Shock absorbers are devices that regulate the impact and rebound movement of a vehicle's suspension and springs.
Their main objective is to maintain constant contact between the tires and the road surface, minimizing vibrations and bumps.
Contrary to popular belief, shock absorbers do not support the vehicle's weight; their primary function is to manage the suspension's movement.
Function
Shock absorbers serve essential functions in various applications, particularly in mechanical and automotive systems. They are made to control the repulsion and impact of springs and suspensions, which improves the vehicle's overall stability and safety.
- Absorbing and dampening: The main purpose of a shock absorber is to take up the energy produced when springs and suspensions compress and rebound. They contribute to a smoother ride by reducing excessive spring motion.
- Tire-Road Contact: Ensuring constant contact between the tires of the vehicle and the road is a crucial task. In order to maintain adequate traction, responsive steering, and overall handling performance, this contact is essential.
- Enhancing Braking Response: Shock absorbers play a crucial role in improving the braking response of the vehicle. By preventing excessive bouncing and instability, they allow for quicker and more effective braking, contributing to the driver's safety.
Working Principle
Shock absorbers operate based on hydraulic principles, utilizing the conversion of kinetic energy into thermal energy to control the suspension's movements. They consist of a piston attached to a piston rod, which interacts with hydraulic fluid in the pressure tube.
As the suspension moves up and down, the hydraulic fluid is forced through small openings (orifices) in the piston, creating resistance and slowing down the movement. This hydraulic resistance is the key to absorbing the shocks and vibrations transmitted from the road, promoting a more comfortable ride.
Moreover, shock absorbers possess an adaptive quality, where the resistance they offer varies with the suspension's speed. This adaptability enables them to automatically adjust to different road conditions, providing optimal performance and stability regardless of the terrain.
Structure
The ball joint structure consists of two main components: the ball and the socket. The ball is ordinarily a spherical shape for attaching to one part, while the socket is a hollow sphere that is attached to the other part. For this reason, they are designed to withstand heavy loads and high stresses, making them ideal for use in demanding environments. However, as with any mechanical component, they can wear out over time and may need to be replaced.
Components
- Cylinder: The shock absorber's outer cylindrical housing houses most of the internal parts.
- Piston: Inside the cylinder, a movable piston is attached to the piston rod. It moves up and down, featuring valves or openings that allow hydraulic fluid to flow.
- Piston Rod: Extending from the piston, this rod connects the top of the shock absorber to the vehicle chassis and the bottom to the suspension system.
- Hydraulic Fluid: Filling the cylinder, hydraulic fluid (commonly oil) flows through the piston and piston rod during compression and extension. It provides damping resistance and absorbs energy.
- Valves: Shock absorbers have various valves, like rebound and compression valves, that regulate the flow of hydraulic fluid, enabling adjustments to the suspension's behavior.
- Mounts and Bushings: Shock absorber mounts secure the unit to the vehicle body and suspension. Bushings, often made of rubber or urethane, absorb vibrations, reduce noise, and prevent wear.
- Rod Guide: The rod guide ensures smooth movement of the piston rod.
- Nitrogen Gas and Gas Chamber: A chamber within the compression chamber or cylinder contains nitrogen gas. This prevents the hydraulic fluid from forming bubbles, ensuring consistent performance.
- Washer and Plates: Washers and plates serve as spacers and play an important role among the shock absorber parts.
- Coil Spring or Leaf Spring (optional): In some cases, shock absorbers are integrated with coil springs or leaf springs, resulting in coil-over or leaf-spring-over shock setups.
- Dust Cover/Bellows: A rubberized protective cover wraps around the piston rod, safeguarding it from dust, debris, and contaminants, which extends the shock absorber's life.
All these components work together in harmony to dampen shocks and vibrations, providing a smooth and controlled ride, while also enhancing stability, handling, and overall comfort.
Types
- Twin-tube Shock Absorber: These provide resistance during both compression and rebound of the springs and are often used in modern vehicles with flexible springs. Twin-tube shock absorbers have two cylinders and are mostly filled with hydraulic oils. Twin-tube shock absorbers should only be installed vertically.
- Advantages: This type of absorbers have a few advantages, for example, you would experience a better drive with firm stability of the parts. It reduces harshness and the lean while cornering. As there are two cylinders, the inner cylinder gets protected so the parts also have a long life span. Still twin tube types are more affordable than Mono-tube Shock Absorbers.
- Disadvantages: Yet there are some disadvantages too. Firstly, the launching position can be inconvenient as it should only be installed vertically, reducing the number of choices. Secondly, it can be very sensitive while holding heat.
- Mono-tube Shock Absorber: These offer resistance only during the rebounding stage of operation. Mono-tube shock absorbers have single cylinders filled with gas. These Mono-tube shock absorbers can be installed either upside down or right side up, and it will still work just fine.
- Advantages: Mono-tube shock absorbers also have advantages; they allow secure ride with better control and responsiveness in steering. They also have better heat dissipation making it less stressed out. Additionally, you can install these absorbers in any angle, yes, even bottom up.
- Disadvantages: Of course mono-tube shock absorbers also have little drawbacks. Firstly, they have a shorter life span as these are exposed directly to outer pollution. Secondly, they could be more expensive than twin-tube shock absorbers.
Failure of Shock Absorber
A shock absorber, also called a damper, is a part that literally absorbs shocks from suspension and other movements. It can go leaking by simple aging, but in some cases, the damper would not stand and start to leak.
- Nuts tightened too hard: One of the parts building up a shock absorber is a strut. A strut is connected with several parts with nuts, and if it is mis-tightened, some serious problems can happen since the whole system’s balance breaks.
- Excessive Suspension Loads: Hitting road obstacles, like potholes, can lead to immediate shock absorber pressure, causing slight oil leakage through gaskets and seals.
Symptoms of Failure:
- Knocking Noise: If a driver hears a knocking sound when driving over bumps, it could indicate worn shock absorbers. The noise may be caused by worn rubber bushings in the shock absorber's ends.
- Vibrations: Worn shock absorbers with damaged valves or piston seals can cause vibrations in the steering wheel when driving over bumps.
- Fluid Leak: Leaking fluid along the shock absorber's body can indicate worn seals, leading to decreased shock absorber functionality.
- Swerving: Faulty shock absorbers can cause swerving or nose-diving when braking and turning simultaneously, making it harder to maintain control.
- Slow Braking Response: If your car takes longer to slow down and stop after pressing the brake pedal, it could be due to faulty shock absorbers.
- Uneven Tire Wear: Bad shock absorbers can lead to uneven tire contact with the road, resulting in certain areas of the tires wearing faster than others.
Reasons for Shock Absorber Leakage:
Excessive Suspension Loads: Hitting road obstacles, like potholes, can lead to immediate shock absorber pressure, causing slight oil leakage through gaskets and seals.
Time and Distance: Over time and with a high mileage, shock absorber seals can wear and get damaged, leading to oil leakage and reduced performance.
Driving with Leaking Shock Absorbers:
Driving with leaking shock absorbers is not recommended. It can result in intense car body movements even over minor road imperfections, affecting handling and braking performance. Ignoring the issue can lead to faster wear of other suspension components and increase the risk of accidents. If a driver notices oil leakage in your shock absorbers, it's essential to have them repaired or replaced promptly to ensure safe and smooth driving. Additionally, check the drivetrain for any related issues that may require attention.
Tests
CTR offers a comprehensive range of verification tests for shock absorber - sealing test and damping force test.
