1, choose the wheel material: first consider the use of the road the size of obstacles, using the residue field (such as iron, oil), the environmental conditions (such as high temperature, normal temperature or low temperature) weight under different conditions and the capacity of the wheel to select suitable wheel material. For example, rubber wheels are not resistant to acids, Oils and chemicals. Super polyurethane wheels, high strength polyurethane wheels, nylon wheels, steel wheels and high temperature resistant wheels can be applied to different special environments.      

      2, calculate the carrying weight: in order to be able to calculate the load capacity of various casters, we must know the weight of the transport equipment, the maximum load and the number of single wheels and casters.     

       The load capacity required for a single wheel or a caster is calculated as follows:    

        T= (E+Z) /M x N:   

         ---T= the bearing weight required for a single wheel or a caster.      

      ---E= self weight of transportation equipment;    

        ---Z= maximum load;    

        The number of single wheels and casters used in ---M=;     

       ---N= safety factor (about 1.3 - 1.5).     

       3, determine the size of the wheel diameter. Generally, the larger the wheel diameter is, the easier it is to push, the greater the load capacity, and the better protection of the ground. The choice of the wheel diameter should first consider the carrying capacity and the starting thrust of the truck under the load.     

       4, wheel material hardness and hardness selection: usually, there are nylon wheels, super polyurethane wheels, high strength polyurethane wheels, high strength artificial rubber wheels, iron wheels and air wheels. Super high strength polyurethane wheels, polyurethane wheels in both indoor and outdoor ground vehicle, can meet your requirements of handling; high strength artificial rubber wheel can drive to the hotel, for the ground up medical equipment, floors, wood floors, ceramic tile ground requirements when walking noise quiet; nylon wheel, iron wheels on the ground rough or iron filings and other substances on the ground; and the pump wheel is suitable for light load and pavement soft uneven situation.        

    5, the flexibility of rotation: the greater the single wheel, the more laborer it saves. The roller bearing can load heavier loads, and has greater resistance when turning. The high quality (Zhou Chenggang) ball bearings on single wheel can load heavier loads, make the rotation more portable, flexible and quiet.   

         6, temperature condition: severe cold and high temperature occasions have great influence on casters. Polyurethane wheels at low temperatures below 45 degrees, rotate freely and high temperature wheels at high temperature 275 degrees.    

        Special attention: because a plane is determined at 3 points, when the number of casters is 4, the load should be calculated by 3.