Hi Chris:
I was thinking about the Whirlwind prop also. The concerns I had also
matched yours, vis a vie having to go electric because of the loss of
the PTO to the pump. The expense is notable. Another consideration I had
was the fact that using a 914 you use Wirlwinds 2 blade prop in a condition
where the tips of the prop blades are not trimmed shorter as in Kim Prout's
application. My concern is the greater suseptibility of a prop
strike with the larger diameter disk. I am anticipating a ride on the
"wild side" while getting used to the monowheel landing configuration during
initial flights.
At Sun and Fun I saw the Airmaster prop and was fairly impressed. Another
Europa owner swears by it. Being electrically activated you are not constantly
running a pump. They are supposed to offer a fully feathering model shortly so
you can feather it with a totally dead engine. Handily increasing engine
out glide (theoretically). One concern I have with the geared Rotax engine
is being able to air start a dead engine with a bad starter. Being able to
dither the pitch may be of some use in an emergency to get the prop turning in
the air. The warp drive prop blades are also pretty easy to come by when
dings occur.
Just some thoughts.
Steve Hagar
A143
N40SH
Mesa, AZ
----- Original Message -----
From: Chris and Susan Beck
Subject: Re: Speeding up the
Rotax 914 Vacuum Pump PTO
This is a timely topic for us here, too. I've
been exploring the options of what instruments, prop, etc. I want to start
planning now for down the road a bit. I really don't want to hang a vacuum
pump on the Rotax, with the extra complexity and maintenance. A good,
solid, all electric system seems the way to to. However, electric horizons
and DG's are over 2x as expensive as the vacuum powered brethren. That blows
away any savings of loosing the vacuum system, no? It's hard to justify
$2K more on the panel to have electric instruments.
I was also thinking of the Whirlwind prop, I think it is, that is hydraulic
constant speed? Seems like a great prop, if expensive, but that will suck
up the space needed for either a separate alternator or vacuum pump. I
guess we can't have our cake and eat it too...
Chris
A159
Shaun Simpkins wrote:
Hi, me again. I've been exploring going all-electric and was looking
at the B C Specialties alternators that run off the vacuum pump PTO on the
Rotax 914. An extra 5-10 Amps would be quite nice to have, as well as the
redundancy, given that only about 10-12A is left over for everything in the
plane after the engine pumps and computer take their
portion. The little 8-amp
alternator would be great, except for the fact that the Rotax PTO runs at only
54% engine speed, which at typical cruise RPMs is below the knee of the
alternator's output curve - only 3.2 to 4.3 A are available. Their 20-A
alternator could also be used, and would generate about 10A, but it's twice as
heavy and quite tall. Bill at
B C told me that someone at Sun'n'Fun claimed to have made a simple change
to the PTO gearing in the engine block to get the PTO RPMs up to the 3500 range
that these alternators prefer. So - anybody know anything about this? Is
this possible without tearing the engine block apart, and, more importantly,
voiding the warranty? Anyone install the 20A
alternator? Yep, you guessed
it, the prop will be electric, too. Motorglider. Thanks, Shaun SimpkinsA207
--- Steve Hagar
--- hagargs@earthlink.net
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