Today's Message Index:
----------------------
1. 07:03 AM - Re: elec. noise in antennas (Robert L. Nuckolls, III)
2. 09:23 AM - Re: elec. noise in antennas (Fred Klein)
3. 09:43 AM - Re: Re: EAA SPORTAIR Workshop attendee has question (Jeff Luckey)
4. 10:43 AM - Sizing the wires (Robert L. Nuckolls, III)
5. 11:54 AM - Re: Relay for Critical Power Feed (Robert L. Nuckolls, III)
6. 11:54 AM - Re: Relay for Critical Power Feed (Robert L. Nuckolls, III)
7. 12:27 PM - Re: Re: EAA SPORTAIR Workshop attendee has question (JOHN TIPTON)
8. 03:58 PM - To twist . . . or not to twist . . . (Robert L. Nuckolls, III)
9. 06:07 PM - To twist . . . or not to twist . . . IMAGES CORRECTED (Robert L. Nuckolls, III)
10. 06:09 PM - Re: To twist . . . or not to twist . . . (Robert Reed)
11. 06:11 PM - Re: EXP 2 Bus workaround (Robert L. Nuckolls, III)
12. 07:14 PM - Re: EXP 2 Bus workaround (Fred Klein)
13. 08:56 PM - Re: EXP 2 Bus workaround (Robert L. Nuckolls, III)
14. 09:28 PM - Re: EXP 2 Bus workaround (Fred Klein)
15. 10:15 PM - EXP Bus workaround (Fred Klein)
Message 1
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| Subject: | Re: elec. noise in antennas |
>I don't in fact "know" that I need 2 AWG feeders...I used that size
>solely for the purpose of emphasizing that the problem I was facing
>was caused by some VERY large wires; I note however that Z-19RB
>calls for 2AWG feeder from battery contactor to starter contactor.
>
>My "battery-to-firewall runs" are exactly 9 feet; firewall to
>starter is another 3 to 4 feet.
>
>Fred
Understand. Recall that the Z-Figures are ARCHITECTURE drawings
and that wire gauge callouts need to be validated against
the real needs of your proposed system. Let's do a little
sharp pencil work with your FAT wires:
4AWG wire has a resistance of 300 micro-ohms per foot. Your
FAT wire engine cranking loop is 24 feet log. This means
that the loop resistance in wire is on the order of 300 x
24 = 7200 micro ohms or 7.2 milli ohms. Assume a difficult
cranking event at 200A for your proposed engine. 200 x .0072
= 1.4 volts drop. You've got 2 RG batteries in parallel with
something on the order of 7 milliohms each or 3.5 milliohms
paralleled for cranking. 200A tosses off an additional 0.7
volts at the battery terminals.
A rule of thumb target for terminal voltage at the starter
is 9.0 volts. Starting with 12.5 volt battery
we give up 1.4 volts in wire at 0.7 volts at the batteries
This says we can toss off another 1.4 volts in contactors,
terminals and bolted joints. Seems like ample head-room.
Your FAT wire runs are analogous to cranking somebody else's
car on a cold morning with a 12' long set of jumper cables
fabricated from 4AWG wire. The first hi-performance set
of jumper cables I built were made of 2AWG welding cable . . .
got the cue from a service truck operator who's jumper
cables were obviously ROBUST. In subsequent years and
repeats of the jumper-cable fabrication task, I deduced
that the AAA Truck was rigged for worst case situations
involving vehicles a lot larger than aunt Minnie's
Dodge Dart. A little sharp pencil work deduced that
for us little guys, 4AWG offers adequate performance
with some left over.
Suggest you can re-size your deliberations about
space in your wiring conduits assuming the smaller
wire.
Bob . . .
Message 2
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| Subject: | Re: elec. noise in antennas |
On Oct 19, 2013, at 7:03 AM, Robert L. Nuckolls, III wrote:
>
> Understand. Recall that the Z-Figures are ARCHITECTURE drawings
> and that wire gauge callouts need to be validated against
> the real needs of your proposed system. Let's do a little
> sharp pencil work with your FAT wires:
>
> 4AWG wire has a resistance of 300 micro-ohms per foot. Your
> FAT wire engine cranking loop is 24 feet log.
