light twins?

I think there are theoetical factors against the Wankel-type rotary.

The combustion chamber shape is far from ideal and there isn't a straight
forward way to correct that. As a result, the engine leaks a lot of heat in
exhaust gasses as well as through the cooling system so there is less energy
going into producing power. All else equal (and it rarely is), the rotary
will have worse specific fuel consumption than a crank and piston.

Old pistons have one rarely discussed advantage. In the interval between
ignition and the beginning of the power stroke, piston motion is very low
and the volume of the combustion chamber is close to constant. This allows
combustion to run to completion under near ideal conditions of temperature
and pressure. That squeezes more heat calories, and therefore power, out of
the fuel-air mixture.

Bill Daniels
(I loved my RX-7)

A rotary made by Midwest (originally used in Norton motorcycles) and
now produced by Diamond has been very successfully used to power self
launched sailplanes made by Alexander Schleicher. I fly an ASH-26E
powered by a 50hp single rotor wankel.

More info is at
http://www.as-segelflugzeuge.de/engl...ash26_main.htm

-Tom

The Norton engine is alive and kicking - now being produced by Diamond
and they're thinking of making a 2 rotor version with 100 hp.

-Tom

On Wed, 27 Jul 2005 10:08:35 -0500, "Bellsouth News Server"
wrote:

How can you say that Mazda hasn't made this successful? Sure, the initial
introduction had it's share of problems, but since the RX-7 made the
re-introduction of the rotary here in the US, the engine has been as
troublefree as any engine produced. Emissions was one of the biggest
problems, but the newly redesigned Renesis engine cleaned that up, as well
as taming a bit of the bark, and overly hot exhaust. Fuel consumption in
aircraft use does not seem to be any worse than any other engine of the same
power range. The truth is that other manufacturers tried the rotary, but
didn't feel like it was worth developing, since they were perfectly happy to
churn out piston engines. Only Mazda seems to have had the willingness to
stick with it, and make it successful.

Now now Bellsouth, let's not get too worked up over this. I agree on
most aspects of the rotory but a raging success in the automotive
world it has not ever been. Sure you can get it in old RX-7's and new
RX-8's, but that's it. If it were such a great alternative, everyone
would be trying to build one.

I don't quite understand how Tracy manages to get the kind of fuel
burn he claims but I suspect he isn't running it very hard because the
amount of surface area the rotors are exposed to as they rotate is
much greater than that in a piston type engine. This much greater
combustion chamber exposed surface area means much more fuel can
condense on the surface. It means it's going to get poorer gas milage
inherently, unless you unleash the electronics engineers to do their
magic with fuel injection and all the other gadgets that are used to
emeliorate the situation.

The problem is, you don't get that stuff when you put it in a
homebuilt airplane unless you rip out all the sensors and the entire
wiring harness to go along with it.

So yes, it's a very very solid engine but like so many things in
aviation, it has it's compromises.

Corky Scott

Now now Bellsouth, let's not get too worked up over this. I agree on
most aspects of the rotory but a raging success in the automotive
world it has not ever been. Sure you can get it in old RX-7's and new
RX-8's, but that's it. If it were such a great alternative, everyone
would be trying to build one.

Hi Corky,

Finally fixed the "Bellsouth News Server" name. I left that all generic
after the last time I got spam attacked on one of these groups. We'll see
if it comes up as my real name this time.

Certainly the rotary cost's Mazda a bit more to make, but I would assume
that's true of any automakers flagship engine. They also don't put their
top engine in everything they make. Ever heard of a Dodge Hemi Neon :-)
Seriously, the rotary is a bit of a specialty engine, but those of us who
bet our lives on them believe that those special qualities are what makes
them the best choice. Still, if they have to be in every vehicle on the
road to be a raging success in the automotive world, then I guess they're
not :-)

Breaks over, back to the single rotor in the garage.

Cheers,
Rusty

Bill Daniels wrote:
I think there are theoetical factors against the Wankel-type rotary.

The combustion chamber shape is far from ideal and there isn't a straight
forward way to correct that. As a result, the engine leaks a lot of heat in
exhaust gasses as well as through the cooling system so there is less energy
going into producing power. All else equal (and it rarely is), the rotary
will have worse specific fuel consumption than a crank and piston.

