Helical Gears

GEAR TALK WITH CHUCK | 2018-04-17

How Many Teeth Do You Want?

Designing gears is somewhat of a mathematical puzzle. You have lots of interconnected factors to play with in hopes of finding the “best” overall s...

GEAR TALK WITH CHUCK | 2018-04-03

How Much Helix Angle?

The most obvious difference between a spur gear and a helical gear is the presence of that “helix” angle. Civilians will call them “straight-cut” a...

GEAR TALK WITH CHUCK | 2018-03-29

Back to Basics: Helical Gears

Most of the gearboxes I have been involved with use single helical gears. Its excellent power capacity per mesh makes it the default system for man...

GEAR TALK WITH CHUCK | 2018-03-06

Nothing Remains Constant

We cannot leave our lesson about tooth depths without covering bevel gears. There is a tendency to think of bevels and worms as being best left to ...

GEAR TALK WITH CHUCK | 2018-02-01

Understanding Spur Gears

Spur gears have been around “forever.” That ancient astronomical device recovered from the Mediterranean Sea a few years ago shows the antiquity an...

GEAR TALK WITH CHUCK | 2018-01-18

Avoiding the Potholes

No one becomes a gear expert overnight. You might be abruptly assigned the title by your employer, but it takes some time before you can really ful...

GEAR TALK WITH CHUCK | 2017-11-30

Still Pumped About Herringbones

I rambled on about herringbone gear in my last posting but still have more to share on these once commonplace gears. Today we’ll cover the use of c...

GEAR TALK WITH CHUCK | 2017-11-28

Department of Corrections

It was brought to my attention that the graphics used in my recent “herringbone” postings actually show double helical gears. I have a great suppor...

GEAR TALK WITH CHUCK | 2017-11-14

Herringbones 101

I try to avoid technical matters here in the blog on the grounds that we have an entire magazine to cover the “hard stuff.” Besides, very few topic...

GEAR TALK WITH CHUCK | 2017-04-19

Convergence in Design

One of the old car magazines I subscribe to has had an ongoing discussion on left-hand- threaded wheel studs. At one time the engineering community...

ASK THE EXPERT | 2016-08-01

In terms of the tooth thickness, should we use the formulation with respect to normal or transverse coordinate system? When normalizing this thickness in order to normalize the backlash (backlash parameter), we should divide by the circular pitch. Thus, when normalizing, should this circular pitch be defined in the normal or traverse coordinate system, depending on which formulation has been used? Is the backlash parameter always defined with respect to the tangential plane or normal plane for helical gears?

TECHNICAL ARTICLES | 2016-08-01

Transient EHL Analysis of Helical Gears

This paper addresses the lubrication of helical gears - especially those factors influencing lubricant film thickness and pressure. Contact between gear teeth is protected by the elastohydrodynamic lubrication (EHL) mechanism that occurs between nonconforming contact when pressure is high enough to cause large increases in lubricant viscosity due to the pressure-viscosity effect, and changes of component shape due to elastic deflection. Acting together, these effects lead to oil films that are stiff enough to separate the contacting surfaces and thus prevent significant metal-to-metal contact occurring in a well-designed gear pair.

TECHNICAL ARTICLES | 2015-09-01

Gear Tooth Surface Roughness of Helical Gears Manufactured by a Form Milling Cutter

Manufacturing involute gears using form grinding or form milling wheels are beneficial to hobs in some special cases, such as small scale production and, the obvious, manufacture of internal gears. To manufacture involute gears correctly the form wheel must be purpose-designed, and in this paper the geometry of the form wheel is determined through inverse calculation. A mathematical model is presented where it is possible to determine the machined gear tooth surface in three dimensions, manufactured by this tool, taking the finite number of cutting edges into account. The model is validated by comparing calculated results with the observed results of a gear manufactured by an indexable insert milling cutter.

GEAR TALK WITH CHUCK | 2014-03-26

Where Do Allowable Stresses Come From?

One of the most important aspects of a gear rating standard is the allowable stress charts. For spur and ...

