Spring Rates, Wheel Rates, Motion Ratios and Roll Stiffness Stiffness Appendix 1
ME 470 Vehicle Structural Design Dr. Richard Hathaway, P.E., Professor Mechanical and Aeronautical Engineering
Spring Rate Calculations
Spring Rate Calculations Calculations
Coil Spring Calculations: K =
G d 4 64 R3 N
K = Spring Rate in lbs/in G = Modulus of rigidity lbs/in d = Spring R = Mean Radius of the Spring Spring Wire Diameter N = Number of Active Coils Squared and Ground Ends -1.75 turns Squared or Closed Ends ---Plain Ends -0.5 turns Plain ends Ground -1.0 turns
G =
E 2 (1 + µ )
Spring Rate Calculations Calculations
Coil Spring Calculations:
If Steel is used: psi
K ≅
E = 30,000,000
1,500,000 d 4 3
D N
Spring Rate Calculations Calculations
Torsion Bar Rates:
θ =
TL
T JG
JG
θ
L
=
d
L L = Bar Length
π d 4 J = 32
d = Diameter
r
Bar
4
T = π d G θ 32 L Let the deflection at the end = δ