Casters

2026-04-21 02:13

**Caster** is a general term that includes swivel casters, rigid casters, and swivel casters with brakes. Swivel casters, also known as universal wheels, have a structure that allows 360-degree rotation. Rigid casters, also called fixed casters, have no swivel structure and cannot turn. Typically, these two types are used together. For example, a hand truck often has two rigid casters at the front and two swivel casters at the back near the pushing handle. Casters are made from various materials, such as PP, PVC, PU, cast iron, nylon, TPR, iron-core nylon, and iron-core PU.

- **Chinese Name**: 脚轮 (Jiǎo lún)

- **English Name**: Casters

- **Also Known As**: Rollers, wheels, trundles

- **Includes**: Swivel casters, rigid casters, swivel casters with brakes

- **Structure**: Allows 360° rotation

- **Classification by Load Capacity**: Micro casters, light-duty casters, medium-duty casters, heavy-duty casters, extra-heavy-duty casters

## Table of Contents

1. Introduction

- Origin

- Structural Characteristics

- Application Fields

- Materials Used

- Load Capacity Calculation

2. Classification of Casters

- By Steering Capability

- Detailed Caster Types

- By Application Industry

- By Material

3. Selecting Casters

- Wheel Selection

- Caster Frame (Rig) Selection

- Bearing Selection

- Important Considerations

## Introduction

### Origin

Tracing the exact history of casters is difficult. After the invention of the wheel, moving objects became much easier, but wheels could only travel in a straight line. Changing direction, especially for heavy objects, remained very difficult. Eventually, people invented a wheel with a steering structure—what we now call a caster or swivel wheel. The advent of the caster revolutionized the handling and moving of objects, allowing not only easy transport but also movement in any direction, greatly improving efficiency.

With the Industrial Revolution, more and more equipment needed to be moved, leading to the widespread global application of casters across nearly all industries. In modern times, with continuous technological development, equipment has become more functional and frequently used, making casters an indispensable component. The development of casters has become increasingly specialized, forming a distinct industry.

### Structural Characteristics

- **Mounting Height**: The vertical distance from the floor to the equipment's mounting surface. The caster's mounting height is the maximum vertical distance from its mounting plate to the edge of the wheel.

- **Kingpin Offset / Swivel Lead**: The horizontal distance from the vertical line of the central rivet (kingpin) to the center of the wheel.

- **Swivel Radius**: The horizontal distance from the vertical line of the central rivet to the outer edge of the tire. Proper clearance allows the caster to swivel 360 degrees. The appropriate swivel radius directly affects the caster's service life.

- **Rolling Load (Dynamic Load)**: The load capacity of a caster while moving. This varies depending on the manufacturer's testing methods and the wheel material. The key factor is the strength and quality of the caster frame (rig) to withstand impact and vibration.

- **Impact Load**: The instantaneous load a caster can withstand when the equipment is subjected to shocks or vibrations.

- **Static Load**: The weight a caster can support while stationary. Static load should generally be 5-6 times the rolling (dynamic) load and at least twice the impact load.

- **Steering**: Hard, narrow wheels are easier to steer than soft, wide wheels. Swivel radius is a crucial parameter for steering; too short a radius increases steering difficulty, while too long a radius causes wheel wobble and reduces lifespan.

- **Rolling Flexibility / Ergonomics**: Factors influencing rolling ease include the frame structure and steel grade, wheel size, wheel type, and bearings. Generally, larger wheels roll more easily. On smooth floors, hard, narrow wheels require less effort than soft, flat-edge wheels. However, on uneven floors, soft wheels protect equipment better and provide shock absorption.

### Application Fields

Casters are extremely widely used, primarily on hand trucks, mobile scaffolding, workshop carts, etc.

Often, the simplest inventions are the most important, and casters possess this characteristic. Interestingly, the level of development in a city is often positively correlated with the usage rate of casters. Cities like Shanghai, Beijing, Tianjin, Chongqing, Wuxi, Chengdu, Xi'an, Wuhan, Guangzhou, Foshan, Dongguan, and Shenzhen have a very high caster utilization rate.

