Electric vs mechanical fans
Bob Bartch (bbartch@jps.net)
Fri, 25 Apr 1997 10:42:08 -0700
I've been following the discussion over electro-magnetic clutched vs
other fans. I'm using both at the moment. I have a pair of 14 inch
electrics on my Chevy truck and the electro-clutch on my 82 505 TD. I
think the electrics are far superior for 2 reasons not yet mentioned.
Number one, they're independent of engine RPM, working far better than
anything mechanical when you're stuck in slow or non-moving traffic. No
mechanical fan is going to run max RPM when you're idling... the
difference in my truck in traffic is astounding. Number two, electric
fans are not coupled to the engine and so they don't have to accomodate
engine movement; they are extremely closely shrouded making them much
more efficient. My 505 TD has been modded for the lightweight fan, but
still I have to allow the 1 inch gap around the fan blades for possible
engine movement. If you ever run a smoke test thru the air stream when
the fan is engaged you might be surprised at the wasted airflow and
turbulence. I've seen it done on aircraft engines with "ducted" fans
(shrouds) and the effect on airflow is nothing short of phenomenal!
My money's on electrics and I'll do it to the 505 soon as I figure out
what to do with the crazy mag clutch and bearing assy. I believe it
would provide an opportunity to double-belt at least the alternator and
water pump, providing badly needed redundancy in those areas. Shame on
French engineering for putting the most important belts at the BACK of
the belt cluster!! They'd never get away with that in aircraft.