The Meredith Effect, reducing drag in liquid cooled engines.
Charles K. Scott
In the Fall 96 Issue of "Air Power History", vol. 43 no. 3 is an
article entitled "Mustang Margin, a reappraisal" by J. Leland Atwood.
In it Mr. Atwood takes another look at the Mustang and why it managed
to make such a huge impact on the air war during W.W.II.
The gist of the article is not so much the Mustang but the cooling
system that it used which the author feels is the reason this fighter
had such a clear speed advantage over not only the Luftwaffe's
fighters, but similar engined fighters such as the Spitfire Mk IX,
which had the same engine and horsepower.
Why am I bringing this up in this group? Because it's about cooling a
liquid cooled engine which as most of you are aware, is a subject of
some controversy here.
The article focuses on Report no. 1683 by F.W. Meredith of the Royal
Aircraft Establishment in Farnborough, England, published in 1935 and
by a follow-up article by R.S. Capon also of the RAE in 1935 which
elaborated on the effect first studied by Meredith.
Both of the authors assumed a fully enclosed air duct, directing free
stream air to an enclosed radiator but spoke little of the duct itself
leaving that up to the designers of aircraft intending to use this
effect. The design of the duct was non trivial and resulted in the
first duct to be held away from the fuselage to keep the opening out of
the turbulent fuselage boundary layer which was creating big vibration
problems with flush openings.
The conclusion, as stated in the article is as follows: "The Meredith
Effect involved preventing excessive cooling air from flowing through
the radiator at high speed by partly closing the outlet and developing
a pressure behind the radiator, which, being less than on the forward
face, created a jet of exhaust air. As with any pressure jet, this put
a forward reaction force on the airplane which partly offset the drag
of the radiator. The temperature increase in the exhaust air (from the
air being heated by the radiator) expanded its volume and augmented
this force appreciably because the size of the exit opening could be
somewhat larger with the same internal pressure."
No direct comparisons of the amount of horsepower saved by this effect
were ever made although the cooling drag for the Mustang was estimated
at only 3 percent of the total which means it used only 40 horsepower
for cooling purposes. Estimates of the two fighters indicate that at
400 mph the Spitfire required as much as 200 horsepower more than the
Mustang to maintain that speed.
So properly engineered, the Meredith Effect reduced the amount of
cooling drag of the engine, and as any aerodynamics engineer will tell
you, and one in particular in this group has said frequently, cooling
drag is not a trivial effect and in this case the reduction of drag
made the Mustang a highly effective weapon with a higher speed when
first deployed than any other fighter then flying.
How does this relate to homebuilding? The Meredith Effect is still out
there and still available for those who wish to use it. You don't need
a 400 + mph fighter to take advantage of a cooling system that reduces
drag although the faster the airplane, the more pronounced the effect.
While this might not make much difference in the performance of the
airplane I'm building, every bit of drag reduction improves efficiency
and the faster homebuilts, such as the Glassair's, Lancairs, RV's and
others would benefit from a cooling system designed with this research
in mind, if they were to use a liquid cooled engine.
Those of you who have seen pictures of the new Legend, will notice that
it too has a belly scoop set off from the fuselage, ducted to a
radiator with what appears to be an adjustable air exhaust door just
like the Mustang. If this has been designed properly, and one such
luminary as Paul Lamar has claimed it was, this should minimise drag
giving it a good chance to reach it's design speed.
Corky Scott
jj...@dow.com
In article <52rdbf$r...@dartvax.dartmouth.edu>, Charles...@dartmouth.edu says...
>
>
So Mr. Atwood's opinion was that a laminar flow wing was not the major
factor in the Mustang's speed?
brian whatcott
>you, and one in particular in this group has said frequently, cooling
>drag is not a trivial effect and in this case the reduction of drag
>made the Mustang a highly effective weapon with a higher speed when
>first deployed than any other fighter then flying.
>
>Corky Scott
>
I guess I have to say that most any aero engineer would tell YOU that
when first deployed, the Mustang was a dog, and was relegated to ground
attack - you know - Warthog style duty...
This does not exactly enhance your patriotic enthusiastic reportage,
Corky...
brian whatcott <in...@intellisys.net>
Altus OK
me
On 3 Oct 1996 03:40:09 GMT, in...@intellisys.net (brian whatcott)
wrote:
The Mustang aka the A-36 was equipped with a low level engine
that had rapid power fall off in medium and high altitudes. The
allison hauled it around fine down low, and the air frame would go
around corners quit well down low, but the problem was it was needed
up high as escort. Other than the change to the merlin and minor
changes the airframe remained the same until the D or MkIV.
John R. Johnson
On 1 Oct 1996 jj...@dow.com wrote:
> In article <52rdbf$r...@dartvax.dartmouth.edu>, Charles...@dartmouth.edu says...
> >
> >
>
> So Mr. Atwood's opinion was that a laminar flow wing was not the major
> factor in the Mustang's speed?
>
Actually, the laminar flow wing was the major factor in the Mustang's
endurance, that enabled it to function so admirably as a bomber escort.
Because of the laminar wing, slowing the Mustang down to only about
200 mph to stay in sight of B-17's allowed them to cut the power so
far back that their fuel burn went down to about 70 gallons per hour.
Other aircraft in use in that theater, like the P-47, didn't gain as
much range by throttleing back. They didn't have the laminar wing.
The cooling system on the Mustang was a marvel of efficiency and has
not been bettered for its cooling drag/horsepower rating. It did
contribute a lot also to the airplanes ability to slow down and go
for miles.
Everyone thinks it was the Mustang's ability to go FAST that was so
wonderful. We had a number of airplanes that could go pretty darned
FAST. What really made the P-51 great was its ability to slow down
and go for MILES and MILES and still have some reserve to FIGHT when
it got there! It really made a difference to the guys who were sitting
in cold, drafty, rather exposed B-17's for hours at a time on those
missions.
The P-47 was much better than the Mustang for the close ground support
operations and for busting trains in France. There is at least one
reported story of a P-47 that flew through a brick wall and made it
back to base!
John
David Lednicer
Paul Lamar wrote:
>
> Charles K. Scott wrote:
> > If this has been designed properly, and one such
> > luminary as Paul Lamar has claimed it was, this should minimise drag
> > giving it a good chance to reach it's design speed.
> >
>
> correctly. The devil is in the details. Much work in a windtunel was
> expended on the P51 duct. The point is; this type of cooling system duct
> work uses up a lot of volume inside the fuselage. That necessary volume
> is not available in a lot of homebuilts.
>
> Never the less your fairly good post indicates there is hope for you
> yet Corky :)
>
> Paul Lamar
>
> Paul Lamar
For cooling a radiator OR an air cooled engine, if you don't use
the necessary internal volume to properly diffuse the incoming air, you
will end up with a lousy cooling system with large losses and lots of
drag. There is no way around this.
I designed a new cooling system for the F1 racer #96, Madder Max,
that appeared at Reno this year. We used a full 10 degree diffuser, that
yes, took up a lot of internal volume, but the losses were a lot less and
the airplane went faster.
BTW - on the P-51 - yes, it had a laminar flow wing, but in
service it got very little laminar flow, due to the waviness and
roughness of the wing skins. I have a NACA report detailing what they
had to do to a P-51's wing to get the lower drag possible from the
aircraft.
-------------------------------------------------------------------
David Lednicer | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc. | email: da...@amiwest.com
2133 152nd Ave NE | tel: (206) 643-9090
Redmond, WA 98052 USA | fax: (206) 746-1299
Charles K. Scott
In article <52vcip$6...@zoom2.telepath.com>
in...@intellisys.net (brian whatcott) writes:
> I guess I have to say that most any aero engineer would tell YOU that
> when first deployed, the Mustang was a dog, and was relegated to ground
> attack - you know - Warthog style duty...
>
> This does not exactly enhance your patriotic enthusiastic reportage,
> Corky...
You might bone up on you airplane performance history Brian, when it
originally was deployed in England in 1943, it was an Allison engined
airplane. It was useful for low level work only because it had a low
output supercharger. The British were disappointed with it's
performance at high levels but VERY impressed with it's speed at low
level and it's range. A dog it was not. The British were so impressed
with how efficient the airframe was that they cobbled up two with Rolls
Royce Merlin engines for testing. The test mules boosted the top speed
from around the high 300's at low level to well over 400 mph at high
altitude, with no other changes. This proved the efficiency and
performance of the airframe. At the same time, North American was
factory upgrading the installation of the Merlin and re-introduced the
fighter as the Mustang (I think, in the US anyway it was originally
called the Apache, the British named it the Mustang, the first models
were called Mustang I's and the later marks II's and III's) in late
1943. The impact this model (initially the B) had on the war is
history.
Just because an airplane has a low output supercharger doesn't make it
a dog. The same basic airframe with the Merlin engine became one of,
if not the single most famous fighter of WWII. The most recent
engineering analysis indicates that the Mustang airframe was the most
efficient of any fighter of that era judging by the amount of
horsepower the cooling system required versus that of other
contemporary fighters.
I'm only unhappy that this kind of research did not spill over into
civilian aircraft. But that would have required that civilian aircraft
use liquid cooled engines and that hasn't happened until recently with
the advent of auto powered homebuilts. Now, that old research is being
dug up again.
Corky Scott
Karl Andrews
brian whatcott wrote:
>
> I guess I have to say that most any aero engineer would tell YOU that
> when first deployed, the Mustang was a dog, and was relegated to ground
> attack - you know - Warthog style duty...
>
Not the fault of the airframe design. The P-51A had a 1550 hp, normally
aspirated, air-cooled engine, so it was not only underpowered, but lost
performance above 12,000 ft. This made it less than ideal for use as a
high altitude bomber escort. The P-51B, introduced in late 1943, had the
Merlin engine, which had about 300 more horsepower and was supercharged,
giving it substantially improved performance.
Even the P-51B spent a lot of time in ground attack mode, largely because
of Doolittle changing the mission of Eighth Air Force Fighter Command from
bringing the bombers back alive to destroying the Luftwaffe. In his 1944
New Year's Day address to the Eighth Air Force command, General Arnold
said, "My personal message to you -this is a MUST- is to destroy the enemy
air force wherever you find them, in the air, on the ground and in the
factories". While it might not have been as glamorous, this was a much
more effective use of valuable resources.
- Karl
--
The avalanche has already begun. It is too late for the pebbles to vote.
- Kosh Naranek
David Lednicer
> >>you, and one in particular in this group has said frequently, cooling
> >>drag is not a trivial effect and in this case the reduction of drag
> >>made the Mustang a highly effective weapon with a higher speed when
> >>first deployed than any other fighter then flying.
> >>
> >///
> >>Corky Scott
> >>
> >when first deployed, the Mustang was a dog, and was relegated to ground
> >attack - you know - Warthog style duty...
> >
> >Corky...
