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A shock absorber, also known as a damper, is a mechanical or hydraulic device designed to absorb and dampen shock impulses. It achieves this by converting the kinetic energy from the shock into another form of energy, typically heat, which is then dissipated. Most shock absorbers function as dashpots, which are dampers that resist motion through viscous friction.
In addition to smoothing out bumps and reducing vibrations, the primary role of a shock absorber is to keep the vehicle’s tires in constant contact with the road surface. This ensures optimal control and braking performance, contributing to the overall safety of the vehicle.
Shock absorbers perform two essential functions. They control the movement of the springs and suspension system and ensure that your tires remain in constant contact with the ground. Whether the vehicle is at rest or in motion, the only part of your vehicle that maintains contact with the road is the bottom of the tires.
If the tire's contact with the ground is interrupted or diminished, it significantly compromises your ability to drive, steer, and brake effectively.
Shock absorbers dampen the movement of the springs by converting the kinetic energy of the suspension into thermal (heat) energy. These devices are essentially oil-filled cylinders. When the vehicle’s suspension moves, a piston travels up and down through the oil-filled cylinder.
To simplify, shock absorbers take the kinetic energy (movement) of your suspension and convert it into thermal energy (heat), which is then dissipated into the atmosphere through heat exchange. This process is less complex than it might seem.
Shock absorbers function similarly to oil pumps. A piston, attached to a piston rod, works against hydraulic fluid in the pressure tube. As the suspension moves up and down, the hydraulic fluid is pushed through small orifices (tiny holes) within the piston.
These orifices restrict the flow of fluid, which slows down the piston and, consequently, the movement of the springs and suspension.
Shock absorbers adapt to road conditions automatically; the faster the suspension moves, the more resistance they provide.
- Shock Absorber Mounts: Shock absorber mounts are parts that secure shocks to the vehicle body and suspension. There is the upper and lower mount. Both of these can be of the same design, featuring an “eye into” in which a bushing and bolt are inserted.
- Shock Absorber Bush: These are located on the mountings. Usually made of rubber or urethane, bushings absorb vibrations and separate metal parts to prevent noise and wear. Bushings are among the shock absorber components that can be replaced.
- Shock Absorber Coil Spring: Some shock absorber types feature a coil spring as part of the shock absorber assembly. These are commonly known as coil-over shock absorbers or spring coil shock absorbers.
- Shock Absorber Piston and Piston rod: The shock absorber piston contains valves or openings. The working of the shock revolves around the movement of oil through these passageways.
- Shock Absorber Cylinder: This is the tube that forms the body of the shock absorber. It contains the compression oil and forms the tube inside which the shock absorber piston moves.
- Shock absorber bolts: The fasteners that hold the shock to the body of the vehicle on one end and suspension at the other end. These must be torqued to the right torque values. Under torquing can cause loose shocks that do not work as expected.
Hydraulic shock absorbers are commonly used in passenger cars. They enhance resistance to spring action by forcing fluid through check valves and small holes.
These absorbers offer resistance during both the compression and rebound phases of the springs.
Single-acting shock absorbers provide resistance only during the rebound phase.
Friction-type shock absorbers have largely become obsolete due to their unpredictable damping characteristics.
This indirect-acting type is bolted to the chassis via a lever and link. As the axle moves up and down, a double piston arrangement forces oil through a valve.
A direct-acting shock absorber mounted between the axle and the frame. Its upper eye is attached to the axle, and the lower eye to the chassis frame. The telescopic design includes valves and cylinders that manage fluid flow for effective damping.
This type consists of an inner and outer cylinder. The inner cylinder contains oil, with the piston rod connected to the piston valve, while the outer cylinder acts as a reservoir with low-pressure gas. The base valve controls the oil flow, and the low-pressure gas absorbs vibrations.
Mono-tube shocks have a high-pressure gas and a pressure tube containing two pistons: a dividing piston and a working piston. They offer greater surface area and carrying capacity, dissipate heat more quickly, and reduce fading. They can be mounted either upside down or right side up.
Spool valve dampers use hollow cylindrical sleeves with machined oil passages, differing from traditional flexible discs or shims. They can be used with monotube, twin-tube, and position-sensitive packaging, and are compatible with electronic control.
Shindary Automotive Parts Co., Ltd.
