REFLECTOR: ram air vs filter

Fri Jun 15 09:14:08 CDT 2007

Scott,

Yep, my air intake does take a turn over 90 degrees and I will have some
measure of disturbed flow in there.  It is a compromise design like so much
of this is.  I am not sure we need a ram air.  The engine intake will suck
air sufficiently, hopefully,  thru that turn-it is shortest distance I can
make it with a pretty straight run after that.  We are talking a short
distance.  I know airliners are not a good comparison, but I did have these
jet experiences that I included (best I recall) as Collier and I discussed
the issue.   The B-727 center engine is actually in line with the two pod
engines thru a big S duct.  I was unheard of at the time.  Compressor stalls
were is big issue on start up or even on the ground when I guy would make a
rolling takeoff in a big crosswind the pour the coals to it with inlet air
all disturbed.   It took some testing in the early development years but it
works.  Douglas, in the DC-10, rejected it in its bigger trijet, while
Lockheed in the L-1011 included it.  

Of course cylinders sucking air are different than compressor blades which
are more flow sensitive.  I opted for what we did.  My thinking for anybody
not up to this point could include these points:  I saw Chuck Jensen's
intake.  He uses a portion of what would be cooling air by ducting out of
his roof NACA's.  (And his intake ducting took some big turns too, and
didn't have a lot of ram quality to it per se.)  He never mentioned any oil
temp/cooling issues that I recall.  I think a good hunk of that approach
would have to include a good cooling plenum.  I never asked him about this,
but I am glad myself to have the space free for other stuff in the
engine-block-to-firewall real estate.  Lots of stuff has to go there.  

Belly intakes maybe like Rene would be the best for ram air advantage.  His
has worked too,  based on his 500 hours.  I would worry about sucking in
water/slush kicked back from the nose tire.  That was a problem in the later
stretched versions of the DC-9.  In fact they put mud flaps on the nose
tire.  For us.well we are not all weather operators.  Personally, I would,
and I bet most others would delay a takeoff or landing if there was active
moderate precip that could otherwise be avoided for lots of reasons other
than intake debris.  Just my 2 cents.  Oh, and thanks.  I guess it is a K&N
filter not K&M. 

Terry

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Thursday, June 14, 2007 9:34 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: ram air vs filter

Terry,

are you blowing air backwards through the K&N?  Does it matter which way the
air flows. into the cone or out of the cone?

Scott

Terry Miles wrote: 

Keith,

Here's what I got...mostly this is a Malcolm Collier/Hangar 18 effort.   He
did the actual carving, and it was his idea.  I took it from there.   I can
send more pics if you need them.  It is the carved foam block routine.  Note
the scoop is away from the underside of the wing, and you can see the outlet
duct going into what would be the eng compartment.  We will use a short hunk
of hose to connect.  The wing root section fits the standard size
rectangular K&M filter and has the suction 2ndary door on a spring for
filter bypass.

The intake plenum that came with the engine didn't work.  Mine now goes off
to the right at about 35 degrees (to the left if you talk to Don George!)
He was good about swapping out the straight on one we had to begin with.
I've got the Ly 540.  I think there are 3 different induction
chambers/plenums whatever they are properly called.  They come on and off w/
a couple of bolts.   

Hope this inspires!  Good luck.  

Regards,
Terry

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Keith Hallsten
Sent: Tuesday, June 12, 2007 9:05 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: ram air vs filter

Rene',

This sounds like a pretty practical set-up for induction.  Do you have any
pictures?  Is the "midline scoop" available, or was that a one-off custom
part?

I am in the midst of engine installation, and the induction system seems to
be the part I'm having the most trouble with.  I have made a couple of air
boxes using the "lost foam" method, but found their design to be
unsatisfactory.  I'm definitely looking for inspiration on this.

Keith Hallsten
XLFG, Roseville, CA

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Rene Dugas
Sent: Tuesday, June 12, 2007 4:22 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: ram air vs filter

I use the midline scoop mounted to the lower cowl and the rear of the
fire wall.  I used a K & N cone shaped filter mounted to a 3 inch
aluminum flange with an identical flange mounted the opposite direction
in a fiberglass box.  This is attached to the induction by 3 in. scat
tubing to allow for vibration.  I mounted a spring operated door in the
side of the box for emergency air that sucks open if I close the scoop.
I made the box by forming foam and coating it with glass.  I used
acetone to dissolve the foam and presto custom air box.  I seem to get 1
to 2 inches of MP based on side by side flights with others at the
Velocity Symposium.
My scoop starts out about 1.75 by 2.25 inches and opens up into
approximately a one foot square air box with the K & N in it.
Just FYI.  I can remove the lower cowl and the scoop screws to the box.
I can remove the two screws in the scoop and remove the filter for
cleaning.
Rene'

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Tom
Sent: Thursday, June 07, 2007 8:01 PM
To: reflector at tvbf.org
Subject: REFLECTOR: ram air vs filter

My problem was that I went from ram air to what was too small of a 
filter. It was a 3" diameter x 5" long. I clamped it directly to the 
induction air tube. I really need a larger filter with filtration on the

end also (this was closed). Very space limited under there as I share 
the ram air inlet with a 2nd oil cooler mounted on the baffling. (large 
aeroduct hose). I may just go with a screen.
_______________________________________________
To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector

Visit the gallery!  www.tvbf.org/gallery
user:pw = tvbf:jamaicangoose
Check new archives: www.tvbf.org/pipermail
Check old archives: http://www.tvbf.org/archives/velocity/maillist.html

_______________________________________________
To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector

Visit the gallery!  www.tvbf.org/gallery
user:pw = tvbf:jamaicangoose
Check new archives: www.tvbf.org/pipermail
Check old archives: http://www.tvbf.org/archives/velocity/maillist.html

_______________________________________________
To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector

Visit the gallery!  www.tvbf.org/gallery
user:pw = tvbf:jamaicangoose
Check new archives: www.tvbf.org/pipermail
Check old archives: http://www.tvbf.org/archives/velocity/maillist.html

  _____  

  _____  

_______________________________________________
To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector

Visit the gallery!  www.tvbf.org/gallery
user:pw = tvbf:jamaicangoose
Check new archives: www.tvbf.org/pipermail
Check old archives: http://www.tvbf.org/archives/velocity/maillist.html

-- 

-
    The only security of all is in a free press. The force of public opinion
cannot be resisted when permitted freely to be expressed. The agitation it
produces must be submitted to. It is necessary, to keep the waters pure.

    Thomas Jefferson to Lafayette, 1823. ME 15:491 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.tvbf.org/mailman/private/reflector/attachments/20070615/66f08191/attachment.htm 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 56119 bytes
Desc: not available
Url : http://www.tvbf.org/mailman/private/reflector/attachments/20070615/66f08191/attachment-0001.jpe 