Swivel castor

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Castors on an office chair

A steering roller (also Castor roller or castor wheel called from English castor , variant of caster ) is pivotable about the vertical axis roller. Castors serve as non-powered support wheels that are able to align themselves independently to the current direction of movement. This makes them the counterpart to the fixed castors that cannot be swiveled and that can only move in one direction.

Castors are known primarily as components of office chairs , wheelchairs and shopping carts . Roller boards, which are used to transport furniture, for example, are equipped either with four swivel castors or with two swivel castors and two fixed castors.


Swivel castors usually consist of one or two rotatable castors, which are mounted on the object to be moved with an additional axis of rotation, but in a vertical direction. It is crucial for the function that the roller axis of rotation does not intersect with the vertical axis of rotation ( skewed wind ), but that they have a certain distance, also known as caster , so that the rollers are dragged along.

Depending on the material (e.g. air-filled rubber tires, solid rubber tires or hard plastics) and the load, the rollers are more or less deformed or not at all during use.

Exercise behavior

If the swivel castor is forced by the moving object in a direction that does not correspond to the current alignment of the castors, the wheel rotates around the vertical axis of rotation in the new direction of motion until the direction error is compensated. Then she rolls straight across the floor again. The rolling resistance is much lower on a hard floor than on a carpet, for example.

If the swivel castor is swiveled in a different direction while standing or when starting up, there is friction on the ground. This requires additional energy , especially with chair casters on carpets or when rubber castors are compressed by a heavy load, so that a larger rubber surface rubs on the floor. If the overrun is smaller (typical example: smaller chair castors), more force is required due to the law of levers, so that the object is temporarily more difficult to move. This annoying effect is particularly common in office chairs with castors with a diameter of 50 mm on carpets.

Alternatively, omnidirectional gears could mostly be used. These do not require any additional energy for alignment, but are structurally more complex and have poorer running properties due to their small compensation rollers.

Individual evidence

  1. a b Markus Wagner: Mechatronic directory . Teaching material Wagner, S. 557 ( limited preview in Google Book search).