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Articles About helical twist


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1 Finish Hobbing Crowned Helical Gears without Twist (January/February 2006)

New tool from LMT-Fette provides combination of operations.

2 How Are You Dealing with the Bias Error in Your Helical Gears (May 2009)

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.

3 Calculation of Optimum Tooth Flank Corrections for Helical Gears (September/October 1988)

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.

4 Transmission Errors and Bearing Contact of Spur, Helical, and Spiral Bevel Gears (July/August 1990)

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.

5 Helical Gear Mathematics, Formulas and Examples Part II (July/August 1988)

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.

6 A Rational Procedure for Designing Minimum-Weight Gears (November/December 1991)

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.

7 Helical Gear Mathematics Formulas and Examples (May/June 1988)

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.

8 Improvement in Load Capacity of Crossed Helical Gears (January/February 1987)

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.

9 Helical Gears With Circular Arc Teeth: Simulation of Conditions of Meshing and Bearing Contact (July/August 1987)

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.

10 Grinding of Spur and Helical Gears (July/August 1992)

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.

11 Practical Optimization of Helical Gears Using Computer Software (May/June 1993)

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.

12 Predicted Scuffing Risk to Spur and Helical Gears in Commercial Vehicle Transmissions (November/December 2012)

AGMA925–A03 scuffing risk predictions for a series of spur and helical gear sets of transmissions used in commercial vehicles ranging from SAE Class 3 through Class 8.

13 Producing Profile and Lead Modifications in Threaded Wheel and Profile Grinding (January/February 2010)

Modern gearboxes are characterized by high torque load demands, low running noise and compact design. In order to fulfill these demands, profile and lead modifications are being applied more often than in the past. This paper will focus on how to produce profile and lead modifications by using the two most common grinding processes—threaded wheel and profile grinding. In addition, more difficult modifications—such as defined flank twist or topological flank corrections—will also be described in this paper.

14 New Developments in Gear Hobbing (March/April 2010)

Several innovations have been introduced to the gear manufacturing industry in recent years. In the case of gear hobbing—the dry cutting technology and the ability to do it with powder-metallurgical HSS—might be two of the most impressive ones. And the technology is still moving forward. The aim of this article is to present recent developments in the field of gear hobbing in conjunction with the latest improvements regarding tool materials, process technology and process integration.

15 New Guideless CNC Shaper for Helical Gears (March/April 1998)

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.

16 Influence of Gear Design on Gearbox Radiated Noise (January/February 1998)

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.

17 Generation of Helical Gears with New Surface Topology by Application of CNC Machines (January/February 1994)

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.

18 The Geometry of Helical Mesh (September/October 1997)

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.

19 Lubricant Jet Flow Phenomena in Spur and Helical Gears (January/February 1987)

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.

20 Controlling Tooth Loads In Helical Gears (March/April 1986)

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.

21 Gear Tooth Scoring Design Considerations for Spur and Helical Gearing (May/June 1985)

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.

22 Hobbing Precise, Uniform End Chamfers (March/April 2004)

The seemingly simple process of placing a uniform chamfer on the face ends of spur and helical gears, at least for the aerospace industry, has never been a satisfactory or cost effective process.

23 Gear Grinding Techniques Parallel Axes Gears (March/April 1985)

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.

24 Longitudinal Tooth Contact Pattern Shift (May 2012)

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.

25 Longitudinal Load Distribution Factor of Helical Gears (July/August 1985)

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.

26 Thermal Behavior of Helical Gears (May 2007)

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.

27 An Investigation of the Influence of Shaft Misalignment on Bending Stresses of Helical Gears with Lead Crown (November/December 2008)

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.

28 Computer Aided Design (CAD) of Forging and Extrusion Dies for the Production of Gears by Forming (January/February 1985)

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.

29 Determining the Shaper Cut Helical Gear Fillet Profile (September/October 2006)

This article describes a root fillet form calculating method for a helical gear generated with a shaper cutter.

30 Development of Conical Involute Gears (Beveloids) for Vehicle Transmissions (November/December 2005)

Conical involute gears (beveloids) are used in transmissions with intersecting or skewed axes and for backlash-free transmissions with parallel axes.

31 Pitting Load Capacity of Helical Gears (May 2008)

Influences of Load Distribution and Tooth Flank Modifications as Considered in a New, DIN/ISO-Compatible Calculation Method

32 Gear Finishing with a Nylon Lap (September/October 2005)

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.

33 Determining Power Losses in the Helical Gear Mesh (September/October 2005)

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

34 New Approach to Computerized Design of Spur and Helical Gears (January/February 2005)

Applying "Dynamic Block Contours" allows the designer to predict gear quality at the earliest stage of the design process.

35 Tooth Flank Corrections of Wide Face Width Helical Gears that Account for Shaft Deflections (January/February 2005)

This paper discusses the influence of tip relief, root relief, load modification, end relief and their combinations on gear stresses and transmission errors due to shaft deflections.

36 Gears for Nonparallel Shafts (September/October 1986)

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.