1. introduction
2. suspension
lessons
3. stressing
4. chassis
101
5. Autodynamics
6. jet
set
7. sun
set
8. Raceware
9. enter
the Seven
10. skin
deep
11. the
DSK concept
12. the
list list
13. DSK
hits the road
14. postscript

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2. Suspension Lessons
Working as a crew member of Sam
Posey's Can-Am Team in the late 1960s was a real education in
automotive engineering. Ray Caldwell had designed, and Autodynamics
had built, the D-7 (FIA Group 7) race car to replace Sam's Mk
III McLaren. As we toured the country with the new car in the
SCCA Road Race of Champions Series and the Can-Am, the beam front
and DeDion rear suspensions of the Caldwell D-7 sparked controversy
everywhere we raced.
Caldwell believed that tires had grown
so wide that independent suspension at each wheel was no longer
needed and perhaps even counter-productive. The D-7 had beam
axle "cages" front and rear. These adjustable tubular
parallelograms linked the wheels together in a fixed geometric
relationship. Unlike a conventional solid axle, the cage permitted
adjustable static camber and toe-in. The cage held the static
relationship between the wheels throughout the dynamic range
of the suspension. The relationship of the wheel angles to the
chassis varied together, as with any live axle. Caldwell believed
it would act like "one big roller," maintaining the
maximum tire contact patch throughout the dynamic range. He thought
that would give an advantage in cornering force. The team struggled
for a few seasons trying to make the beam axles work, but never
did sort out the system to behave properly at speed. One wonders
how Sam managed to control that monster at 200 mph. He had only
one spectacular crash and fortunately survived it.
As we traveled from race to race, the
D-7's controversial suspension often drew interested professional
racers to our pit and paddock to talk about it. I clearly recall
Roger Penske and Mark Donahue were the most intrigued with our
car generally, but thoroughly critical of the unique suspension
design. They stopped in frequently to talk shop with Ray and
Sam and even talked to us lowly "wrenches" at times.
They were always telling Sam to "order" Ray to go to
a more conventional independent set-up, at least up front. Jim
Hall, Bruce McLaren, Carl Haas, Dan Gurney and many other Can-Am
competitors struck up conversations about our odd suspension
during pit visits and at restaurants near the tracks. We had
long exchanges about "camber change with roll," differential
caster and camber changes in bump and rebound between wheels,
toe changes due to cage flex under hard braking and many other
esoteric aspects of suspension dynamics.
I remember one dinner at a greasy
spoon ("Fat Boys" I think) near Laguna Seca. Several
of the racers named above, some others and their crews argued
loudly, albeit in good humor with Ray. The topic ranged from
suspension control arm flexing to the difference in the dynamic
aspects of the polar moment of inertia between an independent
set-up and our "beam axle" arrangement. A 22-year-old
race mechanic, my growing understanding of suspension performance,
precision alignment and track tuning was nourished by these lively
conversations. Caldwell's unique perspectives about suspension
design ("anti-squat and anti-dive are really anti-suspension,"
he would quip in the shop) intrigued me. Dozens of technical
brain teasing conversations with him and others back in those
racing days taught me to think logically about suspension dynamics.
At first, I just listened, but as I learned, I began to participate.
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