>>  Sorry, Mike, about missing who your previous post was directed
to. I read
 >>  the other post after I had responded to yours and realized my mistake.
 >>
 >>  Unfortunately I can't go "cheekless". My pickup scoops will
all be outboard
 >>  of the firewall. The cooler will run longitudinally through
the wing root
 >>  area above the duct. This gives me about four inches between
the main duct
 >>  and the oil pan.
 >>
 >>  Since I won't have the big fan in front, I won't have much airflow to
 >>  deliver the water spray to the radiator and cooler. My opinion
is that fans
 >>  are a necessity in a pusher configuration. The choice is
whether to put a
 >>  fan in the main flow and shorten its life, or find an
alternative like the
 >>  side duct. As far as the fan for the water radiator, it will
be behind the
 >>  rad. Since its cross section will be about 3 times that of the
inlet, its
 >>  airspeed will be about a third, minus the reduction from the
pressure drop
 >>  through the system. If its bearings wear out, I will just have
to replace
 >>  it. That's part of the price I pay for my choice of
installation. I don't
 >>  consider it a safety issue since it is only used on the ground, and my
 >>  takeoff checklist includes verification of all temperatures.
 >>
 >>  Dick Gregory

 Dick,  While my installation is in a Tractor aircraft,  I have
 installed fans on the  fuselage mounted radiator.  I am not the least
 concerned that a free wheeling fan may eventually have bearing
 problems.  If it does, I will replace it.  I have an  electric fan on
 my RX-7 that has been free wheeling for more than 100,000 miles and
 is still in good shape.     I don't know what your schedule is, but I

 > should be running this engine early next  year and   should be able

 to come up with real data about what it takes to cool a 13-B on the
 ground.  I think that  the fan will prove to be entirely adequate for
 all ground ops.   This should allow for a  SMALLER inlet scoop.  I am
 going to size mine   to become  fully effective in an airstream of
 125 m.p.h. plus.  The advantage of the fan is that the engine will
 not be overheating prior to starting the take-off roll.  By the end
 of the runway, I will be going fast enough to no longer need the fan.
 BTW,  the manufacturer of my fan, Flex-a-lite, claims that the fan
 does not impede airflow through the rad when the fan is free
 wheeling.   I don't know if you can believe them or not.     Jerry

One MUST run the numbers on things. A car averages 50 mph.
The dynamic air pressure that spins the fan is FOUR times higher at
100 MPH and it is SIXTEEN SIXTEEN SIXTEEN times higher at 200 MPH!

That still does not mean the fan will live to the corresponding number
of revolutions. If the fan is zinging along at two or three times as
fast as it is likely to in a car it may fail in just a very few minutes
because the bearings might over heat.

Car experience is of little use when it comes to aircraft applications
of the same parts. The absolutely amazing thing about the Mazda rotary engine
is its extraordinary and exceptional life in aircraft use compared to
other car engines.

Paul Lamar

By the time I'm doing 200 I will have it so choked down by closing
the exit cowl flaps  the fans will think I am parked.  Jerry

You got a good point there Jerry.

Paul Lamar
 
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