Today's Message Index:
----------------------
1. 04:30 AM - Re: Larger D-Sub pins (Stuart Hutchison)
2. 04:47 AM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III)
3. 06:36 AM - Re: Instrument Earth Bus cable size (Eric M. Jones)
4. 07:01 AM - Re: Re: Fuses instead of breakers (Valovich, Paul)
5. 07:56 AM - fuses, breakers, and hydraulic pumps (Glen Matejcek)
6. 09:17 AM - Re: fuses, breakers, and hydraulic pumps (Robert L. Nuckolls, III)
7. 09:28 AM - Re: Larger D-Sub pins (Robert L. Nuckolls, III)
8. 09:54 AM - Re: Larger D-Sub pins (Bruce)
9. 12:07 PM - Re: Fuses instead of breakers (bcondrey)
10. 12:46 PM - Re: Fuses instead of breakers (Jeff Page)
11. 12:57 PM - Re: Re: Fuses instead of breakers ()
12. 03:44 PM - Re: Fuses instead of breakers (Ed Holyoke)
13. 05:02 PM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III)
14. 05:21 PM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III)
15. 06:57 PM - Re: Larger D-Sub pins (Stuart Hutchison)
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Subject: | Larger D-Sub pins |
Thanks for your help everyone.
The current-carrying capacity of the wires isn't a factor in my installation
... they're only carrying signals or minor currents off to relays. The
Infinity grips have a mix of 17 different 22AWG and 20AWG wires each, but I
have already terminated each of those wires at a 25-pin D-Sub connector. The
two grip functions are wired in parallel for the most part, so my aim is to
connect both FWD and AFT grips via a "Y" loom terminating at one 25 or
37-pin D-Sub connector to mate with a main central loom. The "Y" loom will
be fabricated entirely of 22AWG wires (disgregard the AWG ratings in my
pic), but I thought it would be more convenient to use 18AWG pins where the
wires come together at the top connector, rather than trim or fold away
strands so that 2 x 22AWG wires fit into 20AWG pins. As Bob said, 2 x 22AWG
wire insulation won't fit in the connector and makes pin removal difficult,
so I thought it would also be more convenient to use 18AWG pins for this
reason (but I haven't tried removing them).
I found 18AWG pins at this site (bottom of the page), but they're asking $2
each ... http://www.aircraftelectronicssupply.com/garmin_install_supp.htm
Cheers, Stu
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Thursday, January 26, 2012 4:26 AM
Subject: RE: AeroElectric-List: Larger D-Sub pins
--> <nuckolls.bob@aeroelectric.com>
At 10:31 AM 1/25/2012, you wrote:
>--> <stein@steinair.com>
>
>Most every shop has extras laying around because they almost never use
>all of them supplied. Gimme a call if you need a few.
>
>BTW, unless the runs are long an AWG20 wire will work fine in place of
>an AWG18.
You beat me to it my friend. I will also suggest that it's
perfectly okay to peel a few strands out of the "too large"
wire to get them all into the 20AWG crimp cup of a standard
pin. You'll have to leave the bare strands exposed over a
greater length because the insulation will not go down
into the wire opening of the connector. Experiment with
an extra pin and a chunk of wire to establish the new strip
dimensions.
When somebody calls for putting overweight wires into
a d-sub connector, the design goal is to REDUCE WIRE
PATHWAY IMPEDANCE. Putting the larger wire into the
pin does not increase the pin's current handling
ability. Hence my suggestion for peeling out extraneous
strands is not a technically 'evil' thing to do in
terms of the physics. It would have an immeasurable
impact on design goals that called for the larger wire.
I think this is preferable to the FAT pin. It adds
no bulk to wiring immediately behind the connector
and leaves less exposed conductor.
However, pulling this trick in an ISO/FAA/PP driven
TC aircraft shop would probably get you fired or
at least a 'ding' in your employment record.
Bob . . .
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Subject: | Re: Fuses instead of breakers |
At 09:47 PM 1/25/2012, you wrote:
Bob, please do. In the meantime, for those of us just getting to
wiring, would this be reasonable, or overkill?
P.S. to previous post.
I too would like to see an ignition system power from
the battery bus. NOT for reasons of noise but for
reasons of risk mitigation. When I have smoke in the
cockpit, I'd like to KILL the entire electrical system
without causing the engine to stop. This is why I've
advocated that ANY electrically dependent engine get
power directly from battery busses. This philosophy
is illustrated in the Z-figures.
