wheel rate contradiction

[GeetFsae]

http://www.miracerros.com/mustang/t_wheel_rate.htm


this is completely undecodeable.
Now since when did we start doing
WR = ((M.R^2) * spring rate * sine(spring angle))

can't understand why such different formula, when everywhere in the forum it's

W.R = Spring Rate * IR^2
where IR = DR * cos (spring angle)


help

[Zac]

Have you tried doing a free body diagram?

[Francis Gagné]

Search the forum for wheel rate, installation ratio and motion ratio. There is plenty of information in here! Also try to read Race Car Vehicle Dynamics from Milliken and Milliken.

The definition of the Installation Ratio in RCVD is the Displacement of Spring (Or compression) to displacement of Wheel

So IR = SpringTravel/WheelTravel (1)

The installation ratio will depend on your configuration. The formula you have is specific to an outboard suspension type with the shock end at the lower balljoint. If you have any other suspension configuration this equation is not appropriate. You will have to deduce the IR for your specific geometry.

For the Wheel Rate you want N/mmWheel, and you start with N/mmspring

All you have to do is find the force at the wheel for equal mechanical work (Energy conservation).

ForceWheel * DispWheel = ForceSpring * DispSpring (2)
ForceSpring = RateSpring * DispSpring (3)
Replace 3 in 2.
ForceWheel * DispWheel = RateSpring * DispSpring^2 (4)
ForceWheel = RateWheel * DispWheel (5)
Replace 5 in 4
RateWheel * DispWheel^2 = RateSpring * DispSpring^2 (6)
Isolate RateWheel
RateWheel = RateSpring * DispSpring^2 / DispWheel^2 (7)
Replace 1 in 7
RateWheel = RateSpring * IR^2 (8)

That should get you going. Search this forum and read suspension books to find out techniques to calculate the Installation ratio (Test Jigs, Cads, Matlab programs, etc)

[Adambomb]

Unfortunately I can't look at the source page because the web filter at work has blocked it because it is a "blog." Perhaps blogs aren't a good source for vehicle dynamics equations...

[Drew Price]

Originally posted by Adambomb:
Perhaps blogs aren't a good source for vehicle dynamics equations...



h t t p [colon] //fsae1000.blogspot [dot] com/

[Zac]

Originally posted by Drew Price:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
Perhaps blogs aren't a good source for vehicle dynamics equations...



h t t p [colon] //fsae1000.blogspot [dot] com/ </div></BLOCKQUOTE>

Perhaps blogs aren't a good source for vehicle dynamics equations. Scallop recipes are a different story.