Aircraft engines...
Taglia
Can anyone explain me the differences between a radial engine (ex. engine on
F4F "Wildcat")
and a on-line engine (ex. engine onKi-61 "Hien") ??
Thanks....
Taglia
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Bill Shatzer
In a previous article, tagl...@hotmail.com ("Taglia") says:
>Hi
>Can anyone explain me the differences between a radial engine (ex. engine on
>F4F "Wildcat")
>and a on-line engine (ex. engine onKi-61 "Hien") ??
A radial engine has its cylinders arranged in a circle around
the crankcase. The inline engine has its cylinders arranged
in one or more "banks" of cylinders.
Generally, but not always, radial engines were aircooled while
inline engines were liquid cooled.
Generally, inline engines were similar in arrangement to the
modern V-8 engines on automobiles although they were generally
V-12s. Inverted "V" engines and "W" engines (three banks of
cylinders) were also used.
Cheers and all,
--
Bill Shatzer - bsha...@orednet.org
"You don't need a weather man to know which way the wind blows."
-Bob Dylan-
Darryl Gibbs
Taglia wrote in message <7issuh$14p2$1...@nntp6.u.washington.edu>...
>Can anyone explain me the differences between a radial engine (ex. engine
>on F4F "Wildcat") and a on-line engine (ex. engine onKi-61 "Hien") ??
Radial engines are cooled by the airflow passing over the engine cylinders.
Most inline engines in fighter aircraft are liquid cooled (Similar to a car)
and have a cooling radiator placed somewhere on the airframe. Air cooled
engines are generally less vulnerable to damage due to enemy fire, but they
have the disadvantage of being much less streamlined than a liquid cooled
engine.
Some inline engines are also air-cooled, the Gipsy Major used in aircraft
such as the Tiger Moth is and example of this. A lot of modern light
aircraft also have horizontally opposed air-cooled engines. This is where
the crank case is situated between two rows of cylinders.
Hope this helps to clarify things for you.
Darryl Gibbs
Emmanuel.Gustin
: engine on F4F "Wildcat") and a on-line engine (ex. engine onKi-61
: "Hien") ??
A radial engine has cylinders that are radially arranged around a
crankcase. The cylinders form what one could call a "star-shape", always
with an odd number (5, 7, 9) of cylinders. Such a star was called a "row".
Up to four "rows" of cylinders could be arranged behind each other, but
most WWII radials had one or two. The R-1830 engine installed in most F4Fs
was a two-row radial.
With few exceptions, radials were air-cooled. The absence of a vulnerable
cooling system made them more resistance to battle damage (it was not
unheard of for an engine to continue running after a cylinder had been
shot away) and made them lighter. They were less efficient than
liquid-cooled engines and had a larger frontal area than in-line engines,
but with careful design of the cowling good streamlining could be
achieved.
Radial engines became popular during the 1920s, with the Bristol Jupiter
as the first really successful (and widely copied) example and the later
Wright Whirlwind as the engine that powered many record-setting aircraft.
The high drag of uncowled radials lead to some loss of popularity during
the 1930s, but they returned to the forefront during WWII. Radial engines
designed during WWII produced up to 3000 hp.
In-line engines are engines in which the cylinders are arranged in a bank
in line with each other, in a fore-and-aft row. The term "in-line" is
usually extended to include combinations of such banks to Vee, inverted
Vee, W, X and horizontal or vertical H shapes. (A Vee engine has two banks
on one crankcase, a W three, and X four. A H engine has to have two
crankcases, with two banks of cylinders each.)
In-line engines can be air-cooled, such as the German Argus and the US
Ranger engines, and in fact most engines used in today's light aircraft.
But during WWII in-line air-cooled engines were resticted to about 700 hp
or less. Most in-line engines installed in combat aircraft were
liquid-cooled V-12 engines. These engines had become popular before the
war because of their low frontal area, which allowed a streamlined
cowling, and high power: 1000hp at the beginning of the war, up to 2500hp
at its end. Their main disadvantage was the need for a cooling system; a
single bullet hole in it would case loss of coolant and destroy the
engine.
Another important distinction, often overlooked, is that between
poppet-valve and sleeve-valve engines. Poppet-valve engines have
conventional inlet and outlet ports at the base of the cylinder;
sleeve-valve engines had a metal "sleeve" with holes in it sliding and
rotating inside each cylinder to allow the air-fuel mixture in and the
combustion products out through corresponding openings in the cylinder
wall. Sleeve-valve engines were much quieter and probably more efficient,
but they were costly and difficult to manufacture. AFAIK only the British
made successful sleeve-valve engines.
