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Re: effect of inclined roll axis on handling?

To: nihal@berkeley.edu
Subject: Re: effect of inclined roll axis on handling?
From: james creasy <jcreasy@perforce.com>
Date: Wed, 19 Jul 2006 11:12:59 -0700
>The higher rear roll center
>would help transfer weight off the inside rear wheel very quickly, and
>thus help rotate the car since.

this is the precise effect i am interested in, since it gives better turn-in 
and then steady state is tuned with bars and springs.

>you could just use the
>standard weight transfer equations involving track width, lat accel, and
>CG height.

here is where i get fuzzy.  i dont think we can consider the front and rear 
systems in isolation since they are coupled by the chassis.  or at least, i 
dont have a good answer for those that say i cant :)

is there a substantial effect on corner weights caused by the car twisting 
under roll due to the inclined axis?

how much of an effect does the rotational inertia of the car play- weight will 
be transferred slightly ahead of the deflection of the springs/bars, and i 
think this force is applied to the tire sidewalls.  

james




nihal@berkeley.edu wrote:

>You will have to know the lateral accelertaions on both axles in order to
>calculate the specific weights on each wheel. This is very difficult
>unless you hada good data acq. system.
>If you had the lateral accels at on both axles you could just use the
>standard weight transfer equations involving track width, lat accel, and
>CG height. From there you can take the ratio of RC height to ground height
>vs. Cg height to RC height on each axle. But since this isn't steady state
>you won't know the affects of your shocks, friction, preload on the actual
>amount of weight being transferred instantly through the RC (or chassis if
>you prefer) vs. your springs, shocks, and sway bars.
>
>At the very first instant when the turn is initiated I would see the
>inclined roll axis having little affect due to the lack of rear lateral
>acceleration, but after say the first .1seconds it would since the rear
>axle would then have lateral acceleration. The higher rear roll center
>would help transfer weight off the inside rear wheel very quickly, and
>thus help rotate the car since.
>
>If this doesn't make sense I'll try and clarify it more.
>  
>
>>specifically, im interested in the transient effect on corner weights at
>>the start of a turn.
>>
>>by inclined roll axis i mean the rear and front roll centers are not at
>>the same height.
>>
>>does someone have the math for this handy?  i havent been able to reason
>>it qualitatively.  thanks,
>>
>>james
>>OSP - Oculating Suspension Permutations




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