4 link suspension geometry
 

Hi everyone! I have been lurking around this forum for a little while as a guest and finally decided to sign up. Great forum!!!! I am trying to do some homework before i start my project and i was wanting to learn more about suspension geometry. For example: I know with a solid axle rear end what ever is used to hold the rear end laterly (panhard bar,triangle upper links, watts link and so on) is where the roll center is located. My question is don't you want the roll center as high as you can go so it is closer the the Center of Gravity? I read somewhere that if you have too high of a roll center then it won't work right either. So with a four link suspension how much is too much on the roll center height? Also how critical is it. Would you notice it if it was a little lower roll center? I think that make sence. Thanks in advance for any clarification or tips.

Jeremy

Short answer, no you don't want your RRC as high as you can get it. Actually, a common practice now days in road racing is to set it as low as possible, as in mounting the Watts under the diff. You have to consider many variables when deciding on a RRC height. CG height, FRC height, roll steer %, rear roll axis, vehicle roll axis, anti-squat %, just to name a few. Some of these variables get used to determine where you want the RRC height, others are determined by the RRC height.

May I suggest Herb Adams book Chassis Engineering. It's a great read, very easy to understand. Good place to start. And then every other book you can get your hands on.

What kind of 4-link are you thinking about?

Kevin

THANKS for responding! I guess it is a little more complicated than i thought. I am trying to learn more about how the suspension geometry and how everything works. Cause and effects kind of thing. I am thinking about a trianglated 4 link for my project. I was hoping to make it from scratch. I have the herb adams chassis engineering book (great book). Is there any other books that might help me? Thanks again for helping

Race Car Engineering & Mechanics
by Paul VanValkenburgh


Competition Car Suspension: Design,Construction,Tuning
by Allan Stanforth


And the top of the ladder is,

Race Car Vehicle Dynamics:
by the Milliken brothers

RCVD isn't an easy read, nor is it cheap.


Kevin

triangulated 4 link has the downside of mooving the RRC.. as it is located where the two (usually upper) arms theoretically meet... on a g bar suspension that is compensated by keeping the mounts low on the rear end.. you should do a satchel link instead or ideally a paralell 4 link and a frame mounted propeller- wattslink that keeps the rollcenter fixed in relation to the c of g.