Castors are the unsung heroes of the material-handling world. From meandering your groceries through supermarket aisles, to transporting hundreds of kilos of raw materials and finished goods in warehouses and factories. They come in a huge selection of materials to run smoothly and effortlessly across all surfaces, in different load ratings to handle both light and extremely heavy loads, and in varying designs, sizes and features when attached to the proper equipment.
Choosing the right caster for your application may be the hardest part, considering how many variables affect what you buy.
What Exactly are Castors?
Castors are defined as the complete assembly that attaches to the bottom of things like trolleys, carts and hand trucks. This includes both the wheels and the mounting hardware to securely fix the assembly to the equipment. A castor wheel is undriven, as opposed to driven wheels in powered gear. Its main task is to provide a secure, safe and effortless way to carry the load and help maneuver and transport it to the desired destination.
You’ll see a wide selection of casters used in shopping trolleys, office chairs, laundry carts, hospital beds, tool cabinets, pallet jacks, manual scissor lifts, and a range of industrial equipment used in handling, sorting, storing and transporting goods. This also means hundreds of different businesses and sectors, from warehousing and manufacturing, to hospitality and general material handling in areas as diverse as offices, schools, retail shops, workshops, airports and more.
There are many questions you need answered before setting out to buy casters. What will they be used with? How heavy is the load? Do floor surfaces or settings call for specific requirements? What size is right for the equipment? These are just a few considerations, so let’s break things down so you can make an informed purchase.
Floor Surfaces and Caster Materials
For smooth handling across the intended floor surface, caster wheels need to be of the right materials. The most common materials include Nylon, polyurethane, polypropylene, and a range of other hard plastics, as well as iron, aluminium, and rubber. Nylon wheels, for instance, are ideal in areas where the wheels can come in contact with various chemicals, water and other liquids. They’re equally good on both hard and smooth surfaces, like concrete, wood flooring, and tiles, durable enough to manage medium to heavy loads, and also very quiet. Another plus is that they’re no marking, so ideal for indoor use with floors of softer materials. You’ll find Nylon castors used in workshops, offices and manufacturing plants, among other settings.
On the industrial end of things, steel and cast-iron casters are designed for extremely heavy loads and hard surfaces, like you’d find in heavy industrial facilities. The materials are durable, resistant to chemicals such as acids and solvents, and also ideal in settings with temperature extremes. Typical settings include the auto, chemical, and construction industries, as well as freeze storage rooms and bakeries. Choose materials that suit the floor surface, are durable enough for the intended loads and potential environmental factors, and where possible are non-marking and quiet.
Castors differ in size, ranging from 50 to 200mm in most uses. This has as much to do with the handling equipment as does the setting and the speeds at which the goods need to be transported. Smaller diameters are better for smooth and hard floors, like carpet or concrete. Uneven surfaces and those littered with obstacles require bigger caster wheels to get the job done with minimal effort. Bigger wheels absorb bumps and provide lower rolling resistance, so roll faster. However, they limit maneuverability in tighter spaces and raise the equipment higher, so can also affect stability, such as in abrupt turns. Go with recommended sizes for the material handling equipment, or size castors up or down as needed.
How much each caster can safely carry (in a setup of 4 or more) is vital when you consider what you’ll be loading on the equipment. Load capacity varies from 75 kilos to over a ton, and is also dependent on the materials used. Generally, thermoplastics have lower weight ratings, so in line with light to medium loads, while metal castors are more suited for heavy-duty use. Caster wheel materials are only part of the equation though, and how the castors are attached to the equipment and the types of bearings they have also play a part. Roller bearings, for instance, can take heavier loads than ordinary ball bearings. Ensure you get variants that can handle the heaviest load designed for the equipment, as this also determines the durability and the rate of wear.
There are two basic designs -swivelling and fixed. Swivelling casters are often at the front of trolleys, carts etc., and ensure easy movement. Fixed types are often at the back of the equipment, and are usually braked. This is a general setup though, and buyers can choose different configurations to suit the settings, handling and safety needs.
In terms of how they’re attached, the mounting hardware can be a plate bolted to the handling equipment, or have a threaded attachment, usually a centre bolt or stem mount. Plate varieties offer better weight distribution with heavier loads and feature in bigger equipment. By comparison, threaded types are adequate for lower load ratings, but are cheaper and easier to maintain.
Wheel profiles and widths, differences in brake designs, and how the casters are configured on the equipment also determine stability, safety and handling. What’s important is to get types made of materials suited to the loads in terms of weight loadings and the surfaces they’re being used on. Sizes determine ease of use and manageable speeds in the equipment, while specifics like bearing types and mounting options play a major role in durability.