> Dick Gregory wrote:
 >
 > > What I was concerned about with the downdraft was that the nosewheel
 > would
 > > kick up a pebble and aim it directly at the input scoop. With the
 > radiator
 > > unprotected would it be susceptible to damage?

 Perry Mick wrote:
 >
 > That's possible I suppose. I've had a couple small hits on my prop.
 > I switched to a slick tire on the nose wheel, a recommendation of
 > George Graham.  Also, I started putting the landing brake down while
 > taxiing.  The inlet lip and ducting is about 6 inches deep before the
 > radiator, hopefully the pebble will hit the sides of the ducting and
 > loose energy.  When you pull an oil cooler out of an RX-7, they
 > are usually full of small stones, because the oil cooler is mounted so
 > low.  The stones get in the "fins" and cause a loss of airflow, but
 > don't
 > damage the oil passages.
 >
 > > You guys are giving me lots of good information. I have been watching
 > this
 > > list now for about 4 months and have lots of the messages and

pictures

 > saved
 > > on my hard drive.
 > >
 > > Perry, could your 3X5 inlet be too small for the oil cooler? It seems
 > like a
 > > rule of thumb I have seen states 25 percent of the radiator area

which

 > I
 > > think would be more like 25 square inches. Based on your experience I
 > think
 > > I will make mine about 4X6.
 > >
 > It's possible, my previous inlet was an armpit, slightly larger in

area,

 > but
 > probably had more boundary layer.  Good idea to make it larger.
 >
 > > I'm also fiddling with the idea to put a fan in a short parallel duct
 > with a
 > > swinging door. When on the ground the fan would run and keep the door
 > open
 > > and supply air to the cooler. In the air the fan would be shut off

and

 > the
 > > air from the inlet would keep the door closed.
 > >
 > > I hope this doesn't get reformatted too badly. This is a top view

with

 > the
 > > front to the left. The fan branch would be inside the firewall line,
 > inboard
 > > from the main branch, and level with it.
 > >           ___________
 > >          /    fan >  \
 > >    _____/   ______    \______
 > >                   \
 > >           door open\
 > >    __________________________
 > >
 > > Dick Gregory
 > > LongEZ N613NC

 > Good idea but there's very little room!
 >
 > --
 > Perry J. Mick
 > Duckt N7XR
 > http://www.ductedfan.com

 In theory the airflow going through the rad is much reduced so
 a screen like square hardware wire directly in front of and in
 contact with the rad should protect from large stones. I would
 not use mosquito screen however.

 Try it with and with out on the same day to check for
 affect on cooling.

 Paul Lamar

Yes, space is a concern. Like I said, I am just fiddling with the idea. I
will get a better idea of how things will fit once I get the engine nailed
to the firewall. (or should I use glue? ;-)

Thanks, Paul for the suggestion of the screen. I am still a long ways from
flying but will put that on my list of things to try.

Dick Gregory

 
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