Search Results

This paper addresses a common problem associated with data analysis when a 1st failure in n, Weibull analysis is used. This is known among Weibull practitioners as the method of “sudden death”. Weibull analysis is a widely used reliability assessment and prediction technique. The “sudden death” method was initially developed to help reduce test time. In a “sudden death” test, k groups of n parts each are tested. In each test group testing is halted when the first failure occurs. This is referred to as the “first failure in n” and is usually detected by periodic inspection or by automatic/electronic test shut-off when the first failure occurs. It may happen that the first failure is not detected and there are two or more failures found upon inspection. In such cases the first failure time is lost since there are now 2 or more failures. If the second or third failure time is used as if it were the first failure time, overestimation of the reliability will result.

Power shift transmissions used in off-highway agricultural and construction tractors are subjected to rugged duty and the planetary type using needle bearings has proved its reliability when good design practices are followed. This pa per reviews the types of bearings, design data, and applications, and provides the formulas used in calculating speeds, loads, and shaft slopes in planet gears. Discussion of the subject matter by representatives of other companies in the industry conclude the paper.