Re: [alfa] Re: installing roll bar on Spider

[Richard Welty <rwelty@xxxxxxxxxxxxxxx>]

On Mon, 19 Jul 2004 15:00:46 -0400 "Dean W. Cains" <dwc@domain.elided> wrote:

> My biggest worry with a street roll bar in a Spider would be cracking my 
> skull on it if I was rear-ended. 

there is a second consideration. most of the street bars i've seen
don't have much if any lateral bracing inside the bar.

suppose you back into a solid object -- guardrail or t-rail (aka new jersey
barrier) at high speed. the stock seats are held in toothed sliders. stock
toothed sliders generally don't hold up in significant rearward accidents.
your seat will come loose and will slide backwards. without lateral bracing,
you will fit under the roll bar, one way or another. think about it.

i am aware of two incidents where drivers at the track, with roll bars,
OE type toothed sliders, and inadequate seat back support, were killed
when they backed into extremely solid objects and their necks snapped
as they went backwards and their helmets failed to clear the main
roll hoop. neither was at an SCCA event, but subsequently we became
much harsher in our seat mounting requirements. adjustable seating
position forward and backward is all well and good, except for when
it kills you.

note that FIA approved toothed sliders will hold up; it's the OE type ones
that don't. FIA approved sliders are generally found in the same context
as FIA seats, and an FIA seat on an FIA mount is the only type of seat
that the SCCA permits without substantial seat back support (even the
very high end aluminum stock car seats from Butler and Kirkey still
have to have a real seat back support; they're engineered differently
from FIA seats.)

> >     On a spider, if the top goes up and down over it, it isn't tall enough.
> >There must be 2" clearance between a line from the top of the windshield frame
> >to the top of the roll bar and the top of your helmet when seated normally in
> >the seat.

actually, the SCCA rule involves placing a level on top of the
roll bar and measuring 2" perpendicular downwards to the
top of the helmet. there is also a clause relating to full
cages with low front hoops, which involves a straight edge
from the front hoop to the rear hoop which must clear the helmet.

richard
-- 
Richard Welty                                         rwelty@domain.elided
Averill Park Networking                                         518-573-7592
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