I got this from a book called "Chassis Engineering" by Herb Adams and thought they'd come in handy around here. Pretty good book, but dedicated to sports car suspension and definetly not Jeep related. These formulas are universal tho, obviously.
Coil spring rate= Gd^4 / 8ND^3
Where:
G = Torsional modules of steel (11.25 x 10^6 or 11,250,000)
d = wire diameter in inches
N = Number of active coils
D = mean coil diameter in inches
8 = constant for coil springs
Leaf spring rate= (WN / 12) X (1000t / L)^3
Where:
W = width of leaves in inches
N = number of leaves
T = thickness of 1 leaf in inches
L = Length of spring in inches
12 = constant for leaf springs
I haven't verified any of this or tried it on my own springs to see how well it jives, and I do have a couple of questions about it. On the length of leaves, the example in the book uses the entire length of the pack and doesn't take into consideration the different lengths of the leaves in the pack...I don't know if this is a generalization or what.
He also states that a spring rate stays the same over the life of the spring. If it sags its load rating has dropped, but the actual spring rate stays the same.
Anyway, just thought this might be of some use to someone around here.
-Skits
Coil spring rate= Gd^4 / 8ND^3
Where:
G = Torsional modules of steel (11.25 x 10^6 or 11,250,000)
d = wire diameter in inches
N = Number of active coils
D = mean coil diameter in inches
8 = constant for coil springs
Leaf spring rate= (WN / 12) X (1000t / L)^3
Where:
W = width of leaves in inches
N = number of leaves
T = thickness of 1 leaf in inches
L = Length of spring in inches
12 = constant for leaf springs
I haven't verified any of this or tried it on my own springs to see how well it jives, and I do have a couple of questions about it. On the length of leaves, the example in the book uses the entire length of the pack and doesn't take into consideration the different lengths of the leaves in the pack...I don't know if this is a generalization or what.
He also states that a spring rate stays the same over the life of the spring. If it sags its load rating has dropped, but the actual spring rate stays the same.
Anyway, just thought this might be of some use to someone around here.
-Skits