Bob,
Yes...being an architect, I do keep in mind that your Z-xx diagrams are
conceptual frameworks subject to computation for sizing.
I humbly bow...no joke...to the knowledge and experience embedded in
your "sharp pencil work"...case in point...while I'm aware of the fact
that calculating resistance in the length of wire is a critical factor
when sizing wires, I would not have used the "loop" dimension...rather,
I would have used the distance from battery to starter. :-((
A question:
In your "sharp pencil work", you used 200 amps as a load for
cranking..I'm astonished that the load could be so high...even on a cold
morning. At the moment, I'm seeking the rating of my starter motor, and
have been anticipating to use that rating to determine the max. current
flow in order to size the wire to it.
Is that not the way to do it?
Fred
Message 3
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| Subject: | Re: EAA SPORTAIR Workshop attendee has question |
=0AHere we go into a deep dive:=0A=0A"I believe its better not to twist the
=0A wires before insertion into a crimp terminal. Better gas tight=0A
crimp."=0A=0ATwisting the conductors of a fresh strip probably has lit
tle effect on the "gas tightness" of the joint in a properly-crimped wire t
erminal.=C2- Getting all of the strands of the conductor into the termina
l is the goal and twisting can really facilitate this.=C2- Also, when usi
ng certain types of splicing terminal like: =0A=0A=0Ahttp://tinyurl.com/lsv
jhfy=0A=0Ait is standard practice to twist all conductors together then cri
mp the cap in place.=0A=0ANow, going deeper, the type of wire has a lot to
do with it.=C2- When working w/ high-quality aviation wire, twisting is u
sually not necessary because if you look carefully at the end of a freshly
stripped piece of MIL-W-22759 ("Tefzel") wire, it is already twisted and th
e strands tend to lie together quite nicely.=C2- =0A=0A=0Ahttp://tinyurl.
com/kqssbro=0A=0AThis is not the case w/ other types of wire - strip a piec
e of zipcord & you'll see what I mean.=0A=0ANow, it is possible that contam
inants from fingertips could be left behind on the conductor and that's pro
bably not the best thing.=C2- (When I'm doing electrical work, I try to k
eep my hands as clean as possible)=C2- I've made a whole bunch of termina
tions over the decades and I'm unaware of any problems caused by this pract
ice.=0A=0A=0A=0A"...I find that it holds onto the insulated part and then t
he =9Cclaws=9D then ruin the copper strands by squashing them.
"=0A=0AI just stripped a piece of wire w/ my Klein "Katapult" and technique
has a lot to do with it.=C2- I notice thatI pull the wire out of the cla
mping jaws as soon as it will come free by keeping tension on the wire as I
(slowly) release the tool after stripping.=C2- This pulls the wire clear
of the tool before the stripping dies have a chance to snap back and whack
the newly-stripped end.=0A=0AHere are a couple of tips:=0A1. Squeeze the t
ool fully, until it stops when performing the strip.=C2- This sets whatev
er sequencing mechanism in the tool.=0A2. Release the tool slowly (keeping
tension on the wire, as mentioned above) - duration of the release should b
e around a second.=0A3. Do some "dry runs" and watch when the wire clamping
jaws begin to move on release.=C2- If you play w/ it, you will notice th
at when operating the tool quickly, sometimes the wire-clamping jaws do not
release before the heads slap back together, hence the suggestion to slow-
down the release.=0A=0AYMMV (WTMI)=0A=0A=0A=0A-Jeff=0A=0A=0A=0A=0A_________
_______________________=0A From: John W Livingston <livingjw@earthlink.net>
=0ATo: aeroelectric-list@matronics.com =0ASent: Friday, October 18, 2013 11
:19 AM=0ASubject: Re: AeroElectric-List: Re: EAA SPORTAIR Workshop attendee
has question=0A =0A=0A=0AI believe its better not to twist the wires befor
e insertion into a crimp terminal. Better gas tight crimp.=0A=0AJWL=0A=0A
=0AOn 10/18/2013 1:39 PM, Jeff Luckey wrote:=0A=0A=0A>=0A>I've not had that
problem, but the suggestion below is probably a good one.=C2- Also, I al
ways give the strands of a freshly stripped end a good twisting - it makes
insertion into the wire terminal easier.=C2- I'm not aware of any setting
s or adjustments on the tool that would help.=0A>=0A>=0A>=0A>-J=0A>=0A>=0A>
