Originally posted by mxbundy
What I am talking about here is a 2 spring setup on one shock. Like the shocks on the front ends of quads or old vintage bikes.
What I need to know is what is the formula for figuring out what your spring rates should be.
I know that one spring is softer than the other and combined they equal a rate that is the addition of the 2. Then when the softer spring coil binds the rate increases to the rate of the stiffer spring, there by giving you a rising spring rate.
I need to know what the formula is for this. What is your rate when you combine the 2 springs? How do you determine at what point the rate increases. I know it is a function of the softer spring, and I would assume that you would vary the rate and lenght of this spring to determine at what point in the travel where it will cancel it self out. How do you determine this?
I am not a math major so I go easy on me! :thumb:
Thanks
Mxbundy
Mxbundy,
It is pretty easy to do the math, but not so easy to understand why it works like it does. The formula for the actual spring rate is (A x B) / (A + B). So it is the product of the 2 spring rates divided by the sum of the 2 spring rates. Same goes for a 3 spring stack, which I have seen done with older WP shocks. When you figure this out, you will be surprised to find out that the actual spring rate is WAY less than either of the single spring rates! They do NOT add together. Strange but TRUE! With the old WorksPerformance stack system, it used travel limiters to effectively "bottom out" the softer spring in the stack. It normally doesn't happen that the softer spring bottoms out completely and then the stiffer spring is a straight rate. This is why WP developed the bottoming stack, which was a set of rings that sat inside the spring around the shock body. With a spring collar between the 2 springs, it was possible to "tune" the poing of crossover where the dual rate springs traveled enough to bottom the collar out against the ring stack. THEN the second stiffer spring would act as a straignt rate spring. Formulas are available to figure out what rate a straight rate sprint is, but it is pretty difficult to figure the true rate of a tapered spring, because it changes as the spring coil binds the closely wound end and again, like the stacked springs, it is a complex system.
Hope this helps.
Swiss