It remains to be added that during WWII high-powered engines were geared
to retain propeller efficiency --- the best rotational speed of the
propeller was well below the rpm of the engine --- and that to retain good
power at higher altitude, they needed supercharging. Mechanical
superchargers were developed in Germany and the Britain; especially the
Rolls-Royce developed two-stage supercharger of the Merlin 61 series was
excellent. The USA had neglected the development of mechanical
superchargers, but they did have the first reliable exhaust-driven
turbo-superchargers, installed in the P-38, P-47, B-17 and B-24.
Emmanuel Gustin
Emmanuel.Gustin
Keith B. Rosenberg
shaft. The cylinders have large heat sink fins (like those on some
motorcycles) on them and are air cooled. Disadvantage is that
this makes for a large flat surface at the front of the plane.
Advantage is that you do not need a cooling system making the
plane lighter and less complex with fewer things that can take
your engine out.
The "inline" engine has the cylinders in a straight line and is
liquid cooled. Advantage to this design is a very thin profile
which makes the plane more aerodynamic. Disadvantage is
that you need a cooling system built into the plane which
adds weight and complexity. The liquid cooled system is
also more vulnerable to very minor damage which would
cause the loss of the aircraft.
Either type of engine can be made to power a 500 MPH
aircraft.
Taglia wrote:
> Hi
> Can anyone explain me the differences between a radial engine (ex. engine on
********************************************************************
enor...@ix.netcom.com (Keith B. Rosenberg) (EN][)
For it's Tommy this, an' Tommy that, an' "Chuck him out, the brute!"
But it's "Saviour of 'is country" when the guns begin to shoot;
df
A radial engine is an air-cooled engine, with an odd number of
cylinders arranged around the crankshaft like the spokes of a wagon
wheel. By WWII, radials were typically double-row (e.g. 7 cylinders
behind 7 cylinders) and eventually they became four-row, with
consequent cooling difficulties.
An in-line engine is a liquid-cooled engine, in WWII aircraft usually
two rows of six cylinders arranged in a V with the crankshaft at the
bottom, similar to the V-8 automobile engine popular in the U.S. at
the time. The coolant was generally ethelene glycol, trade name
Prestone in the U.S.
The in-line engine was state of the art in 1939 and was adopted by
most European air forces because it offered possibilities for
streamlining that weren't available to the air-cooled engine, which
the U.S. (and particularly the US Navy) tended to favor--as did the
Japanese. However, the U.S. was able to overcome that problem with
brute force, as in the Republic P-47 Thunderbolt and Vought Corsair,
and postwar the radial engines remained popular in aviation for about
ten years while the in-lines died out.
All the best - Dan Ford
See "Nothing New About Death" at http://www.danford.net
and the message board at http://www.delphi.com/annals/
Dirk Lorek
wrote:
>With few exceptions, radials were air-cooled.
>But during WWII in-line air-cooled engines were resticted to about 700 hp
>or less.
This cooling thing has always puzzled me. What is it exactly that
makes radial engines less prone to overheating than inline engines?
And why did the Germans consider it necessary to equip the BMW 803
with a fan while the Americans didn't need one even for the much more
powerful Wasp Major?
Dirk
_______________________________________________________________________
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cells, which work they know not why, which never halt, myself unwitting
where their Master dwells. - John Masefield -
Emmanuel.Gustin
: makes radial engines less prone to overheating than inline engines?
In an inline engines, the cylinders are in each others wake, and the air
heats as it flows throuigh. The purpose of the radial design is to give
all cylinders equal exposure to the air flow. Of course four-row radials
such as the R-4360 defeat this, and this engine did indeed have some
cooling problems -- the thrid row tended to run hot, at least on
Stratocruisers.
: And why did the Germans consider it necessary to equip the BMW 803
: with a fan while the Americans didn't need one even for the much more
: powerful Wasp Major?
The fan allowed a thighter, more aerodyanmic cowling. Some US aircraft did
have fan-cooled engines, IIRC the Republic XP-72 and XR-12. It did of
course add some technical complexity.
Emmanuel Gustin
C.C. Jordan
>: This cooling thing has always puzzled me. What is it exactly that
>: makes radial engines less prone to overheating than inline engines?
