Technology Hydraulic Shock Absorbers: Basic principles |
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| In the standard twin-tube shock absorber design, a piston slides inside an oil-filled cylinder. Calibrated holes in the piston allow oil to pass between the upper and lower parts of the cylinder thereby damping the oscillation of the spring. As the piston moves up and down, forcing the oil through the holes, the piston rod moves in and out of the tube. As it moves in and out, the rod changes the volume available to the oil. When the volume is reduced, there is momentarily an excess of oil: this excess is forced back in the oil reservoir (reserve tube) through the base valve. When the rod moves out again, it creates a vacuum and a volume of oil equivalent to the displaced rod is drawn through valves in the piston and, at the same time, through an orifice in the base valve. |  |