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Fig. 6. Proposed redesign.

6. It is believed that the first two changes would have the greatest effect and if made it would avoid
the need for specifying a stronger and inevitably a more expensive material.
It is not thought likely that any of the suggested changes would add significantly to total machining
costs.

7. CONCLUSIONS
Clearly, the detail design of the wheel shaft hub assembly is found wanting. Even when operating
under ideal circumstances, the predicted life is relatively short and leaves no margin for vehicle
misuse, a distinct possibility with such an application. Recognition of the vulnerability to fatigue of
a rotating component subjected to bending and torsion loading should lead automatically to taking
fatigue preventative measures at the detail design stage. It is essential to avoiding having high stress
concentrations at locations of greatest nominal stress if at all possible. Even taking relatively simple
measures, such as those described, will greatly improve component reliability without affecting
manufacturing costs and prolong the life of components.

REFERENCES
1. Deutschman, A. D., Michels, W. 1. and Wilson, C. E., Machine Design-Theory and Practice, Collier McMillan, New
York, 1975.
2. Juvinall, R. C. and Marshek, K. M., Fundamentals qfhfachine Component Design, J. Wiley, 1991.
3. Shigley, J. E., Mechanical Engineering Design, McGraw-Hill, 1986.
4. Ryder, G. H., Strength of Materials, Macmillan Press Limited, 1969.