Evaluation of failures in mechanical crankshafts of automobile based on expert opinion

• Expert opinions are required in taking decisions as regard reliability of crankshafts.
• The crankshaft failures can be determined by the conditions of use of vehicle.
• The failure pattern of crankshafts indicating stability of reliability.
• The choice of vehicles should be based on the conditions at which it will be operated.

In this study, mechanical crankshaft failures for automobiles are evaluated based on experts’ opinion. This was done using data obtained using techniques based on oral interviews and questionnaire administration on mechanical failure of crankshafts from the experts working in the areas of automobile maintenance and crankshafts reconditioning. The data collected were analyzed using statistical methods based on probability. With this technique, probability of failure for each category of automobiles namely private, commercial cars and buses were evaluated. The results obtained show that private cars had lowest failure rate at the initial stage while commercial buses had the highest failure rate. At later periods all categories of automobile crankshafts considered had their failure rates converged steadily with stable reliability. Application of 6-sigma continuous improvement tool to the process indicated a further reliability improvement through improved oil lubrication system, especially in the thrust bearing. This showed that increased enlightenment campaign among the various stakeholders in automobile industries will improve on the choice of reliable mechanical crankshafts.