In a message dated 5/1/2003 7:40:03 AM Eastern Daylight Time,
npenney@mde.state.md.us writes:
Referring to my earlier post about rollbars and harnesses...
> Crushed vertebrae or ruptured spinal disc is an all to common problem
> resulting from the equally all to common improper mounting of a double
> shoulder harness rig like this one.
<<Clipped>>
I would agree with you almost entirely, though I have to say I have always
been a bit suspicious of the stock Spitfire shoulder harness since it still
goes up and over the seat back unlike modern setups that have a higher
mounting point or a loop. James' injuries also indicate that the stock setup
is not very effective.
>
> On the stock 3 point harness the shoulder harness has its mount up
> roughly even with the shoulder, preventing downward forces. A racing
> application of the double shoulder harness rig requires both shoulder
> straps be routed at the same shoulder height, normally over a bar on
> across the roll bar, or mounted directly to the roll bar. When a double
> harness rig is mounted by a novice, it is routinely routed from the
> floorboards directly up to the drivers shoulders, with no roll bar.
> This results in tremendous down force on the drivers shoulders in a
> collision, resulting in the spinal damage already mentioned.
>
>
> There is also a theory that a racing harness can result in more severe
> accident injury in a roll over without a roll bar then a 3 point harness
> would. The claim is that with a 3 point harness, if you are in a roll
> over accident you can crawl down under the dashboard. A racing harness
> prevents that ability. Having been in some serious crashes that
> involved a lot of vehicle motion (never rolled a car, but I did fly off
> a canyon wall once in Colorado), I find the notion of crawling around
> the passenger compartment while crashing and flipping the car upside
> down to be absurd on its face.
>
> To the above roll over concerns, most Spitfire roll bars are too low to
> do any good, so the point is moot. You are just as dead with the top 4
> inches of your body crushed as you would be with the top 24 inches of
> it crushed. As well, most Spitfire street roll bars are so poorly
> mounted as to be ineffective in a roll over, they just punch out through
> the floorboard. <<Clipped>>
I have to agree about the rollbar height as well, though, I think it's
better than no rollbar at all because it adds a little crush resistance in
some circumstances. Our plan is to secure the rollbar mounting points by
through-bolting into plates on the underside that match the size of the
interior mounting plates. If I can figure a way to attach to the chassis,
we'll do that, too.
Based on this discussion, I think we'll add shoulder harness loops that mount
on the rollbar so the stock harnesses can hang above the seat. That should
also make the harness a little easier to reach.
Tom Burke
80 Spit (in no immediate danger of rollover)
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