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.
Since the design of involute splines and
their manufacture requires considerable
knowledge, not only of the basic properties of the involute profile, but also of various other elements which affect the spline fit and the sometimes complex principles underlying manufacturing and checking equipment, the question is frequently raised as to why the involute profile is given preference in designing splines over the seemingly simpler straight sided tooth profile.
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.
This article describes a new technique for the size determination of external Involute splines by using a span measuring method. It provides application performance information
demonstrating how this method and its
measurements correlate with the traditional spline ring gage sizing method.
Austempering heat treatments
(austenitizing followed by rapid cooling
to the tempering temperature) have been
applied to nodular irons on an experimental basis for a number of years, but commercial interest in the process has
only recently come to the surface.
As we approach the problem of hard gear processing, it is well to take a look at the reason for discussing it at this time. In our present economic atmosphere throughout the world, more and more emphasis is being placed upon efficiency which is dictated by higher energy costs.
The gear hobbing process is a generating type of production operation. For this
reason, the form of the hob tooth is
always different from the form of the
tooth that it produces.
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.
The effect of various lubricant factors on wormgear efficiency has been evaluated using a variety of gear types and conditions. In particular, the significant efficiency improvements
afforded by certain types of synthetic
lubricants have been investigated to determine the cause of these improvements. This paper describes broad wormgear testing, both in the
laboratory and in service, and describes the extent to which efficiency can be affected by
changes in the lubricant; the effects of viscosity, viscosity index improvers and, finally, synthetic lubricants are discussed. The work concludes that lubricant tractional properties
can play a significant role in determining gear efficiency characteristics.