Understanding Axial Load vs Radial Load: A Guide for Proper Selection

When it comes to machinery and engineering, understanding the loads that components endure is crucial for ensuring longevity and optimal performance. Enter axial load vs radial load two fundamental concepts that can make or break your design decisions. 

Whether you’re a seasoned engineer or a DIY enthusiast, grasping the differences between these two types of loads is essential for selecting the right bearings, gears, and other critical parts. 

In this comprehensive guide, we’ll demystify axial and radial loads, breaking down their characteristics, applications, and how to choose wisely for your projects. Get ready to enhance your knowledge base and elevate your mechanical game!

What Is an Axial Load?

An axial load is a force that pushes or pulls directly along the length of a shaft or bearing, following its axis. This force is important because it affects how parts like bearings are chosen to ensure machines remain strong, stable, and work properly.

Examples of axial loads in machines

1. Elevators: The cables holding the elevator pull straight up and down, carrying the elevator’s weight.
2. Hydraulic presses: Hydraulic presses use bearings that handle axial forces to control the press’s movement and shape materials accurately.
3. Cars: Parts like steering systems and gearboxes experience axial loads during movement.
4. Airplanes: Parts like landing gear and control surfaces face axial forces during takeoff, landing, and flying maneuvers.

How axial loads affect bearings and parts

1. Choosing the right bearing: Some bearings handle axial loads in one direction, while others can handle loads from both directions.
2. Stress on parts: Axial loads push or pull parts, causing stress that affects their strength and durability. Proper design and material choice are key to handling these forces.
3. Risk of damage: Too much axial force can bend or misalign parts, causing problems.
4. Machine performance: If axial loads aren’t handled correctly, machines wear out faster and don’t work as well.

What Is a Radial Load?

A radial load is a force that pushes straight toward the center of a shaft or bearing but from the side, at a right angle to the shaft’s length. This force acts along the radius of the bearing and is very common in machines.

Examples of radial loads in machines

1. Electric motors: The rotor’s weight and magnetic forces push sideways on the bearings.
2. Car wheel bearings: They support the car’s weight and handle side forces when the car moves.
3. Conveyor belts: The rollers carry the weight of items on the belt, creating radial loads.
4. Gearboxes and tools: Gears and shafts push sideways on bearings during use.

How radial loads affect bearings and parts

1. Load sharing: The force moves from the inside ring, through rolling parts like balls or rollers, to the outside ring of the bearing. The part under the most pressure bears the highest load.
2. Bearing types: Bearings such as deep groove ball bearings and roller bearings are designed to handle radial loads effectively.
3. Stress points: Stress points occur when uneven forces concentrate pressure on specific parts of a bearing. This extra pressure can cause those areas to wear out faster, reducing the bearing’s lifespan and performance.
4. Damage risk: Too much radial load can bend or damage the bearing parts, hurting performance.

Knowing about radial loads helps you choose the right bearing, so machines work well and last longer.

Key Differences Between Axial and Radial Loads

1. Direction of Force
   • Axial Load (Thrust Load): The force pushes or pulls along the length of the shaft, like pushing a plunger or pulling a rope. It goes in the same direction as the shaft.
   • Radial Load: The force comes from the side, pushing inward toward the center of the shaft, like pressing on the side of a spinning wheel. It goes across the shaft, not along it.
2. Effect on Machine Parts
   • Axial Load: It tries to compress (squeeze) or stretch the shaft. If the bearing can’t handle it, parts may slide out of place or become misaligned.
   • Radial Load: It can bend the shaft or cause it to wobble if the load is too much. Over time, this may cause the shaft or bearing to wear out or break.
3. Bearing Design Needs
   • For Axial Loads:
   • Use thrust bearings that are made to handle forces going in the same direction as the shaft. Examples:
     1. Thrust ball bearings
     2. Tapered roller thrust bearings
   • For Radial Loads:
   • Use bearings designed to take sideways pressure. Examples:
     1. Deep groove ball bearings
     2. Cylindrical roller bearings

Advantages and Disadvantages

Axial Load (Thrust Load)

• Advantages
  • Precise Linear Motion: Axial loads are important for machines that require accurate straight-line movement. They help parts move smoothly in a controlled way, such as in hydraulic presses and elevator systems.
  • Compact Bearing Design: Thrust bearings designed for axial loads are usually small and compact, making them ideal for machines that don’t have a lot of space.
• Disadvantages
  • Limited Radial Load Handling: Thrust bearings mainly handle axial loads and aren’t good with radial forces, limiting their use where both types of loads occur.
  • Sensitivity to Misalignment: Improper alignment during installation causes uneven load distribution, leading to increased wear and a shorter bearing life. Proper alignment is key for smooth, long-lasting performance.

Radial Load

• Advantages
  • Efficient for Rotating Machinery: Radial loads are well-suited for rotating components like wheel bearings and electric motors, as they effectively support forces perpendicular to the shaft axis.
  • Versatility: Bearings designed to handle radial loads, such as deep groove ball bearings, can accommodate both radial and limited axial loads, offering flexibility in various applications.
• Disadvantages
  • Limited Axial Load Capacity: While radial bearings can handle some axial load, their capacity is limited compared to thrust bearings. Overloading in the axial direction can lead to premature failure.
  • Sensitivity to Misalignment: Poor alignment can cause radial bearings to wear out faster by making the load spread unevenly. Proper installation and alignment help prevent this and extend bearing life.

By understanding these advantages and disadvantages, engineers and technicians can make informed decisions when selecting bearings, ensuring that mechanical systems operate efficiently and have a prolonged service life.

Bearings for Combined Loads

Several bearing types are designed to accommodate both axial and radial loads:

1. Angular Contact Ball Bearings

Angular contact ball bearings have grooves angled to the bearing’s center. This helps them handle strong pushing or pulling forces in one direction (axial loads) as well as side forces (radial loads). They’re often used in pairs or sets to handle both types of forces well.

2. Tapered Roller Bearings

Tapered roller bearings have angled inner and outer rings that let them support both radial and axial loads at the same time. Their design spreads the forces evenly, making them ideal for situations where parts face both types of pressure.

3. Combined Needle Roller Bearings

Combined needle roller bearings provide support for both radial and axial loads in a single, compact design, making them perfect for use in tight spaces.