________________________________=0A> From: Dave Saylor <dave.saylor.aircraf
ters@gmail.com>=0A>To: "aeroelectric-list@matronics.com" <aeroelectric-list
@matronics.com> =0A>Sent: Friday, October 18, 2013 7:21 AM=0A>Subject: Re:
AeroElectric-List: Re: EAA SPORTAIR Workshop attendee has question=0A> =0A>
=0A>=0A>I know exactly the problem you're describing. I think you'll find t
hat if you=C2-just=C2-release the handles a little more slowly that the
grip=C2-will release the wire before the blades can smack the freshly st
ripped section.=C2- =0A>Hi Jeff,=0A>>I bought the same tool a few months
ago.=C2- But I am reluctant to use it because I have difficulty in using
it properly: it strips the insulation off the wire fine, but when I open th
e handles to release the wire, I find that it holds onto the insulated part
and then the =9Cclaws=9D then ruin the copper strands by squas
hing them. =C2-Its nothing major, but then I have to go and twist the str
ands together again by hand.=0A>>Do you have the same problem? Is there a w
ay to set it so it doesn=99t do that?=0A>>Sac=0A>>_ =0A>=0A>-- =0A>--
=
Message 4
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| Subject: | Sizing the wires |
>
>A question:
>
>In your "sharp pencil work", you used 200 amps as a load for
>cranking..I'm astonished that the load could be so high...even on a
>cold morning. At the moment, I'm seeking the rating of my starter
>motor, and have been anticipating to use that rating to determine
>the max. current flow in order to size the wire to it.
>
>Is that not the way to do it?
In the best of all worlds, you bet. But like the
quest for OPERATING numbers for electro-whizzies
on your engine, the manufacturers of those devices
are generally ignorant of operating conditions.
The 'ratings' on the box or data sheets usually
speak to limits. "Operate my gizmo at or below these
numbers and you may expect it to perform as I have
otherwise detailed in this data sheet . . . and do
it for a long time."
So a rating on your starter motor will probably
speak to some torque-RPM curve at some voltage . . .
or perhaps a family of voltages. It will also
set a limit on temperature rise. The wizard
Charles Kettering first demonstrated how you
can flog a 1 hp motor to 5 hp of output . . .
as long as you don't expect it perform for
more than a few seconds with plenty of time
to cool off between cycles.
Someplace in that array of torque-rpm vs. voltage
curves exists an envelope of demands that your
engine may place on the motor. The system
integrator that selected the motor looked at
the data, purchasing looked at the price
and between them decided to try it. It "did
the job" but it's almost a given that nobody
plotted the full family of starter demands based
on battery condition from new to soggy, plugs
from new to perhaps past recommended life, temperature,
mixtures and fuel flows all over the charts,
oil, etc. etc.
To be sure, if you plot likelihood of extremes
for those combinations, you'll get a kind of
bell shaped curve for severity of demand where
the vast majority of starts are well inside the
motor's design limits and the engine starts in
one or two blades. But the point to be made here
is that there is little or no connection between
'ratings' on your starter motor and how the
system is going to perform.
I've got a high speed data acquisition system
that I'm planning to apply to the fleet of
vehicles in my drive to get some energy demands
in real life situations. Maybe I can get that
set up before the next -10F overnight temps
hit this winter.
Given that we have no "real" numbers for your
airplane, the next best data for doing the
sharp pencil work is to assume a worst case.
Yeah, that number should be astonishing
and it's probably for come condition that
lies out at the worst case limits on the bell
curve. If we could PROVE that those limits
are un-realistically large, cool. But we
have to move forward with what we have and
strive to refine it as we go.
I've often theorized about the possibility of
doing a "Watt-Second Study" on a constellation
of flying hardware. Maybe at a series of fly-ins.
Of course, those always tend to be fair-weather
events. I'd still need to get data somewhat
displaced from the center of the bell curve.
