Home » Public Forums » GMCnet » [GMCnet] Under Bumper Air Scoop
| [GMCnet] Under Bumper Air Scoop [message #104121] |
Mon, 25 October 2010 11:08  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Since I mentioned adding an Under Bumper Air Scoop for the AL radiator, I
decided I'd better post some photos:
http://www.gmcmhphotos.com/photos/showgallery.php?cat=5632
<http://www.gmcmhphotos.com/photos/showgallery.php?cat=5632>It's a very
simple project: A 12" x 48" piece of 12 g. AL diamond plate bent to match
the curve of the bottom of the radiator surround and bolted to that frame.
The leading 1" of the scoop was folded back 180* using a big electrically
powered sheet metal brake, but that could have been done without much
difficulty (though not quite as neatly) by clamping the AL with a beam to
the edge of a workbench and progressively bending it with a wide hammer.
All the other cuts and bends were done with hand tools and clamps.
It's my belief that the scoop will force more air through the bottom
section, and perhaps all, of the radiator since the air cannot easily divert
to the sides and bottom. But I have no "before" data to compare with
"after". The new AL radiator will just gain the benefit on top of whatever
improvement it inherently affords.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Under Bumper Air Scoop [message #104124 is a reply to message #104121] |
Mon, 25 October 2010 11:20  |
GeorgeRud
Messages: 1380
Registered: February 2007
Location: Chicago, IL
Karma: 0
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That scoop looks great, and I like the rock guards as well. What I really enjoyed is seeing your ramp/work area - much nicer than having to use floor jacks and jackstands!
George Rudawsky
Chicago, IL
75 Palm Beach
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| Re: [GMCnet] Under Bumper Air Scoop [message #104126 is a reply to message #104121] |
Mon, 25 October 2010 11:24 |
Nelson Wright
Messages: 147
Registered: May 2004
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Ken,
That scoop looks great and I believe that it will help catch more air,
however in looking at your grill with the expanded metal screen I
think maybe this your problem. That screen probably restricts 50% of
the air flow. I remember years ago when we tried running with a bug
screen covering the grill that we had higher temps that went away upon
removal of the screen.
But anyway thats a nice looking scoop.
Nelson Wright
Orlando FL
78 Royale rear bath
On Oct 25, 2010, at 12:08 PM, Ken Henderson wrote:
> Since I mentioned adding an Under Bumper Air Scoop for the AL
> radiator, I
> decided I'd better post some photos:
> http://www.gmcmhphotos.com/photos/showgallery.php?cat=5632
>
> <http://www.gmcmhphotos.com/photos/showgallery.php?cat=5632>It's a
> very
> simple project: A 12" x 48" piece of 12 g. AL diamond plate bent to
> match
> the curve of the bottom of the radiator surround and bolted to that
> frame.
>
> The leading 1" of the scoop was folded back 180* using a big
> electrically
> powered sheet metal brake, but that could have been done without much
> difficulty (though not quite as neatly) by clamping the AL with a
> beam to
> the edge of a workbench and progressively bending it with a wide
> hammer.
> All the other cuts and bends were done with hand tools and clamps.
>
> It's my belief that the scoop will force more air through the bottom
> section, and perhaps all, of the radiator since the air cannot
> easily divert
> to the sides and bottom. But I have no "before" data to compare with
> "after". The new AL radiator will just gain the benefit on top of
> whatever
> improvement it inherently affords.
>
> Ken H.
> Americus, GA
> '76 X-Birchaven w/Cad500/Howell EFI+ & EBL
> www.gmcwipersetc.com
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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List Information and Subscription Options:
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| Re: [GMCnet] Under Bumper Air Scoop [message #104129 is a reply to message #104126] |
Mon, 25 October 2010 11:41 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Nelson,
You're right about the screen restricting air flow. I bought the 4x8 sheet
from which that was cut in Tampa years ago when we were spending a lot of
time down there. The specifications for that material always specify the
percentage of blockage it imposes. IIRC, that pattern is 28% blocked (72%
open). That seems to me a small price to pay for the protection if offers
-- it's probably more open than most of those being sold for the same
purpose.