A caster consists of a single wheel mounted on a frame (rig) and is installed under equipment to allow free movement. Casters are mainly divided into two categories:

- **A. Rigid Caster**: A fixed frame (rig) with a single wheel, allowing movement only in a straight line.

- **B. Swivel Caster**: A 360-degree swiveling frame (rig) with a single wheel, allowing movement in any direction.

Caster wheels come in many types, varying in size, tread shape, and material. Choosing the right wheel depends on several conditions:

- A. The environment where it will be used (floor conditions).

- B. The load capacity required.

- C. Exposure to chemicals, blood, grease, oil, salt, etc.

- D. Special climatic conditions like humidity, high heat, or severe cold.

- E. Requirements for impact resistance, shock absorption, and quiet operation.

### Materials Used

Polyurethane (PU), Cast iron/steel, Nitrile rubber (NBR), Natural rubber, Silicone-fluorine rubber, Neoprene rubber, Butyl rubber, Silicone rubber (SILICONE), EPDM rubber, Viton (fluorocarbon rubber), Hydrogenated nitrile (HNBR), Polyurethane rubber, Rubber-plastic blend, PTFE, Nylon gears, Polyoxymethylene (POM), PEEK, PA66 gears.

**Common types mentioned in the original text include**:

- Light-duty white PP casters

- Light-duty white-core, red-surface PVC casters

- Light-duty maroon PU casters

- Light-duty black PP casters

- Light-duty black rubber casters

- "Diamond" casters (brand/model)

- "Fat Boy" casters (brand/model)

- Medium-duty nylon casters

- Medium-duty twin-axle maroon PVC casters

- Medium-duty twin-axle TPR casters

- Medium-duty open-frame casters

- Medium-duty single-axle PVC casters

- Heavy-duty "Fire Wheel" casters (brand/model)

- Heavy-duty Korean-style PVC casters

- Heavy-duty Korean-style iron-core PU casters

- Heavy-duty nylon casters

- Leveling casters

### Caster Load Capacity Calculation

**Formula**: T = (E + Z) / (M × N)

- **T** = Required load capacity per caster

- **E** = Weight of the transport equipment

- **Z** = Weight of the object being moved

- **M** = Effective number of wheels carrying the load (see note below)

- **N** = Safety factor (typically 1.3 – 1.5, considering uneven weight distribution and positioning)

**Note**: Because three points define a plane, when using 4 casters, the load capacity should be calculated based on **3 casters**.

## Classification of Casters

### By Steering Capability

- **Rigid Caster (Fixed Caster)**: Has no swivel structure and cannot turn.

- **Swivel Caster (Universal Wheel)**: Its structure allows 360-degree rotation.

### Detailed Caster Types

This includes extra-heavy-duty, super-heavy-duty, specialty-shaped, brake casters, shock-absorbing casters, adjustable casters, light-duty, medium-duty, heavy-duty casters, etc.

*(Examples from the original text include Light-duty, "Fat Boy", "Diamond", Medium-duty Nylon, Heavy-duty "Fire Wheel" casters, etc.)*

### By Application Industry

Industry, commerce, medical equipment, machinery, logistics transportation, environmental cleaning products, furniture, electrical appliances, beauty equipment, mechanical equipment, craft products, pet supplies, hardware products, and many other sectors.