Bob . . .
Message 3
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Subject: | Re: Instrument Earth Bus cable size |
(partial repost) I sell lots of Copper-Clad Aluminum cable to 300 mph fuel dragster
and racecar builders, and weird groups doing strange things where the weight
is important. I even sell the stuff to the companies building remote-controlled
drones. Predator drones and the more advance secret stuff...
Airbus and Boeing use similar CCA configurations, and they won't sell you any.
I sell Super-2-CCA, Super-4-CCA, AWG-6-CCA (same dimensions as AWG-6 but CCA with
Tefzel insulation), and Super-CCA RG+142
See my website. CCA is 60% the weight of copper for the same conductivity.
If you have the battery on the firewall, you are okay. Otherwise, use CCA.
Also see Bob's most excellent article, http://www.aeroelectric.com/articles/economics_of_weight_reduction.html
and on my website: http://www.periheliondesign.com/fatwires_files/Coppercables.pdf
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=364872#364872
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Subject: | Re: Fuses instead of breakers |
I built my RV-8A referencing Z13/8: forward mounted battery, one LSI, one m
ag. Three fuze blocks in fwd baggage compartment inaccessible in flight. Th
ree panel mounted CBs - Alt Field, Aux Alt Field and LSI.
I do not feel that a fuze-blowing event for most circuits would benefit fro
m restable CBs - something caused the initial overvoltage and chances that
the fix is a reset CB are very slim. Design redundant systems, include inte
rnal avionics batteries where it makes sense, execute proper failure proced
ures, land as soon as practicable - or as soon as possible - and sort it ou
t on the ground.
For the normal and backup alternators - and LSI - I felt that there was ben
efit from a reset capability. Nuisance trips, one time spikes, intermittent
short, etc. I just might need the few minutes (perhaps) between trigger ev
ents to land.
140 hours of trouble-free electrons so far.
Paul Valovich
N192NM
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Subject: | fuses, breakers, and hydraulic pumps |
Hi Jeff-
With regard to:
>How about another example ? The popular approach is to use a pullable
>breaker for the hydralic pump for the amphibious landing gear. If I
>use a switch and a fuse, what size fuse ? I appreciate that I can
>always install a bigger fuse if nuisance pops occur, .....
......Are there any other reasons why a pullable circuit breaker would be
>preferred for this situation ?
There are two seperate potential issues here. First, is there an alternate source
of hydraulic pressure? If you have a practical hand pump available, then
the nuisance trip issue is just that. If the electric pump is your only practical
source of hydraulic power, then things are a little different. I could envision
a scenario where the motor for the hydraulic pump has degraded such that
the current draw trips the circuit protection, leaving you with a gear up landing,
or potentially worse, a partial gear landing. Personally, I would prefer
resettable circuit protection in that scenario.
FYI, YMMV, ETC, ETC
Glen Matejcek
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Subject: | Re: fuses, breakers, and hydraulic pumps |
There are two separate potential issues here. First, is there an
alternate source of hydraulic pressure? If you have a practical hand
pump available, then the nuisance trip issue is just that. If the
electric pump is your only practical source of hydraulic power, then
things are a little different. I could envision a scenario where the
motor for the hydraulic pump has degraded such that the current draw
trips the circuit protection, leaving you with a gear up landing, or
potentially worse, a partial gear landing. Personally, I would
prefer resettable circuit protection in that scenario.
Cogent thoughts my friend. In spite of the fact that
a Beech Sierra was a pig with wings, I appreciated the
fact that the standby-gear extension system was a simple
valve on the floor that allowed gear-up pressure to be
relieved allowing the wheels to fall free.
Personally, I would prefer resettable circuit protection in that scenario.
I would offer the notion that if power to the motor
is sufficiently robust (current limiter style
protection) then a nuisance trip is entirely out
of the picture. Any time you open a current limiter,
something is REALLY BAD WRONG and being able to
"give 'er one more try" is an incalculable long
shot.
Bob . . .
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Subject: | Larger D-Sub pins |
At 06:24 AM 1/26/2012, you wrote:
>Thanks for your help everyone.
>
>I thought it would also be more convenient to use 18AWG pins for this
>reason (but I haven't tried removing them).
Hmmm . . . hadn't thought about that. I'm not sure they
CAN be removed with the legacy extraction tools.
Given the complexity of your stick grip wiring I think
I would give serious thought to building an etched
circuit board for the relay-deck and stick-grip-junction-
box.
