On Tue, 11 Jun 2002, Jerry Shaw wrote:
> Hi
Hello.
> I bought a TR6 with a roll bar. I'm dubious about it effectiveness, since it
>isn't supported by frame members, only the sheet metal
> of the rear shelf floor.
If the roll bar is only mounted to the parcel shelf (the area behind the
seat but above the floor pan), then the effectiveness in a rollover is
probably marginal.
Without going into a lot of detail, there's two reasons for the lack of
effectiveness:
1. Most of the parcel shelf bars have very little fore/aft strength. In
the case of most of the bars that I've seen, the "feet" are only about 12
inches apart (fore/aft). A hard shunt to the bar with the car travelling
with any forward motion component will collapse the bar.
2. There is _no_ diagonal support in the parcel shelf bars. Therefore, a
crash/rollover with any sideways component will cause the bar to pancake.
Your assesment is correct, these bars are mor for show than for
protection.
That being said, even marginal rollover protection is better than nothing,
so seeing that the bar is installed already, why not leave it installed?
> Any listers have thoughts about roll bar effectiveness? I'm thinking
> seriously about removing it.
I have lots of thoughts on the matter, but I wanted to point out one more
point about roll bars in street cars. If you do leave the bar installed, I
would suggest or even plead from a safety standpoint that you at least
cover the roll bar with a padding of some kind. The reasoning for the
padding is that in a collision of any type, it is very likely that your
head will come into contact with the steel of the roll bar. This won't
just hurt, it could be fatal. Please consider this.
I had the "pleasure" of watching on the tele' a vintage race in Palm
Springs some years ago. A fellow (a medical doctor, ironically) in a Lotus
9 got hit from behind by an Alfa that lost his brakes going from the
fastest straight into one of the slowest corners. The closing speed was
high, perhaps a delta velocity of 50 MPH or more. At any rate, the ensuing
action spun the Lotus into the tire wall backwards.
Here's the part that still amazes me: on the initial impact, the Lotus
Driver's head thumped the boot lid. Hard. The driver then rebounded
forward and hit his head on the steering wheel. As the car rotated into
the tire wall, there was still a lot of speed to get rid of and the car
hit the wall back end first. The drivers head hit the boot lid _again_
putting an obvious dent in the bootlid.
This was a driver that was completely belted into a racing seat with a
shoulder harness. If I had never seen that crash, I would have never guess
how much deflection a human body is capable of... that guy was stretched a
good foot or more at very awkward angles in order to hit his head on the
bootlid.
Bottom line - anything that is hard that you could possible come in
contact with your body and especially your head should be padded.
Otherwise, your asking for trouble in the "unlikely event of a water
landing", as they say on board aircraft.
Play it safe.
> Thanks,
> Jerry Shaw
> '74 TR6 Saphire Blue CF20490U
> '75 TR6 BRG CF39873U
regards,
rml
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