<VV> Re: Fanz

[Padgett]

>One downside with electric fans is the life, they are not made to run
>continuously.  In a radiator application this is ok, and 1000 hour life may
>give 150,000 miles of operation with the intermittent use

Well not a full shout but my wife runs the a/c all year round and on a GM 
car that means LO (half speed) through both fans. Have had the Bonne since 
new in 1990 and no trouble there. In fact we have four other cars of the 
same era and only had one fan bearing requiring replacement in over 400,000 
combined miles & 60 vehicle-years.

This is part of the reason I suggested stacking two fans with series (half 
speed) and parallel (full speed) wiring which also provides a measure of 
backup since both are unlikely to fail at once. All you need are two 
thermal switches and a pair of relays. No big.

As to the stock fans, one look at the straight vanes says "crude" as in the 
difference between an elderly C-130 (Hercules) and new C-130J (Xena). Note 
the curved blades on the electric fan in the jpg. That and proper shrouding 
(why a "turbo" fan moves a lot more air than a box fan) make a big 
difference in efficiency. Would like to see more overlap between the 
leading and trailing edges but that is a niggle.

Could probably rig a mechanical drive but unless a CVT (expensive) would 
again be two slow at idle and too fast at high speeds (would not be 
surprised if the tips were found to go sonic at very high rpm and then the 
flow would stop. (See: "choked flow").

Bottom line: yes, fans are a lot more efficient today than they were in 
1964. And electric motors are a lot lighter. Is a matter of design.

Padgett