What is a landing gear used for?

When driving, bumps in the ground lead to strong vertical accelerations and decelerations that are proportional to the moving mass of the car. Springs are used to ensure that these shocks are not passed on to the vehicle and the occupants without being sprung. They turn the entire car into a vibratory structure that is characterized by a certain natural frequency. If the car drives over an obstacle, the spring is tensioned and the body is catapulted upwards by the spring force. The force of the spring also has the effect that this movement is braked in order to then tension the spring again in the opposite direction. The up and down movement (vibration) of the body converts the initial kinetic energy into heat through air and spring friction. One speaks of a damped oscillation with decreasing amplitude. The suspension serves not only for the comfort and health of the passengers but also for driving safety. Together with the shock absorber and stabilizer, it ensures that the wheels are always in contact with the road. This is the only way they can transmit braking and driving forces so that the car remains controllable. The same applies to cornering.

ACS overview (source Mercedes)
ACS overview (source Mercedes)

What is a shock absorber?

Shock absorbers support the springs by converting vibration energy into heat. In this way, the body reaches its rest position much faster than without additional damping. Today, almost exclusively hydraulic vibration dampers are used in the automotive sector, in which a piston moves in a cylinder and forces oil or gas through small bores or valves. By changing the resistance, shock absorbers can be adapted to the vehicle properties. Modern shock absorbers are even electronically adjustable and allow comfortable or sporty damping, as well as adjustments to the load condition of the car.

Structure of the shock absorber
Structure of the shock absorber (source: Mercedes Benz)

What is the body vibration number and its meaning?

The natural frequency of the body can be measured by vibrating either the rear or the front of the car. The number of vibrations per minute is then referred to as the body vibration number. Vibration dampers do not influence the number of oscillations but the oscillation amplitude.

What is a soft chassis used for?

Airmatic chassis (source Mercedes Benz)
Airmatic chassis (source Mercedes Benz)

A natural frequency of less than one Hertz, ie a number of vibrations of 60 or less, can lead to nausea and significantly reduce driving comfort. Soft springs are mainly used in larger cars because the unfavorable weight ratio in small cars (payload compared to their own weight) does not allow this.

What is a hard suspension used for?

At a body vibration rate of 90 or more vibrations per minute, shocks reach the spine, which also affects comfort and health. High payloads on the rear axle compared to their own weight make hard springs necessary for small cars. When unloaded, the comfort is therefore only mediocre.