Fixed Castors are available in numerous versions, which differ in terms of their materials, diameter, or load-bearing capacity. Fixed Castors are suited for straight travel as they are fixed to the conveyance. In some cases, devices can only be equipped with Fixed Castors, such as when they are moved forwards and backwards in only one direction.
Swivel Castors allow frequent changes of direction. A vehicle fitted only with Swivel castors makes it easy to turn in all directions even on the spot and would therefore not be suitable for applications which are required to only move forwards or backwards in one direction.
For applications requiring good straight travel and manoeuvrability, it is therefore common to combine Swivel Castors with Fixed Castors. The most common arrangement is to mount two Swivel Castors on the side where the equipment will be pulled or pushed and two Fixed Castors on the other. The advantage: This makes the vehicle ideal for moving straight ahead and around bends.
The centre point of the Swivel Castor is placed with an offset to the rotational axis. Therefore the wheel will follow the direction the trolley travels in.
Generally speaking, Swivel Castors with a large offset have a lower load-bearing capacity and more wear on the back bearing, but ensure smooth running characteristics. With a smaller offset, however, the load-bearing capacity is higher and there is less wear on the back bearing although the running performance is not as smooth. For the respective requirements, the optimum projection of the castor housing must therefore be selected.
For many devices, not only movement but also a safe stance is extremely important. Whether at the point of sale or on mobile scaffolding - Castors without a wheel lock or brake can be very dangerous. Therefore, some Swivel Castors are equipped with various locking mechanisms.
The load-bearing capacity of the individual Castors and Wheels is determined under ideal conditions, i.e., on level ground, at a specified temperature of approx. 15 - 28°C, moving straight ahead at walking speed. Since the actual conditions of use are usually different, an additional safety factor should be included in the calculation. The more the operating conditions differ from the test environment, the larger the safety factor needs to be.
A distinction is made between the dynamic and static load-bearing capacity. While the dynamic data describes the load that a castor or wheel can bear when moving, the static value applies when stationary. The dynamic load capacity is therefore relevant for transport equipment, mobile machines and other such equipment. However, if the Wheels and Castors are mainly exposed to static loads, this can be taken into account in the calculation. It can then be assumed that the actual load bearing capacity is higher than the dynamic specification.
The Load Capacities shown on our website are Dynamic Load Capacities.
The dynamic load capacity T per Castor is calculated using the following formula:
The calculation is based on standard conditions, i.e., moving straight ahead on level floors at walking speed with uniform load distribution and a moderate ambient temperature (15°C to 28°C). If the actual conditions deviate from these, the load capacity will change. The actual conditions must therefore be taken into account from the start. For heavy-duty Castors that can carry particularly heavy loads, it is also important to add a safety factor to the formula: the greater the load, the greater the safety factor.
A wheel centre can be made of sheet steel, plastic or cast metal, for example. The versions made of sheet steel consist of two-wheel discs which are joined together by riveting or flanging. Unlike the models made of plastic, these wheel rims only form a unit in combination with the rubber tyre and the bearing. Plastic wheel centres are subdivided into different versions, and can be made of polyamide, polypropylene or polyethylene, for example.
The cast metal wheel centres are also subdivided: versions made of aluminium, malleable cast iron or die-cast zinc are possible. They are all very hard-wearing, break-proof and shock resistant, so that they can be used even on difficult floors and surfaces. The cast metal versions are produced with solid rubber tyres or a vulcanised-on rubber tyre.
A wide variety of profiles can be used for the wheel centre. The profile used depends on numerous factors. The most important of these are the size of the wheel, the wheel centre material, the desired tyre cross-section and the tread material. The type of application and the required load capacity of the wheel also play an important role.
A distinction is made between hard and soft tread materials. The harder materials include; plastics such as polyamide or polypropylene and cast iron. Cast iron in particular can withstand extreme temperatures from -100°C to +600°C and has a very high load-bearing capacity. Harder treads can cause damage to floors, so they are not recommended for sensitive floors. Marine paint can be used on wheel centres on bespoke requirements (maybe offshore sectors) to add more protection.
Softer materials include rubber and polyurethane (PUR). These are extremely kind to floors and can be used in many areas. In the case of polyurethane, a distinction is also made between the cast and injection-moulded versions. Cast PUR is of higher quality, whereas injection-moulded PUR is slightly easier to manoeuvre.
Different applications require different tread materials. The possibilities are huge and heavily depend on the customers’ expectations, applications, flooring, etc., which makes it difficult to give general advice about different tread materials.
Great compromise between push and pull forces and ground pressure with medium shore hardness around A92 is in most cases the best choice.
Gives the lowest push and pull forces due to hard tread material and shore hardness of Shore D75. Ground pressure is very high and only recommended with extra heavy loads where a low overall height is required. Check the flooring before choosing PA material because high and concentrated ground pressure may leave wheel ruts and may damage expensive flooring. Keep in mind that once the equipment is rolling it may be difficult to stop safely.
This is probably the most well-known tread material. It has a noise-free movement and has the highest push and pull forces and the lowest ground pressure with shore hardness around A67. The load capacity of rubber is usually lower than of any other material. It is great for transporting sensitive equipment, as it provides a cushioned ride.