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.
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.
Without some sort of cross-chest strap, it is quite easy to get shot
out from between the dual shoulder straps in a collision. This is why
infant car seats have that chest clip, as do many military applications.
The three point harness avoids this problem by crossing the body and
having the body wrap around that cross chest strap in a collision.
Racing cars also partially avoid this problem by their very restrictive
seats and superior mounting of the harness (though this is far from an
absolute). Novice mountings are made even worse by generally mounting
one harness base to the outboard sill, the other to the transmission
hump, resulting in a harness that is wider then the drivers shoulders,
helping ensure ejection in a collision, though frequently not until the
driver has had their spine at least partially crushed from the downward
forces.
Many times the shoulder straps are adjusted too short, resulting in the
lap belt riding up in the abdomen area, and not down over the pelvis.
This results in severe abdominal organ injuries in a crash.
All harnesses (including just a 2 point lap belt) suffer from
submarining. The more the seat is reclined, the worse the problem. A
crotch strap (5 point harness) helps tremendously. A double crotch
strap (6 point harness) reduces groin loading in a collision by 40% over
the single crotch strap, and almost completely eliminates the testicle
ruptures that can result from the single crotch strap of the 5 point
harness.
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.
There are also some substantial inconveniences with a more complex
racing type harness, especially one that does not use inertial reels.
You will no longer be able to lean over and roll down the passenger
window, leaning forward to pull out your wallet becomes a near
impossibility, and the job of buckling all these straps together takes
appreciably longer than the quick buckling of the stock belt.
It would have a potential advantage over the stock harness in a severe
rear end collision. The Spitfire seat back is weak, and will collapse,
resulting in possible ejection. The 4 point harness will do nothing to
lessen the collapse of the seat back, but it will more likely hold the
occupant in the car. Considering the proximity of the gas tank and the
potential for its rupture in a collision severe enough to eject the
passenger, I'm not sure how much is truly gained by reduced ejection
possibilities. None the less, I would expect reduced ejection to
result. Having been rear ended in a car that did allow for rearward
ejection (Dodge Shadow), I can say I didn't care for it and would prefer
automobiles that didn't come so equipped with this auto eject feature.
Make no mistake, a 3 point harness can be very effective if maintained
properly, worn properly, and if the base vehicle has it mounted properly
(and the Spitfire basically does).
>>> James Carruthers <j.carruthers@rave.ac.uk> 04/30/03 04:46PM >>>
Whilst we're on the subject of seatbelts...
4-point harness belts like this one (just an example):
http://store3.yimg.com/I/soloracerdotcom_1735_220056
What are the benefits and draw backs of using such a harness in a Spit?
I want the good, bad and the ugly...
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