Quote:
Originally Posted by Laird Scooby
Something i think Clifford said several post (pages?) back is that although the alloy is lighter (in terms of relative density) they tend to be thicker for the strength. As such, you may well be right.
Time will tell!
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One would expect the possible weights for a steel and aluminium wheel to be quite similar Dave: Young's modulus for steel is about 3 times greater for steel (about 30 vs 10 Mpsi), but it is about 3 times as dense (something like 8 vs 2.5 g/cc) so all things being equal (but they never quite are of course) the two metals should give similar results for something like a wheel.
[My apology for mixing units in the above - the important thing is that the Young's moduli for steel and aluminium, as well as their densities are in the ratio of 3:1 - good engineers should be able to switch units easily, unless they worked on the Mars Climate Orbiter of course].
I suspect (and it is only a feeling, I'm not a mechanical engineer) the steel wheels for road cars will generally be lighter because they are functional and have no adornments (it doesn't matter what they look like - just cover them up with a plastic hub cap), whereas alloys are mostly designed to be seen and admired (hence all those funny shaped but largely superfluous spokes and things). If alloy wheels were just made to a similar, simple design as a steel wheel (a bit like the racing Jaguars in the 1950s) then they would be about the same weight as steel ones of the same rigidity, perhaps a bit lighter as the steel wouldn't need to be as thick as it is practical to make it in places.
Anyway - I hope I remembered the above correctly - I attended a few lectures on materials science as part of my physics degree in about 1980 (there may be a mechanical or structural engineer out there that will correct me if my memory has failed me in this respect).
It will be interesting to see the results of your experiment: my money is still on the plain-Jane steel wheels being lighter than the flash alloys.
Alan