Your mating connectors then solder to the board. The
board can mount the relays and perhaps a speed adjustment
system. the mating connectors get 'really clean' with
respect to materials and techniques.
Express PCB has free software and really reasonable
prices on double-sided, plated-thru boards laid
up and ordered via your computer.
Emacs!
Bob . . .
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Subject: | Larger D-Sub pins |
Stu,
On a personal preference note, it's generally not a good idea to put any
function on a control stick that, if inadvertently activated, would in
danger the aircraft. In your particular application, I would put engine
start and flaps in that category.
Bruce
WWW.Glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Stuart Hutchison
Sent: Thursday, January 26, 2012 7:24 AM
Subject: RE: AeroElectric-List: Larger D-Sub pins
Thanks for your help everyone.
The current-carrying capacity of the wires isn't a factor in my
installation
... they're only carrying signals or minor currents off to relays. The
Infinity grips have a mix of 17 different 22AWG and 20AWG wires each,
but I
have already terminated each of those wires at a 25-pin D-Sub connector.
The
two grip functions are wired in parallel for the most part, so my aim is
to
connect both FWD and AFT grips via a "Y" loom terminating at one 25 or
37-pin D-Sub connector to mate with a main central loom. The "Y" loom
will
be fabricated entirely of 22AWG wires (disgregard the AWG ratings in my
pic), but I thought it would be more convenient to use 18AWG pins where
the
wires come together at the top connector, rather than trim or fold away
strands so that 2 x 22AWG wires fit into 20AWG pins. As Bob said, 2 x
22AWG
wire insulation won't fit in the connector and makes pin removal
difficult,
so I thought it would also be more convenient to use 18AWG pins for this
reason (but I haven't tried removing them).
I found 18AWG pins at this site (bottom of the page), but they're asking
$2
each ...
http://www.aircraftelectronicssupply.com/garmin_install_supp.htm
Cheers, Stu
Message 9
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Subject: | Re: Fuses instead of breakers |
FWIW, this subject has been discussed before on the AeroElectric list. Use the
search function for the words "Klaus" and "crowbar" and you'll find a couple
threads from early 2009. Turns out that it's not just over-voltage events that
will cause them to crowbar but apparently over-temp. This was posted on Feb
1, 2009:
"I have had to do one inflight reset on the Plasma III on one system
once. The reset was successful and power was restored to the unit. I
removed the unit and sent it back to Klaus for inspection. The fault
was determined to be an overheat situation. That unit was located in
an area without any real ventilation and without an form of cooling
while operation in Arizona during the summer. the compartment temp
was estimated to have exceeded 200 deg. F. The unit was modified to
the latest version (lower heat output components and a ventilation
port. The aircraft was modified to provide air circulation in that
compartment. After 300+ hours on that unit no faults noted. The
point, when the unit faulted it tripped the CB and was then reset and
provided service throughout the remainder of that flight. "
Without getting into the discussion of whether the design should or shouldn't be
modified, my purpose on posting (now and back in early 2009) is simply to make
those with dual LSE ignition setups aware that fuses can't be arbitrarily substituted
for CBs in this case.
Bob C
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=364895#364895
Message 10
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Subject: | Re: Fuses instead of breakers |
At 04:27 PM 1/25/2012, you wrote:
> The reference to the FARs regarding battery bus circuits was useful.
> My design doesn't exceed those specifications. Fortunately, with an
> amateur-built aircraft, no bureaucrat can claim that a 5A circuit
> protective device would be the size of both the fuse and the circuit
> breaker.
> Who said anything about regulations? Just because it's
> in a holy-watered book doesn't mean it's not a
> valuable ingredient in a recipe for success.
I merely meant that a 5A fuse and a 5A breaker behave differently, but since
the protection type is not specified, the rule could be interpreted as
a maximum
of a 5A fuse.
> Are there any other reasons why a pullable circuit breaker would be
> preferred for this situation ?
> What controls the pump motor . . . a contactor?
> Is it tailored for intermittent duty, hi-inrush
> service like a starter-contactor? Sticking of this
> device might pose an in-flight concern. However,
> if you have a dual path e-bus, you can kill the
> main bus and shut down a runaway pump motor while
> retaining the electro-whizzies needed for comfortable
> completion of flight.
