Are Schroth clip in harnesses safe to use? - The Unofficial BMW M5 Messageboard (m5board.com)

glowrider · 6th December 2002, 01:02

I'm interested in getting Schroth clip in harnesses for my M3. However, I've been reading that they can cause more harm than good in the even of a crash if not used in conjunction with a roll bar. These will be used on the street mostly to get a better feel of the car, and sometimes on the track. These are 4 point clip ins...Link below. Thanks for the advice in advance.

Schroth 4-point harnesses

mottati · 6th December 2002, 01:34

Well first off, I have these for my 528, i put them in for track use, and take them out for street use. I'm certainly no expert, but have heard that these could cause a spinal compression injury in the event of a roll over accident. Ideally, a harness should not angle downward after going over your shoulders; i.e. if it went straight back to a roll bar or maybe somewhere on the parcel shelf you'd be ideal. I've also heard some argue that in the event of a roll over, if the roof caved in your head would be in the way!! Those people argue that with stock 3 point belts, you could duck down or lean across the seat, probably banging heads with your instructor in the passenger seat. At any rate, i've seen a few roll overs in bmw's on track, the roof maintained itself quite well. It really does make me feel more comfortable in the car, being held securely in place rather than trying to brace myself in with the foot rest, center console and hanging on to the wheel.
Mike

6th December 2002, 01:46

I would recommend getting racing seats if installing a harness. Harnesses are designed to work with racing seats, and look dangerous when used with stock seats.

Here are some photos of my application:

glowrider · 6th December 2002, 02:36

Why racing seats, your harnesses seem to bolster down into the back seat (under shoulder level)...How much do racing seats go for? I really just want the application for myself, not my passenger...Car is only going to the track a couple times a year...How often are M3's flipping on the road?

FAST 5 · 6th December 2002, 03:53

check out the site:
WWW.STABLE-ENERGIES.COM/DEIST/DEIST.HTML

Restraint Systems
Deist maintains the most complete safety equipment testing laboratory in the industry, and uses it to continually develop and refine effective new products to benefit competitors in all forms of motorsports.

All Stable Energies systems include all necessary hardware and shoulder harness pads. Our harness systems are custom configured extra long to fit properly especially in street cars using harness bars and stock or racing seats. The harness pads are sewn onto the harnesses to prevent slippage and maintain their position. Please specify 5 or 6 point, bolt-in or snap-in, and choice of color. Package price discount with purchase of Guide Bar, Rollbar or Cage, or Konig Seat. Stable Energies unique "NO HOLES" mounting system is now available for those who do not wish to drill holes in their pride and joy!!

Pricing and Ordering Information:CHECK OUT THE WEB SITE.

greg · 6th December 2002, 06:51

The following article came across my path about a year ago from the Tracquest board. I thought it was good enough to save then, and I'm glad I did. This is probably more than you want to know, but it is excellent reading no matter what.

As far as I'm concerned, the more "points" the better provided, of course that the "clip-in" mounts are not actually weaker than the stock belts. I agree about roof integrity. If you have a severe enough impact to collapse the roof you're going to get your neck broken whether you're in 3, 4, or 5 point harnesses. If you think you're going to fast, or strong enough to think "duck" and do so - fuggeddaboudit. Of course, if you were only in a standard 3-point belt, you would probably be already dead from submarining or twisting out of the harness on the 1st impact.

Quote:

Notes On Race Car Harnesses - Design and Installation
©Michael Henderson. Written for "The Greasy Rag", an Australian vintage
racing publication. Reprinted in its entirety and with the author's
permission from CSRG News, a monthly publication of the Classic Sports
Racing Group.

During private practice at Amaroo recently, a very quick Sports 1300
went straight on over the hill and down into the earth-filled tire wall
outside the sweeper. The car was badly damaged, with most chassis rails
bent and the engine/gearbox shifted substantially forwards.

The driver, David Williamson, was extensively injured:
? fractures and dislocations both feet and ankles, necessitating a
wheelchair after discharge from hospital;
? undisplaced fracture of cervical vertebra;
? fractured ribs, punctured lung;
? bruised spleen;
? fractured left lower arm.

Most of these injuries, if only slightly worse, could have been fatal or
caused permanent disability. David has readily agreed to my telling his
story.

