×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

four-link suspension

four-link suspension

four-link suspension

(OP)
I need some help designing a four-link rear suspension for a 70 Camaro.  I’m not sure where to start with my analysis.  I’m going to be driving the car on the street so I’m not trying to design a race car.  I know that if I were designing a race car I would look at the track conditions in which I would be racing, i.e., turn radius.  I’m not sure what driving situations I should be concerned with.  Should I decide on a critical speed and design around that?  I understand the kinematics of the four-link from reading Race Car Vehicle Dynamics by Millikin and Millikin and have constructed a 2-D drawing of the plan and side view for the suspension.  I’m not sure how to figure out how much understeer I want to achieve from the rear geometry.  Some insight into this would be helpful.

Chris

P.S.  I’m also curious how to find specification on the car, like radius of gyration.

RE: four-link suspension

Critical speed should be considered but is unlikely to be of much concern for a street car.

Really you want a suspension that doesn't steer too much in any condition, and that generally tends to oversteer the axle (ie understeer the car), rather than the opposite. Of course to work this out you need to know what the front suspension is up to...

You also want to hold the wheels square to the road, or slight neg camber for the outboard wheel.

With a 4 link suspension your options are pretty limited. Start by laying out the longest lower arms you can sensibly package. In side view then adjust your upper arm length to give you antisquat.

In plan view angle your upper arms in to give you some steer.

Getting the radius of gyration is tricky - if you can find a figure for a similar sized car use that, or else build sa spreadsheet with all the components in and enter the centre of gravity and mass of each component, and an estimate of the component's radius of gyration, or if all else fails use Rzz=1/8*width+1/3*length. Doesn't Milliken give some guidelines?

There is a way of measuring it directly using a trifialr suspension, but it is not practical unless you have a 30 foot high gantry and a suitable platform.



Cheers

Greg Locock

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources