nuckollsr(at)cox.net Guest
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Posted: Thu Jan 05, 2006 10:46 am Post subject: More SD8 Installation Questions |
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At 10:25 PM 12/26/2005 +0100, you wrote:
Hello Bob
> This alternator was very popular
> with Rutan's Variez builders looking for the ultimate in
> light weight installations with no starter and minimum
> battery. As the ONLY source of engine driven power, many
> of these builders flew VFR night conditions where nav lts,
> strobe and one radio were the only loads.
As far as I know they had a Conti O-200 so they had the 1 : 1.5 gear
From my old load analysis this would be (measured with 12.5 V):
Strobes 3.1 A
Nav 3.96 A
Position 3.44 A
KX-125 0.4 A
In cruise with 12.5 V I see that the SD-8 delivers around 10.6 A the
load without transmission would be according the numbers I measured on
my Aeroflash units 10.9 A. Did I calculate someting wrong or did they
use lower consumation units? The advantage without starter is, that the
battery is still plenty full, but on the ground we would drain the whole
load on the battery only and in cruise we just generate as much energy
as in a NVFR situation is used. I guess this is a thight situation on
the electrical side and one has to make a good calculation as to decide
what to do.
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Sorry for the delay in responding. I had to think about this
a bit. First, it was my error to cite the SD-8 as popular with
B&C's earliest customers building the Rutan Ez series airplanes.
The 200G was driven from a gear drive pad on the -12 case for
the O-200 and runs faster. This alternator is rated at 12.0A
and probably good for a tad more at depressed bus voltages still
high enough not to discharge the battery.
You're correct, an SD-8 would be undersized to support
a night vfr load without going to LED nav lights and perhaps
a lighter strobe.
Bob . . .
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