light twins?

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)."

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.

Thanks Gordon. BTW, Richard Sohn's 12A single rotor is peripheral ported.

PP vs the normal side ports is a hotly contested issue on the rotary list,
and I personally believe it's not worth doing for our 7500 rpm range. I've
been told that a good porting job on 3rd gen housings will get you the same
power as PP at the same rpm. The side ports will lose big if you're going
to run up to 9000 rpm or so, but we don't. There are a number of folks who
are very committed to the PP tests, and are using smaller than "normal" PP
ports, to improve the performance at our rpms, but until some of them are
running, and can be compared to what's already out there, we won't know.

Numbers I've heard for 7500 rpm for a single rotor with side ports are
upwards of 120 HP. Since you have to have a muffler of some type, and since
turbos seem to work pretty well as mufflers, I'm planning to use a small
Garrett turbo as my muffler. It's probaby not much heavier than a muffler,
and associated pipe would be, so it's not that much of a weight penalty. If
you choose to run the boost that you could get from the turbo, it should be
closer to 180 HP. For the Kolb, this would be insane, so I'll have to limit
the rpm, and boost to keep the power down to what the airframe can handle.
Folks have used 100 HP Rotax engines on the SlingShot, so the plan would be
to not exceed that by much, unless some 912S driver needs a lesson :-)

As you may know, Mazda went to NO peripheral ports on the Renesis, which
means they took the exhaust port off the rotor housing as well. Now all
ports are on the side housings, which allows them to have no overlap, but
still have improved power. This also has the benefit of slowing the
exhaust, which helps quiet it some, as well as reducing the temp of the
exhaust. Unfortunately, the temp seems to be picked up by the cooling system
now, so there's a bit of a trade-off there.

Cheers,
Rusty

What is the installed weight of a 12A?



"Russell Duffy" wrote in message
...
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.

Thanks Gordon. BTW, Richard Sohn's 12A single rotor is peripheral ported.

PP vs the normal side ports is a hotly contested issue on the rotary list,
and I personally believe it's not worth doing for our 7500 rpm range.
I've been told that a good porting job on 3rd gen housings will get you
the same power as PP at the same rpm. The side ports will lose big if
you're going to run up to 9000 rpm or so, but we don't. There are a
number of folks who are very committed to the PP tests, and are using
smaller than "normal" PP ports, to improve the performance at our rpms,
but until some of them are running, and can be compared to what's already
out there, we won't know.

Numbers I've heard for 7500 rpm for a single rotor with side ports are
upwards of 120 HP. Since you have to have a muffler of some type, and
since turbos seem to work pretty well as mufflers, I'm planning to use a
small Garrett turbo as my muffler. It's probaby not much heavier than a
muffler, and associated pipe would be, so it's not that much of a weight
penalty. If you choose to run the boost that you could get from the
turbo, it should be closer to 180 HP. For the Kolb, this would be insane,
so I'll have to limit the rpm, and boost to keep the power down to what
the airframe can handle. Folks have used 100 HP Rotax engines on the
SlingShot, so the plan would be to not exceed that by much, unless some
912S driver needs a lesson :-)

As you may know, Mazda went to NO peripheral ports on the Renesis, which
means they took the exhaust port off the rotor housing as well. Now all
ports are on the side housings, which allows them to have no overlap, but
still have improved power. This also has the benefit of slowing the
exhaust, which helps quiet it some, as well as reducing the temp of the
exhaust. Unfortunately, the temp seems to be picked up by the cooling
system now, so there's a bit of a trade-off there.

Cheers,
Rusty