INDUSTRY NEWS | 2013-09-25

KISSsoft Offers Fine Sizing for Worm Wheels and Crossed Helical Gears

For the calculation of worm wheels and crossed helical gears, fine sizing modules are now available (module ZD5 and ZE6). The KISSsoft fi...

TECHNICAL ARTICLES | 2012-10-01

Differential Gears

What are the manufacturing methods used to make bevel gears used in automotive differentials?

TECHNICAL ARTICLES | 2012-05-01

Longitudinal Tooth Contact Pattern Shift

After a period of operation, high-speed turbo gears may exhibit a change in longitudinal tooth contact pattern, reducing full face width contact and thereby increasing risk of tooth distress due to the decreased loaded area of the teeth. But this can be tricky—the phenomenon may or may not occur. Or, in some units the shift is more severe than others, with documented cases in which shifting occurred after as little as 16,000 hours of operation. In other cases, there is no evidence of any change for units in operation for more than 170,000 hours. This condition exists primarily in helical gears. All recorded observations here have been with case-carburized and ground gear sets. This presentation describes phenomena observed in a limited sampling of the countless high-speed gear units in field operation. While the authors found no existing literature describing this behavior, further investigation suggests a possible cause. Left unchecked and without corrective action, this occurrence may result in tooth breakage.

EVENTS | 2012-05-01

Technical Calendar

The complete Technical Calendar from the May 2012 issue of Gear Technology.

TECHNICAL ARTICLES | 2012-01-01

Accelerating Validation Testing

Bringing new or improved products to market sooner has long been proven profitable for companies. One way to help shorten the time-to-market is to accelerate validation testing. That is, shorten the test time required to validate a new or improved product.

TECHNICAL ARTICLES | 2011-08-01

Manufacturing Method of Large-Sized Spiral Bevel Gears in Cyclo-Palloid System Using Multi-Axis Control and Multi-Tasking Machine Tool

In this article, the authors calculated the numerical coordinates on the tooth surfaces of spiral bevel gears and then modeled the tooth profiles using a 3-D CAD system. They then manufactured the large-sized spiral bevel gears based on a CAM process using multi-axis control and multi-tasking machine tooling. The real tooth surfaces were measured using a coordinate measuring machine and the tooth flank form errors were detected using the measured coordinates. Moreover, the gears were meshed with each other and the tooth contact patterns were investigated. As a result, the validity of this manufacturing method was confirmed.

VOICES | 2011-06-01

Gear Expo: Changing with the Times

AGMA president Joe T. Franklin Jr. talks about how the AGMA Gear Expo has grown and changed since its beginnings as a table-top show in 1987.

TECHNICAL ARTICLES | 2010-11-01

Zerol Bevel Gears: Tribology Aspects in Angular Transmission Systems, Part III

Zerol bevel gears are the special case of spiral bevel gears with a spiral angle of 0°. They are manufactured in a single-indexing face milling process with large cutter diameters, an extra deep tooth profile and tapered tooth depth.

EVENTS | 2010-11-01

Technically Speaking, a Huge Success

A recap of the AGMA 2010 Fall Technical Meeting.

FEATURE ARTICLES | 2010-08-01

Building Repeat Business: What Gear Buyers Really Want from Gear Manufacturers

In this article, gear buyers have been given an opportunity to discuss quality, value, customer service and how gear manufacturers can improve business practices.

TECHNICAL ARTICLES | 2009-05-01

How Are You Dealing with the Bias Error in Your Helical Gears

This paper initially defines bias error—the “twisted tooth phenomenon.” Using illustrations, we explain that bias error is a by-product of applying conventional, radial crowning methods to produced crowned leads on helical gears. The methods considered are gears that are finished, shaped, shaved, form and generated ground. The paper explains why bias error occurs in these methods and offers techniques used to limit/eliminate bias error. Sometimes, there may be a possibility to apply two methods to eliminate bias error. In those cases, the pros/cons of these methods will be reviewed.

TECHNICAL ARTICLES | 2008-11-01

An Investigation of the Influence of Shaft Misalignment on Bending Stresses of Helical Gears with Lead Crown

In this study, the combined influence of shaft misalignments and gear lead crown on load distribution and tooth bending stresses is investigated. Upon conclusion, the experimental results are correlated with predictions of a gear load distribution model, and recommendations are provided for optimal lead crown in a given misalignment condition.

