②Types of Casters & Wheel Guide

Grainger Editorial Staff

Maneuverability: Rigid Casters, swivel casters, Kingpinless Swivel Casters

When considering maneuverability, there are two basic kinds of caster: rigid casters and swivel casters.

· A rigid caster, also known as a fixed caster, is only able to roll forward and backward.

· A swivel caster has a raceway that allows the wheel to turn. The raceway is the cylindrical portion of a swivel caster containing the Ball Bearing track or tracks.

The traditional swivel caster design relies on a kingpin, which is a bolt or rivet that holds the raceway together. In this design, the kingpin is subject to high levels of stress, especially from the shocks that result when the equipment runs into obstacles or when heavy weights are dropped onto it. Because of this, the kingpin is a frequent failure point for traditional swivel casters.

A kingpinless caster is a special type of swivel caster with a raceway that is not held together by a bolt or rivet. Stress is distributed more evenly, which means that Kingpinless casters typically last longer than traditional swivel casters. They are recommended for powered towing applications because they can better withstand the stress caused by turning at speed. They are also better at handling shock forces such as rough terrain, obstacles and drops. However, kingpinless casters typically have a higher initial cost than traditional swivel casters.

Rigid and swivel casters can be used in different configurations for different applications:

· The most common caster configuration uses two parallel swivel casters and two parallel fixed casters. This gives the cart good turning and straight-line travel capabilities.

· Carts with only swivel casters are easy to move in any direction, which is useful for maneuvering lighter loads in tight locations, but they are hard to control. Swivel locks on two of the casters can make straight-line travel easier in this configuration.

· Four rigid casters in a diamond pattern can be a cost-effective arrangement. In this configuration, the central pair of casters on the left and right sides is typically slightly taller than the pair on the front and back sides. This makes the cart relatively easy to turn and pivot when the load is arranged over the central fixed casters.

Caster Wheel Materials and Dimensions: General Characteristics

Wheel materials and dimensions are important to consider when selecting casters. What a wheel is made from, and how large or small it is, influences how easily it moves (which in turn influences the ergonomics of the cart) , how durable it is, how much noise it makes and more.

Carts with wheels made from harder materials will generally be easier to get moving than those with wheels made from softer materials. That's because wheels made from harder materials have lower starting resistance, especially as the weight of the load increases. Starting resistance is the force the must be overcome to put the wheels in motion when they're at rest. Wheels made from harder materials also have lower rolling resistance, which means it takes less force to keep them moving at a constant speed.

Wheels made from softer materials are generally quieter and more comfortable to use because they transmit less vibration. They can also help preserve soft floor materials, such as hardwood or tile, which might be damaged by a harder wheel.

Comparing Wheel Hardness: Shore A, Shore D, Brinell

In general, rubber casters are softer than plastic casters, which are softer than metal casters. The hardness of specific casters is rated using three scales:

· The Shore A scale is used for softer rubbers.

· The Shore D scale is generally used for harder rubbers and plastics.

· The Brinell scale is used for metals, which are given a Brinell hardness number (BHN).

Within each scale, higher numbers indicate harder materials.