> I was working the station where this happened. The wind was
> extremely strong, so much so that we were getting stung by the
> sand it was carrying. As the cars exited an uphill righthander on
> the South Course, the sidewind became a tailwind. All the AM cars
> were getting loose here due to the sudden loss of airspeed. The
> car in question came all the way around, at which point the
> outside wheels regained grip. In this position, the end plates on
> the wing made pretty good sails, and the force of the wind plus
> the mass of the wing helped to swing the car over. It made a half
> roll and landed on its top. Several workers righted the car after
> the driver told us he was OK. The car was pushed off course, and
> runs started back within about ten minutes of the incident. It
> got my attention pretty good. 8<0
>
> I'd say the likelihood of such an event recurring is probably
> pretty low, although one of the other guys at my station said
> he'd seen the same car bicycle more than once before. The
> combination of narrow track, high and heavy wing, and strong wind
> seems to be what did it. Good thing he had a strong roll cage.
>
> Jay
>
>
>
Jay,
I own the sidewinder (with a 42lb wing on the roof) A-Mod with arguably
the most downforce/lb in all of autocross. (at the huge expense of HP) If
anything, I was the most likely to experience this so-called problem with a
high huge wing. Believe me that the roll over that happened was due to too
narrow track and too high a CG. It has little to nothing to do with wind on
the side plates. That load is most likely in the range of 10 to 30 pounds
(20lbs wind * 48" end plate height = 960 in-lbs) by comparison to the 1500
or so lbs of cornering load(1500lbs cornering * 12"cg height = 18000
in-lbs). We were pulling higher cornering loads in the right-left setup
(1.65g) to that corner than we pulled in the upwind section of walls(1.35g).
The issue is If a car is up on two wheels caused by cornering then the side
plates could be the LAST straw that broke the camels back not the biggest
straw.
Andy Whittle 39/139 a-mod
St Louis
|