> >
> >Altus OK
> The Mustang aka the A-36 was equipped with a low level engine
> that had rapid power fall off in medium and high altitudes. The
> allison hauled it around fine down low, and the air frame would go
> around corners quit well down low, but the problem was it was needed
> up high as escort. Other than the change to the merlin and minor
> changes the airframe remained the same until the D or MkIV.
Not so fast there - the "minor changes" included moving the wing
down 5 inches and a totally new cooling system. The cooling system on
the Allison engined Mustangs needed a lot of revision. The boundary
layer on the bottom of the fuselage was being ingested into the duct,
which didn't work, the variable inlet was a big mistake (you don't
control inlet flow this way) and there were other problems in the system.
David Lednicer
John R. Johnson wrote:
>
> On 1 Oct 1996 jj...@dow.com wrote:
>
> > In article <52rdbf$r...@dartvax.dartmouth.edu>, Charles...@dartmouth.edu says...
> > >
> > >
> >
WRONG! When NACA tested a Mustang for laminar flow in the "as
received" state, they found very little. In the "as manufactured" there
was a little more, but not much. Sanding down the painted helped a
little. What helped a lot was reducing the surface waviness down to less
than .004" or so on a 2" span. The British found the same thing on a
P-63 they tested.
A distinction to note: ALL wings have at least a little laminar
flow. On a DC-3 this might be less than 5% of the chord. The Mustang
SHOULD have been able to have roughly 50% of the chord be laminar. The
P-47 airfoils weren't that bad. Working from memory, I think they were
capable of 30% or so.
What enabled the P-51s to throttle back and go a long way was low
induced drag and lots of fuel, NOT low laminar flow. When you reduce
speed, you increase the lift coefficient of the wing, which increases the
induced drag. With good design - most importantly, lots of span - you
can keep the induced drag down. This, a low level of junk hanging off
the airframe, a great engine (the Merlin) plus low cooling drag is what
gave the Mustang its performance.
P. Wezeman
As Mr. Scott has pointed out, the radiator air scoop on the Mustang had
to be extended out a few inches away from the fuselage so as to avoid
ingesting the turbulent boundary layer into the duct. As far as I know, this
problem was not predicted from wind tunnel tests, but was encountered in
test flights, and had to be diagnosed and fixed very quickly as North
American had promised the British to have the plane finished within
something like six months from the initial order.
An interesting sidelight is that several years later Lockheed ran into
exactly this same problem with the wing-root air intakes of the XP-80A
Shooting Star jet fighter, and Kelly Johnson had to quickly figure out
what was causing the engine to malfunction and rig those little ducts on
the fuselage side of the inlets to shunt the boundary layer air aside.
Like the Mustang, the Shooting Star had also been promised to the buyer in
an extraordinarily short time.
Peter Wezeman, anti-social Darwinist
"Carpe Cyprinidae"
Brian Case
>fighter as the Mustang (I think, in the US anyway it was originally
>called the Apache, the British named it the Mustang, the first models
>were called Mustang I's and the later marks II's and III's)
Actually the US order a few (about a hundred I think) of the Allison
powered mustangs as Ground attack Aircraft. There where fitted with
dive brakes and designated the A-36 Apache.
John R. Johnson
On Fri, 4 Oct 1996, David Lednicer wrote:
>
> WRONG! When NACA tested a Mustang for laminar flow in the "as
> received" state, they found very little. In the "as manufactured" there
> was a little more, but not much. Sanding down the painted helped a
> little. What helped a lot was reducing the surface waviness down to less
> than .004" or so on a 2" span. The British found the same thing on a
> P-63 they tested.
>
> A distinction to note: ALL wings have at least a little laminar
> flow. On a DC-3 this might be less than 5% of the chord. The Mustang
> SHOULD have been able to have roughly 50% of the chord be laminar. The
> P-47 airfoils weren't that bad. Working from memory, I think they were
> capable of 30% or so.
>
> What enabled the P-51s to throttle back and go a long way was low
> induced drag and lots of fuel, NOT low laminar flow. When you reduce
> speed, you increase the lift coefficient of the wing, which increases the
> induced drag. With good design - most importantly, lots of span - you
> can keep the induced drag down. This, a low level of junk hanging off
> the airframe, a great engine (the Merlin) plus low cooling drag is what
> gave the Mustang its performance.
>
You do make some good points David, and we ALL know that surface waviness
is critical in maintaining laminar flow. When you try to tell me that
the P-47 could maintain laminar flow over 30% of its wing and the Mustang
couldn't come close to that with an airfoil with the proper pressure
gradient all the way back to over 50% chord, I have to question your
judgement. Your data does not agree with mine.
John
Charles K. Scott
In article <52s1nh$7...@lex.zippo.com>
jj...@dow.com writes:
> So Mr. Atwood's opinion was that a laminar flow wing was not the major
> factor in the Mustang's speed?
Well he didn't say that exactly in the article but that is essentially
correct. The laminar flow wing was a good idea but it's unlikely the
flow over the wing in real life was truly laminar. Almost anything
could and did trip the laminar flow into turbulence negating it's
laminar characteristics. Dents, butt joints, raised metal edges,
screws and rivets all contributed to disrupting the laminar flow. This
was a combat airplane after all and guys were standing on the wing,
removing panels and repairing combat damage by riveting in patches.
Besides, there were plenty of fighters late in the war that were as
fast or faster than the Mustang which weren't using laminar flow wings.
The Tempest, later versions of the P-47, the TA 152 all had speeds in
the middle 400's which originally was the exclusive territory of the
P-51.
The biggest factor in fighter comparisons turns out to be the cooling
drag. My point in mentioning the article, to bring this back to
homebuilts, is that the "Meredith Effect" is something worth thinking
about in todays homebuilts. At the very least, research should be done
on the shape of cooling ducts, and how they should be contoured to
decelerate the air to the most effective speed when it encounters the
radiator and then accelerated to exit thus contributing, if only a
little, toward negating the drag of the cooling system. If you want an
efficient airplane, everything counts.
You can't just hang a radiator out in the air and hope it will cool the
engine. If the air moves through the radiator too fast, insufficient
cooling will occur. If the fins are too close together, the radiator
acts like a dam and slows the air down too much (which is why several
experts are saying that radiators placed in direct flow ducting must
have fins designed for fast flow air, not auto radiators which are
designed for flows from 0 to 60 mph). Obviously, since the airplane is
going to be going both slow and fast, climbing and cruising which
entails different power settings and different speeds, the ducting
should somehow be variable. In the Mustang, the exit door was hinged
and opened and closed automatically as needed depending on heating
demands. This isn't out of the relm of possibility for the average
homebuilder but the research needs to be done that will give everyone
the facts they need to construct such a system.
Right now, everyone does there own thing and spends a LOT of time
working on the cooling system. To my knowledge, nobody has put
together a manual for liquid cooled homebuilts yet. Builders have put
radiators everywhere so far with varying amounts of success. I've seen
them mounted behind the engine, on top, on the bottom, horizontally, in
front of the engine, split and hung either side of the engine, in the
belly, behind the cockpit and in the wings. One guy was talking about
hanging one in his vertical stabilizer. The original research I cited
was intended for military aircraft but the principles remain the same
for all airplanes.
Corky Scott
P. Wezeman
On 8 Oct 1996, Charles K. Scott wrote:
> Right now, everyone does there own thing and spends a LOT of time
> working on the cooling system. To my knowledge, nobody has put
> together a manual for liquid cooled homebuilts yet. Builders have put
> radiators everywhere so far with varying amounts of success. I've seen
> them mounted behind the engine, on top, on the bottom, horizontally, in
> front of the engine, split and hung either side of the engine, in the
> belly, behind the cockpit and in the wings. One guy was talking about
> hanging one in his vertical stabilizer. The original research I cited
> was intended for military aircraft but the principles remain the same
> for all airplanes.
I am inclined to think that the designers of the Mustang had the right
idea as to placement of the radiator, at least as far as single engine
planes are concerned. Most planes have a big, empty, rear fuselage, with
plenty of space for a large enough inlet diffuser to slow the cooling air
as much as necessary. The effect on the center of gravity can be easily
compensated in a new design by wing and engine placement. Having an aft
radiator means that if it leaks you won't get coolant on the windshield.
I would just make very sure I couldn't get a major coolant leak from a
broken hose in the cockpit or cabin; maybe even route the coolant lines
outside the fuselage structure at that point, perhaps through the wing
root fillets. There has been at least one fatality in a Mustang where
coolant from a broken line caused the pilot to lose control of the
aircraft.
Cole L. Corey,BE643
Charles K. Scott writes:
[P-51 Deleted]
> You can't just hang a radiator out in the air and hope it will cool the
> engine. If the air moves through the radiator too fast, insufficient
> cooling will occur. If the fins are too close together, the radiator
> acts like a dam and slows the air down too much (which is why several
> experts are saying that radiators placed in direct flow ducting must
> have fins designed for fast flow air, not auto radiators which are
> designed for flows from 0 to 60 mph). Obviously, since the airplane is
> going to be going both slow and fast, climbing and cruising which
> entails different power settings and different speeds, the ducting
> should somehow be variable. In the Mustang, the exit door was hinged
> and opened and closed automatically as needed depending on heating
> demands. This isn't out of the relm of possibility for the average
> homebuilder but the research needs to be done that will give everyone
> the facts they need to construct such a system.
>
> Right now, everyone does there own thing and spends a LOT of time
> working on the cooling system. To my knowledge, nobody has put
> together a manual for liquid cooled homebuilts yet. Builders have put
> radiators everywhere so far with varying amounts of success. I've seen
> them mounted behind the engine, on top, on the bottom, horizontally, in
> front of the engine, split and hung either side of the engine, in the
> belly, behind the cockpit and in the wings. One guy was talking about
> hanging one in his vertical stabilizer. The original research I cited
> was intended for military aircraft but the principles remain the same
> for all airplanes.
>
Back in school, during a senior design project, we were looking at using a
liquid cooled engine and shunting some of the coolant out into the leading edge
of the wings (not direct xfer from the engine, as we didn't want any leaks to
jeopardize the cooling system) kinda like the system used on jets (only they use
bleed air)...NASA didn't think it was a good idea though, as they picked KSU's
fiberglass wonder "sure we'll sell 200,000 airframes a year" design.
Corey Cole
corey....@boeing.com
Disclaimer: These aren't my employer's opinions, so there!
Jay Hardin
"John R. Johnson" <jo...@siu.edu> wrote:
>You do make some good points David, and we ALL know that surface waviness
>is critical in maintaining laminar flow. When you try to tell me that
>the P-47 could maintain laminar flow over 30% of its wing and the Mustang
>couldn't come close to that with an airfoil with the proper pressure
>gradient all the way back to over 50% chord, I have to question your
>judgement. Your data does not agree with mine.
John,
I think David meant that the P-47's airfoil would have been capable of
30% laminar flow assuming a clean surface with low waviness, not that
it actually produced 30% laminar flow. Likewise, the P-51's airfoil
was capable of 50% laminar flow, but production airplanes were never
capable of reaching that value.
