The way I heard it, the reason for the uneven location of blades on
auto fans is for noise reduction. The uneven pattern breaks up, or at
least minimizes the "siren" effect you would get if the pattern was
symmetrical. You just get a "whoosh" rather than any trace of a tone
that tracks engine speed. I don't recall any mention any airflow
advantage.
Lets Calculate: The fan turns at about the same speed as the crank,
so let's pick 3000 RPM, or 50 turns per second. With 4 blades, that
would be a 200 Hz tone, easily in the audible range. In a Tiger, it
would be quite difficult to hear the fan over the rest of the din, but
in an LTD or something, it might make a difference.
Stu
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