Five different castors and their jobs
With so many castors out there, narrowing your choice isn’t the easiest job.
In this article we explain the basic types of castors and what you need to think about when making your selection. Understanding what you need and just as importantly, what you don’t need, can make all the difference.
In this article, we cover different types of castors and their applications to make it easier for you to decide which castor wheels are right for your application, whether that's heavy duty, hardwood floors, carpeted floors or smooth surfaces.
Types of castors
What does your castor need to do?
Types of castors
There are two types of castors – everything falls under one of these two categories:
- Swivel castor (or swivels): these castors can move in any direction, rotating 360°, even with heavy loads. Swivel castor offers so many different options and can be used in industrial applications.
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Rigid castor: unlike swivels, they can not be steered. Rigid castors only move in a straight line. Rigid castors are extremely durable, partly because they offer such limited movement. They're rated as carrying the same load as swivels, yet a common perception among engineers is that they can carry heavier loads. Being extremely durable is one of the biggest advantages of rigid castors.
Braking and locking castors
Some people use these terms interchangeably, but they’re actually different. Castors with brakes immobilise the wheel. Castors with locks prevent the swivel from rotating. Then there’s something called total locking castors, which lock both the swivel and the wheel.
There are different types of brakes too:
- Brakes that press against the side of the wheel
- Brakes that press against the tread of the wheel
- Brakes that push against the floor (called floor brakes)
Braking or locking, the aim is the same: to prevent movement. If your application needs an element of safety, you’ll want a braking or locking castor. The main point of difference to remember: locks stop swivel while brakes stop the wheel.
Kingpin castors
These are a type of swivel castor. It uses a stem, rivet or bolt to fasten together the lower part of the swivel section. The design relies on a load bearing and a thrust bearing to transmit the load. Kingpins are usually the weakest point of the castor and should never be used for towing applications.
- One advantage of kingpin castors is that you can tighten the kingpin to achieve varying levels of swivel resistance. This is especially desirable when a heavy load has to sit on an incline.
When not to use kingpin castors
Don't use kingpin castors if you plan on towing your application. This is due to the thrust loads being transmitted through the kingpin. It's this area that often becomes a failure point of the castor.
Kingpinless castors
If high impact is expected, or even the norm, these are an excellent alternative to traditional swivel castors. This design eliminates the kingpin and spreads the load over a larger area. It's for this reason that the swivel section can be used in higher-speed castor applications, compared to the kingpin swivel section. The kingpinless swivel section also swivels more easily. It requires less maintenance, because there isn’t a nut that needs to be re-tightened.
These castors are much stronger than castors with kingpins, which is why they’re often used in demanding shock-load applications.
Plate Castors
Plate castors provide mobility for a variety of environments and applications. Also known as plate mount castors, they’re available as rigid or swivel castors. The plate is what affixes to the appliance being moved. The plate is rectangular, usually with four small drill holes for fastening to the appliance with screws. You can get various hole patterns to match numerous types of mounting needs.
For rigid castors, the plate and the castor’s stem are moulded as one piece. Plate castors with swivel motion are pretty much identical, accept for one very big difference – the castor mounting and top plate are two separate pieces. They’re constructed so that they move independently of each other.
Essentially, plate castors are castors with the mounting already fastened to it. It’s worth noting that rigid plate castors usually cost less than swivel plate castors, as the manufacturing process is easier, because one piece is being produced versus two separate pieces.
Stem castors
This type of castor uses a stem of some type to fasten to your application. Sometimes referred to as stem-mount castors, these are a must your application offers limited space to its connection point. Think chair legs, table legs, furniture, and some medical equipment and it’s stem castors you want.
Stem styles typically include threaded, round or square with mounting holes, friction ring & expandable stems.
What does your castor need to do?
Focus on your application and ask yourself:
- How much space will my application have to negotiate?
- What sort of surface will my castor wheel need to move on?
- How much weight does my application need to move?
- Over how far a distance will my application need to move?
Load weight
The heavier the load, the larger the wheel your castor will need.
How to calculate load capacity of castors
To do this, divide the combined weight of your application and its maximum load by the number of castors you want to use. The answer is the load that each castor and wheel must carry. As a general rule, always choose a castor and wheel with a greater capacity than your calculations. This ensures that your castors can stand up to any unexpected conditions.
Also, use castors with roller or ball bearings for loads over 400 pounds.
Floor conditions
Your wheel needs to be large enough to travel over cracks in the floor, tracks, mouldings and other obstructions. A rule of thumb: hard tread wheels (hard castors) tend to perform better on soft or smooth floors, while soft-tread wheels (soft castors) react well to hard or rough surfaces, eg, outdoors.
Your best bet for floor protection, be it linoleum, tile or carpet, is either polyurethane or Performa rubber wheels.
Environment
Each wheel material offers characteristics that respond to certain conditions. If your application will be exposed to acids, oils, chemicals and other conditions harmful to rubber, then go for polyurethane, polyolefin, Maxim, phenolic or steel wheels.
Mobility
The larger the wheel, the easier it rolls. Roller bearings carry heavier loads. Ball bearings are easier to roll but carry lesser loads. When possible, use the largest ball bearing wheel for best results.
To help choose castors for heavy duty applications, read our guide, The Different Types of Heavy-Duty Castors
Extreme temperatures
Extreme cold or heat can limit the mobility of castors, but lubricants are available that can keep your castor rolling in temperatures ranging from -42.7° C to 126.7°C (-45°F to 260°F).
Download free CADs and try before you buy
Free CADs are available for most solutions, which you can download. You can also request free samples to make sure you’ve chosen exactly what you need. If you’re not quite sure which solution will work best for your application, our experts are always happy to advise you.
Whatever your requirements, you can depend on fast despatch. Request your free samples or download free CADs now.
Questions?
Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.