Search Results

The aspects of real engineering surfaces are discussed with regard to their three-dimensional nature. A review of potential uses of surface finish measurement methods are discussed for characterization of functional surfaces. The use of an optical-based system and measurement procedures are discussed as a means of differentiating surface roughness and its texture of functional surfaces by surface engineering parameters. Using an optical-based system and a set of specific measurement procedures, two functional surfaces with different roughness were analyzed to illustrate a typical surface topography evaluation. A simple sliding test is then utilized to show that a special finish produced by a proprietary finishing process can provide improved performance, as measured by wear differences, frictional properties and operating temperature of the system.

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.

Tapered roller bearings have proven successful in a number of high-volume automatic transaxle designs. Typically, tapered roller bearings are required to carry high loads generated by helical and hypoid gears. To meet the demands of a successful design, a number of factors must be considered in the selection and application of tapered roller bearings. This paper presents a discussion of these factors as well as results from Chrysler's transaxle testing. Selection of tapered roller bearings is based on the transmission duty cycle developed using load and speed histograms, gear data, size constraints, and life requirements. A bearing life analysis considering the total transaxle system is conducted using a sophisticated computer program. Various system effects are analyzed including the load/speed cycle, housing and shaft rigidity, lubrication, bearing setting, thermal effects, and bearing internal design.

This paper describes how one American steel producer has been able to provide value which has benefitted the automotive industry in the past and how it is striving to provide value now and intends to do so for many decades into the future. As an alloy steel bar and tube manufacturer serving the automotive industry since its infancy, the Company has had to conquer many serious problems and challenges over the years. The current challenge is doing business as an American company in today's growing global society. In addition to overcoming the obstacles created by today's business environment, it will take continued innovativeness to provide value to the customer. THE THOUGHT OF MAKING STEEL probably never entered the mind of Henry Timken, the Company's founder, who spent most of his career producing carriages, buggies, and wagons. He was more concerned with friction in the axle bearings and what he could do to reduce it.

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.

Improved fuel economy translates into significant savings over the life of a fleet vehicle. Aside from fuel cost savings, tighter emissions regulations require truck Original Equipment Manufacturers (OEMs) to improve the fuel economy of the products they bring to market. OEMs are dependent on Tier 1 suppliers for many systems which have a direct impact on vehicle fuel efficiency. Tier 1 suppliers are then dependent on sub-suppliers for components which affect the fuel efficiency of the system. Improvements in tapered roller bearing design and technology can significantly improve the fuel efficiency of driveline systems. This paper summarizes the improvement in bearing efficiency by applying advanced design and technology solutions. Analysis was used to predict the affect of design changes, leading to an optimized solution. Testing was performed to verify the improvement in bearing efficiency.

Advances in computer technology and the published results of extensive bearing research and empirical testing, have allowed designers to expand the traditional catalog approach and optimize the selection process for tapered roller bearings. This paper explores many of the factors influencing bearing selection where fatigue life is the primary concern, and describes how the Bearing Systems Analysis (BSA) approach, as used by The Timken Company, incorporates the effect of many of these environmental variables. Particular attention is paid to the formation and analysis of the load-speed spectrum, or histogram, and to the vital part it plays in the bearing selection process.

Increased size, payload and horsepower requirements are the trend in today's off-highway industry. This paper discusses the role of new anti-friction roller bearing technology in avoiding problems created by changing design considerations and the performance/cost/EPA triad currently squeezing designers and manufacturers of rubber tired earthmoving machinery. A comparison is made of bearing fatigue life determined by several methods including those derived from vehicle instrumentation and purely empirical criteria. Some common problems relating to the mounting and set up of large wheel bearings are also reviewed together with corresponding remedies.

Building quality into products requires the dedication of a total team that includes the product designer, process engineer, production personnel, process maintenance personnel, and a total process control system. Operating a process to a known state of capability and sustaining it must be recognized as a multiple functional task as technological changes occur. The understanding of how to manage with changed capability requires a team to understand the characteristics of both the process and the product which need to be monitored to assure that quality is built in. With the increased usage of computers into a manufacturing environment, the task of real time, preemptive management of a process can be achieved. Competitive advantage is a result of the improved capability of the total process that provides maximum yield, process up-time, and sustainability of results.

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.

This paper is focusing on the performance enhancement of the tapered roller bearings supporting the transfer shaft in a push belt type Continuously Variable Transmission (CVT). It also provides an objective comparison, based on test results, with the fixed/floating ball bearings alternative arrangement. The influence of different design parameters such as cup and cone race profile, roller length / diameter ratio, surface finish etc., is quantified in the analytical and experimental investigation. The bearings power loss is calculated and measured for operating conditions that are relevant in a vehicle fuel economy cycle. Additional specific aspects related to the use of tapered roller bearings, such as setting and mounting procedures, are discussed under similar considerations. The paper contains a system analysis of the transfer shaft interacting with the variator output shaft and with the differential.

Debris resistant bearings are being promoted by various bearing manufacturers as a solution for many contaminated lubrication environments. The baseline for such claims is often unclear for the bearing user and leaves questions as to how the information relates to specific field applications. In order to determine the benefits, if any, of these new product offerings and to assess their effectiveness, a standard method of evaluation is needed. An approach to satisfying this need is described and typical results are provided for several commercially available bearing products.