Jay D. Hardin
Terry Schell
"John R. Johnson" <jo...@siu.edu> writes:
>On Fri, 4 Oct 1996, David Lednicer wrote:
<comments from a real (and fairly well known) aerodynamicist snipped>
>You do make some good points David, and we ALL know that surface waviness
>is critical in maintaining laminar flow. When you try to tell me that
>the P-47 could maintain laminar flow over 30% of its wing and the Mustang
>couldn't come close to that with an airfoil with the proper pressure
>gradient all the way back to over 50% chord, I have to question your
>judgement. Your data does not agree with mine.
>John
Ummm... why do you think that is impossible? It is enirely possible
to have *less* laminar flow over a NLF section than under one of the
old 4-digits. While NLF sections have much more laminar flow under
ideal conditions... they are much more sensitive to surface roughness
and reynolds numbers than other sections.
Said another way... the pressure gradient of a laminar section is
favorable over a larger section of the wing, but the gradient is
much less steep than for other sections, so it is much more subject to
being disturbed. Just witness the L/D of some sections when they get
a little rain on them.
Sincerely,
Terry Schell
(neither a real nor well known aerodynamicist)
Charles K. Scott
In article
<Pine.A32.3.91.961007...@black.weeg.uiowa.edu>
"P. Wezeman" <pwez...@blue.weeg.uiowa.edu> writes:
> As Mr. Scott has pointed out, the radiator air scoop on the Mustang had
> to be extended out a few inches away from the fuselage so as to avoid
> ingesting the turbulent boundary layer into the duct. As far as I know, this
> problem was not predicted from wind tunnel tests, but was encountered in
> test flights, and had to be diagnosed and fixed very quickly as North
> American had promised the British to have the plane finished within
> something like six months from the initial order.
The article explaned that severe vibration and drumming was encountered
during wind tunnel testing with the original flush mount belly scoop.
That is when the changes were made and then retested in the wind tunnel
to confirm the fix. Sorry I didn't make this clear.
Corky Scott
John R. Johnson
On Wed, 9 Oct 1996, Paul Lamar wrote:
<snip>
> 200 HP. The size of the hole in the front seems to be a function of the
> top speed. What happens if you block the flow downstream? Do you get a
> drag rise around the hole in that case?
>
> I assume in a liquid cooled airplane if you are going to use an
> automotive radiator you need to get the air velocity through the core
> down to the optimum car speed value? We don't really have a chance to
> design the cores. We need to use off the shelf cores. As you and I (in
> an earlier post) pointed out the best placement is in the back of the
> fuselage to allow a stright shot through the core.
>
> What is the optimum air speed through the automotive core?
>
> Is there even a simple answer?
>
Some good questions here, Paul. I don't know that I can give you
specific answers without some specific info.
To get the air to flow through the radiator you have to establish a
pressure difference across it. Generally, in aircraft, and in cars,
this is done by converting some of the energy in the airstream from
dynamic pressure to static pressure. This is just our friend
Bernoulli again, wearing a slightly different suit.
Basically, we have a hole that allows air in, hopefully without forcing
it to give up its velocity too soon, we have our heat exchanger, and
we have a hole to let the air out again after it has gone through the
radiator.
If the flow out of the pressure chamber is lower than the flow in is
trying to be, the static pressure will rise. It can only rise until
it reaches the stagnation pressure of the incoming air. This is a
function of velocity and is the way your "airspeed" indicator works.
It stagnates a bit of air and compares the "stagnation" pressure with
the "static" pressure of the unconstrained air. The difference is a
function of your "airspeed." When the pressure in your chamber in
front of the heat exchanger reaches that point, there is NO MORE FLOW
into the front opening. It looks to the airstream like a blunt body
and the air hitting it is merely redirected around the opening.
Anything that will produce a pressure rise before reaching the heat
exchanger will slow down the flow. The most effective way to convert
this dynamic pressure to static pressure is with a "divergent duct."
This directly slows the velocity and increases the static pressure.
It is seriously hampered if your intake ingests boundary layer, because
the boundary has ALREADY lost its dynamic energy. The boundary layer is
essentially flowing the same speed as the aircraft/car and has no
dynamic head to contribute. All it can provide is turbulence which
mixes up the input stream and lowers the dynamic energy sooner than you
would like. On the P-51 they just modified the scoop to move it outside
of the boundary layer. I believe the NASA inlet with its smoothly
expanding shape is designed to do a similiar thing. It would be worth
an experiment, perhaps.
The standard aircraft cowling give up a little thermodynamic efficiency
for aerodynamic reasons. It requires a larger static pressure above the
fins, because it is forcing the air DOWN through the fins and heating it
on the way. The air would be happier RISING as it is heated. It will
also, of course, expand somewhat as it is heated. It will also expand
somewhat as it moves into the lower pressure area on the back side of
the heat exchanger. This usually means the outlet area has to be
somewhat larger than the inlet area, although what we are actually
dealing with is the mass flow, so we have to consider area, velocity,
and density. All of these are changing as a result of being passed
through the heat exchanger. The ideal would probably throttle the
exhause until the pressure directly in front of the heat exchanger
approached the stagnation pressure. That would give maximum FLOW
through the heat exchanger. Of course, that may also contribute to
OVERcooling, indicating that perhaps more throttling would be desireable.
Fin spaceing, core density, core surface area, all of these questions
are thermodynamic questions concerning effective thermal transfer to
the air. ALL ENGINES are AIR COOLED. Some air cool directly, and
some use an intermediate hydraulic heat exchanger to move the heat
from where it is generated to a location where it is easier to transfer
it to the air. We can also alter the thermal "density" somewhat this
way as well, by varying the area of the respective heat exchangers at
each end of the intermediate system. Which system is better? I would
have to say, "It depends ..."
Remember, air is an excellent thermalinsulation! The thermal capacity
of a cubic centimeter of air is,generously speaking, LOUSY. The thermal
transfer between adjacent cubic centimeters of air is very poor.
The only way to get air to carry away any substantial quantity of thermal
energy is to transfer a little heat to the air and then move it away so
we can transfer a little to another bit of air. The air that is a little
ways away from our heat exchanger surface doesn't pick up much heat at
all, because of the excellent insulation properties of air! That says,
for a good anything to air heat exchanger, we have to move lots of air
through it and keep that air right up against the hot surface!
Of course, we know from aerodynamics that if we squeeze a lot of air
through a small hole the flow will be turbulent and we will build up
a boundary layer against the surface that stagnates the air close to
the surface so it doesn't go away. This is just the opposite of what
we want to happen! How in the world can we improve this situation?
Well, we know that if we can keep the flow laminar, the boundary layer
is real thin and our heat exchanger should exchange heat more effectively.
How can we do that? Use laminar airfoils for our fins? I think not.
That leaves us with only one solution. If we can get the Reynolds
number low enough, the flow is likely to stay laminar. It will certainly
help us keep a thin boundary layer. How can we get a low Reynolds number?
Well, we can either reduce the critical length or the critical velocity,
or both. The critical length here is the distance the air moves through
the heat exchanger. With cylinder fins we are pretty much stuck. The
only way to shorten that path is to reduce the bore! However, with a
radiator we can always make it thinner and broader. The higher the
flow velocity through the radiator the thinner it should be! We can
then also control the critical flow velocity by controlling the pressure
difference across the core. That says we really want a static plenum
at the end of a divergent duct, then the heat exchanger above that,
with a convergent duct above the heat exchanger leading to a variable
outlet with minimal restriction.
All of that theoretical stuff gets pretty hard to fit into any kind of
vehicle. Perhaps Paul you might have had better luck with those race
car radiators if you had dropped the radiator down and provided a static
pressure plenum above the radiator, fed by a relatively small ram air
opening located far enough away to be out of the boundary layer! You
would, of course, also have to duct it away from underneath to an
appropriate point, with an appropriate convergent duct, to release the
air into the free stream at a pressure close to the free stream pressure.
It looks at first blush, with current "state of the art" technology, like
the most efficient cooling system for an aircraft might be a high pressure
intermediate hydraulic transfer exchanger system with an appropriate
low velocity, high volume hydraulic to air exchanger situated in a well
designed divergent/convergent duct system with carefully located inlet
and outlet, with the outlet of variable size to maintain optimum pressure
gradients across the hydraulic/air exchanger at the desired thermal
flow rate.
John
John R. Johnson
On 8 Oct 1996, Terry Schell wrote:
>
> Ummm... why do you think that is impossible? It is enirely possible
> to have *less* laminar flow over a NLF section than under one of the
> old 4-digits. While NLF sections have much more laminar flow under
> ideal conditions... they are much more sensitive to surface roughness
> and reynolds numbers than other sections.
Yes, Terry, that is true. For example, the 23012 section has less drag
at standard roughness than the 65-215 laminar section that has largely
replaced it in light aircraft designed in the sixties. However, that
is not the case for the sections used on the P-47 and the P-51. I will
concede that manufacturing imperfections limited the laminarity of the
flow on the P-51. That would be more evident at high speeds than at
the low speeds used for escort duty. Reynolds number also has a lot
to say about how much imperfection it takes to break the laminar flow.
<snip>
JOhn
Ed Wischmeyer
> Back in school, during a senior design project, we were looking at using a
> liquid cooled engine and shunting some of the coolant out into the leading edge
> of the wings
Vague recollections are of reading that an Italian airplane tried this in the 30s. The heated air so screwed up
the wing aerodynamics that the leading edge radiators were abandoned. (a) Do I remember this story right? (b)
Did the author have his facts straight?
Ed Wischmeyer
John R. Johnson
On 9 Oct 1996, Brian K. Michalk wrote:
> In article <Pine.SOL.3.91.961009081216.10389J-100000@reliant>,
> John R. Johnson <jo...@siu.edu> wrote:
> >It looks at first blush, with current "state of the art" technology, like
> >the most efficient cooling system for an aircraft might be a high pressure
> >intermediate hydraulic transfer exchanger system with an appropriate
> >low velocity, high volume hydraulic to air exchanger situated in a well
> >designed divergent/convergent duct system with carefully located inlet
> >and outlet, with the outlet of variable size to maintain optimum pressure
> >gradients across the hydraulic/air exchanger at the desired thermal
> >flow rate.
>
> Excellent Post!!
> That was one hell of a last sentence though.
Thanks, I thought so too! :-)
>
> You know, I've thought about radiators for a while, and now it's good
> to know that what I've been thinking is kinda close to the mark.
>
> I remember watching a show a few years ago where they talked about
> the physical characteristics of water. And that the Kodak place
> at Epcot center used this laminar flow water. They made it
> laminar by forcing it through an array of straws. Anyway,
> I thought, hmmm, maybe do the same with air.
