Sam_68 wrote:
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.
Fair enough. Your comments seemed, and continue, to mostly focused on the advantages of aluminum and disadvantages of steel, while simultaneously minimizing the equivalent disadvantages of aluminum and advantages of steel. There is still an air of 'scaremongering' in this approach, just a bit more subtly so than with fiery death.
Quote:
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.
This is where I was really looking for empirical data.
One hypothesis states that the holes in the aluminum floor has an elevated probability of insufficient sealing allowing moisture to enter the system. The competing hypothesis is that the welded steel floor has an elevated probability of insufficient finish integrity, allowing for surface exposure. Both are technically true. Based on the answers in this thread, there is anecdotal evidence supporting that both options can realistically result in an acceptably rust free chassis on these types of cars. However, there is no empirical data available regarding which potential problem is actually more likely to occur under what individually experienced circumstances.
Since external corrosion is also much more easily observed than internal rust, that's the one almost guaranteed to get more publicity. However, it's also more easily removed and repaired. Without cutting open the lower chassis tubes on a variety of well used older cars, you'll never know just what the insides of the tubes look like by comparsion. So it's all just speculation and opinions based on each persons differing experiences, that won't necessarily all lead to the same conclusions, and there is (well, at least there should be) absolutely nothing wrong with that.
I'm also by no means saying that my
opinion disagrees with yours on aluminum vs steel both probably providing a similarly reasonably similar (if not equivalent) amount of fire protection while the driver is still alive, just that I have not seen anybody present enough objective analysis on the matter of materials and survivability in car fires to pass it off as a totally indisputable objective fact. Racing rules may indicate that aluminum is sufficient to meet the bare minimum required to achieve acceptable legal risks for the organizations, but do not necessarily imply a demonstrated complete equivalence either.
Unfortunately, the weight difference of steel vs aluminum is frequently overstated. Steel may be considerably more dense than aluminum, but used correctly in a thinner gauge it is not nearly as much so as often implied while still being stronger. Granted, there are also further practical limitations for welding the steel as well. Is there realistically going to be a weight penalty? Absolutely. Is it necessarily going to ruin the lightweight nature of the car? Absolutely not. I figure that there is roughly a whopping
15 pound difference, at a CoG helping height, between an 18ga steel and 16ga aluminum floor under the cockpit area. My personal 'common sense' says that realistically I would have enjoyed one of these cars just as much 15 pounds ago as I would now...and no less so than if I drop another 15 pounds.
Standard practice should by no means be used to imply best practice for any given set of conditions. That's why discussions like this, where we can get multiple different points of view on a topic, even if there are points of
civilized disagreement, are something to be encouraged.
On a final note: Colin Chapman did not exactly design his cars with an overt emphasis on safety, or reliability, so that does not necessarily make his the ideal model to follow in
all regards either.
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