Just think of the heat evolved by the internal air (or gas) being pumped around the tires.
I wonder, once you get up to speed, do you even need any gas in the tires, or would centrifugal force hold them out?
There aren't any tires, its a solid disk/rim
I was thinking more about wheel bearing temps but those probably are not aluminum. I would have thought the stresses alone would be too much for aluminum wheels. They might need to end up with titanium or something.
Aluminum is in this case almost as good or better than titanium. What matters under this kind of loading is "specific strength" (tensile strength divided by density) which makes aluminum and titanium very nearly the same, but the added thermal conductivity of aluminum (and greater flexibility) gives it an edge (not to mention titanium at that size is both unbelievably expensive and prone to microcracks that for most structures are okay, but for high cycle structures like a wheel, are bad)
The article mentions that when spinning, at full speed the wheel heats to over 200F from air friction.
But - spinning it in a test chamber doesn't fully account for air passing over the balance of the wheel at 1100 MPH or the effects of load on the wheel . . . I wonder how they're accounting for that?
And I wonder how they're accounting for things like boundary layers, compressibility, etc . . . I'm not an aerodynamic engineer, but these would seem to be non-trivial effects.
The load is actually minuscule compared to the tensile load from the spinning. At 10krpm and 1m in radius, the acceleration at the edge is 1000g, meaning the tensile load is >>> the compressive (weight of car) load
Also, on airflow, the heating is actually dominated by the air on the upper edge, where the wheel's rotation brings the edge forward into the air, so its hitting air at 2200mph. The air over the side of the wheel averages half that (and the stagnation energy of the air goes with the square of the speed).
