Static Load and Capacity
Condition No.6 is the peak loading. In most applications this maximum load occurs momentarily. It is usually induced by shock of some form, rapid acceleration or deceleration. If the bearing is on mobile equipment, it may be desirable to compute the peak load which comes from traveling over rough surfaces. With vehicles moving at substantial speed, forces resulting from pitching and rolling must be considered. If the application is a crane-like device, consideration must be given to stopping a load while it's being caught before if reaches the ground. If the gearing is used for steering on a multiple wheeled device, consideration must be given to times when the wheel or truck sees more than its share of the load due to uneven terrain. In general, any time a machine element stops, starts, or changes direction, forces are produced which, if passed through the bearing, should be considered. The first consideration in sizing a bearing is making certain that the static raceway capacity is adequate to handle the peak loading. The static capacity must be considered regardless of whether the bearing is rotating or stationary when the peak load occurs. If the bearing is inadequate in capacity to handle these loads, indentations or grooves will be formed in the raceway. This is referred to as brinnelling. In some slow speed applications, slight brinnelling may not be harmful. However, overloads that produce indentations will lead to rough operation and very short bearing life. Overload may also, of course, lead to structural failure. In bearings subjected to continuous or frequent rotations, even slight brinnelling will shorten raceway life.

Dynamic Load and Capacity
Based on a load spectrum as shown above, a prediction can be made for the life of a specified bearing or, more precisely, it is possible to predict the probability that an individual bearing will survive a specified load spectrum. The dynamic raceway capacity deals with the resistance to fatigue flaking or spalling of the raceway and rolling element surfaces. The basic parameters were determined statistically after years of research into the relationship between contact stresses and material properties.

The L10 life of a bearing is the predicted life that 90% of a group of bearings will meet or exceed when subjected to the same loads and operating conditions. The average life for ball bearings will be approximately 5 times their L10 life and may be referred to as L50 life. If the above information on loading can be developed and stated along with the life requirement and dimensional limitations, Avon Engineering can promptly recommend bearings to meet these requirements. The design of the mounting structure has a substantial impact on the bearing and capacity and must also be considered. Please refer to the page on mounting structures.