A caster is an undriven wheel that is designed to be mounted to the bottom of a larger object so that it enable that object to be easily moved. They are available in various sizes, and are commonly made of rubber, plastic, nylon, aluminum, or stainless steel.
Casters are found in numerous applications, including shopping carts, office chairs, and material handling equipment. High capacity, heavy duty casters are used in many industrial applications, such as platform trucks, carts, assemblies, and tow lines in plants. Generally, casters operate well on smooth and flat surfaces.
The diameter of a caster wheel affects how easily the caster moves over particulate, rough or irregular surfaces. Large diameter caster wheels are able to bridge gaps like between the floor and an elevator car. However, the larger the diameter of a caster wheel, the higher the caster support arm must be. Either the base of a low-hanging object must be lifted higher above the wheels, or the casters must hang out to the sides straddling the low-hanging supported object. While rotating around the vertical shaft, swivel caster wheels sweep out a space. Larger wheels require more of this space.
An aircaster is a pneumatic lifting device used to move heavy loads on flat, non-porous surfaces. It operates like hovercraft, as it uses a thin layer of air as a way to float a very small distance off the ground. Compressed air enters an airbag, and when the bag is filled it creates an airtight seal with the ground, and forces more air into the center of the torus, eventually causing the air to flow over the bag and to raise the load above the ground. Because air casters are virtually friction-free, the force required to move them is very low, often around one to five lbs. per 1,000 lbs. of weight. Air casters are also omni-directional, meaning they move with equal ease in any direction.