>
> Stick your intake out into the air. Throughout the ducting
> you have your array of increasing diameter "straws" or
> tubing. They'll keep the air laminar, or at least reduce turbulence.
> Next, pipe this to a radiator that had non-turbulent properties,
> then repeat the process on the way back out.
that is pretty close to what they do for flow straighteners in a
windtunnel!
John
Charles K. Scott
In article <325B6E...@worldnet.att.net>
Paul Lamar <paul-l...@worldnet.att.net> writes:
> You are making a lot of sense to me David.
> I assume in a liquid cooled airplane if you are going to use an
> automotive radiator you need to get the air velocity through the core
> down to the optimum car speed value? We don't really have a chance to
> design the cores. We need to use off the shelf cores. As you and I (in
> an earlier post) pointed out the best placement is in the back of the
> fuselage to allow a stright shot through the core.
>
> What is the optimum air speed through the automotive core?
>
> Is there even a simple answer?
>
> Paul Lamar
My question here is who has taken over Paul's body and is posting in
his stead. Most of you will remember the Paul (it will never work,
auto cranks will break, the bearing webs will crumble to dust, they
can't take continuous 75% power) Lamar who trampled over any and all
auto engine suggestions with both acute sarcasm or abusive language and
frequently both.
But here we have a civil discourse in which someone calling himself
Paul Lamar is politely asking for information about using an automotive
radiator IN AN AIRPLANE. Is anyone else's hair standing on end? ;-)
Has Paul become a Stepford Engineer? :-)
Corky Scott
Brian K. Michalk
In article <Pine.SOL.3.91.961009081216.10389J-100000@reliant>,
John R. Johnson <jo...@siu.edu> wrote:
>the most efficient cooling system for an aircraft might be a high pressure
>intermediate hydraulic transfer exchanger system with an appropriate
>low velocity, high volume hydraulic to air exchanger situated in a well
>designed divergent/convergent duct system with carefully located inlet
>and outlet, with the outlet of variable size to maintain optimum pressure
>gradients across the hydraulic/air exchanger at the desired thermal
>flow rate.
Excellent Post!!
That was one hell of a last sentence though.
You know, I've thought about radiators for a while, and now it's good
to know that what I've been thinking is kinda close to the mark.
I remember watching a show a few years ago where they talked about
the physical characteristics of water. And that the Kodak place
at Epcot center used this laminar flow water. They made it
laminar by forcing it through an array of straws. Anyway,
I thought, hmmm, maybe do the same with air.
Stick your intake out into the air. Throughout the ducting
you have your array of increasing diameter "straws" or
tubing. They'll keep the air laminar, or at least reduce turbulence.
Next, pipe this to a radiator that had non-turbulent properties,
then repeat the process on the way back out.
--
Brian Michalk |No, the |AWPI, home of *the* online magazine about Austin.
mic...@awpi.com|other one|Providing systems integration and internet solutions.
Glenn Scherer
You sound like you're complaining, Corky. I'm certainly not
Glenn
John R. Johnson
Ed,
I would suspect the author of making up his facts to suit. As I recall
there were a number of "skin" type radiators on wing leading edges and
elsewhere on the wings that were used in the twenties and thirties.
Look at the history of the Schneider Cup. Several Schneider cup racers
used that type of radiator.
John
David Lednicer
> I think David meant that the P-47's airfoil would have been capable of
> 30% laminar flow assuming a clean surface with low waviness, not that
> it actually produced 30% laminar flow. Likewise, the P-51's airfoil
> was capable of 50% laminar flow, but production airplanes were never
> capable of reaching that value.
Exactly!
Jim Root
Check Re:Report from the OMABP
He.....'s Back!
;{) Jim
David Lednicer
In response to Paul Lamar's questions:
First a couple of definitions:
"diffusion" is used here to describe the process by which air is slowed
down,
trading pressure for speed.
a "diffuser" is a duct in which diffusion takes place. As the
cross-sectional area in the duct increases, the flow slows and the
pressure increases.
"losses" are processes that take place in the diffuser that cause a loss
in efficiency. This is seen as not all of the pressure rise being
realized after the air is slowed down. Losses come primarily from
viscous effects.
Now, an attempt at some answers:
The reason putting the radiators out perpendicular to the flow,
with no ducts, worked is that all of the diffusion took place in the free
stream ahead of the radiators. This works, but is not the most
efficient, as Paul says, as it is rather draggy.
Putting the radiators horizontal and trying to turn the air 90
degrees didn't work too well, probably because of high losses in the
ducting. Some of this could be a build up in boundary layer thickness,
and some of this could be outright boundary layer separation. If your
losses are high enough, adding a turning vane won't help.
As to the diffusers used on the Chaparal 2F - what controls
massflow
through a ducted system is not the inlet opening size. Rather, it is the
exit size and pressure outside, at the exit. Changing the inlet size to
change the massflow will only have a slight effect. Changing the exit
size will have a big effect. However, going to too small of an exit area
will decrease the system massflow to such an extent that you can get
inlet spillage. In this case, the stagnation point of the incoming flow
is considerably inside the inlet. Some of the incoming flow comes in,
reverses and goes back out of the inlet. A little spillage is good, as
it produces lip suction. Too much is bad, as the flow can separate and
add a lot of drag.
Many people think that a good inlet "funnels" air in, so they
make the inlet lip highlight area bigger than the hole the air must
eventually go through. This usually causes excessive spillage and lots
of drag. I once talked to the late Don Beck, trying to convince him that
his "funnel" carb inlet was just adding drag, with no success.
Using P-51 type ducts, like was done on the Chaparal 2Es and 2Gs
is a step in the right direction. However, the duct must be very
carefully
designed to work properly with the operating conditions. "That looks
about right" won't work.
The diffuser used on Nemesis is one way to skin the cat. Dan
Bond set it up so that most of the diffusion occurs internally. He did
this because he didn't want the inlet lips to see an apparent angle of
attack (due to the streamtube expansion a the lips). This way, he could
use a sharp inlet lip. However, when I sat down to design the diffuser
that Madder Max (#96) showed up at Reno with this year, I first worked
the trade-offs. I found that it was best to have part of the diffusion
occur in front of the inlet and part internally. This led me to use
inlet lips shaped with a Kuchemann profile (A-30, if I remember right)
which develop and use the lip suction. My experience with other inlets
has shown that lip suction is desirable. Additionally, in my design, I
went to the maximum length of diffuser that we could fit in the cowl. T
his way, the wall angles were kept down (5 degrees a side) and the
efficiency is very high.
The way a cooling system for an air cooled engine turns the flow
90 degrees is that it first stops the flow (nearly) in the plenum and
then it only allows one outlet (hopefully) - straight down (for a
downdraft cooling arrangement). With this said, I have modeled the
cooling system of #96 in a potential flow code (VSAERO) and find that the
air is still moving at a good clip as it goes over the front cylinder.
This is why scoop baffles are used on the back half of the front
cylinder. Stagnation at the rear wall of the plenum provides for the air
for the rear cylinder. So far, I have only modeled the top of the
cooling system. I hope to model the whole thing pretty soon. I would
like to see how lower plenum shaping effects flow through the
inter-cylinder passages.
Dos and Don'ts? Read Dan Bond's two articles in Sport Aviation
and integrate what he says with Stan Miley's NASA engine cooling work.
I did this, writing a computer program to simulate the flowpath. Without
this, you won't get the inlet and exit areas right. Then, stir in some
of
the diffuser results of Klein, and you will get a good cooling system.
For a radiator, as opposed to a air cooled engine, your diffuser will
come
from Kuchemann and Weber's book "The Aerodynamics of Propulsion".
Finning on an air cooled engine is designed with heat transfer
considerations in mind. Judging from the little I have learned about
radiator design, having more, thin fins is a better way to go. However,
there is a critical inter-fin distance that one should not go below.
On a liquid cooled aircraft powerplant, you want to diffuse the
airflow, just like on an air cooled engine. However, now you have the
possiblity of getting rid of the plenum and the losses that go with it.
In this case, you want to use a Kuchemann "streamline" diffuser to slow
the
air. The Mustang has a pretty good diffuser - it is close to being a
streamline diffuser. The Spitfire has lousy diffusers - the wing
boundary layer is ingested and the flow separates almost as soon as it
gets into the diffuser. When Messerschmitt went from the Bf 109E to the
F,
they got around this problem by adding a boundary layer diverter channel
to the wing radiators.
Yes, we have to use existing automotive cores. The Pond racer
was supposed to have custom built cores. Then, Harrison quoted a price,
and we ended up using available cores. However, they were too tall, and
had to be put in at a 45 degree angle. Because of this, the streamline
diffusers I had designed would no longer work, and Burt cut them off and
put the radiator in a plenum. Only in the last year that it was at Reno,
did it have outlet doors to control the massflow. In retrospect, I think
we could have done a lot better.
David W. Taylor
>Both of the authors assumed a fully enclosed air duct, directing free
>stream air to an enclosed radiator but spoke little of the duct itself
>leaving that up to the designers of aircraft intending to use this
>effect. The design of the duct was non trivial and resulted in the
>first duct to be held away from the fuselage to keep the opening out of
>the turbulent fuselage boundary layer which was creating big vibration
>problems with flush openings.
Wasn't this effect demonstrated on the F-16 ?? I seem to recall
the prototypes had the inlet to the turbine much closer to the
fuselage than later versions , It supposedly bought a nice little
power gain when they changed the inlet configuration,,,
Any body with a better memory or some good references got any info??
Just another 2 cents in the machine...
David Taylor dwta...@ptdcs2.intel.com Ph(503) 613-8132 Portland OR.
My opinions are mine ,, and nobody elses.
Charles K. Scott
In article <325C70...@nt.com>
Glenn Scherer <Glenn_...@nt.com> writes:
It's called a joke Glenn. That's what the smilie at the end is
supposed to denote.
Corky Scott
Bruce A. Frank
I don't know about you Corky, but he has seemed so reasonable for the
past few posts that I offered copies of the Ford/ V-6 STOL newsletter.
Maybe its a set-up.
Bruce A. Frank
Glenn Scherer
Let me see, that would be the smiley that I forgot to put in my post,
wouldn't it? Oops.
David Lednicer
P. Wezeman wrote:
>
> As Mr. Scott has pointed out, the radiator air scoop on the Mustang had
> to be extended out a few inches away from the fuselage so as to avoid
> ingesting the turbulent boundary layer into the duct. As far as I know, this
> problem was not predicted from wind tunnel tests, but was encountered in
> test flights, and had to be diagnosed and fixed very quickly as North
> American had promised the British to have the plane finished within
> something like six months from the initial order.
You almost got the story right. Early model Mustangs did swallow
all of the boundary layer off of the lower fuselage into the
radiator/oil cooler/intercooler duct scoop. Pilots complained of a "duct
rumble", mainly at altitude. NACA cut the outer wings off of a Mustang
and put it into a tunnel at the Ames Research Center. They then
proceeded to cut and try fixes until the rumble went away. Engineers
would sit in the cockpit, in the tunnel, during runs and listen for the
rumble.
