I am posting this dialog to all my favorite list-servers.
There's value in everyone having an appreciation for
resources afforded to us by the 'net' and how important
it is that we utilize it to the best of our abilities. I've
guarded our friend's anomnity, I beg him not to take offense
for having quoted him so heavily. This exchange is an excellent
illustration of how the list-server should work. There are lots
of folk out there with knowlege to share. Some of it comes in
little bits, sometimes you can tap a whole career worth but no
piece of fact should be bottled up and not shared. . . .
/I would like to say thanks on behalf of myself and others
/for all the tips and help that you pass along to those of
/us who are very weak in our understanding of things electrical. . . .
Thank you for your kind words. I really enjoy working with the amateur
builders. Unlike beating your head against the wall and wailing to deaf
bean-counters and marketing managers, I believe I can make a real
difference here.
/I have two questions to ask if I may, One is regarding a "terminal block"
/which I purchased from Aircraft Spruce. This looked like such a neat
/approach to a good wiring job that I wanted to install it. I found
/however, That there is no continuous path as in a bus bar, so is this
/just used as a grounding strip ?
Those things are useless in an airplane. I complained about ACS having
them in their catalog . . . the very presence of the device implies
utility. Your goal is to make every wiring path contain as few parts
and wire segments as possible. Those rows of screws are a forest of
potential failures in wiring. Please don't use it in your airplane.
/Second, in regard to bus bars, I have seen strips of copper used
/as in a Cessna, and a friend even cut a strip from 1/2 inch water
/pipe for his . . .
Go to a hobby shop and find a piece of sheet brass packaged up
by a company called KB engineering. Get the heaviest sheet (it's
0.032" I believe) and cut 5/8" wide strips from this nice, clean
and very flat stuff. Flatness is very important and mashed pipe
simply isn't. You can also use pieces of flashing copper, some
plumbers and roofers may have some scrap around you can get for
very little money.
/and yet another friend simply used a length of copper
/house wire threaded through the back of those glass fuse holder
/breakers.
VERY poor practice. First, the cross section of the wire should be
about 10AWG if it's to carry any size of alternator loads. Those
terminals on fuse holders need to be wired with FLEXIBLE sements
so that they don't relieve internal spring tension that is already
marginal. Those fuse holders are not suitable for use in situtations
that get the temperature/humidity cycles of an airplane interior.
Fuseholders with removable caps gave fuses a bad name . . . the holders
went bad (sometimes from poor installation practice), the caps
fall on the floor, etc. . . everyone now believes that breakers are
superior and desirable.
I highly recommend the Bussman fuse blocks for the plastic,
automotive fuses. You can purchse 20 ready-to-wire, protected
circuits all assembled with bus bar for about $35. MUCH less
expensive than fuse holders, INFINITLY less expensive than breakers
and MORE reliable due to reduced parts count and uncorrupted,
gas-tight, thread-less, spring loaded connections between fuse
and fuse holder.
/I did the same since you consider that it normally carries 110 volts,
/so it should be fine and neat for an aircraft 12 volt system. What say you ?
Please consider replacing it with either breakers or pre-fab fuse
blocks. Ideally, fuses should be OUT of REACH under the panel.
You need to design your system for failure tolerance and be a mechanic
on the GROUND, not in the air. When a fuse pops, something is WRONG.
Save the trouble shooting until on the ground. My favorite examples
of how NOT to deal with electrical systems include an L-1011 where
the cockpit crew allowed a perfectly good airplane to fly into the
Everglades with a load of passengers while they were busy "fixing"
a gear-down indicator light. The second is Ricky Nelson's DC-3 which
caught fire after someone kept resetting the heater breaker because
it was getting so cold in the cabin!
Guys, I cannot stress this any too strongly. There are very simple
details which can stack against you. Let's let the spam-can drivers
do their traditional, padded cockpit, federally mandated trips down
the yellow brick road. You folk have it made . . . you don't have
to put up with systems that cost a lot to buy and maintain and will
never be updated because of short-sighted regulation and endless
bureaucracy. Just because it's flying around in 50,000 Cessnas
doesn't make it good or right, just CERTIFIED. It demonstrates,
right or wrong, how much those designs are carved in stone.
/Sorry to be so long and wordy but I have been a sideline observer
/for a few months and appreciate what you and others like you contribute
/to our knowledge base and our confidence.
That's precisely what EAA and experimental aviation is all about.
Critical design review is necessary and good and it will happen
only when we get together on the lists and share the good, bad and the
ugly. Many people are reluctant to share their unhappy experiences
but they do the rest of us a dis-service; the same experience
keeps getting repeated over and over . . . . in secret. If I had
ONE good thing to say about working in a functional design group
(I have the pleasure of participating in the ONLY one at Raytheon-
Beech) it's that we support each other, warts and all. We're damned
good at what we do and it's because we're doing it together and
when one guy stumbles, there's a dozen there to help him up.
/I also would like to keep my antennae inside the airplane ala
/copper strip as Van has done, but I am afraid I would mess it up.
So you mess it up? Then you fix it. We all got our knees
skinned up learning to ride roller skates and bicycles,
why should airplanes be any different? You can minimize the
risks by asking questions an making sure you understand what
is required before beginning the task but risk will NEVER be zero.
You can sure drive it in that direction by continuing with
what you've started . . . get the conversation going on whatever
topic on your favorite list-server.
Hey!!! Anyone out there messed up an internal antenna installation
on a canopy? How bad was it and how would you recommend that he
NOT proceed? Help this guy out and keep him from repeating the
error. . . .
Regards,
Bob . . .
AeroElectric Connection
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(o o)
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72770.552@compuserve.com
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