Share thisNo one knows who invented the wheel. The oldest wheel in existence was discovered in Mesopotamia and dates back to 3,500 B.C. For thousands of years, man has known that wheels can make a job a whole lot easier.
In modern lab applications, equipment and heavy loads are moved on casters. A caster is an assembly consisting of a housing (called fork or rig) and one or more wheels. The wheel is affixed to the housing with an axle. This allows it to rotate freely, either directly or with the use of bearing(s). Casters are affixed underneath carts, material handling trucks, or animal cages, to help facilitate their movement within a lab or throughout a facility. Swivel casters have the ability to rotate 360 degrees, whereas rigid casters permit straight-line travel only.
The Right Caster for the Job
When transporting a load on casters, it is important to match the caster to the job. Choosing the right caster requires an assessment of the load to be moved, the floor surface, and environmental conditions. For lab animal facilities, ergonomics, maintenance, and cleaning also play an important role in caster selection and operation. Identifying the applications and conditions where casters will be used can increase efficiency and safety.
Determining Caster Load
There are several important questions that are starting points in caster selection. The first of these is the load or capacity that the casters will have to bear. It is recommended to first determine the maximum weight to be moved inclusive of the load and weight of the cart, equipment, or object. Even if a maximum load were only going to occur occasionally, averaging the weight or underestimating the load would only result in choosing casters that won’t roll easily. Incorrectly chosen casters may collapse, bend, or break causing serious problems.
The rated load of a caster is the maximum weight that may be imposed on it for manual operation. The load capacity of a caster is calculated by adding the weight of the object to be moved, plus the apparatus that has to carry that object, divided by the number of affixed casters. In lab animal facilities, the carrying load on casters would consist of the cage system when fully loaded with animals, feed, and related weights. The caster load would be the full load of the cage system divided by the number of casters affixed to the cage unit.
Wheel Selection
When determining wheel size, typically, the largest wheel possible is the best choice. Larger wheels move more easily, carry more load, and can handle uneven surfaces better. Of course, it is important to make sure that the wheel size does not affect the overall height. After the casters are added, the wheeled item still needs to fit through doorways or into smaller openings, depending on the equipment.