Driven5 wrote:
You never stated, indicated, or implied that they are both so up to this moment
Apologies; I joined the thread quite late, when most of the sensible stuff had already been said. I assumed that people would take it as read that I thought steel was OK from the simple fact that I didn't say it
wasn't.
Driven5 wrote:
I'm also still not clear on exactly what evil are you saving us all from with your rancor about the apparent impossibility for tubes having holes in them to be insufficiently sealed, nor for the floor pan to be subjected to fire and/or debris in an accident?...Making a car that's too overbuilt for our own good??
Well for what it's worth the
sole advantage of 'Seven' type cars, when you boil it right down to basics, is their lighter weight compared to production sports cars. So yes, it's really a matter of making a car that's not unnecessarily overbuilt, though I think you'll find that the reality is that a car with a mild steel floorpan is also more prone to rust than one with an aluminium one (due to the fact that aluminum 'passivates' its surface by oxidation, whereas oxidation of steel just keeps on going.
Standard practice here in the UK is bonded and rivetted aluminium. Not that steel won't work, just that nobody seems to think it offers any worthwhile advantage (beyond slight cost reduction) and it offers a couple of significant disadvantages in the form of weight and corrosion... but if neither of these bother you, then it's just fine.
Of course, if you want to over-build a car, that's your prerogative, but it would be disappointing if a self-proclaimed 'expert' put people off simply doing something properly, because his scaremongering went unchallenged.
Driven5 wrote:
Now this is where this thread could actually become beneficial again: I have seen accident scenarios that I would never have otherwise been able to anticipate, and as such am not willing to simply rule out the possibility that the floor could become part of the "firewall" during a car fire after a wreck, or that objects could impact the floor with penetrating force. If you have empirical data to counter any of these potential concerns, beyond anecdotal evidence, I'd honestly appreciated it if you could/would share that with us, or at least point us in the right direction to find it. While I've been leaning towards welding in individual steel patch panels for my floor, for my own (mostly irrational) reasons, I'm also still considering an aluminum floor as well...Although, that too could also be attempted in a manner that would not require drilling into any chassis tubes either.
Empirical data?
The melting point of aluminum is 660 degrees C. Your domestic oven is capable of about 1/3rd that. Try heating up a sheet of aluminium as hot as you can get it in your oven, then placing your hand on it for even a fraction of a second (warning:
it's gonna hurt!). Now imagine the sort of blaze that would be necessary to raise the temperature of a thin sheet of aluminium (which is naturally conductive of heat), in the wreck of a
completely open-top and doorless car, to the point where that aluminium sheet starts to lose integrity. Trust me, if you're sitting in the middle of a wreck that's got
that hot, the structural strength of the sheet will be the least of your worries.
We had a similar argument against timber monocoques from Miatav8,MstrASE,A&P,F, on the grounds that there's some nasty stuff in the smoke of plywood once it gets burning well, but completely disregarding the fact that its actually
quite difficult to get plywood burning well, and if a blaze has gone that far (fueled by petrol, no doubt, which also isn't the best thing to be breathing the combustion products of), then the chemical effects of smoke inhalation will once again be the
very least of your worries.
This is all just plain common sense stuff, and having a sense of perspective.
For what it's worth, I'd refer you to race regulations on firewalls. These have been formulated on the basis of many years of painfully-obtained empirical data, yet do not stipulate steel for firewalls. Not even a minimum thickness for aluminium. Just that they need to be of a non-flammable material, and that magnesium is prohibited (I'm quoting from UK regs... I assume that US regs will be similar, because all need to be consistent with FIA global rules at the end of the day).
The inference you can draw from this is that empirical experience has demonstrated that in a major accident, containment of the fire in the engine bay becomes pretty much irrelevant; your driver will be sitting in the middle of an inferno that envelops the whole car, and the best you do for him is to get him out of there fast and/or protect him by means of fireproof clothing for the few seconds it takes to extract him. Everything else is pretty much irrelevant. By the time aluminium starts to melt, he's already dead: witness Lauda's crash, or Roger Williamson's crash (yeah, I know, I shouldn't be watching nasty videos...).
Of course, there's a
very remote possibility that you might encounter a situation where a steel floorpan might improve safety, but it's all about balance of risks and drawing the line at a common-sensical point.. Otherwise, might I suggest that you need to take account of the possibility that a Muslim terrorist has planted an IED under the road, or that your psychotic neighbour has decided to snipe at you because your noisy exhaust irritates them, in which case you'll be needing one of these:
I'm reliably informed that they're not that quick, though, and the handling's
not quite up to Lotus' standards.
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