| Rick Denney - Air Speed indicator [message #65037] |
Fri, 20 November 2009 11:05  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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I just found out that my wife did not mail the air speed indicator. It is sitting here in a box without the address on it. I can not access your old email with your address because my laptop is down.
Please email my wife Laurie with your mailing address.
KD9EU at comcast dot net
Sorry for the delay.
I just got thinking that an altimiter might be a better solutiuon for you as it will be more sensitive. I'll also look for one of those today at the airport. I*'m still sending the airspeed indicator.
Ken
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Rick Denney - Air Speed indicator [message #65040 is a reply to message #65037] |
Fri, 20 November 2009 11:28  |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
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Air Speed, Altimeter ! Somebody better tell Rick that it he is expecting too much from Jaws.
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65059 is a reply to message #65037] |
Fri, 20 November 2009 13:27 |
Rick Denney
Messages: 430
Registered: January 2004
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Ken Burton writes...
> Sorry for the delay.
Delay? Nothing compared to how long it will take me to conduct the
experiment!
I sent you and Laurie an email just now.
For Richard, we were discussing why it is that the fan clutch needs to
engage when the coach is running at highway speed. Normally, ram air
through the grill should provide all the air flow needed to cool the
radiator. We were wondering if the fan itself and the shroud were
restricting air flow at times when the fan was not engaged. That would
create a pressure bubble inside the shroud, and vents in the shroud
covered with flaps that close at lower speeds and when the fan is
engaged might allow much greater flow through the radiator. The
airspeed indicator was a way to measure relative pressure, both static
and dynamic, at various points in the system and at various speeds.
Rick "just another excuse for engineers to be engineers" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65066 is a reply to message #65059] |
Fri, 20 November 2009 13:55 |
dmumert
Messages: 46
Registered: December 2006
Location: Canada
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Hi Rick
You could use a MAP sensor to measure the pressure differential across the
radiator. I'm not sure if the MAP sensors are vented to the atmosphere or
not. If they are vented than place the sensor behind the rad and place a
tube in front of the rad and connect it to the port on the MAP sensor. If
they are not vented you would need to use 2 sensors and measure the
differential voltage. The sensor uses 5 volts for power so don't connect it
directly to the battery.
I would think with this, or the air speed indicator, you should be able to
create a pressure map of the entire rad with and without the fan engaged.
You were looking for a new hobby weren't you?
I think you would see more if you placed a screen in front of the rad and
tied a bunch of wool tufts to it. A stucco screen with 2 inch openings
should work. You would need a video camera and a good mount to record the
data.
Dave
> Subject: Re: [GMCnet] Rick Denney - Air Speed indicator
>
> Ken Burton writes...
>
>
> > Sorry for the delay.
>
> Delay? Nothing compared to how long it will take me to conduct the
> experiment!
>
> I sent you and Laurie an email just now.
>
> For Richard, we were discussing why it is that the fan clutch needs to
> engage when the coach is running at highway speed. Normally, ram air
> through the grill should provide all the air flow needed to cool the
> radiator. We were wondering if the fan itself and the shroud were
> restricting air flow at times when the fan was not engaged. That would
> create a pressure bubble inside the shroud, and vents in the shroud
> covered with flaps that close at lower speeds and when the fan is
> engaged might allow much greater flow through the radiator. The
> airspeed indicator was a way to measure relative pressure, both static
> and dynamic, at various points in the system and at various speeds.
>
> Rick "just another excuse for engineers to be engineers" Denney
>
> '73 230 Ex-Glacier "Jaws"
> Northern Virginia
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Dave Mumert
Olds, AB
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65076 is a reply to message #65066] |
Fri, 20 November 2009 15:40 |
Rick Denney
Messages: 430
Registered: January 2004
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Dave Mumert writes...
> Hi Rick
> You could use a MAP sensor to measure the pressure differential
> across the radiator....
> ...You would need a video camera and a good mount to record the
> data.
Say, Dave, you like spending my money as much as spending my time,
heh, heh.
