Originally Posted by
Big Lee
While in the rc world we can weigh corners and measure the dimensions of our suspension geometry. Knowing our spring rates. There would be a mathematical equation to work out spring frequency and hence match front to back. Anybody know it
I can field this one, my specialty is vibrations.
Undamped natural frequency = (square root of (stiffness/mass))/2pi
With appropriate and matching units of course. (Imperial fans, remember slugs for mass?)
In this case the stiffness is the essentially the effective vertical stiffness at the inner arm pivots (left and right combined). Need to consider the arm leverage on the shock, and the shock angle.
Similarly mass is the effective modal mass at that point. In rough terms the suspended-chassis mass at that end, plus a portion of the arm (would be one half if constant cross section) and the suspended portion of the shock with all of the position and angle considerations. Doesn’t include the wheel-spindle etc mass.
Whew, as alluded to that’s probably a little tricky to actually figure out. But the basic relationship is fairly simple and can be useful to estimate changes. Frequency = sqrt(stiffness/mass)