Today's Message Index:
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1. 07:44 AM - Re: Electrical System with Dual Batteries & Brownout Prevent (user9253)
2. 11:29 AM - Intercom question (jrevens)
3. 02:52 PM - Re: Power Generation without Battery? (ChrisM)
Message 1
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| Subject: | Re: Electrical System with Dual Batteries & Brownout |
Prevent
Updated pdf Feb 3, 2015
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Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=438009#438009
Message 2
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| Subject: | Intercom question |
My EAA chapter has spawned a group of young people known as the "Young Aviators".
They are constructing a mockup of a B-25 that they are planning to transport
to Oshkosh this year. A question has come up... is there a simple way to hook
up 7 individual headsets w/ microphones so that the entire "crew" can talk back
& forth, without having to somehow patch together off the shelf 4 or 2 place
intercoms? Some kind of simple circuitry that could be easily built? Thanks
in advance for any ideas or suggestions.
John Evens
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John Evens
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=438022#438022
Message 3
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| Subject: | Re: Power Generation without Battery? |
Hi Bob,
Thank you for hanging in there with me as I continue to learn. I feel I am getting
my moneys worth.
Most of us here are really interested in how Li will fit in the OBAM aircraft world.
Based on my own study and what I have learned here, I do feel Li is a good
choice for my design. You asked about the definition of design success - Doesn't
that change a bit with each aircraft and mission? Refining success is one
of the satisfying things about working with OBAM aircraft. Each design decision,
by itself, can be considered to be a success or not depending on how wisely
risks and benefits which apply to the specific problem at hand are evaluated
and applied.
I think design success for me does involve a Li battery. Seems to me that Li is
becoming the clear choice for most light weight aircraft with electrical systems
tasking the battery primarily with starting duties. I'll try and explain my
thinking...
One of the major seminal concepts for the plane I am constructing is light weight.
It's a clean sheet design, and weight figured in all the decisions made by
the airframe engineers. If weight had been ignored in a few of those decisions,
it wouldn't have crippled the design. But if weight consciousness was repeatedly
ignored thru a thousand decisions, then it would have resulted in a poor/heavy
design.
I think your question What are the performance improvement numbers..... is narrowly
phrased to provoke thought about the bigger picture. It points to the folly
of making a decision which favors weight savings excessively in favor of other
parameters like cost, reliability etc etc. Practically speaking, a single
decision to adopt a heavy solution in an airplane cannot easily be quantified
from a performance functionality point of view. But I think that still qualifies
as a compromised decision from an engineering point of view, if lightweight
is one legitimate priority for the aircraft. I think decisions as builder need
to remain generally in alignment with the original concept, or one probably
should be building a different aircraft.
My understanding from lurking here is that, aside from endurance, Li with a BMS,
has become a functionally equivalent stand-in for lead acid. If light weight
is one prominent priority for a given design, the 10# or so one saves, for the
$200 or so it costs, is very cost effective when compared with widely accepted
weight saving techniques. The real engineers have already spent a lot more
than that on solutions to eliminate 10#. One of my goals as builder and supplemental
designer, is to not screw up their work. I agree that impact on performance
cannot be specifically quantified, but that has more to do with the nature
of aviation itself. But the 10# weight reduction is objective, and it's a
legitimate achievement because we do know it translates to improved performance.
I think I'll carry a small spare power source until I have personal experience with the Li technology. My single Li battery will be the only way to start the engine. I don't want to be surprised by some nuance of Li technology after landing on a gravel bar. Pmags apparently will not self excite with hand propping they must have some external power to initialize function. The BMS in an EarthX apparently shuts off the battery under certain circumstances need to learn more about it. Resetting the BMS requires external power. EarthX seems to have come up with this device: http://earthxmotorsports.com/shop/earthx-jump-pack/
I appreciate comments questioning costs of presumptively assuming 10 amps for the
EFII, when the figures might be only partially vetted or motivated by some
other issue besides real engineering. If I end up going that route I will explore
thoroughly.
I think no vacuum pump for this plane. Single alternator. If the battery or alternator
fails, I will turn off the electrical system and navigate by tablet or
smart phone. I'll use the radio on arrival at a landing site if it's operational
- or not.
I don't think the SD-8 does anything but add unneeded weight to the Pmag/Bendix
type injection design. I don't need additional inflight power sources with self
sustaining fuel and ignition systems. I think my weakest link could be engine
starting, and the SD-8 won't help with that.
I am going to focus on getting the Li done right!
Chris M
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ChrisM
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=438031#438031
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