How Caster Failures Occur

There are two forces that continually act upon the caster. The direct force and the thrust force. These forces increase several times in magnitude whenever the caster receives a shock by hitting an object such as a door sill or by movement over a broken concrete surface. When this occurs practically the entire load is supported on the rear portion of the bearing due to the lead or offset built into the caster. Less than five steel balls in each race, the load and thrust race, carry the entire load. The thrust forces transmitted to the caster try to rip off the yoke in the counterclockwise direction. The rivet is the only thing that keeps the yoke intact with the top plate. The thrust force is transmitted to the front part of the kingpin. Again, one small area must do all the work. Overstressing results in the failure of the kingpin or bending of the metal around the kingpin to the point where the caster is no longer usable.