Old pistons have one rarely discussed advantage. In the interval between
ignition and the beginning of the power stroke, piston motion is very low
and the volume of the combustion chamber is close to constant. This allows
combustion to run to completion under near ideal conditions of temperature
and pressure. That squeezes more heat calories, and therefore power, out of
the fuel-air mixture.

Bill Daniels
(I loved my RX-7)


Any loss of BSFC at speed is nearly all compensated for through extreme
leaning made possible by charge stratification (centrifugal force throws
gas fumes to the outside of the chamber, where the plugs just happen to
be). In real world airplane (vs. imaginary ones), there is no
difference in rotaries vs pistons. Furthermore, the BSFC Lycoming
et.al. publish is for a engine running on a test stand. In the real
world, most pilots run rich to protect valves.



--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Bob Kuykendall wrote:

And further, since most of the patents that cover the Wankel
innovations are now expired or are about to expire, you'd expect to see
other manufacturers adopting the Wankel. That you don't see this tends
to support Corky's argument that for the vast majority of engine
applications the Wankel's disadvantages outweigh its advantages.


If by "vast majority", you mean automobiles, then you a absolutely
correct. An automobile is one of the worst possible applications for a
rotary. The low end torque isn't there, and Mazda has to go through all
sorts of contortions to get some. Rotaries like to rev fast and stay
that way, and really suck at the low end.

Where the engine will shine is situations where the low end grunt is
unecessary, and they can rev to 6000RPM or more and stay there..
Airplanes and power generation are two examples that come to mind.
Expect to see more AIRPLANE ENGINES using the rotary concepts as the
patents run out.

The biggest disadvantages right now is low volume. GM or Ford won't
touch a design that is meant for a few thousand per year. Mechanics
have neither the time nor inclination to learn about an engine they'll
very rarely see. But Lycoming is already working at those sorts of
volumes. It becomes a non issue.

The second quoted problem is a red herring. BSFC. The rotary leans MUCH
better than any piston engine. In actual practice in real airplanes,
fuel burn is indistinguishable.

But the advantages. An engine that will sacrifice itself to get you
home. A $500 rebuild that takes a weekend. Power to weight ratios that
already beat pistons and continue to climb. Did I mention, an engine
that will sacrifice itself to get you home.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Corky Scott wrote:

I don't quite understand how Tracy manages to get the kind of fuel
burn he claims

he reaches up and turns down that mixture button. The charge stratifies
in a rotary, pushing the fuel charge out to the plugs.

but I suspect he isn't running it very hard because the
amount of surface area the rotors are exposed to as they rotate is
much greater than that in a piston type engine. This much greater
combustion chamber exposed surface area means much more fuel can
condense on the surface.

Running at 6000RPM vs 2500 doesn't leave much time for fuel condensing.
It is true, though. The rotary doesn't get complete fuel burn,
especially at the little pointy ends of the chamber. But the
counterpoint is that most pilot run rich to keep from cooking their
valves. No valves in a rotary.

Besides, all that extra energy left in the exhaust need not be wasted in
an airplane engine.

It means it's going to get poorer gas milage
inherently, unless you unleash the electronics engineers to do their
magic with fuel injection and all the other gadgets that are used to
emeliorate the situation.

The problem is, you don't get that stuff when you put it in a
homebuilt airplane unless you rip out all the sensors and the entire
wiring harness to go along with it.

Tracy is an electronics engineer 8*)
I bought 42lb Ford injectors, still have to get LS1 (from GM I believe)
coils. Tracy's controller is around $800. All the other sensor you
need are attached to the engine when you pull it out of the car. You
get them unless you go through a lot of trouble to leave them behind.


So yes, it's a very very solid engine but like so many things in
aviation, it has it's compromises.

Have I mentioned in this thread that it will sacrifice itself to get you
home. Even on one rotor, it will keep making enough power to keep most
GA planes in the air until you shut it off. To me, it takes a lot to
compromise away that much safety.


--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Mark Smith wrote:
Frank van der Hulst wrote:

Bellsouth News Server wrote:

What would be better than a single, would be a smaller two rotary.

