..........from my friend Brian Evans who reads the list but can't reply to it -
as always well worth reading:
Having followed this debate from the outset, and having done a lot of research
into the issues, here are the answers you are looking for. No guarantee you'll
like them, but facts are facts, unfortunately... Offered to you respectfully,
and with no intent to inflame.
1. SFI rates the belts, and decided that based on their testing methodology
and the materials they allow there is the potential for sufficient degradation
over two years, in some circumstances, that they could not cover belts older
than two years with their "approval". Virtually everybody thinks this is
overkill, the fact that SFI is an industry body setting up standards that
benefit the industry is suspect, but SCCA goes by SFI rating approvals and had
no real choice in the matter. SFI made the change, not really SCCA.
2. FIA rates the belts using a different methodology, requires different
materials, is not an industry body, and issues an expiry date five years after
manufacture. The belts are visibly different, and seem to be of higher
quality. I personally have used FIA belts for the past five years or so. I
personally seem to change out my belts about every four or five years anyway.
3. Six points belts are measurably and significantly better in operation than
five point belts for all cars. The use of rearward attached twin crotch belts
restrains the torso far far better than a lap belt with a single forward
attached crotch belt. Video of the difference is astounding, and I guarantee
that if you saw it you would agree that six point belts are well worth the
investment. A single hard run into a tire wall will give you ample payback.
4. Is there a sudden rash of crashes where the belts have failed? If you
count serious injury or death as a failure, then yes. A Formula Vee driver
died at Shannonville not far from here a few weeks ago, while the final post
mortem is not yet in, indications are that a Hans along with a better belt
installation system may have saved his life.
5. Is the cure worse than the cause? No. Being dead would really suck, in my
opinion...
6. Grade five bolts have about 120,000 PSI tensile strength and about 80,000
PSI strength in shear. That means that a 3/8" dia Gr 5 bolt in single shear
has a strength of about 8,830 pounds. That's a lot of load capacity for one
seatbelt mount. Willans calls for 3,500 pounds load capacity in each seat belt
mount, 3,500 pound is probably a whole lot more than what your belts are
bolted to can support. They are designed to be used in tension, not shear. AN
bolts have about the same strength characteristics as Grade 5 bolts, but need
to be certifiable. Grade 8 bolts are fine, socket head cap screws ("Allen"
bolts) are fine, and there are many different types of MS bolts that are
stronger than all of those, but basically, Grade 5 bolts are perfectly adequate
for the job. There is no such thing as Grade 10. Some manufacturers have come
up with a "9" type bolt that has similar characteristics to a good quality
socket head cap screw, but there is no SAE grade higher than 8.
I've been on the false grid twice now, when word came back that there had been
a driver fatality. I seriously question all aspects of my car preparation and
safety equipment. I've been wearing a HANS for three years now, I bought mine
way before the price started to come down (it cost me the equivalent of two
sets of tires, or four race entry fees). Vintage cars are the most dangerous
cars that race today, all other cars are much safer just because of inherent
improvements over the years. We can be safe, but we have to work a lot harder
at it.
Cheers, Brian
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