Determine the load capacity

The formula for calculating the load one caster has to bear is:

You have to divide by the number of casters minus one because: In perfect theory, a 4 wheel trolley will distribute the weight evenly on each caster. For example, if you stack 400kg, each caster has a load of 400 / 4 = 100kg. However, in reality, it isn't because of the following reasons:

• Goods are unevenly stacked on the floor of the vehicle.
• The casters are not all contact the surface perfectly. Usually only 3 caster have good contact, the other caster may be hang or have little contact.
• Sometimes, casters move on bad surface. In addition to the weight of the goods, they also have to bear additional forces from the impact with obstacles.

Note: The load capacity as seen on website haophong.com is: the optimized load capacity on conditions:

• Temperature of working environment is 20 – 30°C
• Casters is rolling on a flat surface
• Travel speed ≤ 2km/h with wheel diameter ≤ 80mm. Or ≤ 4km/h if the wheel is larger in diameter.

Determine the wheel diameter

The first rule in diameter selection is that you choose big diameter: the bigger the better:

• Large wheels easily roll over ledges, steps and overcome obstacles (according to the lever principle). Over pits, grooves: large wheels do not get stuck, do not sink deeper and avoid causing inertia.
• Wide width helps to spread the load evenly. Therefore, large wheels always have a better load than small wheels.
• The circumference of the wheel is larger, so for the same distance, each point on the big wheel contact the surface less times and receiving less damage and corrosion. So the big wheel always lasts longer.

However, with large wheels, we have to lift the goods to a higher platform, so it will take more effort. You should also check if the car has a height restriction so that it can pass through the door frame or run under the table or bed. The final factor is aesthetics – you can't install too large wheels if the chassis is small and only light loads around the house.

Determine the wheel material

Under normal conditions, rubber wheels are preferable. They are cushion, elastic and floor protection, suitable for mixed terrain. Rubber wheels also ages slower than PU and TPU. For softness: Natural Rubber < ThermoPlastic Rubber (TPR) ≤ Elastic Rubber (ER) < Foam < Pneumatic.

Workplaces with gasoline, grease and chemicals are not allowed to use Natural Rubber. The rubber that resist some is TPR but not completely. To compete with chemical your priority is to use: PA > PP > PU > TPR. Please note that PU and TPR will age faster under the sun or in wet environment. So just keep them under root when unused. In the food industry it is recommended to use PA plastic wheels with 304 stainless steel bracket.

Heat resistant: At about 200°C or less you can use Phenolic resin because it is cheap. However, at temperatures higher than 260°C, heat resistant made by PA with glass fiber is your only option. You must use it according to the manufacturer's recommendations, or else can cause the wheel to blister, deform and damage the structure of the wheel. Cast iron should be used in extreme high temperature. However, cast iron is very harmful to the substrate and should be carefully avoided touching when the trolley has just come out of the oven because cast iron has the ability to retain heat for a long time.

Tear and wear resistant: use PU, PA or metal material. PA plastic or metal is hard so if the heavy systems or heavy trolley stay in one place for a long time: the wheel will not be crushed or deformed.

Some other concerns

1. Should you buy all 4 Swivel Casters or a combination of 2 Swivel and 2 Rigid Casters

Narrow road, many bends: It is necessary to use 4 Swivel Casters to best roll horizontally and diagonally to easily get out of bends and turns (like a trolley in a supermarket).

Straight and wide path: should install 2 Swivel and 2 Rigid Casters to save costs and easy to adjust direction when traveling long distances.

2. Replacement cases

Hao Phong encourages you to remove the old, broken casters and bring them to our shop for inspection. Sometimes we just fixed broken part then the caster can be used again. If you are far away, please refer to some of the articles below:

If you find it too complicated, please don't hesitate to contact us for further advice.