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al p wick wrote:
Wow. The emotional responses! Take a look at my statement: "It only has
three moving parts, therefore it's safer". I can't believe all the stuff
you guys are reading into it!
All other things being equal, YES. A device with
three shoddy parts just might not be as reliable as one with 500
carefully designed and manufactured parts. If the 3-part device is
operated much more strenuously than the 500-part device, it might or
might not be as reliable.
Let me explain. If your goal is to determine if one thing is safer than
another...guess what? Counting the number of pieces is NOT the definition
of safety. You have to look at the whole picture. You don't focus on one
feature.
Early on, absent reliable system failure data,
given roughly equivalent engineering manufacturing standards, it is the
ONLY DEFINITION AVAILABLE. Provided the data is available, one can
study the reliability of parts and components and subsystems and make
an educated guess, but as I said before, other things being equal,
parts count is a PIVOTAL consideration. If you think it's not, what,
pray tell, do you think is a better indicator??
Let's try this word experiment. Our job is to make clocks. Two types are
made. The Alwick 2000 all electronic clock and the billybob100 with 100
mechanical components. Gears, all that traditional stuff. We sell these.
At the end of a year, the customers return 1% of the Alwick 2000
electronic clock.
Customers return 50% of the Billybob 100 multi gear clocks. Seems gears 2
and 17 bind and it stops working.
Which has the higher failure risk? Well the Billybob 100 of course. The
return rate is conclusive evidence.
But what if the return rates were the opposite? Which then would be
higher risk? It would be the Alwick 2000.
So the point is, that parts count is not the definition of risk. Yes, in
many things they coincide. But you don't get to make that assumption. You
have to compare your theory to the facts.
OK. How's this: In the racing circuits:
The recip guys rebuild their engine pretty much after every race.
The rotary guys rebuild their engine at the end of the season whether
it needs it or not.
Why do you suppose that is? We're talking Toyota, Nissan, Porche,
Soob?, whoever.
-al
On Mon, 6 Jun 2005 20:48:09 -0400 WALTER B KERR <jbker@juno.com> writes:
Al W wrote:>
Here's an excellent example. I've seen people describe their
reasoning
for going rotary. Often I would hear: "It only has three moving
parts,
therefore it's safer". I suspect that 80% of you believed that.
That
is a
gross error in perspective. No maybe, it's a huge distortion. It's
a
wonderful theory, it has a component of truth in it, but totally
fails
the tests for significance. If a logical theory is not
significant,
you
dump the theory.
--------------------------------------------------------
Have stayed out of this as long as I can, but it seems strange to me
as a
gas turbine designer of 33 years that Al would make this comment
without
at least backing his words up a bit. I find it hard to believe that
a
modern technology reciprocating engine that is snapping pistons back
and
forth at 5000 rpm with cams and valves is anywhere as safe as a
rotary.
If the modern tech recip requires a PSRU and the addition of water
cooling those things components are canceling.
Having participated in many FEMA studies over the years ,I find some
of
Al's comments a bit strange. His heart may be in the right place to
try
to help us Rotorheads, but am not convinced he is helping us sort
out
what is important to take care of to eliminate failures.
Will never forget my intro to rotary's. A friend at work raced a
rotary
powered car. He took the car to the Daytona 24 hour without detuning
and
after returning he left the car on the trailer and went to miami
next
week without any additional work. This was a totally different story
from
the recip guys. They installed very expensive forged lightweight
parts
and deturned the engine. After the race they replaced all of them
before
the next event. Does that say something to you about the robustness
of
the rotary? Does to me and is one of the big reasons I am flying
one
today.
Bernie Kerr, 40 hours on 13B powered RV9A,
PS. Do I feel as comfortable with the 9A as I did when I sold the
Lycoming powered 6A ? Not Yet!
Homepage: http://www.flyrotary.com/
Archive: http://lancaironline.net/lists/flyrotary/List.html
-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
Homepage: http://www.flyrotary.com/
Archive: http://lancaironline.net/lists/flyrotary/List.html
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