What happened was that the boundary layer was being ingested and
was separating off the ceiling of the duct. The wake of this separation
was then hitting the radiator/intercooler, causing it to vibrate. This
was the rumble heard in the cockpit. By dropping the inlet down below
the bottom of the fuselage boundary layer, this problem went away. For
more info, see NACA WR A-70 "Elimination of Rumble From the Cooling Ducts
of a Single-Engine Pursuit Airplane" by H.F. Mattews, August 1943.
David Lednicer
Karl Andrews wrote:
> Not the fault of the airframe design. The P-51A had a 1550 hp, normally
> aspirated, air-cooled engine, so it was not only underpowered, but lost
> performance above 12,000 ft. This made it less than ideal for use as a
> high altitude bomber escort. The P-51B, introduced in late 1943, had the
> Merlin engine, which had about 300 more horsepower and was supercharged,
> giving it substantially improved performance.
>
NO! The Allison engine in the early model P-51s was NOT normally
aspirated. No Allison engine left the factory without a supercharger,
except the ones intended for P-38s, which were setup for a turbocharger.
The reason that the Allison engined aircraft had such poor performance
was that the supercharger wasn't very good - it was single stage, single
speed. Hence, the aircraft lost power quickly as they went up in
altitude.
The early model Merlins also had single stage, single speed
superchargers. Luckily, the model that went into the Mustangs initially
was the 60 series, which was two stage, two speed. Take a gander at "Not
Much of an Engineer", the autobiography of Stanley Hooker for more info
on the Merlins.
tord.s.eriksson
What happened was that the boundary layer was being ingested and
> > was separating off the ceiling of the duct. The wake of this separation
> > was then hitting the radiator/intercooler, causing it to vibrate. This
> > was the rumble heard in the cockpit. By dropping the inlet down below
> > the bottom of the fuselage boundary layer, this problem went away. For
> > more info, see NACA WR A-70 "Elimination of Rumble From the Cooling Ducts
> > of a Single-Engine Pursuit Airplane" by H.F. Mattews, August 1943.
> Thats interesting the guys at Legend tell me they are going to do away
> with the boundry bypass in the interest of less drag. They claim the the
> Reno racers have done it and picked up several MPH.
>
One way to do it to suck the boundary layer away from the inlet, like many
jet aircraft does with their splitter plates (expression?), that diverts
away the boundary layer. The dam or plate itself produces its own boundary
layer but this is sucked away through numerous small holes in the plates.
should be possible to suck away the basic boundary layer, too!
--
Tord S Eriksson,
David Lednicer
Paul Lamar wrote:
>
> I think a better solution for cooling air intake on the bottom of the
> airplane is what the "eze" guys are doing rather than a P51 type duct.
> Use a NACA flush duct instead. As the airplane slows down in a climb the
> angle of attack becomes greater and the NACA duct works better. At
> higher speeds it may have less drag as the angle of attack lowers.
No, NACA flush inlets aren't the best solution - they don't have
very good pressure recovery. They have their uses, but as inlets for
major internal systems, you can do better.
Incidentally, I made a goof - Allisons in P-38s did have
superchargers downstream of the turbocharger. Hence, no Allison left the
factory without a supercharger.
tord.s.eriksson
Paul wrote:
> I think a better solution for cooling air intake on the bottom of the
> airplane is what the "eze" guys are doing rather than a P51 type duct.
> Use a NACA flush duct instead. As the airplane slows down in a climb the
> angle of attack becomes greater and the NACA duct works better. At
> higher speeds it may have less drag as the angle of attack lowers.
>
and thus increase the drag? Anyone out there who knows the answer?
Yours, Tord S Eriksson, Ovralidsg. 25, S-422 47 Hisings Backa, SWEDEN
.
Terry Schell
Paul Lamar <paul-l...@worldnet.att.net> writes:
<snip>
>Perhaps David but with all due respect to your obvious
>considerably expertise the Eze guys that are going the fastest such as
>Klaus Savier and still cool use NACA ducts on the bottom of thier
>airplanes. Apparently NACA ducts are getting the job done with less
>drag.
With all due respect, the fact that these planes are extremely
efficient does not mean that their intake duct is optimal.
The fact that this duct configuration has less drag than some other
configuration does not mean that it is optimal either.
David Lednicer
Exactly - the fact that the NACA inlet ("female") cowl EZs are
faster than the "male" cowl EZs just shows how bad the "male" cowl is.
Doug Shane's EZ is pretty damned fast and he uses "armpit" inlets.
Charles K. Scott
In article <326A3A...@worldnet.att.net>
Paul Lamar <paul-l...@worldnet.att.net> writes:
> I think a better solution for cooling air intake on the bottom of the
> airplane is what the "eze" guys are doing rather than a P51 type duct.
> Use a NACA flush duct instead. As the airplane slows down in a climb the
> angle of attack becomes greater and the NACA duct works better. At
> higher speeds it may have less drag as the angle of attack lowers.
>
> Paul Lamar
I don't believe this. A point where Paul and I agree. It happens I've
been thinking about this for some time but don't know if it would work
as well in practice as it appears in theory.
In order for this to work as I envisioned, the NACA duct should be
placed far enough forward so that the angle of attack has a chance to
see the duct before it gets deflected by the shape of the fuselage.
Too far back on the fuselage and a change in angle of attack won't
matter that much as the airflow will be essentially parallel.
So how about it out there, can we mash this theory around a bit? If
the duct were truly NACA shaped, would this change the size of the
opening normally needed to move X amount of air for a certain
displacement engine?
What I was picturing was a duct placed somewhere just aft of the chin
of the cowling so that while climbing, with a higher angle of attack,
the opening would be exposed to more inflow. I wanted the air running
in a dedicated duct to a diffuser chamber, through a properly sized
radiator and then out another duct shaped to accelerate the air.
Carrying this one step further, the exhaust tubing could be situated so
as to add to the velocity of the exit air in the out passage. Tony
Bingellis suggests this in one of his books. The end of the exhaust
tubes needs to be just inside the cowling exit and aimed to flow with
the exiting heated air. Tony states that this can augment ground
cooling by accelerating the outflow, which draws more air in from the
nose.
Corky Scott
Bruce A. Frank
>But will not a NACA flush duct produce a turbulent flow inside the duct,
>and thus increase the drag? Anyone out there who knows the answer?
>
>Yours, Tord S Eriksson, Ovralidsg. 25, S-422 47 Hisings Backa, SWEDEN
>.
>
A properly installed NACA scoop is the lowest drag for the air flow that
can be obtained.
Bruce A. Frank
Bruce A. Frank
curve near the nose. On the rear of a fuselage a scoop that sticks out is
required to reach out beyond the boundry layer.
Bruce A. Frank
brian whatcott
In article <326BA5...@amiwest.com>, da...@amiwest.com says...
>
... NACA flush inlets aren't the best solution - they don't have
>major internal systems, you can do better.
>
>David Lednicer
This note just begs for more details.
Please?
brian whatcott <in...@intellisys.net>
Altus OK
Jim Root
So where could a person find out detailed info regarding NACA
scoop/ducts?
--
:{) Jim
**************************************
* http://home.earthlink.net/~jaroot/ *
**************************************
“Remember its better to be on the ground wishing you were in the air,
than in the air wishing you were on the ground...”
old VFR saying, source unknown.
william l kleb
Bruce A. Frank wrote:
>
> A NACA duct has to be located in a high pressure area, like a leading
> curve near the nose.
this is not entirely correct. the part that is correct is
locating _any_ inlet in a high pressure area, otherwise you
will have an outlet. however, for the location suggested,
you are usually better off with a ram air inlet if you desire
high pressure recovery.
> On the rear of a fuselage a scoop that sticks out is
> required to reach out beyond the boundry layer.
>
if you believe this to be true, you are missing one of
the reasons the naca duct is shaped the way it is,
quoting naca rm-a7i30:
"the results of previous investigations [naca acr-5i20]
showed that the ram pressure recovery of the submerged
duct entrance could be appreciably increased by diverging
the walls of the ramp. ... in the instances where the
pressure recovery is increased by diverging the ramp
plan form, the process is apparently one of diverting
the boundary layer outside the ramp around the entrance."
this theory is supported by experimental evidence and limited
analytical analysis, both contained in the report.
i'll see if i can get reports rm-a7i30 and acr-5i20 put online.
(i have part of rm-a7i30 on my www-page.).
---
bil kleb (w.l....@larc.nasa.gov) 72 bellanca 7gcbc
<http://ab00.larc.nasa.gov/~kleb/> 9? cz4 -> aerocanard
David Lednicer
william l kleb wrote:
> > On the rear of a fuselage a scoop that sticks out is
> > required to reach out beyond the boundry layer.
> >
>
> if you believe this to be true, you are missing one of
> the reasons the naca duct is shaped the way it is,
> quoting naca rm-a7i30:
>
> "the results of previous investigations [naca acr-5i20]
> showed that the ram pressure recovery of the submerged
> duct entrance could be appreciably increased by diverging
> the walls of the ramp. ... in the instances where the
> pressure recovery is increased by diverging the ramp
> plan form, the process is apparently one of diverting
> the boundary layer outside the ramp around the entrance."
>
> this theory is supported by experimental evidence and limited
> analytical analysis, both contained in the report.
You are right - the NACA inlet is designed to work this way.
However, if the boundary layer is VERY think, the inlet won't work very
well. Witness the Boeing 737 APU inlet on the right side of the aft
fuselage. It is a NACA inlet, but they couldn't get it to feed very
well due to the thick boundary layer back there. The solution was to
add a huge T shaped vortex generator in front of it, to get some mixing
going with the freestream and supply the inlet with some higher energy
air. Boeing learned their lesson - look at the APU inlets on the 757 and
767. The inlets on these aircraft are big, retractable, "coal scoop"
Richard Isakson
David Lednicer <da...@amiwest.com> wrote in article
<326E42...@amiwest.com>...
> You are right - the NACA inlet is designed to work this way.
> However, if the boundary layer is VERY think, the inlet won't work very
> well. Witness the Boeing 737 APU inlet on the right side of the aft
> fuselage. It is a NACA inlet, but they couldn't get it to feed very
> well due to the thick boundary layer back there. The solution was to
> add a huge T shaped vortex generator in front of it, to get some mixing
> going with the freestream and supply the inlet with some higher energy
Boeing guaranteed that the APU would work both on the ground and in all
flight regimes. It worked fine on the ground and at low speeds but at high
speeds the flow through the APU would actually reverse. There were scorch
marks on the inlet! The solution was the T. It wasn't a vortex generator
but the upper part of the T has a flap on the back which extends when the
APU is working. This flap was enough to change the pressure distribution
at the APU inlet.
