Changing the rack
> position doesn't
> change those lines so the Ackerman stays the same,>
>
Those lines are just used to determine reference for "true" ackerman and
percentages of. Moving the rack fore/aft will affect the ackerman as what
really results is and increase or decrease of the rate of change of the
angle between the steering components (rack, tierods, steering arm). The
difference in the rate of change is what causes one wheel to steer more than
the other. On a rear-steer system moving the rack rearward from a true
ackerman position will result in "more than" true ackerman (i.e. 110%) and
moving it forward will bring it closer to parallel steer.
If you could develop a system to steer the car optimally at all times then
ackerman would not exist and each wheel would steer independantly based on
the corner, weight on that wheel, camber angle, and the slip angle needed to
develope maximum cornering force for those conditions. But for now you can
only design for the corner that you percieve as the most worthy.
Or just throw a fat bar in the front, lift the inside wheel off the ground a
say "screw the calculations"
Ian Green
2003 Team Coleader
Suspension/Steering Leader
UC Davis Formula SAE
http://mae.ucdavis.edu/~fsae
97 Honda Civic CX
http://www.geocities.com/stscxr
"I never let school get in the way
of my education." - Mark Twain
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