Whatever happened to the motorcycle rotaries? IIRC Suzuki had a 500cc
rotary in a motorcycle about 20 years ago. And Norton too?

I'd guess that a rotary of this size would be ideal for a microlight
aircraft.



All this talk about the rotary engine.

If they were this great, would there not be at least a couple cars
running them ?
Mazda RX-8 Renesis. The 6 speed manual transmission model makes around
250 hp without being turbo or super charged. The core 'short block'
engine weighs around 170 lbs. They are perfectly happy making rated hp &
more all day long as long as they have proper oil & water temps.

The reason for so much talk about them as a/c engines is that the core
engine is just about bullet proof at any power level likely to be used
in a GA aircraft. If someone made a small 2 rotor it would likely be
slightly heavier than a 2 stroke of equivalent power but much lighter
than a 4 stroke & have much higher reliability than the 4 stroke. The
guys flying the 2 rotor Mazda engines say the fuel burn is only slightly
worse than Lycomings of equivalent power so there's not much penalty there.

It's actually better suited to a/c use than in cars, due to the way it
responds to intake tuning & the fact that it's not very fuel efficient
until power output is at a high level, unlike piston engines. The cars
have incredible Rube Goldberg intakes to keep the engine 'on the pipe'
over a wide range of rpms; this isn't needed in an aircraft. It responds
to intake tuning like 2 strokes respond to exhaust tuning. (It's a true
4 stroke engine, though.)

More than you ever wanted to know?

Charlie

Excellent points, Ernest.

As far as the combustion chamber efficiency is concerned, the rotary is at a
slight disadvanatage -- at least in theory. However, the piston engine has
more friction and pumping losses.

Think of just the power required to drive the camshaft and open the valves
against the springs. The rotary doesn't have a cam, or valves. Also a lot
less bearing surfaces to cause frictional losses.

I agree with the opinion that the rotary is ideally suited for airplanes. I
understand that with Tracy's controller the engine will happily run 200
degrees lean of peak. Try doing that with a Lycoming.

Most important all, the thing is almost impossible to break, as Ernest
pointed out. As long as the supporting systems are properly implemented --
and therein lies the rub -- the engine itself is practically bullet proof.

Regards,

Gordon.

PS: Rusty, thanks for the info on the gearbox. That Hirth box or something
similar sounds like a good way to go. 170 lbs is outstanding for a 100hp
engine -- could be even more with peripheral porting.

Best of luck with your Kolb project. I hope you will have some pictures
available.


"Ernest Christley" wrote in message
. com...
Corky Scott wrote:

I don't quite understand how Tracy manages to get the kind of fuel
burn he claims

he reaches up and turns down that mixture button. The charge stratifies
in a rotary, pushing the fuel charge out to the plugs.

but I suspect he isn't running it very hard because the
amount of surface area the rotors are exposed to as they rotate is
much greater than that in a piston type engine. This much greater
combustion chamber exposed surface area means much more fuel can
condense on the surface.

Running at 6000RPM vs 2500 doesn't leave much time for fuel condensing. It
is true, though. The rotary doesn't get complete fuel burn, especially at
the little pointy ends of the chamber. But the counterpoint is that most
pilot run rich to keep from cooking their valves. No valves in a rotary.

Besides, all that extra energy left in the exhaust need not be wasted in
an airplane engine.

It means it's going to get poorer gas milage
inherently, unless you unleash the electronics engineers to do their
magic with fuel injection and all the other gadgets that are used to
emeliorate the situation. The problem is, you don't get that stuff when
you put it in a
homebuilt airplane unless you rip out all the sensors and the entire
wiring harness to go along with it.

Tracy is an electronics engineer 8*)
I bought 42lb Ford injectors, still have to get LS1 (from GM I believe)
coils. Tracy's controller is around $800. All the other sensor you need
are attached to the engine when you pull it out of the car. You get them
unless you go through a lot of trouble to leave them behind.


So yes, it's a very very solid engine but like so many things in
aviation, it has it's compromises.

Have I mentioned in this thread that it will sacrifice itself to get you
home. Even on one rotor, it will keep making enough power to keep most GA
planes in the air until you shut it off. To me, it takes a lot to
compromise away that much safety.


--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."