A twin tube
shock or the Twin tube shock absorber is a low pressure shock having tube
inside the outer shock body which contains the piston assembly. In order to
create damping force, different coil springs inside the shock body are used.
The inner tube is known as pressure tube whereas the outer tube is known as
the reserve tube. The reserve tube is used for storing different types of
hydraulic fluid. The mounts used for the shock absorber are many but the
most popularly used rubber mount is rubber bushings between the shock
absorber and the suspension for minimizing suspension vibration.
The piston rod passes to the upper end of the pressure tube through rod
guide and the seal. The rod guide assist the piston to move freely inside
whereas the oil is kept inside by the seal. The movement of the fluid is
controlled by the base valve which is located at the bottom of the pressure
tube.
Working
of a Twin Tube Shock Absorber
The pushing of the piston results in the flow of the oil without resistance
from below the piston through different outlets to the area above the
piston. The oil displaced the rod flows into the reservoir tube filled with
air. The oil encounters the resistance while passing through the foot valve
thereby generating the bump damping.
The oil above the piston is pressurized when the piston rod is pulled out
which the flows through the piston. The oil when encounters an resistance
while passing through the piston, generates the rebound damping.
Types
of Twin Tube Shock Absorber
Twin tube shock absorber can be of different types depending on the
mechanism used. Some of the popular types are as follows:
Gas Charged Twin Tube Shock Absorber
Gas charged shock absorber solved many problems associated with driving.
The design uses low pressure charge of nitrogen gas in the reserve tube. The
pressure of the gas may vary and depends upon the amount of fluid in the
reserve tube.
The gas helps in minimizing the aeration of the hydraulic fluid. The
creation of foam is prevented because the gas compresses air bubbles in the
hydraulic fluid. Reduction of aeration enhances the working capacity of the
shocks. This shock absorber gives more flexibility to the engineers to
design valve. The additional advantage of the shock absorber is that it
creates a mild boost in spring rate to the vehicle.
Benefits of Gas Charged Twin Shock Absorber
- The handling is improved through roll reduction and the reduction of
sway and dive.
- It reduces aeration and give smooth control in different types of
road conditions.
- The heat may lead to the reduction of damping capability in the shock
absorber however in gas charged shocks this is reduced to a considerable
extent.
Position Sensitive Damping (PSD) Twin Tube Shock Absorber
Twin tube shock PSD design is a new technology in the field of shock
absorber. In this twin shock absorber, the position of the valve within the
pressure tube is taken into account. The pressure tube contains the tapered
grooves which enables optimal ride comfort and added control. The grooves in
effect creates two zones within the pressure tube.
In the first zone, the tapered grooves allow hydraulic fluid to pass freely
around and through the piston thereby reducing the resistance on the piston
and ensuring a smooth, comfortable ride. The first zone is utilized in case
of normal ride. In case of demanding situations, second zone called as
control zone is utilized. The fluid flow towards the piston valving for more
control of the vehicle's suspension which gives better control.
Advantages
- Give fine and smooth ride.
- It can adapt itself quickly to different road and weight conditions.
- It has two shocks in itself that is-comfort and control
Acceleration Sensitive Damping (ASD) Twin Tube Shocker
Twin tube ASD shocker brings the benefits of both the comfort and the
control. Twin tube ASD design shocker uses the compression valve which
provides a bypass to fluid flow around the compression valve. The
compression valve is designed in such a way that it senses a bump in the
road and adjust the shock automatically to absorb the impact thereby giving
greater control to the shock.
