# Not All Loads are Created Equal Part 1

When designing a bearing into an application, every engineer consistently needs to know about load capacity. While it’s easy to publish a general number, the type of load should really be considered first, and there are a lot of factors to consider for each type of load. In the first post of a two-part series, I will lay out the different types of surface loads and how each can be compensated for.

Over the years, I have had a lot of customers call and ask me, “How much load can your bearing handle?” For us, it is imperative that we understand the type of load before answering this question. Although we do have load ratings listed within our catalog, certain materials handle each type of load in a different way.

The other common misconception is that we just spit out a load in pounds or lbs. However, we measure load capacity by “psi" (pounds per square inch), which we calculate based upon the total surface area of the bearing that is being used.

Static loads are loads that act upon the bearing even when it is not in motion. More often than not, these loads are present within applications where the bearing does not move for a certain amount of time.

Although static loads might seem like they would present the least amount of problems or issues when designing bearings, there are still a multitude of issues that might arise if certain problems are not addressed. For example, if you are using a ball bearing with a constant static load, the load will essentially act as a “point load”, which would put an excess amount of pressure in one spot.

If the static load is acting upon the entire surface area of the bearing, then great! This means that those numbers listed in most bearing manufacturers catalog were correct. However, if the static load is only acting upon a small portion of the bearing as a “point load”, deformation of the part could occur if it is not accounted for.

Dynamic loads occur when a load acts upon a bearing while it’s in motion. With this, our biggest concern is the relationship between the load and the speed, since PV is a major factor in the lifetime and success of the bearing within an application.

When a dynamic load is present it is important to note that the higher the load, the lower the speed should be, and vice versa. Often, when we have really high dynamic loads, the motion is typically a slow pivot or rotation.