None of us like to think about being hurt in a race car. But while
exploring the edge of control is part of the kick we get from racing, it
seems reasonable and socially responsible to minimize the risk of being
hurt if we crash. I first started analyzing race crashes in 1966, and
successfully convinced a skeptical world that it was better to be belted
into an open car than to be thrown out of it. My development of the
six-point harness with the GQ Parachute Company, taken over later by
"Dumbo" Willans, was part of this work. I still analyze crashes, but
road cars these days. Knowing my background, David asked me to examine
his car and his injuries, to see whether they might have been prevented.

This process was so instructive I thought it was worth writing down some
of the lessons in the context of what new research is showing about race
car harnesses.

- First, we worked out what happened to him in the crash. The actual
speed of impact would be an estimate, but is likely to have been in the
order of 100 km/h. The impact was slightly angled, so the speed might
have been higher than that. The car was effectively crushed about
two-thirds of a meter, and the relatively stiff tire wall probably
compressed about one-third of a meter. The total stopping distance of a
meter then gives the deceleration force on the car at around 40 g. -
Now we know from the black box crash recorders in Indy cars that drivers
can ride out 40 g crashes with no more than bruising (the limit of human
tolerance is being approached at about 50 g). Why not in David's case?

The first reason is that David "submarined". Basically, he slid partly
underneath the lap belt. As it rode up his stomach to his chest it
bruised his spleen, then it went up and broke some ribs, which in turn
punctured a lung. His feet were forced down to the footwell, with
forces being directly transferred into a collection of vulnerable small
bones and joints.

Hanging on to the wheel, his arm was broken as he instinctively tried to
stop himself going forward. This was not enough to stop him being
violently flexed over the lap belt so far that he hit his helmet hard on
the steering wheel, bending the rim about 30 degrees forward. The
impact was enough to break a bone in his neck, just as it was at full
stretch.

Because problems with the harness and its installation and use could
have contributed to these injuries, we studied it carefully. It was a
six-point belt, with two-inch webbing. The shoulder belts had been
routed over a transverse chassis rail behind his shoulders and down to a
lower rail at the bottom of the car. The crotch straps were joined at a
central single latch plate. David confirmed that they were quite loose,
and could be clipped into the buckle very easily.

The submarining happened because there was little to stop it. Crotch
straps are there for two reasons. Not only do they have a direct effect
in preventing sliding underneath the lap belt, they also stabilize the
whole system. Unlike the tree-point belts in a passenger car, the
buckle of a race harness is in the center. This means as soon as the
shoulder belts are loaded, they pull the lap belt upwards and the lower
part of the body tries to shoot underneath. This killed Jochen Rindt,
who told me in 1969 that although he had come to accept a harness in the
Lotus, he would never wear crotch straps. In his crash at Monza his lap
belt ended up near his neck, rupturing his liver on the way. Australian
child car seats, which also have central buckles, have crotch straps for
exactly the same reason.

The excessive flexion of the upper part of David's body started when he
finally got held up by the loose crotch straps, by which time his feet
were mashed in the footwell. The flexion was allowed by the
geometrically loosened shoulder belts and increased by the stretching
allowed by the long length of the straps.

General Motors has been doing Indy car crash simulation (sled) testing,
using dummies, for about five years. We now know far more than we did
about the details of what happens in this kind of crash. It turns that
what we thought was right in the beginning, was later proved to be
pretty right all the time.

At impact, the whole body moves forwards until lap and crotch straps
restrain the hips. Then the torso rotates 30 degrees until the shoulder
belts stop the rotation. Most of this movement is due to changing belt
geometry and shape changes to the body within the belt, even with the
mounting points just behind the shoulder. High-speed movies of a
correctly-restrained dummy reclining at 45 degrees show forward shoulder
movement of about 250 mm in a 40 g crash. About 20% of this forward
motion is due to belt stretch, working out to about 50 mm.

This confirms two things for us. First, to restrain body movement
within the confines of the shoulder straps, the belts must be as tight
as possible throughout the crash sequence. And that means tightness in
both the shoulder and crotch straps, which balance each other. Second,
the shorter the shoulder belts, the less the total stretch. In David's
Sports 1300, fibers in the shoulder belts were melted as the webbing
stretched over the chassis rail.

Not only do slack belts allow more movement - or "excursion", as we call
it in the trade - but they also directly increase forces on the neck and
chest because the body"s deceleration is more violent. The body slams
into the belts at the pre-crash speed of the car, instead of riding the
crash with the car as it collapses. Loose shoulder belts are a threat
to the neck.

