Rates calculations

[Karam Atteia]

On calculating the Ride/Roll Rates for our suspension, my reference is RCVD and Optimum G Tips.

@ Optimum G, in the equation of the (Total ARB roll rates needed to inc. the roll stiffness of the vehicle to the desired roll gradient).. the term Kw which is the wheel rate, does it mean the front or the rear wheel rate??

My second problem is when using the magic no. (TLLTD) if i used the equation here in Optimum G (K_phi_FA = K_phi_A * N_mag.* MR^2 / 100).. Is it right to put N_mag. in % ... the K_phi_FA will not be realistic.

I attached my calculations, to know if i'm on the right way or not.(excuse me it is hand written)

http://img14.imageshack.us/img14/766/dsc01484qf.jpg

http://img89.imageshack.us/img89/531/dsc01485ty.jpg

[Charles Kaneb]

Your results look reasonable.

I don't see the equations you used - it's easier to catch mistakes if I can see them.

What's the load on your inside tires at this lateral acceleration? Off the top of my head, with a 350mm cg height, a 1.3m track, and a 1.6 g lateral acceleration you will be close to roll-over. 2ah/t = 2*1.6g*350mm/1300mm = .86 so 14% more lateral load gets you to zero load on both inside tires combined - and you may lift one inside tire before then, raising the cg height and sending you over.

[Karam Atteia]

@ Optimum G, in the equation of the (Total ARB roll rates needed to inc. the roll stiffness of the vehicle to the desired roll gradient).. the term Kw which is the wheel rate, does it mean the front or the rear wheel rate??

My second problem is when using the magic no. (TLLTD) if i used the equation here in Optimum G (K_phi_FA = K_phi_A * N_mag.* MR^2 / 100).. Is it right to put N_mag. in % ... the K_phi_FA will not be realistic.

For the first equation: the term Kw .. does it relate to average, rear or front wheel rate ?? Why ??

For the second equation: if for an example i used 5% magic no., when applying it in this equation .. K_phi_FA=(500*5*1^2)/100
.. K_phi_FA=25 Nm/deg twist .. which is not reasonable.



What's the load on your inside tires at this lateral acceleration? Off the top of my head, with a 350mm cg height, a 1.3m track, and a 1.6 g lateral acceleration you will be close to roll-over. 2ah/t = 2*1.6g*350mm/1300mm = .86 so 14% more lateral load gets you to zero load on both inside tires combined - and you may lift one inside tire before then, raising the cg height and sending you over.

I know that, but its my first time and i have to assume the CG height. And i found 350 mm is a good start to be on the safe side.

what do you think i can do for that??

[Lemon Lime]

Good to use optimum G !!! Great question I'm waiting for answers as well http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[Karam Atteia]

Please, would any one replay my questions. It is too critical to me.