I only picked Emmanuel's post because I know him.
My point is this: There were no true inline engines used in WWII fighters or
bombers. These were V engines. Just like some cars have an inline 6 cylinder
engine, and others have a V6 engine. The difference is not really important and
as a result is often overlooked.
Just thought I would mention it.
My regards,
C.C. Jordan
Now online: B-10s to Stratojets:
The Amazing Aviation Odyessey of Chuck Baisden.
Mr. Baisden was an original member of the AVG.
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The Planes and Pilots of WWII online magazine
http://home.att.net/~C.C.Jordan/
A member of the Aviation History and WWII Web-rings.
Honor and remember the WWII veterans.
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a lack of the former and a reliance on the latter."
Rob Davis
>This cooling thing has always puzzled me. What is it exactly that
>makes radial engines less prone to overheating than inline engines?
The Bristol Hercules (as fitted to the Handley-Page Halifax III, and
various versions of the Short Stirling) had cowl flaps which were
operated by the flight engineer. Opening the flaps, which encircle
the engine cowling, allows more airflow to pass over the hot cylinders
and escape through the opened flaps. This affords better cooling, at
the expense of aerodynamic "cleanness". So opening the cowl flaps may
cure an overheating engine but uses more fuel due to increased drag.
So, air cooling does not depend on the integrity of a sealed and
pressurised liquid cooling system (like most motor vehicles) which be
damaged by enemy fire or foreign body strike. Loss of coolant soon
renders an inline engine useless scrap, kind of fatal when you are 300
miles off the coast!
This feature is not unique to Bristol engines and is also used on many
other radial aero engines.
Radials must not be confused with rotary engines which may look very
similar but are different, although also air cooled.
My uncle who was a navigator on Beaufighters swore that after one
engagement, their aircraft had a complete cylinder shot out by enemy
fire, but the engine continued to run and although it sounded like a
tinker's barrow, they reached base safely. This could not have
happened with a liquid cooled (inline) engine, as such damage would
have resulted in the cooling jacket around the engine being pierced,
and a complete loss of coolant.
Many air museums have cutaway motorised engines which show various
types in action. Watching a sleeve-valved Herc spin round is an
education.
=====================
Rob Davis MSc MIAP
Telford Shropshire UK
Brad Meyer
Keith B. Rosenberg wrote:
> A "radial" . . .
(snip)
> Advantage is that you do not need a cooling system making the
> plane lighter and less complex with fewer things that can take
> your engine out.
Another practical advantage is that the radial has a shorter crankshaft, and can
stand greater torque and changes in torque without deflecting the crankshaft. In
practice, this meant one could be much rougher with the throttle without risking
damage to the crank.
Brad
Erik Shilling
Brad Meyer <br...@ibm.net> wrote:
snipped some
>Another practical advantage -- the radial has a shorter crankshaft,
snip
>In practice, this meant one could be much rougher with the
>throttle without risking damage to the crank.
snip
>From personal experience I know this to be all too true. The
Allison would take over boosting, but if the throttle was advance
too rapidly, the crank would twist and sooner or later you would
wind up with a thrown Rod.
Regards,
Erik
Dirk Lorek
wrote:
>: And why did the Germans consider it necessary to equip the BMW 803
>: with a fan while the Americans didn't need one even for the much more
>: powerful Wasp Major?
>
>The fan allowed a thighter, more aerodyanmic cowling. Some US aircraft did
>have fan-cooled engines, IIRC the Republic XP-72 and XR-12. It did of
>course add some technical complexity.
I made a typo, I meant to compare the BMW 801 with the R-4360. The
latter is perhaps no good example, as many installations with this
engine indeed seem to have been fan-equipped (but not the F2G I
believe).
I've read (Green) that there were early overheating problems with the
14-cyl BMW 801, and that's why the fan was added. OTOH, the 18-cyl
Double Wasp, devoloping 800 more horsepowers, could do without it, and
we are not even mentioning the fan-less Wasp Major configurations
delivering almost double the horsepower than the BMW 801. Either Green
was wrong, and the BMW 801 fan was added for performance/ lifespan
reasons instead, or there are considerable differences between
different radial designs wrt to cooling.
Another question. Were there any restrictions for the Pratt & Whitney
enginges wrt to ground handling, i e would the engine overheat quickly
with the aircraft standing still or was the draft from the prop
sufficient to cool the engine?
