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Wheel rims and wheel hub bearings are critical components of Heavy Commercial Vehicle (HCV) suspension systems and are subjected to extensive fatigue loading throughout their operational life. Actual loading conditions on wheels are a combination of radial loads (vertical loads) and cornering loads (lateral loads) acting simultaneously and are directly influenced by payload and road conditions. Currently for Indian usage, there are test guidelines [1] only for separate uniaxial Radial Fatigue Test (RFT) and Cornering Fatigue Test (CFT) for wheel rims which might not represent realistic combined loading conditions, and no generic guidelines are available for testing of wheel hub bearings.

A comprehensive exercise for generation of wheel load database and spectrum of different categories of vehicles was carried out. The vehicles have been chosen so as to represent the best possible variation of vehicles all over the country. Dedicated Wheel Force Transducers (WFT) for all corners of all test vehicles have been utilized along with a host of traditional transducers at identified locations of the test vehicles. An exhaustive survey and data acquisition exercise has also been carried out in different geographical regions of India in order to determine the various attributes related to various types of vehicles, type of usage, driving patterns etc. Instrumented test vehicles have been run on identified routes and regions as deciphered from the survey, as well as on proving grounds. Detailed analysis of the test data from different categories vehicles has been carried out to determine the variation of wheel forces, moments and other vehicle durability parameters.

The demands for safe, reliable, lighter, energy efficient and competitively priced products put a new emphasis on predictability of rolling bearing performance. This has prompted designers and engineers to estimate bearing life and optimize the design by taking into account different market requirement. Estimation of actual dynamic bearing load and life for specified class of vehicle depends upon various factors such as usage pattern, vehicle Gross Vehicel Weight (GVW), type of roads, speed, driving pattern, geographical area, ambient temperature, acceleration etc. For estimation and prediction of life of the particular wheel bearing type it is required to identify and measure customer usage loads for different targeted markets. The measurement maps all the affecting parameters to arrive at a generalized duty cycle for bearings. A software tool is developed to predict the bearing life with these measured inputs and this enables designers to optimize bearing designs for target markets.

Suspension development is one of the key steps in a complete vehicle development program. Computer simulation and analysis tools such as Multi Body Dynamics (MBD) simulation are used to refine initial concept and suspension parameters. Later on when a physical prototype is available the suspension system can be experimentally optimized at vehicle level. In this paper a new methodology is proposed which integrates virtual and experimental tools so that design, development and validation of the suspension system is carried out in the early phase of the vehicle development cycle with actual suspension components and without the need of a vehicle prototype. With this new approach, the design of any critical suspension components such as dampers can be optimized at the vehicle level. The new approach consists of combining the actual physical components on loading rig in closed loop with vehicle dynamic model running in real time.

The braking systems for vehicles are undergoing a continuous development and improvement. The recent trend in motorcycle industry is to go for front disc brake system to have the advantage of less stopping distance and efficient braking over conventional drum brakes. In India the present practice of replacing the drum brake assembly with disc brake assembly, without redesigning of complete assembly of shock absorber may adversely affect its durability. This paper presents a detailed study made through service load data acquisition and analysis on the strength of front shock absorber tube. It was observed that with disc brake there is considerable increase in bending stress on the inner steel tube of shock absorber during braking. This paper highlights the comparison of strain distribution of the shock absorber tubes in disc brake and drum brake and concludes with a need for better design/material for shock absorber tube.