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
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