I've had the same experience with bug screens, but they're generally much
more closely woven (bug sized) and restrictive.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
On Mon, Oct 25, 2010 at 12:24 PM, Nelson Wright <f25ccapt@gmail.com> wrote:
> Ken,
> That scoop looks great and I believe that it will help catch more air,
> however in looking at your grill with the expanded metal screen I
> think maybe this your problem. That screen probably restricts 50% of
> the air flow. I remember years ago when we tried running with a bug
> screen covering the grill that we had higher temps that went away upon
> removal of the screen.
> But anyway thats a nice looking scoop.
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Under Bumper Air Scoop [message #104135 is a reply to message #104129] |
Mon, 25 October 2010 12:28 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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We have 3 units that address the ramming/pressure region for the radiator.
J R Wright has a simple but effective unit that creates a high
pressure region on the front side of the radiator and creates a low
pressure region behind it to help pull the air.
He has sold several units and now were carrying them.
The second one isonewe came up with that funnels the air like the one
Ken did, but is designed to funnel in the air from the sides and
bottom with no air directed to the tanks, as it will tabulate and not
do much.
The third one is a Big figerglass air dam with a shied that go up to
the stabilizer bar and is designed to do both the high pressure in the
front and low pressure in the back.
Each has its drawbacks.
Ken's will clear the ground and other barriers, ours are lower to the
ground and will need to be driven carefully around parking curbs and
lifts.
I tested these and found that they all reduce the fan clutch from
coming on by as much as 70%.
We are seriously considering employing a way to lift the lower portion
by some mechanism to create clearance when needed.
On Mon, Oct 25, 2010 at 9:41 AM, Ken Henderson <hend4800@bellsouth.net> wrote:
> Nelson,
>
> You're right about the screen restricting air flow. I bought the 4x8 sheet
> from which that was cut in Tampa years ago when we were spending a lot of
> time down there. The specifications for that material always specify the
> percentage of blockage it imposes. IIRC, that pattern is 28% blocked (72%
> open). That seems to me a small price to pay for the protection if offers
> -- it's probably more open than most of those being sold for the same
> purpose.
>
> I've had the same experience with bug screens, but they're generally much
> more closely woven (bug sized) and restrictive.
>
> Ken H.
> Americus, GA
> '76 X-Birchaven w/Cad500/Howell EFI+ & EBL
> www.gmcwipersetc.com
>
>
>
> On Mon, Oct 25, 2010 at 12:24 PM, Nelson Wright <f25ccapt@gmail.com> wrote:
>
>> Ken,
>> That scoop looks great and I believe that it will help catch more air,
>> however in looking at your grill with the expanded metal screen I
>> think maybe this your problem. That screen probably restricts 50% of
>> the air flow. I remember years ago when we tried running with a bug
>> screen covering the grill that we had higher temps that went away upon
>> removal of the screen.
>> But anyway thats a nice looking scoop.
>>
>>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Under Bumper Air Scoop [message #104229 is a reply to message #104206] |
Mon, 25 October 2010 21:30 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Hardi,
That sounds too easy and too good to do.
I will get on that soon and try it.
With the temperature cooling down, we will get out expensive
electronic monometers to check the pressures and see what angles seeem
to do at various air speed.
I have noticed that when we have wind on the back, there is less load
on the coach,and less air ramming on the radiator.
On Mon, Oct 25, 2010 at 4:30 PM, Hardie Johnson <hardie.j@gmail.com> wrote:
>
>
> jimk wrote on Mon, 25 October 2010 13:28
>> <>Ken's will clear the ground and other barriers, ours are lower to the ground and will need to be driven carefully around parking curbs and lifts. I tested these and found that they all reduce the fan clutch from coming on by as much as 70%. We are seriously considering employing a way to lift the lower portion by some mechanism to create clearance when needed.
>> <>
>
> Don't raise the bridge; lower the water. Spring load the bottom lip so it drops down when the coach is moving, but springs up when you are at parking lot speeds.
> "free ideas"
> --
> Hardie Johnson "Crashj"
> 1973 26 foot Glacier, White Thing
> Raleigh NC
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
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>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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