Whoever brought up the subject of igniting magnesium wheels should be
horsewhipped . . . wait a minute, it was ME!
Please forgive me for having off-handedly raised the issue of igniting
magnesium wheels some time back.
Since then, I've gotten numerous emails, some privately and some from the
list, with various and sundry scientific arguments as to why magnesium
wheels will (or will not - take your pick) ignite . . . and the precise
circumstances under which this might (or might not) occur. I've been treated
to a fascinating display of scientific knowledge regarding boiling points,
ignition temperatures, heat transfer, surface-area-to-volume ratio,
molecular structure, etc., ad infinitum ad nauseum.
None of which I'm qualified to discuss, having abandoned the study of
physics and chemistry early in life when it became apparent that a working
knowledge of electricity would be required in those fields - a deficiency
which dogs me to this day when I press the ignition button and nothing
happens (usually because I've neglected to turn on the master switch, but if
it's any more complex than that I immediately resort to Dan Masters' book on
TR6 wiring and start calling friends).
My original comment was not based on science at all but solely on experience
- having seen it happen at Riverside Raceway many moons ago: a bad crash,
followed by a gasoline fire (no fuel cells then) and subsequent ignition of
the magnesium wheels, creating an inferno which the corner workers'
extinguishers were unable to quench (the car was finally
buried--literally--with a front end loader).
Which tells me two things: I know it can happen, because I was there; and
the vividness of that memory after all these years should be a reminder of
how rare it is.
This was not an incident likely to be repeated on the street, and many of
the so-called "mag wheels" floating around are in fact primarily aluminum
(which I'm told is a superior material for street cars anyway). If you're
driving around on old mag wheels that aren't regularly crack-tested, you've
got far bigger worries than a magnesium fire.
But if anyone has anything to add on this subject, I apologize in advance
for having started the whole mess.
Jim Hill
Madison WI
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