Today's Message Index:
----------------------
1. 05:33 AM - Re: Re: WireViz (Matthew S. Whiting)
2. 07:04 AM - Re: RV10 Single Batt + Dual Alternator (supik)
3. 07:35 AM - Re: RV10 Single Batt + Dual Alternator (supik)
4. 09:38 AM - Let's not loose focus (Robert L. Nuckolls, III)
5. 03:00 PM - Re: Minimum length of fusible link wire segment (Robert L. Nuckolls, III)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
This probably does not meet your ease of learning requirement, but I learned a
couple of weeks ago that the Micro-cap software became available for free last
December when the company that makes it decided to shut down. It is a quite
sophisticated package that formerly cost several thousand dollars. It allows
you to not only draw schematics, but use real components and then get very faithful
simulation results. I am using LEDs to test every switch path and it allows
you to simulate relays and even motors. I can turn on my master switch and
see the bus energized and then I can push the start switch and watch the starter
motor turn. It gives nearly 100% verification of correctness before the
airplane is ever wired. It does require just a little learning, but here are
several good tutorials for Micro-cap on youtube.
I tried the free SolidWorks package from EAA, but I could not get the electrical
package to install correctly on my system (I run Windows 10, but on a Mac using
Parallels Desktop). Maybe if you have a straight Windows/PC combination it
will work. I kept getting an error that it could not install the SQL database
that it needs so I finally gave up and went looking again and stumbled onto
the free Micro-cap. So far, so good. The only thing is that it doesnt really
do harness design, only schematic level work and simulation of said schematics.
The bundling and such will have to be done manually still.
The only real shortcoming I have found is that it does not include a fuse component.
It shows the current during simulation so you can size things, but it would
be great to be able to install a fuse and test all combinations of devices
to ensure that calculations for wire size and such have been done correctly.
Matt
Sent from my iPad
> On Jun 29, 2020, at 8:25 PM, prestonkavanagh <preston.kavanagh@gmail.com> wrote:
>
>
> "I used LibreOffice Draw to make my wiring diagrams. It worked but was pretty
time-consuming."
>
> IF WireViz is the new best choice for documenting cables, what's the choice for
the schematics? I want to add details to a Z101 foundation. Absent software
it will be pencil lines on a paper printout, and that's well short of the standard.
What is the recommended software? Recognize that for me this is rare
and occasional use - I'll give up some functionality for drag and drop simplicity.
>
> Regards, PK
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: RV10 Single Batt + Dual Alternator |
Joe, thank you for your comments.
>
> The schematic diagram is overly complicated.
> The utility bus can be eliminated and those loads can be powered directly from
the Main power bus.
> Both avionics buses can be eliminated and those loads can be powered directly
from the Essential bus.
Utility bus is now eliminated with latest version. I know the avionics buses make
it more complicated and more expensive. I prefer to keep them for convenience.
The risk of loosing all avionics is mitigated by having the PFD with main
Garmin components fed from the MAIN BUS and ESS BUS directly; additionally the
avionics buses are split -should 1 side fail, there will be always one nav/com
awailable on the other side.
> The two alternators will be connected in parallel whenever both contactors are
energized.
> Is one of the alternators set at a lower output voltage than the other one?
> The two relays are unnecessary failure points.
That's correct. ALT-2 is set at lower voltage. It's idle as long as voltage on
the ESS BUS does not drop to 13.8V (ALT-1 set at 14.4V)
> Eventually some other pilot will fly your plane.
> Will that pilot know what to do when some component fails?
The system is designed so that no action is required if a component or alternator
fails.
Action is required in case of emergency only: electrical smoke / elec. fire. And
this was one of my goals -to be able to isolate the MAIN BUS from the ESS BUS.
So that in case of worst scenario: IMC with elec smoke, I could potentially
isolate the the hard fault and be able to land IMC with limited but capable equipment.
I'm still open to suggestions, especially if you see more potential issues or if
my approach is incorrect.
--------
Igor
RV10 in progress
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497095#497095
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: RV10 Single Batt + Dual Alternator |
bobmeyers wrote:
> I would rethink what you are trying to accomplish.
