Mike Wills wrote:
Lets see, assuming we take your previous statement as true these engines
have been in production for only 50 years instead of the 65 years stated
earlier. Now also assuming that the production numbers are anywhere near
what you cite above. What I'd like to know is after 50 years of trying, in
relatively low production numbers, with reams of paperwork certifying the
things, sold for exhorbitant prices, why is it that they still cant get it
right?
ADs out the wazoo that owners are happy to step up and pay for out of
their own pockets. And yet most times when you tell another pilot/builder
you are putting an auto conversion in your plane they assume your some sort
of idiot. These guys paid $20K+ for an engine that may have come from the
factory with a bad crank (just one example) and I'm an idiot ????
Mike Wills
Bill Freeman wrote:
I agree with you and have said repeatedly, that Lyc and Continental are not
doing
a good job. They are inefficient, they are making many mistakes and I'm sure
that they could do a better job. How would you have avoided the crankshaft
AD? Just a pure guess, but I'd bet that Continental farmed it out to a
forging house with a 3 inch stack of specs that the supplier was contractually
obliged to comply with. Apparently they didn't comply. Continental's
failing is probably in not providing adequate testing of what was delivered
by the contractor. Of course, this testing costs a lot of money, which is
another reason why their cranks cost tens of thousands of dollars. Damned
if you do, damned if you don't. I bet I could do better, but might be wrong.
Our primary difference is that I think I at least partially understand how
their regulatory requirements and small production lots makes this a very
difficult job.
Again, I think that Lyc and Continental are not doing a good job. I wish
they could sell enough engines to keep a large staff of excellent engineers
and technicians around and do a better job. The current rate of GA sales
makes it unlikely. In the middle '70s about 15,000 GA aircraft were sold
per year. That production rate would help things a lot.
Also - have you priced a 150hp outboard motor? I think you might be
surprised, they are very expensive. They consist of a motor and a couple
short shafts and a prop. Basically you are buying an engine. Check it
out.
Bill
The Continental crank problem was caused by a defective
tool pressing a bushing into the crank cheek. It caused a
nick in the cheek which rapidly led to a fatigue failure.
These AC piston engines of necessity are highly stressed.
Otherwise they would be a lot heavier than they are for the
power generated and the high duty cycle. In other words
the parts are small for the loads they are required to handle.
That is why HD truck engines are so heavy with similar power
and duty cycle. As such AC piston engines are very sensitive
to manufacturing defects. It is the nature of the aircraft
piston engine beast. There is no way around it. GM, Ford or
Toyota could make them and nothing would change.
On the other hand the rotary is lightly stressed for the
same power to weight ratio. For one example many loads
are more or less contained within the one piece cast iron
rotor. Another example is the e-shaft. It is more or less straight
through the engine with very few stress concentrations that
are highly characteristic of the piston engine crank shaft.
Not to mention no exhaust valves that are banging up and down
at 1300 times per minute while resisting up to 1700 degrees F.
I could go on and on.
The wankle rotary is the engine of the future. It will take awhile
for this to happen in the automotive world but I will bet it will
happen in the light aircraft field in the relative near future.
Paul Lamar
Fred Mooers wrote:
Please allow me to add my 2 cents. the piston vs the rotary. The piston
lost out to a turbine and a jet,
why wouldn't it lose out to a wankel, which is essentially an internal
turbine or jet. It has a single spin
vs up and down, start and stop.
Exisiting plants and investments are what keep the piston engines
running.
Look at the corporations that have heavy investments in piston
technology and you can see the economic forces at play.
Quite a few years ago a turbine challenged at the Indy 500 for a couple
of years. What happened to it. It was outlawed. Why?
Piston technology ruled. Open for speculation, hardly. Some battles are
won one step at a time.
Many are interested enough in rotaries, to push the limits. Thank God
for expermentials and
those who are willing to try someting new.
Saayyyyy, doesen't that sound an awful lot like a couple of Wright
Bros.................
Just my opinion.
Fred Mooers
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