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haveblue1(at)mac.com
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 Posted: Mon Sep 20, 2010 4:23 pm Post subject: Prop |
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Gary,
Some years ago, and this may have been in the 1980s, I read an article in Machine Design about a guy who patented a fixed pitch, constant speed propeller. He was able to cause a "constant speed effect" by blowing air out slots machined into the upper surface of the prop blades. This did require a hollow shaft on his test motor and an air pump to pressurize the slots. Never heard anything about that since. Remember anything from your Propulsion Engineer days?
It would seem to me that you might be able to dispense with the air pump and open the front of the spinner to take advantage of the ram air effect. Might not be perfect, but it might be a start.
Anyone else out there in Team Grumman land remember anything about this?
Thanks.
Bruce
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teamgrumman(at)YAHOO.COM
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| Posted: Mon Sep 20, 2010 7:26 pm Post subject: Prop |
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I don't recall hearing about this. I'm not sure how it would work. Boundary layer control is generally used to control flow attachment.
Do a google search and see if you can find anything.
30 years ago I was reading a Jane's book of planes. At the time, I was designing a plane using a ducted fan. Damn if the Germans hadn't already done that. Forward swept wings were the new thing. Damn if the Germans hadn't done that too. If you have access to a complete set of Jane's going back to the 20's, odds are, it's been done.
From: Bruce Smith <haveblue1(at)mac.com>
To: teamgrumman-list(at)matronics.com
Sent: Mon, September 20, 2010 5:17:38 PM
Subject: Prop
--> TeamGrumman-List message posted by: Bruce Smith <haveblue1(at)mac.com (haveblue1(at)mac.com)>
Gary,
Some years ago, and this may have been in the 1980s, I read an article in Machine Design about a guy who patented a fixed pitch, constant speed propeller. He was able to cause a "constant speed effect" by blowing air out slots machined into the upper surface of the prop blades. This did require a hollow shaft on his test motor and an air pump to pressurize the slots. Never heard anything about that since. Remember anything from your Propulsion Engineer days?
It would seem to me that you might be able to dispense with the air pump and open the front of the spinner to take advantage of the ram air effect. Might not be perfect, but it might be a start.
Anyone else out there in Team Grumman land remember anything about
[quote][b]
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bob.hodo(at)YAHOO.COM
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| Posted: Mon Sep 20, 2010 8:05 pm Post subject: Prop |
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Gary, any chance that doing this at the root of the blade during take-off acceleration would reduce the work load on the prop inboard, allowing the engine to get the working outer half to higher rpms? Kind of like controlling cavitation on a boat? And if this IS what happens, the magic pixie dust could be tweaked even stronger strait and level, no?
Bob Hodo
--- On Mon, 9/20/10, Gary Vogt <teamgrumman(at)YAHOO.COM> wrote:
| Quote: |
From: Gary Vogt <teamgrumman(at)YAHOO.COM>
Subject: Re: Prop
To: teamgrumman-list(at)matronics.com
Date: Monday, September 20, 2010, 10:23 PM
I don't recall hearing about this. I'm not sure how it would work. Boundary layer control is generally used to control flow attachment.
Do a google search and see if you can find anything.
30 years ago I was reading a Jane's book of planes. At the time, I was designing a plane using a ducted fan. Damn if the Germans hadn't already done that. Forward swept wings were the new thing. Damn if the Germans hadn't done that too. If you have access to a complete set of Jane's going back to the 20's, odds are, it's been done.
From: Bruce Smith <haveblue1(at)mac.com>
To: teamgrumman-list(at)matronics.com
Sent: Mon, September 20, 2010 5:17:38 PM
Subject: Prop
--> TeamGrumman-List message posted by: Bruce Smith <[url=/mc/compose?to=haveblue1(at)mac.com]haveblue1(at)mac.com[/url]>
Gary,
Some years ago, and this may have been in the 1980s, I read an article in Machine Design about a guy who patented a fixed pitch, constant speed propeller. He was able to cause a "constant speed effect" by blowing air out slots machined into the upper surface of the prop blades. This did require a hollow shaft on his test motor and an air pump to pressurize the slots. Never heard anything about that since. Remember anything from your Propulsion Engineer days?
It would seem to me that you might be able to dispense with the air pump and open the front of the spinner to take advantage of the ram air effect. Might not be perfect, but it might be a start.
Anyone else out there in Team Grumman land remember anything about
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[quote][b]
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teamgrumman(at)YAHOO.COM
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| Posted: Tue Sep 21, 2010 11:07 am Post subject: Prop |
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You can't accelerate a propeller blade fast enough to cause cavitation at the root or any where else. The magic pixie dust does a pretty good job of letting the prop turn full rpm (as if it had a climb prop) on take-off.
From: Bob Hodo <bob.hodo(at)YAHOO.COM>
To: teamgrumman-list(at)matronics.com
Sent: Mon, September 20, 2010 9:03:13 PM
Subject: Re: TeamGrumman-List: Prop
Gary, any chance that doing this at the root of the blade during take-off acceleration would reduce the work load on the prop inboard, allowing the engine to get the working outer half to higher rpms? Kind of like controlling cavitation on a boat? And if this IS what happens, the magic pixie dust could be tweaked even stronger strait and level, no?
Bob Hodo
--- On Mon, 9/20/10, Gary Vogt <teamgrumman(at)YAHOO.COM> wrote:
| Quote: |
From: Gary Vogt <teamgrumman(at)YAHOO.COM>
Subject: Re: Prop
To: teamgrumman-list(at)matronics.com
Date: Monday, September 20, 2010, 10:23 PM
I don't recall hearing about this. I'm not sure how it would work. Boundary layer control is generally used to control flow attachment.