>
> With all the monkey motion going on, it would seem you would be better served
going with a Z-14 rather than a gummed up Z-101.
>
> Why an avionic bus at all let alone two? I would kill them both and their relays.
>
> A utility bus seems way over the top. If you wish to control a utility device
just have a power switch for that device co-located with it. I would kill the
utility bus
>
> If the motivation for the avionic buses is to avoid brown out of all the avionic
devices not on the GAD 27, a Z-14 system will solve that for you. Most of
the Garmin devices have a second power input you can connect to a second bus.
You can use a bridge rectifier to enable dual power feeds to any device that only
has one power input.
>
> When I wired my RV14 I first drew up something similar to the ideas behind Z-101.
If the current Z-101 had been around I may have been more confident in using
that kind of layout. I went with a Z-14 layout instead.
>
> When I get in my plane, I turn on batt 2 and all the avionics come up and stay
up. I turn on batt 1 as part of my startup checklist. During engine start, no
brown outs to the avionics occur.
>
> This is the only reason I didn't go with my sorta Z-101 back then. I can think
of no other reason to choose between a straight Z-101 or a Z-14.
Bob, thank you for your comments.
I like to stay with 1 battery and 2 alternators. Avoid an extra battery and additional
switch and contactor for the X-TIE.
I agree about the UTIL BUS, it was eliminated with the latest version and the UTIL
switch moved for the specific equpment.
--------
Igor
RV10 in progress
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497096#497096
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Let's not loose focus |
>
>The only real shortcoming I have found is that it does not include a
>fuse component. It shows the current during simulation so you can
>size things, but it would be great to be able to install a fuse and
>test all combinations of devices to ensure that calculations for
>wire size and such have been done correctly.
Is this a simulation app? Calculations for wire size etc?
A word of caution. Take care spending a lot of time
wrestling with software installation and familiarization
that (1) doesn't add to meeting design goals and
(2) simply goes to confirmation of exceedingly rudimentary
decisions . . . wire sizes and fuses . . . really?
The PRIMARY concern is to craft a failure tolerant
system that has low parts count, minimized crew
controls that beg for proper decisions in flight
followed up by minimized weight and cost of ownership.
All those AC43-13 driven 'calculations' and admonitions
are like studying how to boil eggs . . .
There's a thread running now that claims
roots in Z101. ALL of the z-figures
were crafted with a particular airframe/mission
in mind. Occasionally I run a across a builder's
assertion that "I took Zxx and crafted a really
whippy electrical system." Then I find the
drawings only slightly resemble the the
referenced Z-figure due poorly reasoned
changes.
In some cases, the differences created
failure modes hazardous to people and other
living things.
The builder of this airplane attended my
seminar and bought the book . . . but
failed to join us here on the List before
crafting his own "whippy" electrical system:
https://tinyurl.com/msfmldj
There was no critical review of the electrical
system condition/architecture for this
accident . . . but I'd bet $100 that
root cause for this incident would have
been one of those "Gosh . . . I could have
had a V8" moments:
https://tinyurl.com/y7xksy6v
Finally, there's this sad story of a
horrifyingly dismissive attitude toward
the simple physics of flight, aviation
legacy processes/practices and just
common sense.
https://tinyurl.com/mwbk9qs
Root cause for ALL of these (an many
more) bad days in the cockpit was
stone simple.
Years ago, I used this tag on my email
signature:
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
This was in no way intended to be tongue-
in-cheek . . . it's serious . . . some
times deadly serious.
If I've put my foot in a tar bucket,
I'm the FIRST person that needs to know about
it. A teacher's worst nightmare is the
discovery of an ignorant or careless complicity
in the dissemination of poor if not hazardous
information.
If one wishes to exploit a z-figure,
then start with the drawing AS-PUBLISHED.
Study it for failure to meet personal design
goals. If changes are indicated . . . DISCUSS
THOSE GOALS RIGHT HERE on the List. If changes
are warranted or a new z-figure is useful
then by all means let's do it. But make sure
that design goals are (1) realistic
and (2) improve the failure mode effects analysis.