Rich
David Lednicer
Paul Lamar wrote:
> Perhaps David but with all due respect to your obvious
> considerably expertise the Eze guys that are going the fastest such as
> Klaus Savier and still cool use NACA ducts on the bottom of thier
> airplanes. Apparently NACA ducts are getting the job done with less
> drag.
Paul, look more closely at the "male" and "female" EZ cowls. The
male cowl ends with a big upsweep, while the female has a nice closeout.
This is where all the drag is. If you put a decent scoop on the female
cowl, you would have even a better configuration. Once again, a little
real engineering would benefit the situation, instead of people
"experimenting".
David Lednicer
Paul Lamar wrote:
> Thats interesting the guys at Legend tell me they are going to do away
> with the boundry bypass in the interest of less drag. They claim the the
> Reno racers have done it and picked up several MPH.
Strega has a radiator duct that swallows all of the boundary
layer off the bottom of the fuselage. My analysis shows that the
boundary layer then separates almost as soon as it gets into the duct.
When told that the duct does work, I asked "what happened to your spray
bar flow rates, compared to the rates used with the old duct". They
DOUBLED! What is happening is that they are getting less cooling from
the incoming air and more from the spray bar water. Now, does the Legend
have a spray bar?
What grieves me about homebuilts is that people "experiment"
with no clue as to what they are actually doing. A little science
(engineering) would help a lot.
natr...@aol.com
Read about the Meredith Effect authored by Lee Atwood of North American
The North American Trainer Association is a (501)[c]3 association dedicated to the restoration, preservation and safe flying of all North American Aviation built trainer aircraft (AT-6, SNJ, Harvard, NA-64, T-28, TF-51, TB-25). Dues are $40.00 per year USA and Canada, $50.00 all others. "Texans & Trojans" is the quarterly publication of the association. Membership is open to all.
Jim Root
David Lednicer wrote:
>
> What grieves me about homebuilts is that people "experiment"
> with no clue as to what they are actually doing. A little science
> (engineering) would help a lot.
And sometimes it kills us. But you can't put a price on a good time!
(tic) ;{)
Garfield
On Thu, 24 Oct 1996 09:03:45 -0700, David Lednicer <da...@amiwest.com>
wrote:
> What grieves me about homebuilts is that people "experiment"
>with no clue as to what they are actually doing. A little science
>(engineering) would help a lot.
and then in another post,
>Once again, a little
>real engineering would benefit the situation, instead of people
>"experimenting".
David,
If only you knew how many technically trained people inhabit this group
and long to know more "engineering" details regarding aerodynamics! As
an engineer/scientist, you know that the training we receive stands us
in good sted for learning other technical disciplines fairly quickly,
BUT what is sorely missing is guidance on reference works, good texts,
trade magazines, etc.
As an example, some time back, Barnaby Wainfan mentioned in a couple
posts the usefulness of building scale models. When I chided him to
provide us with a good list of references on how to understand the
issues in scalability, I guess something I said made him think I was
just being sarcastic....but not to worry, someone else filled in and
posted a great list of references on that subject, enough that I felt I
had a path to follow to learn a lot more, which I'm now doing.
If you want to enjoy more interesting and informed conversations in this
group, you especially could really help us by doing whatever you could
to help us educate ourselves further. There seems to be a consensus that
Horner's Fluid Drag text is useful, but what about his other book? Or
for those with a technical background, but not in Aero, is there a
better book on the really practical subject of fairing transitional
shapes, etc. Just examples of things wanting an opinion, from someone
qualified. A short tutorial on, or pointing us to where to get, an idea
of the computational/graphics tools you use in airshape design would be
very desirable. There have been a couple of magazine article-like
discussions of a couple of software tool sets for looking at pressure
gradients around cowls and wing-root fairing; is there anything you
could recommend?
Really helpful would be some text recommendations on such things as
boundary layer dynamics. Even a sketch of what we could reasonably
expect to achieve without an extensive education in aerodynamics vrs.
things that only can be done with years of coursework, very expensive
software, and wind tunnels. For example, can a person with an
engineering background (but not in aero) learn the skills to enable
choosing an airfoil for root and tip, design the fuse shape, and
transitional fairings, figure out the size and foil for a conventional
tail section, figure the aileron and flap size needed. Can we really
learn these design skills, or are we consigned to just become a bunch of
annoying armchair dilletantes? I'm talking about the aerodynamic/fluid
dynamic part of this. My sense is the structural skills are a bit easier
to come by.
Here is your open invitation to be our guide in a very fascinating
subject that just about everyone in this group wants to know more about.
And it might be an outlet to some of the frustration you feel at times!
OH, and by the way, I just want you to know how much I appreciate and am
thankful for your presence in this group. I know I am not alone. Great
to have an expert here, even if we do frustrate him sometimes. Hang in
there.
Garfield (MSEE UC Davis '73,
aspiring to as much experimental aircraft design/engineering skills as I
can get, before I go to the rocker in the rest home)
Charles K. Scott
> David Lednicer wrote:
> > What grieves me about homebuilts is that people "experiment"
> > with no clue as to what they are actually doing. A little science
> > (engineering) would help a lot.
>
In article <3270E2...@worldnet.att.net>
Paul Lamar <paul-l...@worldnet.att.net> writes:
> Ain't it the truth. I wish somebody would apply a little engineering
> before they stuck and auto engine in an aircraft.
Uhmmm Paul? David is one of the guys who designed the cooling system
for the Pond Racer. Remember what it used for engines?
I don't know anyone who is not interested in properly engineering their
auto engine conversion. But here's a problem, not every single person
wishing to put an auto engine in his/her airplane is an engineer. I'd
love to know exactly how and where to put my cooling system, how big to
make the radiator, how many fins per inch it needs, the shape of the
duct etc etc. But I'm neither an engineer nor am I a mathematician.
So here's a proposal: you want to see people apply a little engineering
to their auto conversion? Well you're the engineer, how about starting
the ball rolling and doing a study. Post the information here, I for
one would be extremely interested, I daresay there are others.
Corky Scott
Bruce A. Frank
scott rider wrote:
> =
> >So here's a proposal: you want to see people apply a little engineering
> >to their auto conversion? Well you're the engineer, how about starting
> >the ball rolling and doing a study. Post the information here, I for
> >one would be extremely interested, I daresay there are others.
> >
> >Corky Scott
> >
> =
> Corky, (Paul),
> =
> The problem is one of time and ROI. It is hard enough to sneak a few
> minutes to read/write stuff for the 'net.
> =
> What would be the reward for posting the information v the risks?
> =
> Risk? A few failures along the way indirectly causing loss of life, bad p=
ress,
> and great financial loss. Opening for lawsuits.
> =
> Reward? No cash, but perhaps a certificate in a handsome plastic frame.
> (Sorry, Scott Adams gets credit for that one)
> =
> Did you read the posting by the OMAP project guy who was impressed with t=
he
> "engineering" in modern engines? Although he sounded absolutely convinced=
the
> engines are better today than a few years ago, it appears that it is due =
to
> his impressions that are likely gained by the introduction of easier star=
ting and
> idling fuel injection control and fluid filled engine mounts. His impress=
ion
> of engines getting better is not backed up by any material science or
> machine design-like observations.
> =
> Someone should do an apples to apples posting on piston & rod weight vs c=
rank
> journal size and rpm/piston speed. Does an auto engine/motorcycle engine/=
boat
> engine compare to an airplane engine?
> =
> Do the valves compare? Stem size/open close cycles/weight/spring pressure=
?
> =
> Does the crank flange size and main bearing size compare?
> =
> If so, we can move forward to cooling surface areas. Can an Auto engine
> cool it's heads, valves, pistons, etc. as well as it's aero counterpart?
> =
> I know of a diesel engine that was designed/modified (fill in the blanks)=
to
> set all kinds of world records. The Mercedes C-111 test bed's engine used=
> all kinds of exotics like oil-jet cooled pistons to run all-out for 100,0=
00
> miles.
> =
> Own Opinions, naturally,
> Scott Rider
A few issues back there was an article in CONTACT! magazine about Roger =
Mellama's analysis of the structures, dimensions, piston speeds and =
overall ability of a Ford 3.8L to do the job as well as a Lyc. He found =
that the engine met the requirements and from his analysis points =
concluded the Ford was up to the task.
-- =
Bruce A. Frank, "Ford 3.8L Engine and V-6 STOL
BAF...@worldnet.att.net Homebuilt Aircraft Newsletter"
*--------------------------------**----*
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0\(-o-)/ =
AIRCRAFT PROJECTS CO.
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0\___/
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0/ \
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0O O
scott rider
>So here's a proposal: you want to see people apply a little engineering
>to their auto conversion? Well you're the engineer, how about starting
>the ball rolling and doing a study. Post the information here, I for
>one would be extremely interested, I daresay there are others.
>
>Corky Scott
>
Corky, (Paul),
The problem is one of time and ROI. It is hard enough to sneak a few
minutes to read/write stuff for the 'net.
What would be the reward for posting the information v the risks?
Risk? A few failures along the way indirectly causing loss of life, bad press,
and great financial loss. Opening for lawsuits.
Reward? No cash, but perhaps a certificate in a handsome plastic frame.
(Sorry, Scott Adams gets credit for that one)
Did you read the posting by the OMAP project guy who was impressed with the
"engineering" in modern engines? Although he sounded absolutely convinced the
engines are better today than a few years ago, it appears that it is due to
his impressions that are likely gained by the introduction of easier starting and
idling fuel injection control and fluid filled engine mounts. His impression
of engines getting better is not backed up by any material science or
machine design-like observations.
Someone should do an apples to apples posting on piston & rod weight vs crank
journal size and rpm/piston speed. Does an auto engine/motorcycle engine/boat
engine compare to an airplane engine?
Do the valves compare? Stem size/open close cycles/weight/spring pressure?
Does the crank flange size and main bearing size compare?
If so, we can move forward to cooling surface areas. Can an Auto engine
cool it's heads, valves, pistons, etc. as well as it's aero counterpart?
I know of a diesel engine that was designed/modified (fill in the blanks) to
set all kinds of world records. The Mercedes C-111 test bed's engine used
all kinds of exotics like oil-jet cooled pistons to run all-out for 100,000
miles.
scott rider
>> >to their auto conversion? Well you're the engineer, how about starting
>> >the ball rolling and doing a study. Post the information here, I for
>> >one would be extremely interested, I daresay there are others.
>> >
>1. As is the case in all internet postings, information you pick up
>here is for you to use, or not depending on corroberation from other
>sources or your personal belief that the person doing the talking knows
>what he's talking about.
No disagreement here. Use info or walk away from it. Just don't try to hold
the poster liable for damages of any kind due to use, misuse, inability
to use, loss of revenue, etc. of any idea.
>2. I was also taking a shot at Paul
I wasn't trying to step in front of Paul like a secret service agent
trained to catch bullets aimed at others.
>
>If this truly is the case, then this represents yet another shift in
>the Lamar postulation: that auto engines when used to power airplanes
>are sure death, sooner or later.
