When wheels or castors roll along a surface, a force acts against this movement. This is known as the rolling resistance. It is the force that must be applied to keep the equipment rolling steadily along. The starting resistance, on the other hand, is the force needed to set stationary equipment in motion. Another type of resistance is the swivel resistance. This influences the manoeuvrability of the equipment.
Important factors for rolling resistance
The rolling, swivel and starting resistance are influenced by several factors, such as the wheel diameter, tread, wheel bearings and offset. The resistance also changes depending on the properties of the floor. Whether fixed or swivel castors are best suited or whether a combination of the two types is recommended depends on how the castors are to be used. If you only need the equipment to move in a straight line, fixed castors offer better running characteristics. If a great deal of turning and manoeuvring is required, however, swivel castors are ideal. In this case, directional locking mechanisms can ensure good performance when travelling in a straight line.
Measurement of rolling resistance
The rolling resistance of each individual castor is determined under ideal test conditions. The floor must be flat and free of obstacles and dirt, and the temperatures must be within a specified range. The castors are then tested at a speed of 4 km/h with an applied load equivalent to about two-thirds of the maximum load capacity. Under these ideal conditions, different castors and wheels can be compared with each other. It must be taken into account, however, that the actual ambient conditions during use normally deviate from the ideal conditions, which means that the rolling resistance will change accordingly.