This List is more than a SOURCE FOR GOOD
info . . . it's a FILTER FOR BAD info.
To my way of thinking no single failure will
create an emergency situation. Further, your
plan-B checklist should have a minimum of crew
tasks for failure mitigation (like flip two
switches . . . and keep flying?) and no
requirement for in-flight analysis. Save those gray-
mater exercises for in the hangar.
Trust me . . . wire and fuse sizes are
wwwaaayy down the list of your building
concerns.
Bob . . .
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Minimum length of fusible link wire segment |
At 07:18 PM 6/19/2020, you wrote:
>Bob, in a recent post you state that there is a 9-inch rule of
>thumb minimum length for fusible link wire segments. Could you
>explain the physics behind that, please?
>
>Pat
Sorry to take so long on this . . . it took a few
miles of 'asphalt engineering' to figure out how best
to explain it. I THINK I've got a way . . . let's
give it a try . . .
Fusible link performance, indeed performance of any
fusible circuit protective device is tightly bound
to the fact that most electrical conductors have
a positive temperature coefficient of resistance.
This means, it's resistance rises with temperature
of the conductor.
The rate of temperature rises is a
function of power (watts) dissipated in the
conductor mass which is the product of current
(amps) times resistance (ohms). Consider a piece
of wire, any gage, hanging out in space with some
current flowing through it.
Here's a 22AWG wire that has been happily
carrying 20A for some time. Note that I
attached a thermocouple to the sample wire
out in the middle of the rather significant
free span. Suppose I conducted this experiment
with, say a 1" piece of wire? How might we
guess that center-span's rate-of-rise would
differ for the two cases?
http://aeroelectric.com/Pictures/Wire/22AWG_20A.pdf
It's intuitive that heat generated in the
wire is conducted to the ends. Rate of rise
and temp equilibrium is influenced by sinking
effects of the terminals and radiation into
surrounding air. It's easy to deduce that a
short piece of wire is more resistant to
fusing than a longer one.
As a practical matter, the opening of an
electrically fusible segment tends to 'center up'
on the span. This is seen in the pictures of fuses
attached. As temperature begins to rise, heat
is generated all across the span and conducted
in both directions from any single point. The
CENTER of the span is least able to reject heat
to it's adjacent mass . . . it's getting warmed
up from both directions and also rising the fastest
due to effects of positive temperature coefficient.
Rising resistance increases electrical power dissipated
at that location more rapidly than anywhere else along
the span. Hence the temperature rise is regenerative
. . . the hotter it gets, the faster it warms up.
How long does this take? Complex question depending
on a constellation of conditions. Fuse and
breaker manufacturers work diligently to achieve
predictable performance in their products.
Here's a well written piece that explains the
thermal fiddling necessary to achieve predictable
i.e. fast versus slow blowing characteristic in fuses.
How about that little fly-spec of heat sink material
in the slow blo cartridge fuse?
https://tinyurl.com/ybkndmrc
It easy to see that control of the environment
surrounding the fusible event is critical.
A fusible link is in the 'HULK' family
of protective devices. Like its cousins,
the ANL, MANL and similar 'current limiters',
none are suited to the protection of the
more pedestrian appliance feeders. The
fusible link is SLOW and intended to clear
major faults (HUNDREDS+ AMPS) in the system
bus structure while maintaining a robust
indifference to rather severe transient overload.
Unlike our little plastic ATC friends that
can be 'hammered' into lower operating
currents by repeated excursions close to
but still short of their ratings.
Getting back to your question: Would a 6"
piece of fusible link fail to function?
How about a 1" piece? Probably not. They're
still the weakest link in the faulted pathway.
I am GUESSING that 9" figure is probably some
fusible link designer's 'happy place' for repeating
the in-service design goals he was working with.
Or perhaps it's a legacy hand-over from an automotive
industry specification.
In any case, wanting to shorten 'em up a tad is
not seriously significant to our task. My own
'happy place' would be 6". Hope this helps . . .
Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|