The float manufacturer (Montana) supplies the pump and control circuitry
already mounted. The relays are Bosch 12V/20A 0 332 209 137
The diagram shows a 25A pullable breaker feeding the relays. A 1A fuse
protects the relay control wiring. So a pullable breaker would be a
convenient
way to deal with a stuck relay or a defective pressure switch. That
is perhaps
what I should do.
I will be interested in the results of your discussions with Klaus
about powering the Lightspeed ignition. I know two people who are
about to install these.
Thanks again for all the great advice. Even while lurking, I learn
something new
and useful every week !
Jeff Page
Dream Aircraft Tundra #10
Message 11
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Subject: | Re: Fuses instead of breakers |
I tried the "fuse" test once. The test was to install the P-III with a fuse and
see if I could guess where I might be when it fails. Mine failed on the run-up
pad. I promptly pulled up to the hangar and wired it directly to the battery
per Klaus's instructions. I always figured he wrote them for a reason. Been working
ever since. I mounted mine upside down on the bottom of the avionics panel
where they get plenty of fresh air.
Best Wishes,
Glenn
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of bcondrey
Sent: Thursday, January 26, 2012 3:01 PM
Subject: AeroElectric-List: Re: Fuses instead of breakers
FWIW, this subject has been discussed before on the AeroElectric list. Use the
search function for the words "Klaus" and "crowbar" and you'll find a couple
threads from early 2009. Turns out that it's not just over-voltage events that
will cause them to crowbar but apparently over-temp. This was posted on Feb
1, 2009:
"I have had to do one inflight reset on the Plasma III on one system
once. The reset was successful and power was restored to the unit. I
removed the unit and sent it back to Klaus for inspection. The fault
was determined to be an overheat situation. That unit was located in
an area without any real ventilation and without an form of cooling
while operation in Arizona during the summer. the compartment temp
was estimated to have exceeded 200 deg. F. The unit was modified to
the latest version (lower heat output components and a ventilation
port. The aircraft was modified to provide air circulation in that
compartment. After 300+ hours on that unit no faults noted. The
point, when the unit faulted it tripped the CB and was then reset and
provided service throughout the remainder of that flight. "
Without getting into the discussion of whether the design should or shouldn't be
modified, my purpose on posting (now and back in early 2009) is simply to make
those with dual LSE ignition setups aware that fuses can't be arbitrarily substituted
for CBs in this case.
Bob C
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=364895#364895
Message 12
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Subject: | Re: Fuses instead of breakers |
I'll try and find it. I know that Klaus is adamant about having a
breaker and not a fuse.
Ed
On 1/25/2012 9:56 AM, Robert L. Nuckolls, III wrote:
> At 11:24 AM 1/25/2012, you wrote:
> Just one more thing to think about if you are doing this with a
> Lightspeed ignition. From what I've read, there is some sort of
> crowbar inside the ignition module to protect it from an overvoltage
> event. If a fuse is fitted and the crowbar kicks it, you'll not be
> able to reset it as easily as with a breaker - if you can reach the
> fuse at all. I've heard of at least one case where an airplane was
> brought down because it was wired differently than the installation
> instructions in that regard.
>
> Can you elaborate on what you've read and give us sources?
> I'm unaware of any crowbar ov protection built into the
> LSE system. Is this called out in any of their published
> literature? I found this on the Lightspeed site:
> ------------------------
> Electrical System Requirements
>
> All Plasma CDI systems can be used with 12 or 24 volt electrical
> systems. Input voltages above 35 volts or reversed polarity can cause
> system damage.
>
> For this reason it is mandatory that all aircraft using Plasma CD
> Ignitions are equipped with over-voltage protection in their
> alternator charging system(s). Over-voltage protection is a
> requirement for certified aircraft. Power connection must be directly
> to the battery terminals to avoid voltage spikes and electrical
> noise. Aluminum should never be used as an electrical conductor for
> the Plasma CDI. Use only the supplied aircraft quality stranded wire.
>
> Minimum supply voltage for starting is 6.5 Volts.
>
> Minimum operating voltage is 5.5 Volts.
> --------------------------
> This statement argues against any built-in ov
> protection. At the same time, the very wide operating
> voltage for the system guarantees that a properly
> designed 14v system will NEVER offer a threat to
> the LSE system.
>
> I am presently participating in an analysis of
> cause and effect for simultaneous failure of
> dual LSE systems. Root cause for that event
> was a failure to craft a failure tolerant
> architecture . . . a design goal which is foundation
> for all efforts here on the AeroElectric-List.