Do a google search and see if you can find anything.
30 years ago I was reading a Jane's book of planes. At the time, I was designing a plane using a ducted fan. Damn if the Germans hadn't already done that. Forward swept wings were the new thing. Damn if the Germans hadn't done that too. If you have access to a complete set of Jane's going back to the 20's, odds are, it's been done.
From: Bruce Smith <haveblue1(at)mac.com>
To: teamgrumman-list(at)matronics.com
Sent: Mon, September 20, 2010 5:17:38 PM
Subject: Prop
--> TeamGrumman-List message posted by: Bruce Smith <haveblue1(at)mac.com>
Gary,
Some years ago, and this may have been in the 1980s, I read an article in Machine Design about a guy who patented a fixed pitch, constant speed propeller. He was able to cause a "constant speed effect" by blowing air out slots machined into the upper surface of the prop blades. This did require a hollow shaft on his test motor and an air pump to pressurize the slots. Never heard anything about that since. Remember anything from your Propulsion Engineer days?
It would seem to me that you might be able to dispense with the air pump and open the front of the spinner to take advantage of the ram air effect. Might not be perfect, but it might be a start.
Anyone else out there in Team Grumman land remember anything about
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[quote][b]
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bob.hodo(at)YAHOO.COM
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| Posted: Tue Sep 21, 2010 12:40 pm Post subject: Prop |
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Perhaps I am confused. That wouldn't make news.
But my understanding from your post was that the holes in the prop with air being forced through them would detach the airflow on that side of the blade (in the areas near the holes).
In trying to figure out how this would be an advantage I wondered if this might be similar to cavitation on a boat prop. On a boat this results in immediate rpm acceleration, unfortunately killing thrust (almost) all across the blades, since water is being replaced by air. It does make a boat prop a little more constant speed (red line rpms on less than full hp), but is uncontrolled, etc.
On this mythical "fixed pitch constant speed prop", attached airflow would be replaced in the areas where the holes are with a detached flow that would kind of follow the blade, and I am assuming this would eat up less horsepower, allowing the rpms to come up?
I am just trying to find logic in it, and this is the best my mind has come up with so far.
Bob Hodo
[quote][b]
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flyadive(at)gmail.com
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| Posted: Tue Sep 21, 2010 2:14 pm Post subject: Prop |
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Hello Gary:
Cavitation is an occurrence in a LIQUID not in air. It is the separation of
a liquid over a solid moving surface. When the liquid separates it leave
behind AIR.
Hello Bob H.
Doing almost anything to the root of a prop is just about useless. Props do
their work in the last 1/3 of the blade. Experiments have been do in
replacing the root area with nothing more than a piece of flat stock. There
was a GAIN in RPM due to weight reduction and drag reduction. They were
able to increase the pitch in the last 1/3 which increased the IAS.
Take a look at the F4F Wildcat - Just to keep things Grumman. Huge Cowl
with lots of the prop being blocked off.
In the U-Control plane world they did speed records with ONE BLADE a
counter balance weight and only the last 1/3.
Now, to contradict my above statements take a look at
the WHIRLWIND composition prop.
The tip is quite pointed - The blade is quite wide and LQQKing at it from
the end there is almost only ONE pitch. Not progressive/variable like our
props.
Barry
"Chop'd Liver"
On Tue, Sep 21, 2010 at 3:04 PM, Gary Vogt <teamgrumman(at)yahoo.com> wrote:
[quote] You can't accelerate a propeller blade fast enough to cause cavitation at
the root or any where else. The magic pixie dust does a pretty good job of
letting the prop turn full rpm (as if it had a climb prop) on take-off.
------------------------------
*From:* Bob Hodo <bob.hodo(at)YAHOO.COM>
*To:* teamgrumman-list(at)matronics.com
*Sent:* Mon, September 20, 2010 9:03:13 PM
*Subject:* Re: Prop
Gary, any chance that doing this at the root of the blade during take-off
acceleration would reduce the work load on the prop inboard, allowing the
engine to get the working outer half to higher rpms? Kind of like
controlling cavitation on a boat? And if this IS what happens, the magic
pixie dust could be tweaked even stronger strait and level, no?
Bob Hodo
--- On *Mon, 9/20/10, Gary Vogt <teamgrumman(at)YAHOO.COM>* wrote:
From: Gary Vogt <teamgrumman(at)YAHOO.COM>
Subject: Re: Prop
To: teamgrumman-list(at)matronics.com
Date: Monday, September 20, 2010, 10:23 PM
I don't recall hearing about this. I'm not sure how it would work.
Boundary layer control is generally used to control flow attachment.
Do a google search and see if you can find anything.
30 years ago I was reading a Jane's book of planes. At the time, I was
designing a plane using a ducted fan. Damn if the Germans hadn't already
done that. Forward swept wings were the new thing. Damn if the Germans
hadn't done that too. If you have access to a complete set of Jane's going
back to the 20's, odds are, it's been done.
------------------------------
*From:* Bruce Smith <haveblue1(at)mac.com>
*To:* teamgrumman-list(at)matronics.com
*Sent:* Mon, September 20, 2010 5:17:38 PM
*Subject:* Prop
Gary,
Some years ago, and this may have been in the 1980s, I read an article in
Machine Design about a guy who patented a fixed pitch, constant speed
propeller. He was able to cause a "constant speed effect" by blowing air out
slots machined into the upper surface of the prop blades. This did require a
hollow shaft on his test motor and an air pump to pressurize the slots.
Never heard anything about that since. Remember anything from your
Propulsion Engineer days?
It would seem to me that you might be able to dispense with the air pump
and open the front of the spinner to take advantage of the ram air effect
| | - The Matronics TeamGrumman-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?TeamGrumman-List |
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