### By Wheel Material

Main categories include super synthetic rubber (e.g., TPR/TPE), polyurethane (PU), plastic, nylon, steel/iron, high-temperature resistant, rubber, and S-type synthetic rubber casters.

| :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- |

| **Load Capacity (KG)** | 27 – 502 | 31 – 1905 | 31 – 408 | 100 – 1400 | 181 – 2040 | 270 – 450 | 55 – 502 | 60 – 100 |

| **Applicable Temp (℃)** | -43 – 85 | -43 – 85 | -43 – 85 | -43 – 85 | -43 – 126 | -43 – 180 | -43 – 85 | -43 – 85 |

| **Wheel Hardness** | 65(±5)A | 55(±5)D | 65(±5)D | —— | —— | —— | 75(±5)A | 85(±5)A |

| **Non-Marking** | Yes | Yes | Yes | Yes | Yes | Yes | No (Poor) | Yes |

## Selecting Casters

### Wheel Selection

1. **Choose Wheel Material**: First, consider the floor conditions (roughness, obstacles), debris present (e.g., metal shavings, grease), environmental factors (high, room, or low temperature), and load requirements. For example, rubber wheels are not resistant to acids, grease, or chemicals. Super polyurethane, high-strength polyurethane, nylon, steel, and high-temperature resistant wheels suit different special environments.

2. **Calculate Load Capacity**: To determine the required load capacity per caster, use the formula: **T = (E + Z) / (M × N)** (explained in the Introduction section).

3. **Determine Wheel Diameter**: Generally, a larger wheel diameter makes pushing easier, provides higher load capacity, and offers better floor protection. The choice of diameter primarily depends on the load weight and the starting thrust required for the cart.

4. **Choose Wheel Hardness/Softness**: Nylon wheels roll easily but can be hard on floors. Polyurethane offers a good balance. High-strength synthetic rubber is quiet and ideal for hotels, hospitals, and wood/tile floors. Steel/iron wheels are suitable for rough floors or areas with metal debris. Pneumatic wheels are for light loads on soft, uneven terrain.

5. **Rolling Flexibility**: Larger wheels roll with less effort. Roller bearings can handle heavier loads but have higher rolling resistance. High-quality ball bearings (bearing steel) handle heavy loads and provide easier, quieter, and more flexible rolling.

6. **Temperature Conditions**: Extreme cold or heat significantly impacts caster performance. Polyurethane wheels can function flexibly at temperatures as low as -45°C, while high-temperature resistant wheels operate easily at up to 275°C.

**Special Note**: When using 4 casters, calculate total load capacity based on **3 casters**.

### Caster Frame (Rig) Selection

1. **Light-Duty Applications (10-140 kg per caster)** : For smooth floors in supermarkets, schools, hospitals, offices, hotels (light loads). Choose **electroplated steel frames (2-4mm thick)** , which are lightweight, maneuverable, quiet, and attractive. For frequent movement, select **double ball bearing raceways** over single.

2. **Medium to Heavy-Duty Applications (280-420 kg per caster)** : For factories and warehouses with frequent, heavy loads. Choose **hot-forged, welded thick steel plates (5-6mm thick)** with double ball bearing raceways.

3. **Extra Heavy-Duty Applications (350-1200 kg per caster)** : For textile, automotive, and machinery factories with high loads and long travel distances. Choose frames cut from **very thick steel plates (8-12mm thick)** and welded. Swivel frames should use a combination of plain thrust bearings and ball bearings in the top plate for heavy load capacity, smooth swiveling, and impact resistance.

### Bearing Selection

1. **Delrin / Plain Bearing (Thermoplastic)** : Suitable for wet or corrosive areas. Offers average rolling flexibility and higher resistance.

2. **Roller Bearing**: Heat-treated roller bearings handle heavier loads but offer average rolling flexibility.

3. **Ball Bearing**: Made from high-quality bearing steel. Handles heavy loads, suitable for applications requiring high flexibility and quiet operation.

4. **Thrust / Tapered Roller Bearing**: Suitable for high and extra-high loads and high-speed swiveling applications.

### Important Considerations

1. **Avoid overloading** the caster beyond its rated capacity.

2. **Do not apply offset loads** (ensure the load is centered over the casters).

3. **Perform regular maintenance** (e.g., periodic lubrication, checking screws for tightness).

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I hope this translation is helpful. Let me know if you need any adjustments for a specific dialect of English (e.g., UK vs. US spelling/terms).

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Casters

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