The air-speed indicator has the advantage of measuring dynamic
pressure, which to me is useful in a system designed for ram air. A
10-foot length of clear vinyl hose and an ounce or two of water would
probably do just as well.
The questions are simple:
What is the relative pressure (emphasis on the word: relative) between
the air in front of the radiator, within the shroud, and around the
shroud. The pressure behind the radiator has to be less than the
pressure in front of it for air to move. We know it moves when the fan
engages--we can see that effect on a temperature gauge.
If the pressure inside the shroud is higher than behind the shroud,
then the unengaged fan is indeed bottling it up. Vents may help. If
the pressure inside the shroud is less than the pressure behind the
shroud, vents won't help and the solution lies elsewhere. No need to
figure out how to cut vents holes and fabricate flapper valves for
them.
Rick "who likes narrow testing parameters" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65099 is a reply to message #65076] |
Fri, 20 November 2009 18:15 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Rick Denney wrote on Fri, 20 November 2009 16:40 |
Dave Mumert writes...
> Hi Rick
> You could use a MAP sensor to measure the pressure differential across the radiator....
> ...You would need a video camera and a good mount to record the data.
Say, Dave, you like spending my money as much as spending my time, heh, heh.
The air-speed indicator has the advantage of measuring dynamic pressure, which to me is useful in a system designed for ram air. A 10-foot length of clear vinyl hose and an ounce or two of water would probably do just as well.
The questions are simple:
What is the relative pressure (emphasis on the word: relative) between the air in front of the radiator, within the shroud, and around the shroud. The pressure behind the radiator has to be less than the pressure in front of it for air to move. We know it moves when the fan engages--we can see that effect on a temperature gauge.
If the pressure inside the shroud is higher than behind the shroud, then the unengaged fan is indeed bottling it up. Vents may help. If the pressure inside the shroud is less than the pressure behind the shroud, vents won't help and the solution lies elsewhere. No need to figure out how to cut vents holes and fabricate flapper valves for them.
Rick "who likes narrow testing parameters" Denney
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Rick,
An aircraft airspeed instrument is a differential pressure device. Altimeter or MAP instrument or sensor is not - both of those (be it aircraft or automotive) have an internal pressure reference.
I bet you can learn just as much with a loop of vinyl tubing and some dye. (There goes the budget.)
Mark's or a mechanical engineer's handbook will tell you how to build a pitot-static device. I can't find my box that contains that kit. I actually don't recall seeing it since the last move.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65245 is a reply to message #65059] |
Sat, 21 November 2009 21:30 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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"" Normally, ram air
through the grill should provide all the air flow needed to cool the
radiator.""
Where did that assumption come from? The automakers would kiss you up one side and down the other if that was true 
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65359 is a reply to message #65245] |
Mon, 23 November 2009 01:45 |
Rick Denney
Messages: 430
Registered: January 2004
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Bob de Kruyff writes...
> "" Normally, ram air
> through the grill should provide all the air flow needed to cool the
> radiator.""
> Where did that assumption come from? The automakers would kiss
> you up one side and down the other if that was true :)
Well, maybe that's the whole issue.
I keep hearing about people whose fan clutches never engage when they
are driving down the road. But mine does--the temperature creeps up in
moderate Interstate hills until the clutch engages, and then it drops
like a rock. Not much ram air getting through there if 30 seconds of
fan can pull enough heat out of the radiator to offset 20 minutes of
highway cruise.
But those same automakers (at least the ones who made cars I've owned)
put flaps in the fan shroud so that at speed the flaps would sail open
and let air through. I figured they did that for a reason.
Rick "thinking the pressure behind the radiator should never be higher
than the pressure in front of it, if possible" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65388 is a reply to message #65365] |
Mon, 23 November 2009 12:28 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
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Gene,
I look forward to the differential pressure reading across the GMC radiator,
I'll put my money on there not being much pressure behind it trapped in the
shroud area fan or no fan spinning or not as I'd bet the radiator creates
one hell of pressure drop.
One must take into consideration that while the area of face of the radiator
is larger than the exit of the shroud quite a bit of that area is blocked /
restricted by fins and tubes.