It would be nice to have such data to relieve
the task of sizing components or predicting
performance with numbers no better than throwing
darts at a data sheet.
Having an engine that is artfully managed with
electronics is a BIG plus for a battery.
Artful software automatically accounts for many
variables in the cranking mode. Yeah, all those
byte thrashers may give you a bit better fuel
consumption but it also offers an opportunity
for getting 5+ years out of a battery.
A Beech Skipper I used to rent was pretty easy
to figure out the combination of pre-flight
prop swing, throttle setting and seconds of
primer needed to light it off very quickly.
But I recall more than one neophyte pilot flogging
that airplane's battery and starter to near
exhaustion/destruction because they had not
acquired that man-machine connection that makes
life so much simpler.
So add another variable to the constellation
of influences on starter performance . . . pilot
skills.
Bob . . .
Message 5
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| Subject: | Re: Relay for Critical Power Feed |
At 02:24 AM 10/15/2013, you wrote:
>Following up on automotive relays.
<snip>
>Eric
>
Good data sir! Thank you.
Bob . . .
Message 6
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| Subject: | Re: Relay for Critical Power Feed |
<snip>
Relays sat stationary on the bench during tests. Vibration in
real-world use would almost certainly alter these results just bit.
Next I did a very unscientific check of holding force. I crimped
PIDG fast-on connectors to two wires and connected them to the
normally open relay contacts. I fed 5V from a power supply, through
a 100k resistor, through these wires, with an oscilloscope probe
attached across the resistor. I set the relay coil voltage from
another power supply at 14.0V, so that the relay closed and the scope
displayed a constant 5V DC. I set the scope to trigger on a falling
slope at 4.7V. I then slapped the relay against the bench top in
every direction except pins-down, until the contacts bounced. A
typical bounce waveform is attached. I have no idea how many g it
took to bounce the contacts, but it was a pretty solid
smack. Certainly much more severe than any turbulence I care to encounter!
Eric
I delayed joining this thread because I recalled
a conversation we had here on the List some time
back about contactors opening up under vibration . . .
actually shock.
That conversation spooled up after a builder posted
a note stating that while working on his
airplane, battery-only, he dropped a tool on his
battery contactor and the EFIS rebooted. He repeated
the experiment several times and then came to the
List to inquire into the suitability of this device
to its intended task.
Of course, many tens of thousands of this style
contactor had been used as battery master control
on light airplanes for close to a century. Several
companies offered similar products but most notably,
White-Rodgers/Stancore and Cole-Hersee. The builder's
problem presented in a Cole-Hersee part he had
purchased from Van's.
I had an exemplar C-H part which I set up on the bench
not unlike Eric's experiment above. I was astounded to discover
that what I thought was a relatively light tap with a
box-wrench caused a demonstrable discontinuity in the
contactor's conductivity.
Hmmmm . . . bad contactor? I was selling W-R/S contactors
at the time so I put one of those on the same test set up
and guess what? It did it too.
"Holy contacts Batman, how can this be?"
After some thought I came to two understandings about
the nature of this phenomenon. First, striking the steel
enclosure of the contactor with a steel tool was a
shock force. In terms of g-levels it could have easily
reached the big numbers. Certainly 10Gs and 100G would
not have surprised me.
Second, why did this not manifest before? Answer, it HAD,
many, many times over the decades. But all of the
applications that made these contactors popular DID NOT
feature solid state electronics . . . particularly
fitted with microprocessors that would re-set on
microsecond notice.
Then the lights came on. At some time toward the end
of my tenure in the sales of contactors, W-R/S modified
their 70 series devices to add plastic booties over
the mounting feet.
Emacs!
I wrote to W-R/C and called a rep to see if I could
get an explanation for why those 'insulators' were
added to the mounting. Never got a satisfactory
answer . . . in fact never got any answer.
But I'll be you $5 to your donut (used to be
a dollar . . . but you know . . . inflation),
that some new electric vehicle with modern,
CPU driven controls demonstrated the same phenomenon
reported by our brother builder in his
airplane. The good folks at W-R/S couldn't do a thing
about failure of some manufacturer to do DO-160
style qualification to his fork lift controller
. . . the next best thing was to modify the contactor
for better resistance to hi-G pulses or shock.
