Since we have the computer model of the chassis, and we have a computer model of the IRS system as well, it’s time to enlist the aid of another expert in the Rassini camp – Principal Engineer Jim Zeimet. Jim can take my model of the suspension along with the model of the chassis that Chris generated, and put them together in Rassini’s ADAMS software. ADAMS, short for Automated Dynamic Analysis of Mechanical Systems, is the simulation software that we talked a little about in our last installment. We located the trailing link bracket as far forward and inward as we could in the model, and Jim performed his magic.
After creating the unified model and applying simulated loads at the tire contact patch, Jim determined that it was impossible to reach the level of rigidity required with only one lateral link on each side – it was going to require a second link mounted to the front of the spindle mount to keep the wheel stable under cornering loads. Fortunately, we had discussed this early in the design phase, and had made allowances to add another link in just this case. Jim added the links to the model, and another run showed that we had the wheel control we wanted.
Another advantage of the ADAMS software is that it allowed Jim to simulate the performance of the roll stabilizer mechanism we wanted to employ. Jim simulated the suspension loads the CRX's tires would see both vertically and laterally, and we were able to see that the linkage between the upper arms worked as designed – locking the pivots of the composite upper control arms and forcing them to bend, and thus act like secondary springs that add to the roll stiffness of the car. If we just used standard links for the upper control arms, the suspension would lock up under cornering conditions, and the spring rate would instantly go to infinity, causing drastic oversteer – or, more likely, the rate would spike and then something would break – either result being undesirable!