Caster

With steering rollers ( often referred to as castor wheels, ENGL. Castor ) refers to a pivotable about the vertical axis rollers.

Casters are not driven support wheels that are able to align itself automatically to the current direction of movement.

They are known primarily for their use in office chairs, wheelchairs and shopping carts.

Design and function

Casters are usually made of one or two rotatable rollers which are mounted with an additional axis of rotation, but in the vertical direction on the object to be moved. It is crucial for the function that the roller rotation axis not with the vertical axis of rotation intersects ( skewness ), but that they have each other at a certain distance, also called caster, so that the rollers are dragged. The steering roller urged by the moving object in a direction which does not correspond to the instantaneous orientation of the rollers, the wheel is rotated only about the vertical pivot axis in the new direction of movement, until the pointing error is compensated. During the reorientation of the direction of motion rollers for rubbing on the ground are - especially compressed rubber casters and chair casters on carpet ( rolling resistance ) - forced, for which additional energy is required. If the caster is smaller (typical example: smaller castor wheels ), is due to the law of the lever more force is needed so that the object is temporarily harder to move for the realignment of the wheels. This annoying effect is particularly frequently encountered in office chairs with chair castors of 50 mm diameter on carpets. Alternatively Allseitenräder could usually be used. These do not require additional energy to align, but are structurally complex and due to their small compensating rollers worsened run properties.