Of course, hitting the contactor with a wrench
continues to produce the same demonstrable dis-
continuity. The difference being that the same
shocks delivered through the mounting feet are less
likely to interrupt the flow of power through
the contactor.
What's the likelihood of delivering such 10+
G shock to the contactor in your airplane?
VERY low, hence the exemplar service life of
this device in airplanes . . . even machines
fitted with electronics having twitchy reset
characteristics.
Nonetheless, the discovery was a surprise. At the
time I was engaged in some relay life issues at
Hawker-Beech and this discovery on the contactors
prompted some explorations into smaller relays . . .
particularly some mil-spec devices. Guess what?
They do it too.
I couldn't find the data plots I took on the contactor
experiments. If I run across them in the future, I'll
re-post this note alone with the data. I don't
think I recorded any data on the $high$ relays,
those investigations were never formally reported.
Bottom line is that shock . . . fast rise, short duration
high intensity transients are a special kind of
vibration that gets spec'ed separately from the
shake, rattle and roll of the airframe. This further
emphasizes the need for good practice in the design
of input power conditioning for particularly
vulnerable avionics. Design practice that should
happen INSIDE the box at the factory . . . not
outside the box at the airplane.
So the short answer to the topic question of this
thread is, yes . . . plain vanilla contactors
and relays are just as suited to control "critical"
power as they ever were. The companion question is
whether or not the designers of potentially vulnerable
systems understood and considered the wild-and-wooly
nature of DC power systems in all manner of vehicle.
I have referred numerous non-aviation clients to
DO-160 as a set of exemplar guidelines for successful
marketing of a new product.
Bob . . .
Message 7
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| Subject: | Re: EAA SPORTAIR Workshop attendee has question |
What isn't noticed by the majority is that the strands are twisted anti clo
ckwise, so the majority who cannot resist twisting, actually 'un-twist' the
starnds=0A=0A=0A=0A>________________________________=0A> From: Jeff Luckey
<jluckey@pacbell.net>=0A>To: "aeroelectric-list@matronics.com" <aeroelectr
ic-list@matronics.com> =0A>Sent: Saturday, 19 October 2013, 17:43=0A>Subjec
t: Re: AeroElectric-List: Re: EAA SPORTAIR Workshop attendee has question
=0A> =0A>=0A>=0A>=0A>Here we go into a deep dive:=0A>=0A>"I believe its bet
ter not to twist the=0A wires before insertion into a crimp terminal.
Better gas tight=0A crimp."=0A>=0A>Twisting the conductors of a fresh
strip probably has little effect on the "gas tightness" of the joint in a p
roperly-crimped wire terminal.=C2- Getting all of the strands of the cond
uctor into the terminal is the goal and twisting can really facilitate this
.=C2- Also, when using certain types of splicing terminal like: =0A>=0A>
=0A>http://tinyurl.com/lsvjhfy=0A>=0A>it is standard practice to twist all
conductors together then crimp the cap in place.=0A>=0A>Now, going deeper,
the type of wire has a lot to do with it.=C2- When working w/ high-qualit
y aviation wire, twisting is usually not necessary because if you look care
fully at the end of a freshly stripped piece of MIL-W-22759 ("Tefzel") wire
, it is already twisted and the strands tend to lie together quite nicely.
=C2- =0A>=0A>=0A>http://tinyurl.com/kqssbro=0A>=0A>This is not the case w
/ other types of wire - strip a piece of zipcord & you'll see what I mean.
=0A>=0A>Now, it is possible that contaminants from fingertips could be left
behind on the conductor and that's probably not the best thing.=C2- (Whe
n I'm doing electrical work, I try to keep my hands as clean as possible)
=C2- I've made a whole bunch of terminations over the decades and I'm una
ware of any problems caused by this practice.=0A>=0A>=0A>=0A>"...I find tha
t it holds onto the insulated part and then the =9Cclaws=9D the
n ruin the copper strands by squashing them. "=0A>=0A>I just stripped a pie
ce of wire w/ my Klein "Katapult" and technique has a lot to do with it.=C2
- I notice that I pull the wire out of the clamping jaws as soon as it wi
ll come free by keeping tension on the wire as I (slowly) release the tool
after stripping.=C2- This pulls the wire clear of the tool before the str
ipping dies have a chance to snap back and whack the newly-stripped end.
