David Leonard wrote:
Ed, don't forget that the Powersport's engine is putting out a few
more horses - necessarily creating
more heat. I would be very surprised if Keith and the Powersport crew
never bothered to properly
tune and map their engine.
Lets face it, Powersport is doing a better job than most of us. They
make a first class installation
and its only the first class price that has kept many of us away. Of
course, everyone does something
different from the way `I' would do it. In retrospect they see that
they would have done some things
differently, but won't we all? I am very sorry to see this happen. The
negative publicity is
unfortunate and undeserved.
Paul Lamar responded:
Dave, EGT's are the same regardless of the HP. If what you say were
true radial engines would melt
exhaust valves in seconds.
IMHO they need more negative publicity not less :) Most stubborn,
closed minded and not invented here
people I can think of right at the moment:)
Good grief, Paul! Who pissed in your Post Toasties(tm) this morning?
Bad for your karma to wish bad
things on another.
And BTW, I think David's premise has some merit: for the same
displacement, EGT goes as HP goes. This
is because the engine's efficiency at extracting useful work is somewhat
fixed (percentage-wise). As
the amount of useful work extracted goes up, the amount of waste heat
also goes up. But the exhaust
system's ability to shed that waste heat is somewhat fixed (as delta T
goes up it gets better, but not
as fast as the delta T is increasing). Thus, burned exhaust valves,
burned exhaust manifolds, burned
mufflers, ...
Your "melting radial exhaust valves" is a red herring because the radial
engines have a larger
displacement than the usual 4 or 6 banger. I'd speculate that the
radial engine's HP per cubic inch is
in the vicinity of the O-360's HP per cubic inch.
Russell Kent
Power Sport needs a wake up call. I have been talking to them for years
about certain things. I suggested they sell engine parts instead of
complete fire wall forward packages to jump start the market
five years ago. They ignored me. The slow growth of the market for rotary
powered airplanes proves I was right. Only now are we seeing
off the shelf motor mounts and intake manifold parts.
We still have a ways to go on exhaust systems and other needed
parts. Ironically their firewall forward business would be way
head of where it is now.
We had a huge go around in private about
bad mouthing planetary gear boxes. On their web site and on here.
I refused to publish their bad mouthing planetaries on here.
Their overly heavy and too expensive spur gear box was the only
way to go according to them. Tens of thousands of hours behind
rotary engines has proven the light weight Ford planetary
can do the job.
As you pointed out it is bad for your karma and bad for your business
to bad mouth your competitors. I don't give a damn as I am not
in this to make money.
They refuse to move the rad on their RV6 after years of inadequate
cooling. "By God the best place for the rad is in front of the
firewall and we will make it work come hell or high water."
I am paraphrasing of course. The exposure they get on this feature
in Sport Aviation, Kitplanes and the web somehow legitimizes
the location and is a trap for new people starting
out installing the rotary. I offered my hangar space, living
quarters and machine shop free if they wanted to do some cooling
development in a hotter climate than Minneapolis in the winter
time. The offer was greeted with silence.
They never show up with the airplane at Sun & Fun, Arlington
or Copper State. To fly that far and to those locations would
be a real test of the cooling system.
They no longer enter the Sun 100 cross country race as
Everett Hatch and Allan Tolle did religiously. This slowed
the acceptance of the rotary to a crawl. Allan Tolle went
238 MPH and had the fastest time to climb five years ago!
Where would we be today if Everett was still alive?
They continue to put the fuel injection on the hot side
of the engine. We have had four in flight fires and one fatality
mostly due to this feature. All well publicized on this news letter.
Some as long ago as three years.
I have no doubt they ignored the data provided by Tracy and others
on the mapping of the fuel injection computer showing that the
exhaust temps came way down when you leaned the rotary engine
a couple of hundred degrees lean of peak during cruise. The same
as a piston engine but unlike a piston engine the rotary will
run fine at 200 degrees lean of peak.
I will say one thing. They abandoned the oil to water heat
exchanger.
Now as to yours and Dave's education on EGTs. The P&W R2800 was 2800
HP. That is one HP per cubic inch. The Lycoming O-360 is
180 HP or .5 HP per cubic inch. The EGT's are the same.
The same goes for the RR Merlin. Late versions of which were
well over one HP per cubic inch. The EGT's were the same.
The rotary engine is the exception to the rule as a higher percentage
of the total heat is wasted in the exhaust. You and Dave are
confusing the TEMPERATURE of the waste heat with the QUANTITY
of waste heat.
Paul Lamar
You should have posted their bad mouthing of planetary gear sets Paul. I
could have easily won that argument. I have had a discussion with one of
their engineers at Oshkosh about the subject. They really do not seem to
understand torsional vibration or gear box design. Using the technique of
reducing the lash to zero and trying to make as stiff a system as possible
results in a heavy expensive and wear prone gear box. In mechanical
engineering design one of the things you learn is that there must be some
lash in a system to allow for thermal expansion of the system under
operation. If you adjust out all of the lash the gears when cold, they wind
up in a bind under operating conditions. That is why the terms hot lash and
cold lash exist. The gears wear under such conditions, so you have to
continuously decrease the lash to keep the system stiff with resonant
frequency above the operating point. There are two approaches to designing a
gear box, heavy and stiff, or light and springy designed to resonate below
the operating point. The heavy and stiff approach is fine for tractors and
stationary equipment, but not aircraft. Anyway I could write an essay here,
but I digress. The bottom line is the planetary sets probably have more
hours of in flight operation than their gear box and so far none of the
dire,horrible things they predict has happened in an appropriately designed
planetary reduction. Touting a large beefy gearbox with a special way to
adjust the lash to zero may impress people who do not understand the
engineering involved, but it is not the way to go.
Monty
We did some of it. Long before you were on here Monty :)
Thanks for the additional insight.
Paul Lamar
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