>
Accidents will happen. It is just a failure of our society's value system when
we can so easily attack and ruin others for our own losses.
>So we've gone from "It will never work" to the rotory isn't a bad
>choice to " I wish people would engineer the installations better".
>We're making progress here, minds are changing. But he's preaching to
>the choire. I doubt that any one of us is interested in doing a sloppy
>job of installing our engines, I know I'm not. So if Paul really knows
>how to do it better, maybe he'd be interested in sharing some of his
>talent and smarts. If not, well then maybe the remark was just another
>throw away line.
>
>Corky Scott
I have seen the subtle shifts as well. I have no desire to "change anyone",
though. I would rather use my time to gather useful information. And since others
want inputs from self proclaimed experts, and lesser mortals, I freely offer
my opinions when I don't think they will turn around and bite me. I look
under every cowl I can for my own education too.
Look at my situation, I will take a shot at a full custom
never been tried engine installation myself. I approach this project with
confidence, however shoehorning an unknown into a BD-5 MUST be treated with
respect. As much as I think I know, I would like to have people take shots
at my work because I could uncover something before the NTSC does when digging
around in the small smoking hole my plane will leave.
Scott Rider
Own Opinions,
And I am still more afraid of litigation than of bad advice.
David M Parrish
In article <5538u7$k...@ornews.intel.com>,
scott rider <scott...@ccm.hf.intel.com> wrote:
>
>>So here's a proposal: you want to see people apply a little engineering
>>to their auto conversion? Well you're the engineer, how about starting
>>the ball rolling and doing a study. Post the information here, I for
>>one would be extremely interested, I daresay there are others.
>>
>
>The problem is one of time and ROI. It is hard enough to sneak a few
>minutes to read/write stuff for the 'net.
>
>What would be the reward for posting the information v the risks?
Which do _you_ think is the worse risk? Someone being hurt after using someone
else's experience or knowledge, or being hurt out of ignorance because the
people that do have some experience or knowledge are afraid to share it? I
thought the reason we were all here was to freely share what we've learned in
an area that many already think we're suicidal. (i.e. homebuilts) Sure, the
signal to noise ratio around here is pretty bad, but it's worth it in terms of
what I can learn from others.
I think we're really getting a bit overboard here. It would be nice to have
someone say 'this is the perfect engine' and give a detailed scientific
analysis of why it's perfect. But for most of us, the perfect engine will be
too heavy/too light, too powerful/too weak, too big/too small, or just too
expensive. We have lots of options, and what may be more important than the
perfect engine is some good eye-ball engineering and experience that can tell
others if a certain choice is poor, OK, or unusually good. Poor: the engine
weighs a ton, isn't very powerful and breaks easily. OK: The engine has
several problems, but they're well known and can be watched for or corrected.
(The VW might fall into this class.) Very good: Has a good power to weight, is
strong and reasonably available. (Some of the Subarus or the Vortec might fall
into this class.)
This (often off topic) thread started about water cooled systems. What's the
big risk in telling someone a good way to cool any engine? We're not talking
about breaking new ground (Though, that would be nice.), but more about people
that have access to existing information and sharing it with the rest of us.
Is there a shop in your area that makes custom racing radiators? They should
have information from their suppliers on how to size radiators for a
particular HP engine, along with best pressure differentials, fin spacing,
etc. Is there an aeronautical or industrial college near by? Someone should be
able to find how the designers settled on the design of the cooling system for
the P-51 or the basic math for heat exchangers. (For our German readers, you
probably have more research on water cooled aircraft than anyone else, and
it's mostly unavailable to our English only members.)
---
David Parrish
Knowledge is power.
Charles K. Scott
I suggested
> >So here's a proposal: you want to see people apply a little engineering
> >to their auto conversion? Well you're the engineer, how about starting
> >the ball rolling and doing a study. Post the information here, I for
> >one would be extremely interested, I daresay there are others.
> >
> >Corky Scott
In article <5538u7$k...@ornews.intel.com>
scott rider <scott...@ccm.hf.intel.com> writes:
>
> Corky, (Paul),
> The problem is one of time and ROI. It is hard enough to sneak a few
> minutes to read/write stuff for the 'net.
>
> What would be the reward for posting the information v the risks?
>
> Risk? A few failures along the way indirectly causing loss of life, bad press,
> and great financial loss. Opening for lawsuits.
Two points Scott:
1. As is the case in all internet postings, information you pick up
here is for you to use, or not depending on corroberation from other
sources or your personal belief that the person doing the talking knows
what he's talking about.
2. I was also taking a shot at Paul for whining about the lack of
engineering expertise regarding the installations of auto engines in
homebuilt aircraft. The implication is that Paul knows how to do it
better.
If this truly is the case, then this represents yet another shift in
the Lamar postulation: that auto engines when used to power airplanes
are sure death, sooner or later.
So we've gone from "It will never work" to the rotory isn't a bad
Howard Jones
Paul Lamar (paul-l...@worldnet.att.net) wrote:
: Charles K. Scott wrote:
: > I doubt that any one of us is interested in doing a sloppy
: > job of installing our engines, I know I'm not. So if Paul really knows
: > how to do it better, maybe he'd be interested in sharing some of his
: > talent and smarts. If not, well then maybe the remark was just another
: > throw away line.
: You still don't get it do you Corky? I guess since you are not an
: engineer you will never get it. Your IQ is not up to being an engineer
: so why don't you give up. The least thing you could do is read a couple
: of engineering books before you shoot off your mouth. I guess that is
: too much to expect since you are arithmetic challenged as well.
my vote's still with Corky. :) :)
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Howard Jones, (how...@perth.dialix.oz.au) _--_|\
66 Towton Way, Langford 6147, Western Australia / \
Freeflight Aeromodeller,Tyre Kicker & Current Pilot! *_.--._/
Corby Starlet Plans #279....SAAA 4330, Editor "Western Flyer" V
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
scott rider
"Bruce A. Frank" <BAF...@postoffice.worldnet.att.net> wrote:
re: My posting asking for comparisons of engine parts,
>A few issues back there was an article in CONTACT! magazine about Roger =
>Mellama's analysis of the structures, dimensions, piston speeds and =
>overall ability of a Ford 3.8L to do the job as well as a Lyc. He found =
>that the engine met the requirements and from his analysis points =
>concluded the Ford was up to the task.
That is one more positive thing I have heard about Contact!.
So,
Can someone let me know how to subscribe and obtain back issues?
Scott Rider
scott...@ccm.hf.intel.com or SAMR...@teleport.com
Not my companies opinions.
Does Paul also have these articles?
Bruce A. Frank
scott rider wrote:
> =
> "Bruce A. Frank" <BAF...@postoffice.worldnet.att.net> wrote:
> =
> re: My posting asking for comparisons of engine parts,
> =
> >A few issues back there was an article in CONTACT! magazine about Roger =
=3D
> >Mellama's analysis of the structures, dimensions, piston speeds and =3D
> >overall ability of a Ford 3.8L to do the job as well as a Lyc. He found =
=3D
> >that the engine met the requirements and from his analysis points =3D
> >concluded the Ford was up to the task.
> =
> That is one more positive thing I have heard about Contact!.
> So,
> Can someone let me know how to subscribe and obtain back issues?
> =
> Scott Rider
> =
> Does Paul also have these articles?
> =
> >-- =3D
> >
Scott,
You can reach CONTACT! at:
2900 EAST WEYMOUTH =
TUCSON, AZ 85716-1249
520-881-2232
fax602-795-6776
Mick Myal is editor. I think the phone numbers are current. $20/yr/6 =
issues.
-- =
Bruce A. Frank, "Ford 3.8L Engine and V-6 STOL
BAF...@worldnet.att.net Homebuilt Aircraft Newsletter"
*--------------------------------**----*
Mark Kromer
scott rider wrote:
>Someone should do an apples to apples posting on piston & rod weight
>vs crank journal size and rpm/piston speed. Does an auto
>engine/motorcycle engine/boat engine compare to an airplane engine?
A direct comparison will not be meaningful because you don't have apples
and apples in this example. You have to take into account that the
crank and mains in an aircraft engine also support the thrust and
gyroscopic loads from the prop.
>Do the valves compare? Stem size/open close cycles/weight/spring
>pressure?
A direct comparison here will not be meaningful either, unless you take
into account the cam profile, valve train mass etc. However, this is a
system that would be especially susceptable to fatigue failure due to
long term operation at higher rmp. In practice fatigue induced failures
seem to be much more common in valve trains than in bottom ends. The
problem is made worse by the installation of a more radical cam which
seems to be a common in auto conversions.
-)V(ark)<
Charles K. Scott
> : Charles K. Scott wrote:
> : > I doubt that any one of us is interested in doing a sloppy
> : > job of installing our engines, I know I'm not. So if Paul really knows
> : > how to do it better, maybe he'd be interested in sharing some of his
> : > talent and smarts. If not, well then maybe the remark was just another
> : > throw away line.
In article <557hks$p27$1...@perth.DIALix.oz.au>
how...@perth.DIALix.oz.au (Howard Jones) writes:
> : You still don't get it do you Corky? I guess since you are not an
> : engineer you will never get it. Your IQ is not up to being an engineer
> : so why don't you give up. The least thing you could do is read a couple
> : of engineering books before you shoot off your mouth. I guess that is
> : too much to expect since you are arithmetic challenged as well.
Hey Paul, you were the complainer moaning about the lack of engineering
expertise in auto engine installation although as usual, you gave no
examples of installations that lacked engineering, nor did you offer
any explanations as to what could be done to improve the situation.
All I was saying was put up or shut up. You think you can do better?
Then show us, give us at least *SOME* concrete examples of what you
would consider well thought out engineering, hell, give us just one.
So far we've gotten bubkus.
I was guessing that you were simply using this subject as another forum
to shovel your negative male cattle effluent but was willing to give
you the benefit of the doubt. Thanks for clarifying matters. No need
to expect any useful engineering from you.
It's illuminating to look back at several years worth of posts from you
to pick out the helpful particles. There aren't many. Most are just
"it'll never work", or will break/overheat/crumble, is not engineered
properly diatribes. The one engine you've blessed is the Mazda rotory
but guess what Paul, even that needs a PSRU, none of which you claim
work or are engineered properly, not to mention a cooling system that
requires a radiator which again you haven't found workable. Good thing
no one listens to your advice or none of us would be flying.
Have a nice lunch of Tums.
Corky Scott
Charles K. Scott
In article <55a9jh$k...@dartvax.dartmouth.edu>
Charles...@dartmouth.edu (Charles K. Scott) writes:
> In article <557hks$p27$1...@perth.DIALix.oz.au>
> how...@perth.DIALix.oz.au (Howard Jones) writes:
Sorry everyone obviously this is a mistake in attribution, Howard has
demonstrated nothing but tolerance and humour regarding auto engine
conversions.
