...just remember folks, these are trained professionals..... DO NOT TRY THIS
AT HOME !
seriously, Andy is right. An SCCA approved rollbar is designed to
accept - simultaneously - 1.5G lateral, 5.5G fore/aft, and 7.5G vertical.
Here, we see the major strength is in the vertical plane - aka on your head.
It makes sense when you think about the design of a hoop. A w/s frame may
accept a 2 or 3 g vertical load (they are pretty strong) HOWEVER neither the
lateral nor the fore/aft strengths will be remotely close.
Think of this - if you took a sledge hammer (heaven forbid) and smacked the
frame in a fore/aft direction I bet you could do some serious damage. But,
if there was a brace from the frame top back to the parcel shelf, you would
be attempting to deform a triangle. This is almost impossible to do and is
the basis of ALL chassis strengthening. Oddly enough there is no
"comfortable" way to place a brace across the door opening. However, a
steel framed side window (series 2 Lotus Elan, eg) or a convertible top
frame will both add that fore/aft dimension. I have seen a rolled Miata
without a straight panel left on it but the top frame was still intact.
This brings to point another issue. If you drive off the edge of a cliff,
nothing will save you short of a really good prayer. A lateral barrel roll
into a ditch (much MUCH more likely with them silly swing axle cars) at
highway speed will produce more skidding than crushing - until you hit the
proverbial fixed object. Then all bets are off. Until that time, though,
the frme will squish down somewhat on initial impact and, hopefully, you
will "duck and cover". There is n;t much headroom in a spit at thebest of
times (ditto TR anything).
Thus, a conventional rollover, if there is such a thing, is likely well
dealt with by the ws frame.
The likleyhood of a whiplash induced noodle cracking (when some yutz rear
ends you - much more likely) is much much greater than a rollover. Be sure
that either your headrest is set high enough to protect your mellon AND/OR
use an approved rollbar padding (not the "appearance" type coverings often
sold) and remember even they are designed assuming you are wearing a helmet.
Finally, consider that in SCCA and CASC rules, an open car "must not" use
a 4 point (over the shoulder) type belt UNLESS rollover protection is in
place. This is because, if the ws frame DOES squish, you cannot duck into
the passenger seat (or the passenger's lap). The racers have spoken. And
this racer had a cool bar in his TR6 for 6 years - WITH high back seats for
protection since the low back type gave me none.
Flame away, the nomex is still on (but really, I mean all ofthe preceeding)
Dave T
The grass is still green in Winterpeg!
-----Original Message-----
From: Andrew Mace <amace@unix2.nysed.gov>
To: Chip Mautz <clmautz@yahoo.com>
Cc: Laura G. <savercool@email.msn.com>; spitfires@Autox.Team.Net
<spitfires@Autox.Team.Net>
Date: November 2, 1998 4:51 PM
Subject: Re: Totally topless = rollover safety?
>On Mon, 2 Nov 1998, Chip Mautz wrote:
>
>> I think I've asked this one before, but this email brought it back up -
>> how safe is the Spit in a rollover?...the windshield frame slope changed
>> on the MKIV's and on (maybe even the MKIII's?) - does this make it any
>> less/more strong? Anybody know?
>
>I don't "know" if there was any real difference between the "strength" of
>the Mk.IV and later frame v. the earlier bolt-on frame. Frankly, I've seen
>both body styles in all severities of rollover. I've seen frames survive
>only lightly scratched, I've seen them twisted enough to destroy the glass
>but still remain partially "upright"; and I've seen them flatter'n a
>squirrel under a semi. :-)
>
>If anything, the later style might be just a wee bit LESS sturdy? It's
>about the same configuration, and it is integral to the body tub, but it's
>also a bit deeper at the base and therefore has a bit less metal there.
>Whether that makes any difference....?
>
>All depends on how you roll, how fast you roll, how many times you roll
>what you roll onto....
>
>--Andy
>
>* * * * * * * * * * * * * * * * * * * * * * *
>* Andrew Mace, President and *
>* 10/Herald/Vitesse (Sports 6) Consultant *
>* Vintage Triumph Register <www.vtr.org> *
>* amace@unix2.nysed.gov *
>* * * * * * * * * * * * * * * * * * * * * * *
>
>
>
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