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Engineering thermoplastics have greatly improved over the last decade. As a result of these improved performance characteristics and their becoming more cost competitive with traditional cage materials, their use in tapered roller bearing cages has become a reality. Design flexibility, lighter weight, resistance to handling damage, etc. make them attractive. This paper does point out certain characteristics of thermoplastics which must be taken into consideration thus influencing the choice of material and what environments they can endure. Compatibility with lubricants at elevated temperatures, growth from moisture and thermal expansion, solvent resistance, impact resistance, strength and dimensional stability are the major considerations. Thermoplastics have found a place in the tapered roller bearing family.

Environmental effects on fatigue and non-fatigue modes of tapered roller bearing damage are discussed. Primary emphasis is placed on the influence of load, speed, lubricant and temperature on the fatigue modes of damage. Effects of dissolved water in oil, traction fluids and fire resistant hydraulic fluids are included.

Debris particle contamination in lubricants has been identified as a major cause of premature bearing and gear failure, with accompanying costs in equipment downtime, warranty, and lost productivity. Various experimental and predictive methods have been developed to assist the design engineer in analysis and development of equipment that is less sensititive to such contamination. This paper provides an overview and new data comparing bearing life test results and predictive analysis methods for various tapered roller bearings operating under debris-contaminated conditions. As a baseline, some past work in these areas is briefly summarized and referenced. Recent work has refined one analytical method (using a surface characterization technique), correlated this method with bearing test lives in debris conditions, and pointed to design and manufacturing modifications in the bearings themselves, making the bearings live longer in debris-contaminated environments.

The tapered roller bearings employed in axle centers for the pinion support are critical components in determining the noise, fuel economy and reliability characteristics of the vehicle. They represent a relatively complex mechanical and tribological system, with special requirements from the stiffness, lubrication and heat transfer points of view. This paper brings a contribution to the investigation of the intricate dependency between design parameters, environmental factors and the resultant performance of a package bearing in an integral double cup configuration. Axial compactness, reduced weight, and superior rigidity are only few of the multiple advantages recommending this type of double row bearings for automotive driveline applications. Different aspects related to the tapered roller bearing setting are analyzed in a theoretical and experimental manner, also under the consideration of the manufacturing and assembly processes.

Contaminants that find their way into the lubrication system of a mechanism can have significant adverse effects on the useful life of the antifriction bearings in the application. This paper provides a discussion of the more common types of solid and liquid lubricant contaminants and the possible sources from which they originate, plus the different modes of premature bearing damage that can result. Some case histories of applications plagued with contaminated lubrication problems and the resulting difficulties encountered with bearing performance are also reviewed. These views are primarily limited to past experience with tapered roller bearings manufactured from case hardened materials.

Lubricant formulations and lubricant additives have been slanted heavily toward protecting gear concentrated contacts from galling and wear. Much of the performance differentiation of these lubricants has been dependent on highly accelerated standardized laboratory testing. The area of contact fatigue has played a less important role in shaping lubricant formulations, but new test results for several commercially available gear lubricants suggest this area warrants a closer examintion. The implications of these findings for equipment applications are discussed, and suggestions are made for ways to minimize or avoid potential detrimental performance effects.

Over the last ten years fatigue tests or wear tests, with and without debris present, have been performed on at least 11 different bearings including five sizes of ball bearings, five sizes of tapered roller bearings and one cylindrical bearing. After evaluating these tests, which include two series that were conducted in the author's laboratory, six factors have been identified that influence bearing performance when debris is present. These factors are debris (size and distribution), lubricant system, lubricant film thickness, levels of filtering, bearing materials and contact size. The results are summarized in table form.