TECHNICAL ARTICLES | 2007-06-01

Nonstandard Tooth Proportions

With the right selection of nonstandard center distance and tool shifting, it may be possible to use standard tools to improve the gear set capacity with a considerable reduction in cost when compared to the use of special tools.

TECHNICAL ARTICLES | 2007-05-01

Thermal Behavior of Helical Gears

An experimental effort has been conducted on an aerospace-quality helical gear train to investigate the thermal behavior of the gear system as many important operational conditions were varied.

INDUSTRY NEWS | 2007-01-02

Gleason’s New Threaded Grinder Optimizes Fine Finishing of Hard Spur and Helical Gears

Gleason’s new Genesis 130TWG High Speed Threaded Wheel Grinder features a new design that reduces floor space requirements and impro...

INDUSTRY NEWS | 2005-11-01

Industry News

The complete Industry News from the November/December 2005 issue of Gear Technology.

TECHNICAL ARTICLES | 2005-09-01

Gear Finishing with a Nylon Lap

The objective of this research is to develop a new lapping process that can efficiently make tooth flanks of hardened steel gears smooth as a mirror.

TECHNICAL ARTICLES | 2005-09-01

Determining Power Losses in the Helical Gear Mesh

This article reviews mathematical models for individual components associated with power losses, such as windage, churning, sliding and rolling friction losses.

PRODUCT NEWS | 2003-05-01

Product News

Complete Product News for May/June 2003.

INDUSTRY NEWS | 2001-01-01

The Basics of Spiral Bevel Gears

This article also appears as Chapter 1 in the Gleason Corporation publication "Advanced Bevel Gear Technology." Gearing Principles in Cylindrical and Straight Bevel Gears The purpose of gears is to transmit motion and torque from one shaft to another. That transmission normally has to occur with a constant ratio, the lowest possible disturbances and the highest possible efficiency. Tooth profile, length and shape are derived from those requirements.

TECHNICAL ARTICLES | 1999-09-01

Gear Grinding With Dish Wheels

The grinding of gears with dish wheels (Maad type grinding machines) is widely viewed as the most precise method of gear grinding because of the very short and simple kinematic links between the gear and the tool, and also because the cutting edges of the wheels represent planar surfaces. However, in this grinding method, depending on the parameters of the gears and one of the adjustments (such as the number of teeth encompassed by the grinding wheels), so-called overtravel at the tip or at the root of the teeth being ground generally occurs. When this happens, machining with only one wheel takes place. As a result, the profile error and the length of the generating path increases while productivity decreases.

FEATURE ARTICLES | 1998-03-01

New Guideless CNC Shaper for Helical Gears

Product announcements so often trumpet minor, incremental advances with works like "revolutionary" and "unique" that even the best thesaurus can fail to offer a fresh alternative to alert the reader when something really innovative and important is introduced. In the case of Mitsubishi's new CNC gear shaper, the ST25CNC, both terms apply.

TECHNICAL ARTICLES | 1998-01-01

Influence of Gear Design on Gearbox Radiated Noise

A major source of helicopter cabin noise (which has been measured at over 100 decibels sound pressure level) is the gearbox. Reduction of this noise is a NASA and U.S. Army goal. A requirement for the Army/NASA Advanced Rotorcraft Transmission project was a 10 dB noise reduction compared to current designs.

TECHNICAL ARTICLES | 1997-09-01

The Geometry of Helical Mesh

In 1961 I presented a paper, "Calculating Conjugate Helical Forms," at the semi-annual meeting of the American Gear Manufacturers Association (AGMA). Since that time, thousands of hobs, shaper cutters and other meshing parts have been designed on the basis of the equations presented in that paper. This article presents the math of that paper without the formality of its development and goes on to discuss its practical application.

