7 post shaker
The 7 post shaker is a piece of test equipment used to perform technical analysis on race cars. By applying shaking forces the shaker can emulate banking loads, lateral load transfer, longitudinal weight transfer and ride height sensitive downforce to emulate specific racetracks.
The 7 post shaker is used for many vehicles in different driving conditions. Earlier versions were the 5 post shaker and the 4 post shaker. The 4 post shaker is commonly used by vehicle manufacturers to investigate squeaks and rattles. Manufacturers do not normally use a 7 post rig for road cars because these vehicles are not normally subject to the same aerodynamic effects as a race car operating at high speeds. This technology was first used in Formula 1 in the late 1990s, and is now also used by other series such as NASCAR and the Indy Racing League. NASCAR teams with 7 post rigs include Hendrick Motorsports, Richard Childress Racing, Chip Ganassi Racing, Furniture Row Racing, and Roush Fenway Racing. The car driven by Jeff Gordon is shown on a 7 post rig in this video.
Vehicle designers use the results of the testing on the 7 post shaker to adjust spring rates, shock valving and steering ratio to best suit conditions of a specific emulated track.
The 7 post shaker places forces on a vehicle and records the forces that the vehicle puts back into the system. The 7 post applies lift, downforce, road irregularity forces and load transfer due to braking, acceleration and cornering. The vehicle suspension and drivetrain components respond to these forces, chassis and suspension frequency oscillations (under 30 Hz), and tire, engine, transmission and drive axle vibrations at higher frequencies. The forces applied are calculated from a model of the racetrack, the weight of the car and driver, tire pressure, engine RPM, and driveline RPM. The forces that the testing engineers want are placed on the car through the use of four main hydraulic actuators capable of generating 25 kilonewtons (5,600 lbf) of force with a maximum velocity in excess of 1 metre per second (3.3 ft/s) that act on the tires. While the actuators are capable of producing frequencies as high as 500 Hz, this is not necessary as the elasticity of the rubber and air in the tires will absorb most inputs above 50 Hz. The remaining three posts are known as aeroloader actuators, and are responsible for the sprung mass of the vehicle. The forces that these three actuators represent are inertial loads that come from entering a curve or aerodynamic loading and unloading in the form of downforce or lift from a wing. These forces are small on road cars where speeds are not normally greater than 140 kilometres per hour (90 mph), but are significant on a race car where speeds can exceed 300 kilometres per hour (190 mph).
...
Wikipedia