Suspension Modeling

[Flieger]

I also posted this on the Autocross/Racing forum but I figured some of you guys might like it too.

911 Front Suspension (Struts)

or "what engineering students do when they get interested in something and have some free time".

Chassis measurements kindly supplied by Evan Fullerton. Any excessive baseline camber or caster is due to the difficulties in measuring on an assembled car.

Torsion bars, static ride height (A-arms level) and tire diameter are from my car.

Spindle geometry partially from Clint at Rebel Racing.

Now looking to add bump steer, can anyone help?
I need the inner pivot- how high above torsion bar axis (tba) and how far back/forward from the ball joint. Also need the location of the outer pivot in 3D. All these taken while steering wheel straight for now.


911frontwheelrate by Max_911S_fahrer, on Flickr


911frontwheelscrub by Max_911S_fahrer, on Flickr


911frontwheelangles by Max_911S_fahrer, on Flickr

Code is MATLAB. It continues to be refined. I can modify dimensions to suit your car and give you customized graphs.

I also have the velocities and accelerations of all the links. If I could draw accurate models in SolidWorks I could get mass properties and if I could get a damping constant I could model the total force on the tire due to unsprung mass, damping, and spring as it goes through a bump at a certain acceleration, speed, etc.

Sorry to disappoint those of you expecting scantily clad ladies.

[RWebb]

you could put a scantily clad lady in each graph pointing to the stock condition on a level road

this is a good trick for seminar presentations

[Flieger]

I will work on it. I don't think MATLAB has any built-in functions for that, but I will look again.

[JohnJL]

You have 8 degrees of caster at static? She heavy to steer? I'm back against the stock holes in both cars and get max 6 degrees.

Yes to adding naked ladies to the graphs.

[Flieger]

It is a little high. I think I had around 7 or more before the last alignment but I did not receive a print out with the new alignment settings. The casters were not equal before so I told them maximum caster while remaining equal. The camber is high negative too.

I can change the top strut pivot from 3.5 inches back from ball joint to about 2.5 inches and that gets the caster into the 6.5-7 degree range.

I could do something similar for the camber.

These numbers are hard to measure, so I welcome any measurements which would have a higher degree of precision and accuracy.