My apologies.
Corky Scott
jpr
Paul Lamar <paul-l...@worldnet.att.net> wrote:
>Charles K. Scott wrote:
>>
>> > : Charles K. Scott wrote:
>> > : > I doubt that any one of us is interested in doing a sloppy
>> > : > job of installing our engines, I know I'm not. So if Paul really knows
>> > : > how to do it better, maybe he'd be interested in sharing some of his
>> > : > talent and smarts. If not, well then maybe the remark was just another
>> > : > throw away line.
>>
>> In article <557hks$p27$1...@perth.DIALix.oz.au>
>> how...@perth.DIALix.oz.au (Howard Jones) writes:
>> > : You still don't get it do you Corky? I guess since you are not an
>> > : engineer you will never get it. Your IQ is not up to being an engineer
>> > : so why don't you give up. The least thing you could do is read a couple
>> > : of engineering books before you shoot off your mouth. I guess that is
>> > : too much to expect since you are arithmetic challenged as well.
>>
>> Hey Paul, you were the complainer moaning about the lack of engineering
>> expertise in auto engine installation although as usual, you gave no
>> examples of installations that lacked engineering, nor did you offer
>> any explanations as to what could be done to improve the situation.
>> All I was saying was put up or shut up. You think you can do better?
>> Then show us, give us at least *SOME* concrete examples of what you
>> would consider well thought out engineering, hell, give us just one.
>> So far we've gotten bubkus.
>Corky you are denser then I thought. I am going to have to add reading
>comprehension to your list of failings.
>As I said over and over again; it is not the installation, it is the
>auto engine itself that is the problem. Nobody would start with a Piper
>Cub fuselage when designing a supersonic airplane.
>Paul Lamar
Yeah, Corky, doncha know airplane engines are made of airplane iron
molecules and airplane aluminum molecules.. auto engine molecules
just aren't as good.. although with proper application of an FAA
certified sticker, some auto engine molecules can be transmuted into
airplane engine molecules (such as the Delco alternators) - but it's
a very expensive process...
-jpr
ncab...@worldnet.att.net
On Fri, 01 Nov 1996 22:38:35 GMT, j...@ix.netcom.com (jpr) wrote:
>Yea, Corky, doncha know airplane engines are made of airplane iron
>molecules and airplane aluminum molecules.. auto engine molecules
>just aren't as good.. although with proper application of an FAA
>certified sticker, some auto engine molecules can be transmuted into
>airplane engine molecules (such as the Delco alternators) - but it's
>a very expensive process...
>
Your sarcasm is as inaccurate as it is unjustified. The difference
between the aircraft versions and the auto versions is usually a
matter of alloying elements and impurities. So it isn't that the
aluminum or iron atoms are any different but rather that the amounts
of other materials ialloyed with the base metal are different.
ncab...@worldnet.att.net
On 28 Oct 1996 21:35:03 GMT, scott rider
<scott...@ccm.hf.intel.com> wrote:
>
>
>Someone should do an apples to apples posting on piston & rod weight vs crank
>journal size and rpm/piston speed. Does an auto engine/motorcycle engine/boat
>engine compare to an airplane engine?
>
>Do the valves compare? Stem size/open close cycles/weight/spring pressure?
>
>Does the crank flange size and main bearing size compare?
>
>If so, we can move forward to cooling surface areas.
Not quite. You have to compare materials used. This, IMHO, is a big
difference between auto and aircraft engines, determining both
reliability and cost. I have to onder how well the cost difference
from auto engines through truck engines, marine engines, and aircraft
engines is simply a matter of cost of materials.
Cole L. Corey,BE643
ncab...@worldnet.att.net writes:
You mean like when you buy aluminum heads and blocks and they are
AL356-T6? Do you really think that GM (as an example) builds their
aluminum parts out of pot-metal? Granted these parts aren't 7 series
aluminum, but I don't think that 7 series is an appropriate alloy for
these parts.
Corey Cole
clc...@aw101.ca.boeing.com
Disclaimer: These opinions are my own, and do not represent official Boeing
opinions, policies, or views.
Charles K. Scott
Paul Lamar <paul-l...@worldnet.att.net> writes:
> Corky you are denser then I thought. I am going to have to add reading
> comprehension to your list of failings.
> As I said over and over again; it is not the installation, it is the
> auto engine itself that is the problem.
Hmmm, my reading comprehension is pretty good and my memory isn't bad
either. I was positive that Paul had said something different from
this originally so I did a little searching on Dejanews and found the
following original quotes from Paul Lamar:
David Lednicer wrote:
> What grieves me about homebuilts is that people "experiment"
> with no clue as to what they are actually doing. A little science
> (engineering) would help a lot.
To which Paul Lamar <paul-l...@worldnet.att.net> replied:
> Ain't it the truth. I wish somebody would apply a little engineering
> before they stuck and auto engine in an aircraft.
Apparently, Paul is older than I had previously thought and is
beginning to suffer from the effects of memory loss, poor guy. If the
above quote isn't Paul Lamar wishing people would "apply a little
engineering" before installing an automobile engine in an airplane,
what is it? Note, he isn't saying that the engine block itself is
fundamentally flawed, only that better engineering should be applied to
the installation.
It was this quote that prompted me to suggest that Paul use a mediocum
of his self vaunted and much ballyhooed engineering talent and bless us
with what "a little" engineering might look like. Only to watch Paul
go ballistic with another one of his attack snorts. I should have
known better than to ask for something concrete, that would take actual
engineering. Guess we'll have to humour him though and consider what
he first said as "inoperative", it's no fun when the memory goes.
Corky Scott
Cole L. Corey,BE643
> > You mean like when you buy aluminum heads and blocks and they are
> > AL356-T6? Do you really think that GM (as an example) builds their
> > aluminum parts out of pot-metal? Granted these parts aren't 7 series
> > aluminum, but I don't think that 7 series is an appropriate alloy for
> > these parts.
>
> To my knowledge only the aftermarket racing industry alloy heads or
> blocks are 356T6.
Paul,
Next time you're at the Ford dealership, look at their SVO catalog...the
parts in here are real Ford pieces, and those AL heads are 356T6 (they're
even meant for street use and can be bought by Joe Blow)
> In the rare cases when GM and Ford put in forged crank parts instead of
> cast iron or powdered iron rods they use mild steel instead of 4340
> aircraft quality steel. Hot Rod magazine is one of the few auto
> magazines that is reporting materials and alloys used in various auto
> engine parts. Even the Corvette gets these kinds of parts as do the 1/4
> ton (500 pound payload) pickup truck engines.
The GM MTG catalog and Chevy Engine builders guide both show that GM makes
cranks from cast, to nodular to forged 4340...
>
> Fatique is just not the problem in an auto engine it is in an aircraft
> engine so cast iron and powdered metal parts work fine in auto engines.
>
> Cost is much more important so why put expensive materials in an auto
> engine. I have powdered metal rods and a cast iron crank in my Cougar
> V8. The auto engine runs at an average of 30 HP and not 150 HP like an
> aircraft engine.
I'd think of all the auto engines you'd like your modular V-8 best as a conversion candidate. Rigid cross bolted mains, cast oilpan to add stiffness.
Those powdered metal parts that you malign happen to have closer tolerances when
it comes to being cast "near net" so less metal goes into the balance pad and
more metal goes into the beefiness of the rod (o.k. beefy is not a technical term) GMs powdered metal rods outperform forged pinks in terms of fatigue
performance.
Gotta go
Corey Cole
clc...@aw101.ca.boeing.com
Disclaimer: As always, these opinions do not represent any official policies
or points of view of my employer. Only someone with more lawyers
than sense would think otherwise.
Charles K. Scott
In article <328229...@worldnet.att.net>
Paul Lamar <paul-l...@worldnet.att.net> writes:
> They sell racing parts and I have stated they will work. The cost when
> you get done will be no chaeper [sic] than an aircraft engine.
Hmmm, pricing for the Chevy HO Vortec V-6 (200 hp.) has been quoted at
between $1,500 and $2,100. The PSRU is between $1,700 and $2,500 so at
max we are now at $4,600. We need a carburator which could run $500 or
fuel injection at $1,700 so that's $5,100 and ignition which would go
another $500 to $1,000 so call it $6,100, give or take maybe a thousand
depending on the induction system. This is all brand spanking shiny
new stuff. And you're telling me that's the cost of a brand new
certified Lycoming 150 hp engine? The best price I saw for one of
those was in the range of $18,000, and then you had to buy an RV to get
it. That's almost exactly three times the cost of a ready to fly 200
hp auto engine. And that's if you go with a brand new engine. You
could build it yourself using heavy duty parts and save more. My Buick
V-8 aluminum block, for instance, cost me only $75 and the crank $389.
The heads were $75 EACH. Hell, last time I looked, $75 would even buy
me a Lycoming dipstick tube.
Looks like another Paulish hipshot, quick on the draw but wildly
innaccurate.
Corky Scott
David W. Taylor
In article <567c77$8...@dartvax.dartmouth.edu>,
Data poinst to help keep the info moving,,,,,,
Just called 3 engine builders who do either Marine or Sprint Car work.
Also called a local Chev Dealer....
Arias/Wiseco Pistons - Approx 600 dollars depending on exact requirements,
Custom mods add in nice round high dollar increments.
Eagle 4340 H-Beam Rods. 600 Dollars , Forged polished shotpeened and
x-rayed.
Crower 4340 "Forged NO Twist" Crankshaft - Around 1500 depending on
custom requests. If I got it right they can do special
flanges on output end and will do other special work for
some extra $$.
GM Performance also now has a Forged Crank in pre-release, its just starting
to become available thru the dealers, Pricing has not been set but the dealer
parts guy I deal with said he thiks its going to be in the same bracket as the
crower..
THe wild guess that I pried out of two of the builders was that if I budgeted
4.5 to 6 K for the engine I could build a pretty tough motor. Trey both
stressed that the factory parts were pretty good in the vortec but that
for a marine-like application money spent on the block was money well spent.
Mods like large oil galleys de-flashing and polishing would pay back
and weren't too expensive.... They both recomended a Marine Block as the
starting point because it has more of the finess work done from the factory.
If anybody has the spare 6 K around for the motor and 100K for testing I'll
give it a shot :) Lets see wht that baby can do.....
Best thing I've ever heard over a comercial jets intercomm.
(Pilot thought it was off.....)
"Ladies and Gentleman The Captain has turned on the NO WHINING sign"
--
David Taylor dwta...@ptdcs2.intel.com Ph(503) 613-8132 Portland OR.
My opinions are mine ,, and nobody elses.
Howard Jones
Paul Lamar (paul-l...@worldnet.att.net) wrote:
: This dumb shit thinks there are forged 4340 aircraft quality racing
: parts in a crate engine.
spare us this tirade will you. you make as many, probably more, errors
in your posts as most of the other posters put together.
my vote is still with corky.