Rotary engines in WW1

"B2431" wrote in message
...
Just as a matter of curiosity why were rotary engines used?

Dan, U. S. Air Force, retired

see
http://www.aviation-history.com/engi...ary-theory.htm

Keith

On 13 Nov 2003 04:47:58 GMT, (B2431) wrote:

Just as a matter of curiosity why were rotary engines used?

Cooling. It was evidently the only way other than liquid cooling to
dissipate heat in 1914-era aircraft engines. Probably a matter of
technology in building "heat sink" fins. Horsepower advancing more
rapidly than knowledge? The first generation of WWI fighters would
have been designed less than 10 years after the Wrights' first flight.

all the best -- Dan Ford
email: (put CUB in subject line)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

(B2431) wrote:

Just as a matter of curiosity why were rotary engines used?

Dan, U. S. Air Force, retired

Dan, did you mean 'rotary' or perhaps 'radial'?. Also the thought
occurs that you might have meant 'rotary' as in a Wankel?
--

-Gord.

From: "Gord Beaman" )
Date: 11/13/2003 9:49 PM Central Standard Time
Message-id:

(B2431) wrote:

Just as a matter of curiosity why were rotary engines used?

Dan, U. S. Air Force, retired

Dan, did you mean 'rotary' or perhaps 'radial'?. Also the thought
occurs that you might have meant 'rotary' as in a Wankel?
--

-Gord.

This thread is about rotary engines as in "bolt the prop to the engine case and
hold the crankshaft."

I would have thought it would act like a huge gyroscope with the ensuing
handling problebs..

Dan, U. S. Air Force, retired

"B2431" wrote in message
...
From: "Gord Beaman" )
Date: 11/13/2003 9:49 PM Central Standard Time

-Gord.

This thread is about rotary engines as in "bolt the prop to the engine
case and
hold the crankshaft."

I would have thought it would act like a huge gyroscope with the ensuing
handling problebs..


It did, thats one of the reasons why the Sopwith Camel was such
a dangerous aircraft to fly. An expert pilot could use the effect
to advantage but it killed a lot of novices.

Keith

I would have thought it would act like a huge gyroscope with the ensuing
handling problebs..

The rotary did just that.

Of course, the horsepower was comparatively low. The Nieuport 28 was a
late-model fighter with 160 hp.

Even at that, I recall that pilots preferred to turn in the direction
favored by the torque.

all the best -- Dan Ford
email: (put CUB in subject line)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

On 13 Nov 2003 04:47:58 GMT, (B2431) wrote:

Just as a matter of curiosity why were rotary engines used?

Dan, U. S. Air Force, retired

They were a lot easier to manufacture than radials,
fewer moving part (by number, not by mass :-) ).

Al Minyard

Le Rhone, Clerget, and Oberursel rotary engines used conventional
poppet valves in the heads for intake and exhaust.

Gnome rotaries were a little different: intake was through a poppet
valve in the piston crown! There was no actuating mechanism. The
suction of the intake stroke pulled the valve open.

Later Gnomes had no intake valves. In the "Monosoupape" design, the
exhaust valve remained open so long past dead center, it became an
intake valve. The cylinder drew some air in through the exhaust port.
(The port went directly to the air, so it didn't inhale too much of
its own exhaust gas.) After the valve closed, the descending piston
created a suction in the cylinder. Near bottom dead center, the piston
uncovered intake ports in the cylinder wall. A rich mixture rushed in
from the crankcase. Diluted with the air already present, it made a
correct mixture.

Compression and power strokes occurred in the normal fashion.

To prevent blowback into the crankcase at the end of the power stroke,
the exhaust valve opened early and released combustion pressure before
the cylinder ports uncovered.


As far as I know, the crankcase was the "intake manifold" in all
rotary engines. Mixture entered the crankcase via the crankshaft. The
portion that passed through the rear main bearing was hollow, like a
pipe. That passage connected the stationary carburetor to the spinning
crankcase.

Although rotary engines drew air and fuel through the crankcase, they
were not 2-strokes. Crankcase volume remained constant as the engine
revolved, so it couldn't pressurize the mixture like the crankcase of
a chain saw or motorcycle engine. There was no blower either, so
rotaries had to be 4-strokes.

--

Paul Hirose
To reply by email delete INVALID from address.

Paul Hirose wrote:

Le Rhone, Clerget, and Oberursel rotary engines used conventional
poppet valves in the heads for intake and exhaust.

Gnome rotaries were a little different: intake was through a poppet
valve in the piston crown! There was no actuating mechanism. The
suction of the intake stroke pulled the valve open.

Later Gnomes had no intake valves. In the "Monosoupape" design, the
exhaust valve remained open so long past dead center, it became an
intake valve. The cylinder drew some air in through the exhaust port.
(The port went directly to the air, so it didn't inhale too much of
its own exhaust gas.) After the valve closed, the descending piston
created a suction in the cylinder. Near bottom dead center, the piston
uncovered intake ports in the cylinder wall. A rich mixture rushed in
from the crankcase. Diluted with the air already present, it made a
correct mixture.

Compression and power strokes occurred in the normal fashion.

To prevent blowback into the crankcase at the end of the power stroke,
the exhaust valve opened early and released combustion pressure before
the cylinder ports uncovered.

As far as I know, the crankcase was the "intake manifold" in all
rotary engines. Mixture entered the crankcase via the crankshaft. The
portion that passed through the rear main bearing was hollow, like a
pipe. That passage connected the stationary carburetor to the spinning
crankcase.

Although rotary engines drew air and fuel through the crankcase, they
were not 2-strokes. Crankcase volume remained constant as the engine
revolved, so it couldn't pressurize the mixture like the crankcase of
a chain saw or motorcycle engine. There was no blower either, so
rotaries had to be 4-strokes.

Correct me if I'm wrong, but based on your description above the main
reason that WW1 rotaries don't meet the criteria of a "two-stroke" is
because they required 720-deg's of crankshaft rotation to complete one
power cycle as opposed to one power cycle in only 360 degrees of
crankshaft rotation.

Another critical difference is how the crankcase volume remained the
same in WW1 engines. As you said, the pressure varies in the crankcase
of a 2-stroke. When the crankshaft has rotated past bottom dead center
the crankcase pressure is below atmospheric. This is necessary
so as to produce a vacuum and allow a fresh charge of unburned mixture
gasses to flow through the reed valve into the crankcase at the start
of the next compression cycle.