Rolling Rally Cars

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Fri 13 Jul 2007 20:16
Rolling Rally Cars - Imagos
Always been intrigued as to the reason why it seems so easy to roll a rally car at relatively low speeds.

Just been watching one of those car crash complications on Men and Motors and virtually all the roll overs where at very low speeds, maybe less than 20mph!

So why is this? and why aren't our country lane full of rolled over wrecks?

Hit a verge, these cars go over!
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Fri 13 Jul 2007 20:17
Rolling Rally Cars - Pugugly {P}
complications ?
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Fri 13 Jul 2007 20:47
Rolling Rally Cars - bell boy
any car will go over if you get the angle right and if you are probably braking when you hit the kerb as the wheels say no but the body mass and energy say yes.
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Fri 13 Jul 2007 20:46
Rolling Rally Cars - Kuang
Maybe it's a difference in perception on screen between how fast the cars appear to be going and how fast they really are going? Add in the raised suspension and the fact that they generally hit obstacles broadside and it's not so surprising they roll quite often.
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Fri 13 Jul 2007 22:42
Rolling Rally Cars - BazzaBear {P}
Going sideways + sudden stop = laws of physics take over!
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Fri 13 Jul 2007 23:22
Rolling Rally Cars - Number_Cruncher
A very simple first pass analysis, ignoring tyre deflection and suspension deflection

Taking moments about the outer tyre contact pathes;

m*h*a=m*g*t/2

re-arranging gives

a=g*t/(2h)

where

a=lateral acceleration
t=track width
h=height of centre of gravity
m=mass of car

Fairly obvious really, a low slung, wide car is more resistant to rolling.

However, some work done in the US has found that the complications I missed out are important - they looked at the correlation between rollover incidents and so-called "rollover propensity", which is proportional to h/t. They found that the correlation did not explain the incidents of rollover, and that other factors, including the type of person who might buy a particular type of car might be of importance - i.e., the type of person who buys a vehicle with a high c of g might not drive it so aggresively.

Number_Cruncher
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Fri 13 Jul 2007 23:53
Rolling Rally Cars - Altea Ego
well thats cleared that one up for me.
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TourVanMan TM < Ex RF >
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Sat 14 Jul 2007 00:01
Rolling Rally Cars - Number_Cruncher
Always a pleasure - never a chore!
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Sat 14 Jul 2007 00:17
Rolling Rally Cars - BazzaBear {P}
I preferred my equation ! (because I understood it ;) )
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