AUTOMOBILE SHOCK ABSORBER

A shock absorber (damper) converts kinetic energy from the suspension system into heat energy, dissipating it to control vehicle ride and handling. In other words, a shock absorber reduces or eliminates vibrations thereby improving ride comfort and stability.

There are several types of shock absorbers and they are; twin-tube (conventional hydraulic), mono-tube (gas pressurized), coil over, air shock , electronically controlled/adaptive dampers, MacPherson strut, and hydraulic bump stop (jounce bumpers) shock absorbers.

Twin-tube (conventional hydraulic) shock absorber uses two concentric cylinders, an inner working tube and an outer reserve tube. Hydraulic fluid passes through calibrated valves as the piston moves. Examples include; Monroe QEspectrum, KYB Excel-G, Gabriel Ready Mount etc.

Mono-tube (gas pressurized) shock absorber employs a single tube which houses both the piston and a high pressure nitrogen gas chamber separated by a floating divider piston. The gas prevents aeration entirely. Examples include; Bustein BG, Fox performance series, KYB gas-a-just etc.

Coil-over shock absorber uses a mono-tube or twin-tube damper with a coil spring integrated around the shock body. Often fully adjustable for ride height, spring preload and damping force. Examples include; Ohlin’s road and track, BC racing BR series, KW variant 3, Tein flex Z etc.

Air shock absorbers uses compressed air chambers instead of (or alongside) hydraulic fluid to provide variable spring rate and ride heights. They are electronically or manually controlled. Examples include; Arnott air struts, QEM air suspension on Mercedes S-class, BMW 7 series air springs etc.

Electronically controlled/adaptive dampers shock absorbers uses solenoid valves or magneto rheological fluid controlled by an ECU or an electronic control unit in real time to adjust damping, stiffness within milliseconds based on road inputs, speed and driver mode. Examples include; Delphi magne Ride (GM, Ferrari, Audi), Sachs CDC (BMW, VW), Porsche PASM etc.

Macpherson strut shock absorber uses a structural damper to replace the upper control arm entirely, the shock absorber is the suspension link. It acts like a common twin-tube damper inside a strut housing. Examples include; Monroe strut-mate, KYB strut-plus, Gabriel ultra etc.

Hydraulic bump stops (jounce bumper) shock absorbers employs a secondary hydraulic damper that activate only at extreme suspension travel limits, preventing metal to metal contact and providing progressive resistance. Examples include; Fox live valve bump stops, Ohlins TTX bump stop inserts etc.

The advantages of automobile shock absorbers are; it provides for vehicular ride comfort by absorbing road irregularities like bumps, pot holes and uneven surfaces thereby isolating passengers from harsh vibrations. It provides for vehicular stability and safety by keeping the tires in constant contact with the road surface thereby maintaining traction during cornering, braking and acceleration. It provides for handling precision by controlling the body roll, pitch and dive during dynamic maneuvers. It provides for the life extension of the tires by distributing wear evenly across the tire contact patch. It protects other vehicles components such as chassis, steering linkages, wheel bearing and body structure from undue stress, fatigue and hence mechanical failure. It significantly dampens NVH (noise, vibration, harshness) transmitted into the cabin contributing to overall refinement and passenger comfort.

The disadvantages of automobile shock absorber are; it causes wear and degradation as they lose damping efficiency, when they wear out and are nor replaced regularly. The cost of advanced shock absorber system can be quite prohibitive. It adds additional unsprung and sprung mass to the vehicle thereby affecting fuel economy. Electronic and air suspension systems involve sensors, ECUs, compressors and solenoid valves and other components meaning more potential failure points and harder, and costlier diagnostics.

Automobile shock absorbers find applications in the specially for the following reasons; passenger cars for comfort and stability. Performance and sports cars for track racing and endurance driving. Luxury vehicles for premium ride refinement. Commercial trucks for heavy duty payloads and long haul stability. Off-road and 4×4 vehicles for long travels in uncertain and rough road terrain. Motorsports for entertainment and pleasure. Military vehicles for rugged road terrain and under very heavy duty load conditions and so on.

The future of automobile shock absorbers is based on the advances and development of the following technologies; energy regenerative shock absorbers, AI and predictive adaptive suspensions, fully active electromagnetic actuators, software-defined and over the air (OTA) tunable dampers, biodegradable and eco-friendly fluids, integration with advanced driver assistance systems (ADAS) and vehicle dynamics systems, light weight advanced materials specifically reducing damper weight and hence significantly improving fuel economy.

 

SOURCES:

• The shock absorber handbook by Dr John C. Dixon.
• Race car vehicle dynamics by William F. Milliken and Douglas L. Milliken.
• Fundamental of vehicle dynamics by Thomas D. Gillespie.
• Automotive chassis engineering principles by J. Reimpell, H. Stoll and J.W Betzler.
• Chassis engineering by Herb Adams.