25-08-2017, 09:32 PM
Collegiate Design Series Suspension 101
Collegiate Design.ppt (Size: 1.86 MB / Downloads: 172)
Suspension 101
Ride Frequency/ Balance (Flat Ride)
Motion Ratios
Ride Friction
Suspension Geometry Selection
Suspension Layouts- Double A Arm Variations and Compromises
Dampers- A Really Quick Look
Ride Summary
Flat Ride
Improves handling, acceleration, braking performance
Plenty of suspension travel
Allows lower spring rates & ride frequencies
Allows progressive jounce bumper engagement
Good motion ratio
Reduces loads into vehicle structure
Increases shock velocity, facilitates shock tuning
1.00:1 is ideal, 0.60:1 minimum design target
Stiff structure (The 5th Spring)
Improves efficiency of chassis and tire tuning
Provides more consistent performance on the track
Applies to individual attachment compliances, 5:1 minimum design target, 10:1 is ideal
Successful SAE designs in the 2000-3000 ft-lbs/deg range (static torsion), 2X for static bending (lbs/in)
Low Friction
Permits dampers to provide consistent performance
Not masked by coulomb friction (stiction)
40:1 minimum (corner weight to frictional contribution for good SLA suspension
Front Suspension Front View
Start with tire/wheel/hub/brake rotor/brake caliper package.
pick ball joint location.
pick front view instant center length and height.
pick control arm length.
pick steering tie rod length and orientation.
pick spring/damper location.
FSFV: wheel/hub/brake package
Front view instant center is the instantaneous center of rotation of the spindle (knuckle) relative to the body.
Front view instant center length and height establishes:
Instantaneous camber change
Roll center height (the instantaneous center of rotation of the body relative to ground)
RSRV: wheel/hub/brake package
Some independent rear suspensions have a link that acts like a front suspension steering tie rod. On these suspensions, steering tie rod length and orientation (angle) determines the shape (straight, concave in, concave out) and slope of the ride steer curve.