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I had a similar experience with one of
the guys with AutoPSRUs in the alt engine tent a couple of years
ago. Tried to sell me a reduction for a rotary, and it was
blatantly obvious that he was clueless. But their whole concept
has major flaws, so I shouldn't have been surprised.
As a FWIW, if you're serious about a controllable prop it might be
worth finding someone else in the company to question. My
experience at airshows in general is that you might get the CEO,
or you might get a guy that's filling in for his friend who went
to take a leak. :-) I know, because about 25 years ago, I was
occasionally that guy on occasion. :-)
Charlie
On 4/5/2019 8:47 AM, Samuel Hodges samueln462wp@att.net wrote:
Went to Sun n Fun and talked to a
Aeromaster representative to collect information and data on
their Electric constant speed prop combinations. After waiting a
little while a representative of the company approached as asked
what he can do for me. I replied that I am extremely interested
in their design and would like further information. I was asked
about my aircraft engine installation, I explained to him about
the Rotary and what my RPM requirements would be. His response
went something like this " Do you know how much this cost? it
will probably double the cost of your installation/plane" I
immediately took this as an insult and replied " you know
nothing of me, my finances, nor my plane" as I walked past him I
padded him on the arm and said " keep your freakin prop, you
just saved me a lot of money" but I didn't say freakin. One
thing I did find out is that it would be around 26lbs, well
worth the trip, wouldn't you agree?
Sam
Climb at 6800/ 2100 rpm
Correction 6000/ 2100 rpm.
Bobby
Sent
from my iPhone
Bill,
Most takeoffs have been at 7000/2400 rpm with
MP between 34-38” to pattern.
Climb at 6800/ 2100 rpm
Cruise at 5200/ 1824 or 4800/ 1624 rpm
depending on my desired fuel burn and airspeed.
Most cross country flight are at 28-30” MP and
with F/A 15.8. Or 13.5 for higher MP.
Bobby
Sent from my iPhone
Bobby, You push it fairly
hard with your supercharged engine too.
What cruise RPM are you running? P.Sport
always tried to tune for lower RPMS and
higher power to avoid the torsional
vibration problems. With boost you can
make more power at lower RPMs which is a
plus in this case.
The rotary is tough, the engine will
tolerate a lot, but the high revs for long
periods is what causes the need for
attention to torsionals. BTW I moved and
had to take a break from my redrive
efforts, but am getting back to it. Got
some good ideas today from Mark Hatch,
Everett's son.
Bill
My MT weighs 42#’s. The hub is
heavy, blades are light weigh. Gear
lashing appears to have increased a
little over the first 500 hours. End
play is about 5 thousandths with
original snubber.
Bobby
Sent from my iPad
Sam,
I am working with some
originators of Powersport.
The weight of your build
makes a big difference on
the use of a constant speed.
Also in the case of the
rotary the quality of your
muffler! Sound levels really
effect your comfort on
longer flights. Mufflers for
rotaries are tough, I
already have 1 failed design
to my (bad) credit. The
original Powersport
designs used the light
weight and flexibility of a
wood prop to their
advantage. Those engines
were tuned for max power at
6500 RPM. The reductions
were about 1.85 to 2.2:1.
suitable for the lower power
peak. Torsional vibration
issues also favored a wood
prop. How heavy is the
electric Airmaster?
MOST engines including the
rotary are helped by a
variable pitch prop. Whether
the combination is safe
depends on the reduction
drive, ratio, and weight of
the prop on the output
shaft. Powersport's
owners noted significant
torsional vibration problems
with every planetary gear
set, (even their own custom
made straight cut
planetary). Their later
stiff model internal ring
gear reduction gearbox put
the resonances out of the
normal range for the rotary.
Prior to that the only
problem free build with a
planetary was when they
built a pendulous damper
system (like a big radial
engine uses) which worked
great but was so expensive
they figured they would
never sell an engine. So if
you are running a planetary
reduction you need to keep
the weight down as much as
you can. Find out what the Airmaster
weighs. The amount that it
exceeds your wood or carbon
fixed blade prop is your
risk factor. The advantage
is to use a low cruise rpm
that takes advantage of the
props flexibility. As a
thrust producing device it
is better, there is no
doubt. If it is very heavy
though it may cause problems
that aren't obvious as to
origin. Torsional problems
may take hundreds of hours
to develop, or something may
break the first week. Just
be wary. Always keep track
of things like changes in
output shaft end play and
backlash. You can make the
change, and see excellent
results but go in with your
eyes open. Lots of people
will tell you this is
nervous nelly stuff, but the
guys at P.S. probably had
more hours running and
testing rotaries AT HIGH
OUTPUT levels than anyone
other than Mazda.
Bill Jepson
Lately I have been
considering an
Airmaster electric
constant speed prop to
help achieve the
rotaries true
potential. I am asking
for insight to help me
make this decision.
I'm not sure if the
benefits of a constant
speed out weight the
cost, please help.
Sam
RV-7A
Renesis
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