It's very important to get the shoulder belts loaded as soon as possible
in the crash. The best way to arrange this is to place the mounting
points so that the belts leave the shoulders at about 90 degrees to the
spine. If you sit bolt upright, take the belts straight backwards; but
when reclining, the mounting points should be below the shoulder but not
so as to take the belts back along a line 40 degrees below the
horizontal. When the diver is reclining, horizontal shoulder belts don't
get fully loaded until well into the crash, by which time the shoulders
will have moved well forward.

Whatever the car, lap belts should be anchored near vertically (say, 80
to 90 degrees), with the webbing passing over or in front of the hip
bones.

In a 40 g crash, an 80 kg driver will be loading the belt system with a
3,200 kg force, about twice the weight of a fully-laden Falcon. The more
widely that load is distributed, the lower the risk of belt-induced
injury. That‚s why three-inch (75 mm) belts, with reasonably stiff
webbing, are far better than belts with two-inch straps. They'll soon be
mandated by the FIA.

Crotch straps can't be made of three-inch webbing, but in any event they
should bear on the bones of the pelvis between the legs. This allows
them to be really tight without discomfort, and puts crash loadings into
strong (and hard) body parts rather than weak (and soft). Crutch straps
take a heavy beating in a crash. A friend recently stuffed a March very
hard into an earth bank at Oran Park, and two days later - without other
injuries - had two jet-black bruise lines across the top fronts of his
legs.

To get the right geometry the crotch straps must be widely separated as
they approach the lap belt, just like a parachute harness. Easily the
best way to do this is to take them up through D-rings on the lap
belts. Every Formula One car has this kink of system. Taking the twin
crotch straps (or, worse, a single one) via a single latch plate to the
bottom of the buckle is a compromise aimed at cutting cost and adding
convenience, mainly for Sedan cars.

Only a few race harnesses comply with my criteria: three-inch webbing,
D-ring crotch straps, a central rotary buckle of course, and details
such as spring-loaded anti-slip adjusting buckles. They include the
following, and I readily concede there may be more I don't know about:
? Willans 3" Silverstone 6;
? TRW/Sabelt 3" Professional 6-Point;
? Stand 21 STH-36SS 3";
? Simpson 3" 6-point.

The best harnesses don't cost a lot more than the worst, and less than a
couple of tires these days. Fitting and wearing them properly is free.
As David told me when I was writing his story, if only one driver's pain
is prevented by better understanding, then it makes his own pain worth
while.

BIOGRAPHICAL NOTE
Michael Henderson M.D. is a physician and internationally-known motor
vehicle crash researcher. He has also been an auto racer since 1960.
He was the author of the seminal "Motor Racing in Safety" in 1968, and
influential in turning round Formula One and other open-wheel racers to
acceptance of full harnesses. His first prototype harness became the
Willans, now used world-wide. He currently drives a Lola T560 Formula
Atlantic in vintage races, and also has a Lotus Eleven (Dick McGovern's
old car), Elva-BMW and a Ralt RT4. in June, Michael was involved in a
major crash with the Elva-BMW, the car was a write-off, but Michael came
through it with "limited" injuries, and will be racing again soon.

--

glowrider · 6th December 2002, 07:02

Very interesting reading...But, as I don't plan on doing timed racing, I don't think 6 pt harnesses (or a roll cage really) are in my best interest right now. I'm just tracking for fun, and driving fast otherwise. I have been looking at some racing seats, and they seem fairly inexpensive. So I think 4 point with the seats are going to be the way for me, as long as I can swap out the race seats for the stock seats when I desire, without much hassle. Thanks.

6th December 2002, 08:26

You will have quite a bit of trouble swapping out seats. Seats are pretty difficult to move in and out and have a lot of wiring issues. The entire airbag system is connected to the seat-belt pre-tensioners, seat-belt buckles and the passenger seat pressure pad. Basically, if you remove the stock seats without some major wiring modifications, your entire airbad system will be dsactivated. Moreover, your tilt/telescoping steering-wheel will be locked in place.

Just something to think about, as I am in the process of trying to cure these ailments.

glowrider · 6th December 2002, 16:15

Very interesting, I'll have to ask some M3 guys about that. Going to go seat shopping and also pick her up from the shop today.

pmiranda · 6th December 2002, 20:33

Great post, Greg!

I'll definitely look at a 6-point Simpson harness when we build our track car (probably late next year).

Until then, I guess I'll just keep the stock 3-point belts in the M5 and stay within my limits!