Casters are generally classified into two types: RIGID and SWIVEL. The Rigid caster is simpler, and a basic Wheel is mounted on a set of Forks which does not turn. Thus, the Caster Wheel can only move in one axis, and the direction of movement it creates is always straight forward or backward. But it is not possible to steer Rigid Casters in any direction.
Is Rigidity Important
The Rigidity is an important Function. When two Rigid Casters are mounted on the Front of a Cart, with two Swivel Casters on the back, one has a Cart that is fully maneuverable, can move off in a straight line in front, but also turn around as much as 360 degrees when required. Steering becomes easy, with a combination such as this. Placement of the Casters will be like this: the Swivel casters should be mounted at every angle of the Cart and the Rigid at the middle point of the lengthiest part. If the Rigid are selected as ones that are bigger than the Swivel Casters, then the Cart can be turned with a balance on the corner casters with the two central Casters, off the floor. There are also applications where all four wheels on a Cart are Rigid, and, with a mounted push stick can turn the Cart into a Moving Pallet. This demonstrates how important it is to have both Rigid and Swivel Casters for perfect maneuverability of the Cart on which the Moveable Equipment is to be mounted.
The Rigid Carriers
Starting with wooden wheels since the existence of ancient civilizations, various materials have been used for manufacturing better and still better wheels. But the concept of Casters came only in 1876, when the inventor David A. Fisher invented the first metallic Caster. This was mainly meant to create moveable furniture. Prior to this, in the 1700’s, wooden casters were first used, but they were never fully satisfactory in performance, tending to clog on overload. Later, during the Georgian Period, from 1720 to 1760, iron plates were first used to hold Wood Casters, which were Rigid.
The Caster and Camber of Casters, especially if they are Rigid, need adjustment from time to time. If they are uneven, the vehicle will pull, but cause little tyre wear. But toe-ins, while not causing pull, can cause excessive tyre wear. When Casters are Rigid, this factor must be carefully considered before adjusting for caster and camber.