Why does the fan on my alternator have inconsistent blade shapes? Any ideas? Noise?
Also, the fan has a notch cut out signifying it must go on the shaft one way only, however, there is no corresponding key on the shaft for it to line up with. The shaft is perfectly round. Any ideas?. Thanks.

 

The variable spacing is almost certainly done to avoid an acoustic resonance at a specific RPM. The notch is likely used for tooling during fabrication to orient the part. I'm guessing that they cut out a blank first then stamp the vanes, so clocking during that operation is important.