Maybe Griffin has some numbers for the aluminum radiator?
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Gene Dotson
Sent: Tuesday, 24 November 2009 12:28 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Rick Denney - Air Speed indicator
Rick,
I think it is safe to assume there is at least a small pressure inside the
fan shroud if there is no fan installed. The in area the ram air goes
through is much larger than the shroud outlet so some pressure would be
present. With the fan and fan clutch rotating it could be questionable if
the clutch is not engaged. With it engaged I am pretty sure there will be
negative pressure inside the shroud because it really moves a lot of air.
--
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65405 is a reply to message #65365] |
Mon, 23 November 2009 14:11 |
Rick Denney
Messages: 430
Registered: January 2004
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Gene Dotson writes...
> I think it is safe to assume there is at least a small pressure
> inside the fan shroud if there is no fan installed. The in area
> the ram air goes through is much larger than the shroud outlet so
> some pressure would be present.
I'm not so sure. You would know better than any of us what the
blockage of a radiator is, especially with an AC condenser in front of
it.
If the radiator is (guessing by visualizing sitting in my office) 7
square feet with no blockage, and the fan opening is 1.8 square feet,
then the fan opening with no fan would constitue a 75% blockage. I
would not be surprised if the radiator wasn't in that range,
especially with the stuff in front of it.
With the fan, which provides what seems to me like about 60 or 70%
blockage when it's not being driven, it will certainly be higher
inside the shroud than in front of the radiator. But my temperature
gauge had already told me that.
What I'm curious about is whether the pressure behind the shroud is
low enough to effectively pull air out of the shroud without the fan
running.
The shroud exists to optimize the effect of the fan, at the expense of
air flow when the fan is not being driven. But it would be nice if the
fan would freewheel instead of engaging during highway cruise. It
would make my coach, at least, less vulnerable to fan clutch failures,
besides minimizing the power drain caused by the fan.
Rick "just wondering why vehicle manufacturers include those flaps on
other vehicles" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65448 is a reply to message #65405] |
Mon, 23 November 2009 22:51 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Rick,
Laurie assured me she today that she mailed the indicator.
I am thinking what might make a better indicator would be two clear plastic tubes with water loops in them filled the the exact same level. Then place the open distant ends anywhere around the radiator where you wish to measure the difference.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65472 is a reply to message #65448] |
Tue, 24 November 2009 07:10 |
shawnee
Messages: 422
Registered: February 2004
Location: NC
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| Ken Burton wrote on Mon, 23 November 2009 23:51 |
Rick,
Laurie assured me she today that she mailed the indicator.
I am thinking what might make a better indicator would be two clear plastic tubes with water loops in them filled the the exact same level. Then place the open distant ends anywhere around the radiator where you wish to measure the difference.
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Ken,
That tubing with water in it is called a manometer, used on boilers and any where the pressure differential is small. Using it on the motorhome would be a problem unless you could run the tubing end up to the drivers compartment. Dan Gregg could easily us it since he has a glass engine cover.
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
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| Re: [GMCnet] Rick Denney - Air Speed indicator [message #65476 is a reply to message #65472] |
Tue, 24 November 2009 07:43 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
I reckon the steps below would get some rough measurements of the pressures
in and around the radiator / shroud.
Use 2" clear tape to attach a clear plastic (Tygon) tubing loop to either
side of the black center strip on the outside of the windshield leaving
enough on both ends to run it back down through the grill. Inject enough
water into the tube to bring the level on both sides of the loop to the
center of the wind screen.
To measure the delta P across the radiator one open end goes in front of the
radiator the other inside the shroud.
To measure the delta P "across" the shroud one open end goes in the shroud
the other outside the shroud.
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Gene Dotson
Sent: Wednesday, 25 November 2009 12:10 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Rick Denney - Air Speed indicator
Ken,
That tubing with water in it is called a manometer, used on boilers and any
where the pressure differential is small. Using it on the motorhome would
be a problem unless you could run the tubing end up to the drivers
compartment. Dan Gregg could easily us it since he has a glass engine
cover.
--
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements
New Windows and Aluminum Radiators
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_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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