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I'd spoken to Martin at sun n fun last year about an airmaster prop and he recommended his electric hub with whirlwind blades, AP533 blades i think it was. You can choose any blades you like on his hub. If going over 220hp with a p-port he recommended going with 3 blades to soak up the additional hp FWIW. It all sounded good until the price, about $14k with shipping was too big a chunk for me to consider, nice looking equipment though, expecially the electric governor
Alex Molteno Hi guys, I just spoke with Martin of Airmaster at Sun n Fun. He seems to be one of the main engineers(very knowledgable). I asked him if he could make me 2, C/S, electric, reversible, feathering props for my twin 350 hp rotary amphibian. The bottom line is yes, 5 blade to absorb the hp, about45#, around the same price as my MT quote but they will have to work out the details of my operational control requirements over the next few months.( I am at least 2 years from needing the props.) Electric seems to be where I am headed unless someone out there knows where I can get 2 Mistral PSRU's. James whitehurst
Well, now I know that I should proof
read before hitting send....
On 4/5/2019 3:46 PM, Charlie England ceengland7@gmail.com wrote:
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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