Hi, could you please help me? I would like to know the relation between motion ratio (displacement of spring/displacement of wheel), the spring force and tire normal load. Some sites say the relation is Fs = N/MR, other say it is Fs = N*MR. Which one is correct? Thank you!
+Victor Sanchez It depends which way the motion ratio is defined. If it is defined damper/wheel then the force on the spring is Fs = N/MR . If it is wheel on damper then Fs = N*MR
+ChassisSim Thank you ChassisSim. It is because I'm trying to find my ride height. If I have my MR (damper/wheel), and my tire normal load (due sprung weight) I can find my spring load (with the relation you told me, Fs = N/MR). With the spring load I can find its displacement (Fs = k*X), and with X (spring displacement) and MR, I can find my wheel displacement, and my ride height. Is it right? Thank you once more!
Victor once you know the spring load the total movement of the Chassis is d_c = damper_disp/MR + MR*F_s/kt; Where MR = Damper/wheel ratio F_s = Spring force at damper kt = tyre spring rate d_c = displacement of the body and wheel Subtract this from your static ride height and that is your dynamic ride height.
+ChassisSim I'm sorry, but what do you mean by "Subtract this from your static ride height and that is your dynamic ride height."?? Thank you for your help!
Victor when the car is in the garage it's static ride height is say rh_f_0 for the front and rh_r_0 for the rear. So when it is running on track the actual ride height is, rh_f = rh_f_0 - d_c_f rh_r = rh_r_0 - d_c_r Where d_c_f is the total car displacement at the front and d_c_r is the total car displacement at the rear. The formulation for these I discussed in my last comment.
rahul gaur Progressive motion ratios is when the motion ratio goes up with damper displacement. Regressive is the other way around. Progressive are used extensively in IndyCars. The idea is as the car compresses the wheel rate goes up supporting the car. However you need to be careful. WR is a function of Motion ratio squared so this can get out of hand very rapidly. However the advantage is it gives you non linearity without hysteresis
Hi Dan, so ive been reading on this stuff recently and i still cannot figure out an easy way to calculate this all, they say on wiki to square the ratio and then times the spring rate but thats where it gets me! How do i also know what spring rate to times it by? Im bad at maths and nothing online helps make it easier for me, i really would like to learn this but i dont know the best way around it. Is there a way that you can show! ........ well put it the way it is (dumb it down for me) haha please. From what i know my front ratio is 0.75 and my rear is 0.86 and this is where im stuck at! I now dont know the best way to progress to get what info i need from this! If you can help this would be great and i might understand if you can show the workings out etc. All this sqared and numbers that are shown online from examples dont match to what i get on a calculator lol Thanks Bobby
Hi, could you please help me? I would like to know the relation between motion ratio (displacement of spring/displacement of wheel), the spring force and tire normal load. Some sites say the relation is Fs = N/MR, other say it is Fs = N*MR. Which one is correct? Thank you!
+Victor Sanchez It depends which way the motion ratio is defined. If it is defined damper/wheel then the force on the spring is Fs = N/MR . If it is wheel on damper then Fs = N*MR
+ChassisSim Thank you ChassisSim.
It is because I'm trying to find my ride height. If I have my MR (damper/wheel), and my tire normal load (due sprung weight) I can find my spring load (with the relation you told me, Fs = N/MR). With the spring load I can find its displacement (Fs = k*X), and with X (spring displacement) and MR, I can find my wheel displacement, and my ride height. Is it right?
Thank you once more!
Victor once you know the spring load the total movement of the Chassis is
d_c = damper_disp/MR + MR*F_s/kt;
Where MR = Damper/wheel ratio
F_s = Spring force at damper
kt = tyre spring rate
d_c = displacement of the body and wheel
Subtract this from your static ride height and that is your dynamic ride height.
+ChassisSim I'm sorry, but what do you mean by "Subtract this from your static ride height and that is your dynamic ride height."??
Thank you for your help!
Victor when the car is in the garage it's static ride height is say rh_f_0 for the front and rh_r_0 for the rear. So when it is running on track the actual ride height is,
rh_f = rh_f_0 - d_c_f
rh_r = rh_r_0 - d_c_r
Where d_c_f is the total car displacement at the front and d_c_r is the total car displacement at the rear. The formulation for these I discussed in my last comment.
Hey Dan,I am quite confused with the concept of progressive and regressive motion ratios. Could you please explain this to me ?
rahul gaur Progressive motion ratios is when the motion ratio goes up with damper displacement. Regressive is the other way around. Progressive are used extensively in IndyCars. The idea is as the car compresses the wheel rate goes up supporting the car. However you need to be careful. WR is a function of Motion ratio squared so this can get out of hand very rapidly. However the advantage is it gives you non linearity without hysteresis
ChassisSim Thank you ....
Hi Dan, so ive been reading on this stuff recently and i still cannot figure out an easy way to calculate this all, they say on wiki to square the ratio and then times the spring rate but thats where it gets me! How do i also know what spring rate to times it by? Im bad at maths and nothing online helps make it easier for me, i really would like to learn this but i dont know the best way around it. Is there a way that you can show! ........ well put it the way it is (dumb it down for me) haha please. From what i know my front ratio is 0.75 and my rear is 0.86 and this is where im stuck at! I now dont know the best way to progress to get what info i need from this! If you can help this would be great and i might understand if you can show the workings out etc. All this sqared and numbers that are shown online from examples dont match to what i get on a calculator lol
Thanks Bobby
did you find something about that?