I found the email describing why Rootes moved the Panhard rod from the Mk1
location to the MkII location.
Jeff
>
> To those interested in Panhard locations, here is my analysis to answer
some
>
> of the recent questions.
>
> The stock Mark I rod runs from below the wheel centerline of the axle on
the
>
> left side to high on the body on the right side. The Mark II runs the
> opposite direction. The instant roll center of the rear suspension is
> defined
> as the point at which the Rod intersects the centerline of the car.
>
> When accelerating out of a RIGHT turn, the body rolls to the left, raising
> the right pivot. When this happens the instant roll center of the rear
rises
>
> increasing the roll stiffness of the rear suspension. Two things now
happen.
>
> The engine torque into the rear axle as well as the increased rear roll
> stiffness cause vertical loads to be shifted from the right rear and the
> left
> front tires to the left rear tire. As the left front and right rear tires
> lose vertical loads they lose cornering power. These cornering forces are
> additive and transferred to the left rear tire. As the force exceeds the
> tire
> capability there will be an extreme oversteer in right turns and lifting
and
>
> spinning of the right tire.
>
> When accelerating out of a LEFT turn, the body rolls to the right, lowering
> the right pivot. When this happens the instant roll center of the rear
> suspension lowers, decreasing the roll stiffness. Again two things happen.
> The engine torque into the rear axle as well as the decreased rear roll
> stiffness causes cornering force capability to be shifted to the right
front
>
> tire. As the force exceeds the right tire capability the car will have
> understeer. Having a car that handles different when turning left or right
> is
> not fun.
>
> With the Tiger Mark II, which has the Panhard Rod running from the right
> side
> of the axle to the left side of the body, the opposite dynamics happen and
> these loads subtract from each other. The left and right turn differences
> are
> improved and it is easier to balance front and rear roll stiffness.
>
> So, to improve the Tiger rear geometry in order of complexity, you can
> change
> the Panhard Rod to the Mark II design, make the Panhard Rod horizontal by
> lowering the frame attachment pivot or install a Watt's linkage. Good luck
> in
> finding room and feel free to add more ideas.
>
> John Logan
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