Table of Contents

 

Introduction

Many years ago, the Alan Clarinval Supersport 22 racecar had a hydraulic suspension, which, for then unknown problems, caused the race team grief. The team switched to a standard mechanical suspension after some time, with a bit of modification to the car. CSU acquired this car, along with the original hydraulic suspension parts. Unfortunately, the only evidence of how the hydraulic suspension was mounted are the holes drilled in the front plates and two very grainy pictures of the front hydraulic suspension mounted on the car.

With fellow REU student Mike Senger working on reconstructing the hydraulic suspension, Dr. Fitzhorn assigned me to construct the front and rear suspensions in the computer program ADAMS 2003, using the regular mechanical suspension first, then changing the model to implement the hydraulic suspension. Estimating masses and inertias, I was to get a working suspension setup constructed, able to produce accurate test results.

 

Measurements

Before the suspension could be modeled in ADAMS 2003, I needed to acquire the measurements of the car as accurately as possible, so as to simulate the car as realistically as possible. Using string, two straightedges, and a few rulers, Mike Senger, Ethan Coffey and I took measurements of all the major points of the car’s suspension. After all of the measurements were taken, I put the measurements into ADAMS 2003 and began constructing the suspension.

 

Construction

For both the front and rear, I modeled the suspensions in multiple phases. Because the suspension of the racecar is rather complicated, I started with a very simplified version of the each suspension. I took joints that were close together and made them join at the same place. Both front and rear suspensions have a device called an anti-roll, a flexible blade that, when one wheel is pushed up, the other is pushed up as well, so as to prevent the car from rolling.
I initially modeled the suspension without the anti-roll, so as to simplify the model. This would simulate a full-weak anti-roll, so that the car would roll extensively.

I then moved on to a model with a full-stiff anti-roll. The anti-roll blade I used was not flexible, so when one wheel picked up, the other wheel was also picked up immediately. This approach was a bit unrealistic, but increased the complexity of the model in a desired direction.

Next, I modeled the suspension with a flexible blade in place of the anti-roll blade. This meant I had to make a custom flexible body using ADAMS FLEX. Unfortunately, ADAMS 2003 would not recognize the flexible rod as a force to be opposed, and thus would bend the blade completely, then lift up the opposing wheel. To fix this problem, I put springs in the direction of the bend of the flexible blade, thus supplying an antiroll to the car.

Finally, I coincided my front suspension model with Mike Senger’s front hydraulic model to produce a front suspension that had a nearly full stiff anti-roll based on hydraulic actuators attached to the pushrods of the front wheels. Fluid from the actuator pushes the main rod of a bigger cylinder out or in, which pushes on a spring damper. Two of the main cylinders are cross-linked, so that when one extends, the other does as well. This setup does not, however, include the leak valve that provides an adjustment to how stiff or weak the anti-roll is.

Aside from the front and rear suspension, I also modeled other systems of the vehicle, such as the body and steering mechanism, so that I could perform a Full Vehicle Analysis on the S22 with somewhat realistic results. The steering mechanism is a simple rack and pinion system that was relatively simple to model. Combining the front suspension with the steering mechanism allowed me to perform steering analyses throughout a variety of bump and droop heights.

Along with the two suspensions, I also roughed out a model of the body of the S22 using the program SolidWorks. I then imported it into ADAMS and assigned communicators, objects that tell the body where to grab the mounts of the suspension. I also modeled a set of wheels and tires in SolidWorks that looked similar to the S22 wheels.

 

Conclusion

After modeling both the front and rear suspensions in ADAMS 2003, I was able to look at a variety of tests. For the simplified model of the rear, a right single wheel travel produced the same results as a left single wheel travel. When I made the model more complex, namely connecting the anti roll links in a Y shape rather than a direct connection, different results were produced from a left single wheel travel versus a right single wheel travel. A graph of this can be seen in the “Rear Suspension” section. Also, as I started switching the connection points to the more complex model, the results changed slightly, but not in any great fashion as with the anti roll links.

The front suspension, however, produced non-symmetric results in the simplified model. It is my belief that the cause of this is the non-symmetric nature of the suspension itself, where one anti roll link connects on the front of a flat plate, the other on the back. Due to the nature of the suspension, I could not simplify this to test the theory without negating the effect of the anti roll. The front hydraulic suspension worked only in part. The main cylinders would extend when the actuator was pushed in, however, the action would not translate to the other wheel. The cause for this could not be pinpointed by the conclusion of the program.
Unfortunately, time and ADAMS 2003 worked against me in making a full vehicle assembly. Errors plagued the simulation compilation, and prevented me from analyzing the car as a whole. I was not able to insert the wheels and tires due to a lack of ADAMS Tire. I also did not have time to construct a powertrain or brakes custom to the car, so I was forced to use a standard set, something which I believe contributed to the failure of the full vehicle assembly.

For pictures of these results, please see the tables below for the corresponding suspension setup. Click on any picture for a larger version.


 

Front Suspension - Complex


Rear Suspension - Complex


 

Front Suspension - Hydraulic


Full Vehicle Assembly



 

Thanks

Special thanks and acknowledgements to the ARO, NSF, and CSU. Thanks to mentors Paul Heyliger, Patrick Fitzhorn, and Don Radford. More thanks go to Ethan Coffey and Mike Senger for their help.

 

Downloads

If you would like to download any of my files, please see below. Please credit me if you wish to use these anywhere. Some files may not work properly first time out. Please work with it to get some proper results.

Front Suspension (.zip, includes hydraulic)

Rear Suspension (.zip)

Body (.zip with .x_t file)

Wheel (.zip with .x_t file)

 

Contacts

Email me at the following addresses with questions, comments, or concerns.

shoncook@yahoo.com
sm_cook@coloradocollege.edu