TECHNICAL ARTICLES | 1994-01-01

Generation of Helical Gears with New Surface Topology by Application of CNC Machines

Analysis of helical involute gears by tooth contact analysis shows that such gears are very sensitive to angular misalignment leading to edge contact and the potential for high vibration. A new topology of tooth surfaces of helical gears that enables a favorable bearing contact and a reduced level of vibration is described. Methods for grinding helical gears with the new topology are proposed. A TCA program simulating the meshing and contact of helical gears with the new topology has been developed. Numerical examples that illustrate the proposed ideas are discussed.

TECHNICAL ARTICLES | 1993-05-01

Practical Optimization of Helical Gears Using Computer Software

The aim of this article is to show a practical procedure for designing optimum helical gears. The optimization procedure is adapted to technical limitations, and it is focused on real-world cases. To emphasize the applicability of the procedure presented here, the most common optimization techniques are described. Afterwards, a description of some of the functions to be optimized is given, limiting parameters and restrictions are defined, and, finally, a graphic method is described.

TECHNICAL ARTICLES | 1992-07-01

Grinding of Spur and Helical Gears

Grinding is a technique of finish-machining, utilizing an abrasive wheel. The rotating abrasive wheel, which id generally of special shape or form, when made to bear against a cylindrical shaped workpiece, under a set of specific geometrical relationships, will produce a precision spur or helical gear. In most instances the workpiece will already have gear teeth cut on it by a primary process, such as hobbing or shaping. There are essentially two techniques for grinding gears: form and generation. The basic principles of these techniques, with their advantages and disadvantages, are presented in this section.

TECHNICAL ARTICLES | 1991-11-01

A Rational Procedure for Designing Minimum-Weight Gears

A simple, closed-form procedure is presented for designing minimum-weight spur and helical gearsets. The procedure includes methods for optimizing addendum modification for maximum pitting and wear resistance, bending strength, or scuffing resistance.

TECHNICAL ARTICLES | 1990-07-01

Transmission Errors and Bearing Contact of Spur, Helical, and Spiral Bevel Gears

An investigation of transmission errors and bearing contact of spur, helical, and spiral bevel gears was performed. Modified tooth surfaces for these gears have been proposed in order to absorb linear transmission errors caused by gear misalignment and to localize the bearing contact. Numerical examples for spur, helical, and spiral bevel gears are presented to illustrate the behavior of the modified gear surfaces with respect to misalignment and errors of assembly. The numerical results indicate that the modified surfaces will perform with a low level of transmission error in non-ideal operating environments.

TECHNICAL ARTICLES | 1989-09-01

Gear Grinding Fundeamentals

This article deals with certain item to be taken into consideration for gear grinding, common problems that arise in gear grinding and their solutions. The discussion will be limited to jobbing or low-batch production environments, where experimental setup and testing is not possible for economic and other reasons.

TECHNICAL ARTICLES | 1989-03-01

The Wafer Shaper Cutter

In 1985 a new tooling concept for high volume gear production was introduced to the gear manufacturing industry. Since then this tool, the wafer shaper cutter, has proven itself in scores of applications as a cost-effective, consistent producer of superior quality parts. This report examines the first high-production installation at the plant of a major automotive supplies, where a line of twenty shapers is producing timing chain sprockets.

TECHNICAL ARTICLES | 1988-09-01

Calculation of Optimum Tooth Flank Corrections for Helical Gears

The load carrying behavior of gears is strongly influenced by local stress concentrations in the tooth root and by Hertzian pressure peaks in the tooth flanks produced by geometric deviations associated with manufacturing, assembly and deformation processes. The dynamic effects within the mesh are essentially determined by the engagement shock, the parametric excitation and also by the deviant tooth geometry.

TECHNICAL ARTICLES | 1988-07-01

Helical Gear Mathematics, Formulas and Examples Part II

The following excerpt is from the Revised Manual of Gear Design, Section III, covering helical and spiral gears. This section on helical gear mathematics shows the detailed solutions to many general helical gearing problems. In each case, a definite example has been worked out to illustrate the solution. All equations are arranged in their most effective form for use on a computer or calculating machine.

