Moss Motors, Ltd

Aubin:

Bill:

I think that if you check a basic structural materials text you will find that pound for pound aluminum is much stronger than steel.  Its used in aircraft because the same structural strength can be achieved at a lower weight.  However, having said that I agree with you that the floor boards should be steel for number of reasons:

1) You can weld it in, thus the floor boards become strength bearing member of the structure.

2) There will be galvanic corrosion problems unless every part is coated with corrosion preventive and dielectric materials are placed between dissimilar metals.

3) Depending upon the grade of aluminum this material can be very soft and malleable when compared to steel.  The stronger grades are less prone to maleability but are more prone to fatigue/stress fractures.

One of the other posts suggested honeycomb, real expensive but super strong, another exotic alternative would be to laminate carbon fiber over a foam core.  Cost a little more than aluminum and requires skills working with epoxy or polyester resins.  Also either of these alternatives will require use  of high tech adhesives to make the floor board part of the structure.  For the average guy steel is the deal

My thoughts exactly

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72 MGB 80 TR8
Pittsburgh PA

Underdog/Aubin,

You are correct. I misspoke. What I should have stated was that for a given DIMENSION or VOLUME, there is no contest. Steel is the hands down winner. And in fact, You would have to use so much aluminum to equal the steel (non honeycomb) that its use is not practical. Also, the word strength is a bit slippery in this context. Are we talking about bending strength? or shear resistance? or load support? (tensile strength) How about impact resistance?  The problem with aluminum is that by the time you have the various strength qualities (achieved by a heat hardening process), that you need for a given quality (the "T" number), you likely have made the material so rigid as to be brittle. That's where the cracking, and even shattering come in which cause me to feel it just ain't worth it.

As I stated earlier, not only is steel easier to work with in this instance, but putting the admittedly heavier material lower in the racecar will allow you to lower the center of gravity by lightening components higher up. This assumes, of course, that you can "make weight" with the entire car.Worthy sanctioning bodies always leave room for this. At the core, I don't think we disagree on this subject.

I literally spent months laying flat on my back as the result of an injury that was the result of expediency and weight being chosen over strength. It resulted in financial hardship I wouldn't wish on anybody, let alone the pain and the still lingering effects. It was an instance where the "not very likely" happened, and changed my life literally in an instant. I say weld in a very strong chunk of steel on BOTH sides. You'll stiffen the entire structure, which is only good for a racer anyway, and along with a well concieved roll cage you'll have the peace of mind which will allow you to concentrate on the task at hand. WINNING!!

The only disagreement I have with you, Aubin, is that you said steel is the way to go for the average guy. There's nothing average about a guy who takes on the somewhat quixotic, but truly admirable task of racing an MGA in the twenty first century! Good for him!!

Regards,

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon