Re: quattro-digest V4 #448

[Paul Ranson <100270.557@compuserve.com>]

 > The stock size is around 24mm
 > The bar is 35mm in diameter and it is hollow.

According to my book on such things the angular rate of a rollbar  in inch lbs
per degree is

( 19700 * ( OD^4 - ID^4 )) / Bar length.

Where OD is outside diameter and ID is inside diameter, the 19700 comes from the
shear characteristics of mild steel.

So assuming that the lengths of the two bars remain the same, the old bar was
solid and a wall thickness of 2mm for the new one I think your new bar is
actually less stiff than the old one, at about 95% of its stiffness. Any
increased actual roll stiffness will have to come from shorter activating arms
or moving the connection of the bar closer to the wheel.

It may be worth measuring things up precisely and calculating the actual
expected difference on the target vehicle.

Paul