=0A>=0A>Here are a couple of tips:=0A>1. Squeeze the tool fully, until it s
tops when performing the strip.=C2- This sets whatever sequencing mechani
sm in the tool.=0A>2. Release the tool slowly (keeping tension on the wire,
as mentioned above) - duration of the release should be around a second.
=0A>3. Do some "dry runs" and watch when the wire clamping jaws begin to mo
ve on release.=C2- If you play w/ it, you will notice that when operating
the tool quickly, sometimes the wire-clamping jaws do=0A not release befor
e the heads slap back together, hence the suggestion to slow-down the relea
se.=0A>=0A>YMMV (WTMI)=0A>=0A>=0A>=0A>=0A>=0A>-Jeff=0A>=0A>=0A>=0A>=0A>=0A>
=0A>________________________________=0A> From: John W Livingston <livingjw@
earthlink.net>=0A>To: aeroelectric-list@matronics.com =0A>Sent: Friday, Oct
ober 18, 2013 11:19 AM=0A>Subject: Re: AeroElectric-List: Re: EAA SPORTAIR
Workshop attendee has question=0A> =0A>=0A>=0A>I believe its better not to
twist the wires before insertion into a crimp terminal. Better gas tight cr
imp.=0A>=0A>JWL=0A>=0A>=0A>On 10/18/2013 1:39 PM, Jeff Luckey wrote:=0A>=0A
>=0A>>=0A>>I've not had that problem, but the suggestion below is probably
a good one.=C2- Also, I always give the strands of a freshly stripped end
a good twisting - it makes insertion into the wire terminal easier.=C2-
I'm not aware of any settings or adjustments on the tool that would help.
=0A>>=0A>>=0A>>=0A>>-J=0A>>=0A>>=0A>>________________________________=0A>>
From: Dave Saylor <dave.saylor.aircrafters@gmail.com>=0A>>To: "aeroelectric
-list@matronics.com" <aeroelectric-list@matronics.com> =0A>>Sent: Friday, O
ctober 18, 2013 7:21 AM=0A>>Subject: Re: AeroElectric-List: Re: EAA SPORTAI
R Workshop attendee has question=0A>> =0A>>=0A>>=0A>>I know exactly the pro
blem you're describing. I think you'll find that if you=C2-just=C2-rele
ase the handles a little more slowly that the grip=C2-will release the wi
re before the blades can smack the freshly stripped section.=C2- =0A>>Hi
Jeff,=0A>>>I bought the same tool a few months ago.=C2- But I am reluctan
t to use it because I have difficulty in using it properly: it strips the i
nsulation off the wire fine, but when I open the handles to release the wir
e, I find that it holds onto the insulated part and then the =9Cclaws
=9D then ruin the copper strands by squashing them. =C2-Its nothing
major, but then I have to go and twist the strands together again by hand.
=0A>>>Do you have the same problem? Is there a way to set it so it doesn
=99t do that?=0A>>>Sac=0A>>>_ =0A>>=0A>>-- =0A>>--Dave Saylor=0A>>=0A>
=0A>=======================
===================== =0A>=0A>
Message 8
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| Subject: | To twist . . . or not to twist . . . |
At Hawker-Beech we had automated wire cutting, marking,
stripping and termination machines that produced thousands
of ready-to-install wire segments a day. None of these machines
had a 'twisting' function. The as-stripped strands were
immediately fitted with the appropriate terminal and
crimped.
A review of NASA-STD-8739.4 for the fabrication of wire
bundles and terminations, I found no example for terminating
wires were either single or multiple wires were twisted
by the installer before attaching a terminal.
Emacs!
I've never witnessed such a practice by technicians nor am I aware
of a rationale for doing so.
In fact, the 'wire nut' designed for wiring of buildings
achieves gas tight connections at the corners of a square-
wire, conical-spring. As the device is twisted
over the ends of parallel strands, the cone expands and
crawls up and over the ends of the cut strands.
