISO and AGMA standards related to the strength of gear teeth.

Determination of Maximum Possible Contact Ratios for Spur Gear Drives With Small Number of Teeth

1995 ◽  
Author(s):  
M. A. Sahir Arikan
Keyword(s):  
Spur Gear ◽  
Number Of Teeth ◽  
Fillet Radius ◽  
Gear Drives

Abstract Maximum possible contact ratios which can be obtained by making use of x-zero gear pairs are determined for spur gear drives with small number of teeth. Rack cutter tip fillet radius and rack cutter geometry are taken into consideration in the analysis. Results for gear drives with various numbers of teeth and cut by rack cutters standardized by ISO and AGMA are given in forms of tables. Results are also compared with addendum modification coefficients recommended by ISO.

Automated Determination of Spur Gear Form Factors

1999 ◽  
Author(s):  
Thomas M. Overman ◽  
Terry E. Shoup
Keyword(s):  
Form Factor ◽  
Form Factors ◽  
Spur Gear ◽  
Spur Gears ◽  
Not Given ◽  
Microsoft Excel ◽  
Gear Teeth ◽  
Automated Determination

Abstract This paper presents a method for determining the form factor (J) and other form factors, which eliminates the need for manual table lookups to AGMA 908-B89 when designing spur gears. It provides an implementation of the algorithms presented in that earlier paper, in an easy-to-use spreadsheet module in Microsoft Excel 97. The implementation also allows form factor calculation for gear teeth combinations not given in the tables of 908-B89, thus eliminating the work of interpolating or extrapolating the tables in that earlier paper.

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