Erik Shilling
writes:
>
>
>A radial engine is an air-cooled engine, with an odd number of
>cylinders arranged around the crankshaft like the spokes of a wagon
>wheel.
>Dan what happened to that 12 cylinder radial engine you said was on
the Curtiss P-36 airplane. The one you said tht the cylinders were
arranged around the propeller shaft?????????
regards,
Erik
Bruce Burden
Newsgroups: soc.history.war.world-war-ii
X-Newsreader: TIN [version 1.2 PL2]
rob....@MAPSON.wlv.ac.uk (Rob Davis) wrote:
: Opening the flaps, which encircle
: the engine cowling, allows more airflow to pass over the hot cylinders
: and escape through the opened flaps.
:
Another way to (help) cool an engine, whether it be
rotary, radial or liquid cooled, is to enrichen the fuel
mixture. This tends to work better with air-cooled engines
due to less mass to cool. I don't remember who it was, but
an American pilot (in believe in "Fork-tailed Devil") wrote
about wearing his thumb to the bone working the priming
pump in his P-38 after taking damage to the cooling system.
:
: So, air cooling does not depend on the integrity of a sealed and
: pressurised liquid cooling system
:
Don't overlook the importance of oil coolers. While it
is true that radials don't have the complicated coolant systems
of liquid cooled engines, they still have oil coolers, and
oil temp is almost as important as oil pressure.
:
: engagement, their aircraft had a complete cylinder shot out by enemy
: fire, but the engine continued to run and although it sounded like a
: tinker's barrow, they reached base safely.
:
Col. Johnson talked about the number of cylinders left
in his P-47 after getting bounced by three different German
aircraft in his memoirs. I believe he said all of the front
cylinders (9) were damaged to a greater or lesser extent.
The airplace was a total loss, but it got him back to the
emergency field above the Dover cliffs.
Bruce
--
------------------------------------------------------------------------
"I like bad!" Bruce Burden Austin, TX.
- Thuganlitha
The Power and the Prophet
Robert Don Hughes
Emmanuel.Gustin
: I've read (Green) that there were early overheating problems with the
: 14-cyl BMW 801, and that's why the fan was added.
Early Fw 190s used a different engine, the BMW 139, and a large ducted
propeller spinner to get cooling air in. This didn't work very well, so a
conventional spinner and a close cowling were used instead, with a fan to
get enough cooling air. Only later the BMW 139 was replaced by the BMW
801. So there is no direct link between the BMW 801 engine and the use of
a cooling fan. It was mainly a feature of the cowling design.
: Double Wasp, devoloping 800 more horsepowers, could do without it, and
: we are not even mentioning the fan-less Wasp Major configurations
: delivering almost double the horsepower than the BMW 801.
Most US installations of radials made only modest gestures toward
aerodynamics. Some prototypes, for examples that of the F4F-2, had large
spinners and close-fitting cowlings; some more eccentric drag-reduction
schemes for radial engines were tested on the Curtiss XP-42. But when
these attempts caused cooling problems they were simply abandoned.
American aircraft tended to have only small caps over the propeller hub to
protect the pitch mechanism, and large open cowlings. It was a "brute
force" solution, not very sophisticated, but it worked well enough.
There was one attempt to improve cooling --- some propellers, IIRC only
Curtiss Electric ones, had large cuffs around the root of the propeller
blades to boost the airflow to the engines.
Emmanuel Gustin
Rob Davis
> Don't overlook the importance of oil coolers. While it
> is true that radials don't have the complicated coolant systems
> of liquid cooled engines, they still have oil coolers, and
> oil temp is almost as important as oil pressure.
One RCAF pilot preferred the Merlin over the Hercules because he had
nasty experiences with "coring" i.e. oil returning fom the oil cooler
and freezing on the way back.
Rob Davis
>too rapidly, the crank would twist and sooner or later you would
>wind up with a thrown Rod.
That's interesting because one of the more uncommon faults with the
Merlin was a connecting rod coming adrift and piercing the cylinder
block. This often happened on take off and was usually fatal for a
heavily loaded aircraft.
This would have been at the time when the throttles were given the gun
and firewalled to full boost. Although the manual says to advance the
throttles "firmly and steadily" some pilots / flight engineers
doubtless just rammed the levers forwards and pulled the tittie (the
boost cut out, "through the gate"). Maybe this caused the problem you
describe.