mzso wrote: ↑21 Dec 2021, 06:58
So you're implying Mg is stronger considering the loads a wheel gets?
No, rather titanium alloy is not a suitable material for a wheel (racing or otherwise), else it would be used. Instead we have:
Steel < Aluminium Alloy < Magnesium Alloy < Carbon-Fibre
[In order of increasing cost.]
You are welcome to set up a foundry to sell titanium alloy wheels!
I suspect the problem is that once you manufacture the barrel of the titanium alloy wheel at 1/3rd the thickness or less of the magnesium alloy wheel (to obtain the weight-saving from titanium's greater shear/tensile strength as you say), you no longer have a profile with sufficient stiffness and rigidity? But I'm just guessing.
I doubt that the likes of BBS, OZ Racing, Rays and so forth simply lack the data to realise they should have been making their racing wheels out of titanium alloy and not magnesium alloy all along! Titanium alloy racing wheels must therefore not stack up.
Edit: It seems the modulus of elasticity of titanium alloy is about 2.5x more than magnesium alloy, the tensile strength is 4x more, but the density is 2.4x more. So you could make the titanium alloy wheel barrel about 1/2.5x the thickness to obtain the same stiffness as the magnesium alloy wheel but it would weigh about the same anyway while the wheel manufacturers have foundries and tooling for aluminium alloy and magnesium alloy wheels (which are quite similar), not titanium alloy wheels that would need to be made much thinner using different processes.
TL;DR: The non-use of titanium alloy in racing wheels seems to be due its mediocre modulus of elasticity, rather than its extremely high tensile strength... Given the modulus of elasticity, titanium alloy offers no advantage over magnesium alloy.
mzso wrote: ↑21 Dec 2021, 06:58
Tommy Cookers wrote: ↑20 Dec 2021, 19:12
what we call strength-to-weight-ratio is assuming direct loads - not bending loads etc
So you're implying Mg is stronger considering the loads a wheel gets?
Perhaps more stiff as opposed to stronger? Particularly in torsion, perhaps? The shear or tensile strength of the monocoque or wheel is not really the main concern, one presumes, but rather rigidity.