Suspension Geometry Suggestions

[wickedmotorhead]

Below is the initial design of the front suspension for WSS. The fixed components are the spindle and the tire. It is a typical upper a-arm with a strut lower. I an looking for any input thus far until I can get my hands on something like performance trends to check roll center migration. Let me know what you think since this is my first complete scratch design of this type. I included the camber measurements for three static instances. Thanks

[dennis68]

At first glance right away camber gain sticks out as a problem. Less than a degree of gain per inch is pretty weak. It would be interesting to see on an analyzer.

Tell Tyler to step-up and buy his new engineer some software (even if it is for personal use).

[astroracer]

Just looking at dimensions isn't going to prove out your design. You need to get P-T's Analyzer program and plug all of the numbers into it. You can get it as a 9 day trial. That's how I designed the suspension for BAD AST with a ton of help from Salt Racer. I finally broke down and bought the program a couple of weeks ago just so I can rerun my numbers and double check everything AGAIN...
Bumpsteer, Roll, Anti-dive, Caster & Camber gain, even shock placement and inclination angles are all part of the design. You have a start but drawing it 2D is just the tip of the 'burg. I redesigned my entire suspension in 3D 5 times before I was happy with it. I also have the ability to cycle the components through Jounce and Rebound and Full Left/Right steer to check component clearances. Lots of things to think about when you're designing a complete suspension from scratch... Scrub Radius, Ackerman, Roll Center Migration, etc., etc.
Just keep it fun.
Mark

[wickedmotorhead]

Thanks guys thats what I thought, but I was just excited that I got a start on it. I thought the camber curve was a little weak too, but I did get -.89 at 1" and another -1.12 at 2" with the static set at -1*. Just thought I'd share what I got so far in case something looked really wack out of place. Mark, I planned on doing the same thing in modeling the entire frame and suspension with motor, etc. to check clearances. I already pretty much have a lot of the frame done. Now its come down to getting the P-T software. So the initial RCH and SVSA look pretty typical? How about the scrub? I could get less, but I decided against running an excessive backspace and I'm kinda stuck with the 8* KPI. Other than that, back to the drawing board for more fun. These numbers where the very first I tried so I have a lot of experimenting to do. What's a good approach for setting anti-dive? I think I have a good handle on the bumpsteer and shock placement, but I'll post that later. Thanks again for your input.

[Salt Racer]

Like others have said, have Tyler gets you the software as soon as possible.

Camber curve is fine. You have to look at the overall picture. Shortening FVSA is not the only way to gain camber while cornering. Don't forget you'll lose traction under braking as you increase camber gain via altering FVSA. I will let you figure out how to go around this. You will have to design suspension for ATS sooner or later - trying to figure out how suspension works in your own head will make you a better engineer in the end.

Reduce scrub radius to less than 0.75". With 13" wide tires, you'll hate yourself otherwise.

Unless you're widening the fenders, 75" won't give you much steering angle at the ride height you're shooting for. Don't assume anything - mock up the car at the height you want, then measure until you're totally comfortable.

[TurboLark]

Could I get a suggestion on a book to learn more about all the different terms and characteristics about suspensions. From suggestions abouve, i bought PT Analyzer to design my sandrail suspension. Since i am looking at over 20" of wheel travel, there is alot to be concerned with. I know the basics(bump steer, camber curves, etc) but need to learn more about instant center migration, caster changes, anti dive, etc.
Thanks.
Phil

[TurboLark]

Could I get a suggestion on a book to learn more about all the different terms and characteristics about suspensions. From suggestions abouve, i bought PT Analyzer to design my sandrail suspension. Since i am looking at over 20" of wheel travel, there is alot to be concerned with. I know the basics(bump steer, camber curves, etc) but need to learn more about instant center migration, caster changes, anti dive, etc.
Thanks.
Phil

Noone with info?

[dennis68]

Herb Adams or Steve Smith. They are both good, easy to read authors. There are several others once you have a grasp on the basics. Fred Puhn and Miliken are very good but very technical reads.

[astroracer]

Look here...
http://www.gmecca.com/byorc/designpu...ionsbooks.html
and here...
http://www.longacreracing.com/articles/art.asp?ARTID=13
Mark