KW 7-post dyno
The 7-post drive dynamics test stand provides testing facilities in the laboratory which ideally support subjective tests on the road and on the race track. The tests supersede a large part of the elaborate test drives which are performed in order to check the engine- or vehicle durability. Most of all for newly developed cars or such vehicles for which there is not any suspension concept available yet, those stages of development are very important. With the data gained and knowledge of the dynamic behavior of the shock absorbers, mainly the car body vibration can be reduced. By precision work at slight vibrations, also the grip can be positively influenced. Moreover, information about friction and bracing in the suspension and any form of asymmetry between the left and right side of the car can be obtained.
The drive dynamics test stand can be operated in the 4-, 6- or 7-post mode.
For different tests, the vehicle is equipped with following testing methods:
Acceleration sensors are attached to the rim well and control the vertical acceleration.
Car body acceleration at the front and at the back
Acceleration sensors are attached at the chassis, either at the front or the back axle.
Linear potentiometer (optional)
Direction sensors at the dampers.
In addition, also the effective acceleration of the actuators, the wheel load and the movements of the posts are recorded at the test stand.
The 4-post mode is the most popular and also the easiest option to carry out basic developments in the spring/damper unit. The test itself is a continuous sweep text. The vertical acceleration of the main actuators is constantly maintained, but the frequency and the acceleration are increased by making the distance shorter. The usual test is carried out in a frequency range of 1-20 Hz. Tests with motivation speeds from 50 to 300 mm/sec are possible.
The basic objectives of the test are damping optimizations which match the selected spring rate and moreover, the harmonization between the two axles. A suspension which is adjusted according to these basics, offers the best preconditions for detailed improvements at the stabilizers, vehicle height, aerodynamics and geometry at the race track.
In the 4-post mode we distinguish between the options basic and professional.
basic: Detailed adjustment within existing adjustment possibilities of conceptual finished products.
professional: basic + additional distance sensors at the shock absorbers for precise evaluation of eventually necessary adjustments in the damping characteristics.
By using two additional hydraulic cylinders (Aero Loader), a further load is added to two stable attachment points at the chassis. The 6-post mode can be carried out as a support to the 4-post mode in order to simulate aerodynamic loads.
The 7-post mode is reserved for the so-called track replay mode. First of all, data has to be collected at the race track which is then evaluated at the test stand. The data record can only be used for identical car constructions. At the chassis, three solid attachment points have to be created for the three additional hydraulic cylinders which supply lateral inclination, down thrust and other car body movements during the test run.
At the chassis, three solid attachment points have to be created for the three additional hydraulic cylinders which supply lateral inclination, downthrust and other car body movements during the test run.
Klaus Frank, Driving Dynamics / Damping Development