An early example of this technology was not insulated.
Emacs!
A conical spring wound of round wire and fitted
with a 'handle' was simply wound onto parallel
strands. The counter-wind torque expanded the
spring up and over the strands thus increasing
the pressure that kept the wires in good contact.
Later versions deleted the handle, added insulating
cap that also served as a handle . . .
Emacs!
They also wound the spring with square wire having
a corner turned in. This sharp edge would bite into
the strands of wire thus increasing both mechanical
grip for running the spring onto the strands AND
increasing the numbers of high-pressure (gas tight)
joints between conducting elements of the connection.
None of these products would benefit from a pre-twisting
of the wires before installation. Standard practice calls
for twisting the cap on until the strands DO twist slightly,
say 1/2 turn or so. This is your installation limit indicator
that the spring is no longer climbing onto the wires and
further rotation serves only to twist the bundle which
adds nothing to the quality of the finished joint.
Therefore, the short answer for any kind of installer-
twisting of strands in a wire or wires in a bundle
seems to be "not necessary and possibly deleterious
to the finished joint."
Bob . . .
Message 9
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| Subject: | To twist . . . or not to twist . . . IMAGES CORRECTED |
At Hawker-Beech we had automated wire cutting, marking,
stripping and termination machines that produced thousands
of ready-to-install wire segments a day. None of these machines
had a 'twisting' function. The as-stripped strands were
immediately fitted with the appropriate terminal and
crimped.
A review of NASA-STD-8739.4 for the fabrication of wire
bundles and terminations, I found no example for terminating
wires were either single or multiple wires were twisted
by the installer before attaching a terminal.
Emacs!
I've never witnessed such a practice by technicians nor am I aware
of a rationale for doing so.
In fact, the 'wire nut' designed for wiring of buildings
achieves gas tight connections at the corners of a square-
wire, conical-spring. As the device is twisted
over the ends of parallel strands, the cone expands and
crawls up and over the ends of the cut strands.
An early example of this technology was not insulated.
Emacs!
A conical spring wound of round wire and fitted
with a 'handle' was simply wound onto parallel
strands. The counter-wind torque expanded the
spring up and over the strands thus increasing
the pressure that kept the wires in good contact.
Later versions deleted the handle, added insulating
cap that also served as a handle . . .
Emacs!
They also wound the spring with square wire having
a corner turned in. This sharp edge would bite into
the strands of wire thus increasing both mechanical
grip for running the spring onto the strands AND
increasing the numbers of high-pressure (gas tight)
joints between conducting elements of the connection.
None of these products would benefit from a pre-twisting
of the wires before installation. Standard practice calls
for twisting the cap on until the strands DO twist slightly,
say 1/2 turn or so. This is your installation limit indicator
that the spring is no longer climbing onto the wires and
further rotation serves only to twist the bundle which
adds nothing to the quality of the finished joint.
Therefore, the short answer for any kind of installer-
twisting of strands in a wire or wires in a bundle
seems to be "not necessary and possibly deleterious
to the finished joint."
Bob . . .
Message 10
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| Subject: | Re: To twist . . . or not to twist . . . |
The only exception I can point out would be if anything should cause stray s
trands to separate from the bundle.
Bob Reed
Sent from my iPhone
> On Oct 19, 2013, at 5:56 PM, "Robert L. Nuckolls, III" <nuckolls.bob@aeroe
lectric.com> wrote:
>
Message 11
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| Subject: | Re: EXP 2 Bus workaround |
At 04:01 PM 10/14/2013, you wrote:
>On Oct 14, 2013, at 12:16 PM, Ken wrote:
>
>>You are in the ballpark Fred but it's probably safe to round down
>>to 20 amps for a no alternator battery life calculation.
>
>Ken...thank you for your "3rd party validation"...at this stage of
>the game, I'd rather be conservative, and I'm looking forward to
>Bob's assessment.
I think I'm down to the last missing data point.
How do you switch between ECU modules? Do you have
a wiring diagram of this feature you can sketch or scan
to share?
Bob . . .