TECHNICAL ARTICLES | 1988-05-01

Helical Gear Mathematics Formulas and Examples

TECHNICAL ARTICLES | 1987-07-01

Helical Gears With Circular Arc Teeth: Simulation of Conditions of Meshing and Bearing Contact

Circular arc helical gears have been proposed by Wildhaber and Novikov (Wildhaber-Novikov gears). These types of gears became very popular in the sixties, and many authors in Russia, Germany, Japan and the People's Republic of China made valuable contributions to this area. The history of their researches can be the subject of a special investigation, and the authors understand that their references cover only a very small part of the bibliography on this topic.

TECHNICAL ARTICLES | 1987-01-01

Lubricant Jet Flow Phenomena in Spur and Helical Gears

In the gearing industry, gears are lubricated and cooled by various methods. At low to moderate speeds and loads, gears may be partly submerged in the lubricant which provides lubrication and cooling by splash lubrication. With splash lubrication, power loss increases considerably with speed. This is partially because of churning losses. It is shown that gear scoring and surface pitting can occur when the gear teeth are not adequately lubricated and cooled.

TECHNICAL ARTICLES | 1987-01-01

Improvement in Load Capacity of Crossed Helical Gears

Crossed helical gear sets are used to transmit power and motion between non-intersecting and non-parallel axes. Both of the gears that mesh with each other are involute helical gears, and a point contact is made between them. They can stand a small change in the center distance and the shaft angle without any impairment in the accuracy of transmitting motion.

TECHNICAL ARTICLES | 1986-09-01

Gears for Nonparallel Shafts

Transmission of power between nonparallel shafts is inherently more difficult than transmission between parallel shafts, but is justified when it saves space and results in more compact, more balanced designs. Where axial space is limited compared to radial space, angular drives are preferred despite their higher initial cost. For this reason, angular gear motors and worm gear drives are used extensively in preference to parallel shaft drives, particularly where couplings, brakes, and adjustable mountings add to the axial space problem of parallel shaft speed reducers.

TECHNICAL ARTICLES | 1986-03-01

Controlling Tooth Loads In Helical Gears

Helical gears can drive either nonparallel or parallel shafts. When these gears are used with nonparallel shafts, the contact is a point, and the design and manufacturing requirements are less critical than for gears driving parallel shafts.

TECHNICAL ARTICLES | 1985-07-01

Longitudinal Load Distribution Factor of Helical Gears

The contact lines of a pair of helical gears move diagonally on the engaged tooth faces and their lengths consequently vary with the rotation of the gears.

TECHNICAL ARTICLES | 1985-05-01

The Design and Manufacture of Machined Plastic Gears

The use of plastic gearing is increasing steadily in new products. This is due in part to the availability of recent design data. Fatigue stress of plastic gears as a function of diametral pitch, pressure angle, pitch line velocity, lubrication and life cycles are described based on test information. Design procedures for plastic gears are presented.

TECHNICAL ARTICLES | 1985-05-01

Gear Tooth Scoring Design Considerations for Spur and Helical Gearing

High speed gearing, operating with low viscosity lubricants, is prone to a failure mode called scoring. In contrast to the classic failure modes, pitting and breakage, which generally take time to develop, scoring occurs early in the operation of a gear set and can be the limiting factor in the gear's power capability.

TECHNICAL ARTICLES | 1985-03-01

Gear Grinding Techniques Parallel Axes Gears

The fundamental purpose of gear grinding is to consistently and economically produce "hard" or "soft" gear tooth elements within the accuracy required by the gear functions. These gear elements include tooth profile, tooth spacing, lead or parallelism, axial profile, pitch line runout, surface finish, root fillet profile, and other gear geometry which contribute to the performance of a gear train.

TECHNICAL ARTICLES | 1985-01-01

Computer Aided Design (CAD) of Forging and Extrusion Dies for the Production of Gears by Forming

Material losses and long production times are two areas of conventional spur and helical gear manufacturing in which improvements can be made. Metalforming processes have been considered for manufacturing spur and helical gears, but these are costly due to the development times necessary for each new part design. Through a project funded by the U.S. Army Tank - Automotive Command, Battelle's Columbus Division has developed a technique for designing spur and helical gear forging and extrusion dies using computer aided techniques.

VOICES | 1985-01-01

Dear Editor

Congratulations from a number of readers who are impressed with the new magazine.

Helical Gears

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