Alonso wrote:No No please dont get me wrong. Just moved it to the rite forum. tried to do the formulas but very difficult to figure. all the info i can gather will help me more an more.
OK, lets start from the beginning: to se how stiff a suspension is, you have to watch mass and springs altogether. Imagine a 550 pound/inch spring (if you put a 550 pound force to it, it will deform 1 inch) mounted in a bus: that suspension would be way too soft. Now imagine the same spring mounted in a bike: that suspension would be way too stiff. So its all about combining spring and mass.
So, the formula that relates them is the one of frequency:
K is your wheel rate (not the spring rate) and M is the mass of the given wheel corner you are looking at.
Proceed like this: measure corner weights.
Lets supose your 490Kg duratec weights 135Kg at each rear wheel and 110Kg at each front wheel. So to determine rear frequency you will have to use 135Kg in the formula.
Now lets supose your 750 pounds/inch rear springs are mounted in a way that the spring moves 1 cm for every cm that the wheel moves. That is indicating us that the motion ratio is 1. Motion ratio = wheel movement / component movement.
You can measure component movement between shock mounting points if the spring is coilover the shock.
For a motion ratio = 1 you have that the K at the wheel is 750 pound/inch that equals 131.345 N/m. One Newton is 9,8 Kgm/s2 so:
K = 1,287,181 Kg/s2 (Kg mass, not force)
Now, the frequency at the wheel is:
f = 1/2pi * sqrt(1,287,181 Kg/s2 / 135Kg) = 15,54 1/s = 15,54 Hertz.
Its evidently that the motion ratio is not 1 because 15Hz is a very high natural frequency for a racing car. Street cars are arround 1Hz and small racing formulas can be arround 3 Hz.
So, remember K at the spring = K at the wheel *
Once you measure MR you can calculate wich is the K at the wheel you will have to insert in the frequency formula.
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