Figure 5. All four corner...
Figure 5. All four corner transfer functions from the first run on the seven-post to the last run. The red lines represent the first runs and the green lines represent the final run after changes were made. Less deviation means more grip as we can see.
"It's critical to optimize the shock and spring together as a package. The shocks on the car were adjustable. Great gains were made by adjusting the rebound settings but a complete rebuild would have been necessary to achieve optimal grip and body control. Luckily, a good selection of springs was available to find the best match for each shock on the car. The graph in Figure 5 shows how the new combination (green) gave much more consistent behavior throughout the operating range at all four corners of the vehicle.
"A roll stiffness test was performed to calculate the roll stiffness on the front and rear axles. Units are in ft-lbs per degree of roll. It's important to note that the final roll stiffness distribution was very close to the baseline but with an overall stiffer setup. This indicates a similar weight transfer but with an overall more stable platform. Had more springs been available, a closer match would have been possible.
"Performance during the race weekend reflected the significant improvements achieved on the rig. The car attitude was noticeably improved as was the stability and consistency. The driver was able to run consistent, quick lap times and changes made to the vehicle during practice were effective."
The individual wheel loads...
The individual wheel loads are displayed outside the control room so observers can take note.
What we weren't able to do was compare the first test setup against the seven-post rig setup on the same day under the same conditions. Differences that influenced the second test, which was a practice day for the race the next day and was run with the improved carburetor setting, were newer rubber than the fastest runs at the first test, and a track that was hotter and slicker in the second test. All of these caused the comparison not to be apples to apples.
The ideal scenario would've been for us to conduct the second test with both setups to properly evaluate the differences. Then, we may have taken positives from both, applied them to the car, and then run a third setup against the other two hopefully showing improvements. Comparing the performance between the two sessions related to lap times, we see little difference.
Table 2. Front and rear roll...
Table 2. Front and rear roll stiffness and stiffness distribution for all spring/bar changes made on the seven-post. We had conducted a design and refinement of the dynamic balance of the car before and during the initial test. Joe tried to maintain that balance when making changes to the stiffness of the setup.
The three quickest laps run in the pre-seven-post rig test were 17.07, 17.09, and 17.11. Almost all of the remaining faster laps were in the 17.1s. When the team went back to the track on fresher tires, the fastest three lap times were 17.12, 17.13, and 17.16 with most of the other significant laps in the 17.2s, 17.3s, and 17.4s. The team did a mock qualifying run on stickers at the end of practice with the first lap showing 17.07 and the second lap at 16.84. This run was made later in the afternoon and we assume the track had cooled.
Subsequent runs on those same tires yielded three fastest laps of 17.11, 17.15, and 17.16 and a comment from the driver that the car was "tight/loose center." I believe in an overall analysis that the high mid-afternoon track temperatures caused the car to be loose and the team then made changes to compensate to tighten the car. Those changes tended to make the car too tight when the track cooled in the late afternoon.
The tests, the review of the recorded data, and the time spent on the seven-post rig were very beneficial in teaching us how the various components on the race car worked together. That information combined with careful evaluation at the racetrack are all tools that can provide insight into how to improve your overall package. Remember that we are after not only fast lap times, but overall consistency and speed over long periods. Those are what truly win races.