In today’s highly competitive racing industry, driver skill and engine/drivetrain performance are not the only ingredients of a winning race team. Suspension and chassis design can be the deciding factor in a team’s success.
Until recently, fine-tuning a racecar’s chassis and suspension was done at the track through a process of trial and error. Livingston & Haven (L&H) and Accelerating Developments International (ADI) have developed the K-RIG and the KD-RIG to allow crews to conduct testing in a controlled environment that provides high-speed simulation data acquisition.
L&H and ADI designed and developed their semi-dynamic testing systems to broaden the spectrum of diagnostic scenarios for suspension, alignment, and chassis on today’s racecars. Teams are now able to tune vehicles ahead of time, so they are tighter and easier for the driver to control and race at peak performance.
K-RIG is a four-post system that uses sensors and Bosch Rexroth hydraulics to provide motion and capture detailed data about chassis and suspension functions.
Vehicles are driven onto the rig so that each wheel rests on one post, or “tower.” The car is held rigid via tie-downs between the rig frame and the car chassis. The vehicle is then lifted high enough off the floor that technicians can view the underside of the car during testing.
To test, each corner of the rig can be actuated—independently, in combination, or all four synchronously—to measure the effects of different forces on the position of suspension components such as springs and tie rods.
KD-RIG, the newest version of the system, uses a combination of Bosch Rexroth linear ball rails, ball screws, and servo motors and drives for each leg of the rig to provide the movement simulation.
"Simulation is the key—the watchword of the day at NASCAR right now,” explained Clifton Vann IV, President of L&H. “The new generation of crew chiefs and crews have gone from an attitude of ‘feels good, let’s see how it works’ to a different mind-set—they want to see the data.”
The K-RIG uses the Rexroth AA10VSO hydraulic pump, and four 4WREE6 proportional directional valves and CDT4 cylinders in each leg of the rig to lift the vehicle and provide the independent movement that simulates changes in the road surface.
A Rexroth VT-HACD force/position digital hydraulic controller controls the motion sequences. Each tower can be moved as little as 1/1000 of an inch for precise simulation. VT-HACD controllers deliver responsive control, smooth transitions from velocity to pressure regulation, and repeatability to fractions of an inch.
“Using hydraulics for force control was easier because we can maintain hydrostatic balance in the cylinder,” Vann said. “This also lets us measure the pressure in the hydraulics as we are moving through various force and load simulations.”
L&H and ADI developed the KD-RIG to provide faster motion, increase the range of diagnostic simulation scenarios, and enhance high-speed control and data acquisition.
To accomplish these goals, they chose a combination of Rexroth electric drives and linear ball rail and ball screw systems to build the new rig, which has a total of 12 motion axes.
The four KD-RIG towers are each powered by a Rexroth EcoDrive MKD synchronous servomotor with absolute feedback and DKC EcoDrive 03 drive unit.
The EcoDrive system in each tower drives a Rexroth ball screw, which lifts the vehicle to the desired height for simulation. Each tower is also mounted on a Rexroth ball rail linear guide system.
Both rigs have given race teams a new view of their vehicles—in many cases, helping identify and correct issues they were not able to see before.
“Just putting the car up on the rig and being able to stand under it and look at the suspension, the springs, the rocker bars as the car goes through various simulations has been a major benefit,” Vann said.
“They’ve discovered things such as suspension rocker arms rubbing brake lines—a potentially fatal condition for the vehicle; if the line gets broken, that could take the car out of the race in the first 20 laps.”
During a simulation, each tower moves up and down and side to side to subject springs, suspension components, and chassis frame to accurately captured track surface conditions at a specific raceway.
Sensors in each tower can capture data on various conditions. The rigs can measure such things as force over position curves. This helps teams understand how vehicle suspensions are performing, compared to original design and engineering assumptions.
To make the simulations as accurate as possible, the teams can run a test car equipped with sensors for multiple laps at a specific racetrack. Road surface condition data captured in this way can be loaded into the KD-Rig and used to re-create how that raceway’s surface will impact the car’s suspension—its attitude in the straightaways, in the turns, high up in the curve or down low.
The crew can inspect all the suspension elements—coils, rocker bars, etc.—and understand exactly what is happening and the best way to adjust the settings for the starting line, and throughout the race.
Matthew Monaghan edited this article for AEI based on information provided by Dave Giffels, Business Planning Manager for Bosch Rexroth.