Considerations for Casters
The wrong set of casters on a cart can significantly increase the force exertions required by an operator. Luckily, there are a number of different caster and wheel combinations available that can help push you straight away from those high MSD risks. Here are some questions to ask your vendor when selecting casters to ensure they’ll be the best fit for your operation.
What surface will the cart be used on?
The surface type the cart is used on has a direct correlation with the ideal durometer, or hardness, of the wheel which is then in direct correlation with the push/pull force of the cart. The trick to remember with both is when you want to decrease your push or pull force, the harder the wheel and surface, the lower the force. This means that if you have a very hard surface, you have the option to easily use a high durometer wheel such as iron or steel. However, when the ground is softer, textured, or uneven, a lower durometer wheel such as rubber or polyurethane, is the better option to maneuver the rougher terrain. Unfortunately, the softer wheel increases force requirements, resulting in a compromise between the ease of push/pull on the carting surface and the reliability of the wheel itself.
What size of wheel does the cart need?
Size of wheel is very important in limiting push/pull force. The bigger the caster the lower the force. A wheel with diameter between 6″ and 8″ is highly recommended. However, a large wheel can sometimes infringe on height restrictions depending on the purpose of the cart and its existing height. A wheel that is 6″ to 8″ tends to maintain a wheel and caster combination height of less than 10″ total, allowing for ease in push/pull forces without creating a large height concern.
What is your load capacity and push/pull criteria?
The variation in casters for a high-capacity cart vs. a low-capacity cart is dramatically different. Harder casters are required to bear the weight of a higher capacity. Therefore, a forged steel or iron caster is a better fit than an air-filled rubber or soft urethane caster commonly used for lower capacity loads.
Likewise, a cart with a high capacity generally requires a caster configuration with two swivel and two rigid casters, with the consideration of adding two additional casters. A lighter capacity cart might be outfitted with 4 rigid casters, or a diamond shape with center point pivot. Other factors to consider include the directions that the cart will be pushed. If it is moving forward in a consistently straight manner, a 4-corner rigid wheel formation could be a great option. However, if the cart has to be maneuvered in multiple directions, providing 2 swivel wheels will ease the maneuverability. Lastly, when in a very confined space, having all casters able to swivel will give the maximum ability to maneuver.
It is also important when providing swivel casters that the handles of the cart coincide with the casters. Therefore, if the cart is being pushed the swivel casters as well as the handle should be at the back of the cart, and if it is being pulled the swivel casters and handles should be at the front of the cart.
What other environmental considerations are there for the cart?
Lastly, it is important to know the different environmental factors that are going to affect the casters and wheels. If the casters will be exposed to water, snow or slush, for example with wash-down requirements or locking requirements, then a sealed caster bearing is recommended. The sealed ball bearing will protect the caster from damage and requires minimal maintenance. The sealed bearing may also be a great option when looking for casters that can last with little maintenance, regardless of external environmental factors.
Another important environmental factor is noise. Many casters, especially those that are harder, can make a lot of noise. If the desired function of the casters is in a quiet setting such as a hospital, casters shocks can help reduce a lot of the noise created by the caster and wheel itself.
For more information, check out this video on mistakes companies make with casters.