Message 12
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| Subject: | Re: EXP 2 Bus workaround |
On Oct 19, 2013, at 6:09 PM, Robert L. Nuckolls, III wrote:
<nuckolls.bob@aeroelectric.com>
>
> At 04:01 PM 10/14/2013, you wrote:
>
>> On Oct 14, 2013, at 12:16 PM, Ken wrote:
>>
>>> You are in the ballpark Fred but it's probably safe to round down to
20 amps for a no alternator battery life calculation.
>>
>> Ken...thank you for your "3rd party validation"...at this stage of
the game, I'd rather be conservative, and I'm looking forward to Bob's
assessment.
>
> I think I'm down to the last missing data point.
>
> How do you switch between ECU modules? Do you have
> a wiring diagram of this feature you can sketch or scan
> to share?
>
>
>
> Bob . . .
Bob...the guts of the ECU is in a box mounted on the cockpit side of the
firewall...is is connected to a small control console mounted on the
panel via a D Sub cable. This small control panel includes a switch
which toggles between the "A" motherboard and its back up, the "B"
motherboard. In the D Sub connector, there are separate power inputs for
A and B. I have no wiring diagram explaining this feature. Here is a
photo of the panel mounted control console...the toggle switch obscures
the "A".
Check it out in the lower right of the panel...then view close up:
Message 13
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| Subject: | Re: EXP 2 Bus workaround |
>Check it out in the lower right of the panel...then view close up:\
I guess I missed that in the original set of
photos. Do these separate inputs need to be
switched . . . or is ECU power control accomplished
from the little panel?
Bob . . .
Message 14
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| Subject: | Re: EXP 2 Bus workaround |
On Oct 19, 2013, at 8:54 PM, Robert L. Nuckolls, III wrote:
>> Check it out in the lower right of the panel...then view close up:\
>
> I guess I missed that in the original set of
> photos. Do these separate inputs need to be
> switched . . . or is ECU power control accomplished
> from the little panel?
We will need a switch or circuit breaker between the
battery and the ECU...ditto for the fuel injectors, coils, and fuel
pumps.
Message 15
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| Subject: | EXP Bus workaround |
Bob...I'm not sure what you're up to, but I have been looking at the implications
of some variations under these givens; namely, that:
- Batteries aft, wired together...act as one battery
- Bat Contactors aft...ALL buses forward on either side of firewall to be determined
- EXBus serves as Main Power Distribution Bus
- Endurance Bus has alternate feed from Engine Bus
ALTERNATIVE # 2
- EXP Master Switch fed thru Contactor #1
- Starter fed from Contactor #1 and EXP Bus
- Engine Bus fed thru Contactor #2
CRITICAL IMPLICATIONS:
- If Master switch is OFF, starter cannot be energized
- If Contactor #2 fails, engine will not run
- If Bat #2 switch is turned OFF unintentionally, engine will NOT run
- Long feeder from aft contactor to Engine Bus is NOT always hot and is protected
by contactor
ALTERNATIVE # 3
- EXP Master Switch fed thru Contactor #1
- Starter fed from Contactor #2 and Engine Bus
- Engine Bus fed thru Contactor #2
CRITICAL IMPLICATIONS:
- If Master Switch is OFF, starter can still be energized thru Contactor #2
- If Contactor #2 fails, engine will not run
- If Bat #2 switch is turned OFF unintentially, engine will NOT run
- Long feeder from aft contactor to Engine Bus is NOT always hot and is protected
by contactor
ALTERNATIVE #4
- EXP Master Switch fed thru Contactor #1
- Starter fed from Contactor #2
- Engine Bus fed direct from Battery
CRITICAL IMPLICATIONS:
- If Master Switch is OFF, starter can still be energized thru Contactor #2
- If Contactor #2 fails engine will continue to run
- If Bat #2 switch is turned OFF unintentionally, engine will continue to run
- Long feeder from aft (Battery side of) contactor #2 is ALWAYS HOT and unprotected
by CB or fuse
I'm just tryin to eat the elephant one bite at a time...in doing so, I tend to
favor Alternative #4 if risk of ALWAYS HOT feed to engine bus is sufficiently
mitigated w/ a non-conductive airframe and possibly other considerations.
Fred
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