Castors and wheels are everywhere on all our cars, planes, machines, trains, machinery, equipment, and even if you look down now, they may even be on your office chairs. It's probably a component that you have never spent much time thinking about. Nor should you! Castors and wheels are a part of every day life, and experts agree that the invention of the wheel in Mesopotamia in the 5th Millennium BC, was one of the most important developments ever made. In the late Neolithic period, they could never have imagined the importance of wheels and castors to their future ancestors every day life!
Castors are simply wheels, usually in a metal housing, easing the attachment to machinery and equipment. Without the castor housing wheels would need to be attached via an axel, and would therefore be fixed directionally. For example, imagine a cart, with the wheels on an axel; movement is restricted to either forwards or backwards, with a very wide turning circle. The invention of the swivelling castor enabled the wheel to move in a 360 degree direction, and not to be restricted to the singular forward backward motions. This simple invention has revolutionised the movement of equipment and machinery in our every day life!
The castors online housing is essentially a mini axel, housed in a metal casing. The metal casing has then a ball bearing head, which has either a square top plate for fixing, or a bolt hole fixing. Top plate fixing castors have four bolt holes enabling attachment to the underside of a trolley or machinery that is to be moved. These are one of the commonest types of castors, as it allows the spread of the load over the top plate swivel head. Bolt hole castors, on the other hand have a single bolt fixing, which by design may carry less weight. Bolt hole castors can be fitted with wither a threaded stem or expanding adaptors to fit into square or round tubing. All of these impressive castors can be fixed with a locking mechanism making braked castors. However if you still want uni directional castors, they are still available and are called fixed castors.
As there are so many choices between fixed castors, swivelling castors and braked castors, one is often faced with a dilemma? What is the most optimal combination of castors? There are two extremes on the scale. At one end imagine four swivelling castors on a shopping trolley, making the trolley out of control, moving in all directions and hard to manage! The other extreme is having four fixed castors, with the option of going either forwards of backwards, offering no ease of movement or flexibility! So in between these castor extremes there is a variety of castors combinations. As always this will depend upon your specific application, the load to be moved and the floor surface.
Castors are available in a huge variety of sizes and designs. From the smallest twin trolley wheels castors used on office equipment up to the largest heavy duty castors used in manufacturing processes carrying several tonnes of weight. Not only are there varieties of sizes of castors, but also a variety of wheels housed in the castors. To simplify the mind blowing array of options you may be faced with, the best rule of thumb is that hard wheels are easier to push, having less resistance with the floor. The downside is that castors with hard wheels, such as nylon castors, may be noisy and damage the floors.
Alternatively castors with softer wheels have more resistance against the floor and they may take less weight. Their benefit is they are less noisy and do not wear the floor surface. So next time you are sitting at your desk on your moving office char, or shopping at the supermarket, have a thought for the castors and wheels, that over the years, have enabled the world to be in motion.