>
> It's a certainty that no builder who participates
> here on the List will suffer such an event.
>
> Bob . . .
>
> *
>
>
> *
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Subject: | Re: Fuses instead of breakers |
At 02:43 PM 1/26/2012, you wrote:
At 04:27 PM 1/25/2012, you wrote:
I merely meant that a 5A fuse and a 5A breaker behave differently, but since
the protection type is not specified, the rule could be interpreted as
a maximum of a 5A fuse.
Oh absolutely. The fact that such a level was
given without an accompanying I(squared)T time
constant goes to suggest the arbitrary nature
of the value. As we've discussed here before,
seeing a 5A number on a protective device
is a small bit of knowledge about how the
device performs. I'd have to go arm-wrestle with
dragons to get a 10A fuse attached to a battery
bus in a TC aircraft . . . but you and I know
that a 10A ATC fuse is faster than a miniature
5A breaker and is . . . therefore . . . a
rational crash safety substitute for always-hot
feeders.
What controls the pump motor . . . a contactor?
The float manufacturer (Montana) supplies the pump and control circuitry
already mounted. The relays are Bosch 12V/20A 0 332 209 137
The diagram shows a 25A pullable breaker feeding the relays. A 1A fuse
protects the relay control wiring. So a pullable breaker would be a
convenient way to deal with a stuck relay or a defective pressure
switch. That
is perhaps what I should do.
Agreed. Those relays are not specifically
crafted for motor control service. Having
a crew-operated means by which a runaway
can be controlled seems prudent.
I will be interested in the results of your discussions with Klaus
about powering the Lightspeed ignition. I know two people who are
about to install these.
There are no doubt many hundreds if not
thousands of these flying. To the best of my
knowledge, they are not "special" devices
deserving of extra-ordinary attention.
Discussions not withstanding, the published
current draw values for LSE products say that
the greatest current draw for a 6-cylinder
system is 2.1A at 13.8 volts.
Emacs!
Given that the device features a switchmode power
supply with a wide range of operating voltages,
we know that this is a constant-power mode of
operation. So 2.1 x 13.8 sez the critter needs
right at 30 watts for operation at MAX RPM. One
can expect the current to climb as voltage goes
down . . . so if you're operating battery only
and the battery is down on that 11-volt-slide-
to-darkness, the ignition system current will
have risen to something around 2.7 amps.
Likewise, operating current on a 29 volt bus
will be down around 1.0 amps. The 4-Cylinder
systems are still more frugal in their demands
on the electrical system.
Thanks again for all the great advice. Even while lurking, I learn
something new and useful every week !
Thanks for getting involved and asking. It's
through EXCHANGES of observation and events that
I learn useful things too. Folks have often
asked why the 'Connection is up to Revision 12
in "just 23 years of publication". I tell
them that my education came from a collaboration
with colleagues who spoke engineereze. And we
hammered on a different class of airplane. When I
sat down to do the first chapters of the
'Connection, I realized that I could not answer
questions without knowing what the questions
are. Further, they needed to be written in
OBAMeze.
It's the collective participation of all
the builders on the List/emails/telephone/
seminars that drive what goes into the
next revision. It's truly a work in progress
that would not have happened without this
join venture arena.
Bob . . .
Message 14
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Subject: | Re: Fuses instead of breakers |
>Without getting into the discussion of whether the design should or
>shouldn't be modified, my purpose on posting (now and back in early
>2009) is simply to make those with dual LSE ignition setups aware
>that fuses can't be arbitrarily substituted for CBs in this case.
I would agree that when the installed system is
at risk for an event triggered by conditions
of installation and/or manufacturing mod levels
then the system is indeed still 'experimental'.
Now that the 'student installer' has graduated
from the lab to the working environment, I'll
suggest that the risk for substitution is
microscopically low.
This is something that we must always keep in
mind. Instructions and ratings are important.
When in doubt, go measure it. It's entirely
possible that the builder who experienced this
event might not have survived to give us his
particular dark-n-stormy-night narrative.
We wouldn't be having this discussion about that
particular event . . . indeed we wouldn't even
know the details.
But the fact is that he DID experience a trip in
a critical system power feeder which prompted further
investigation and he shared his discovery with
the rest of us. That information goes to making
us MORE confident, not less.
I recall a discussion here on the list a some
time back where wires in the wreckage were found
pulled out of the terminal crimps. Hmmm . . .
we'll never know if this failure-to-follow the
instructions precipitated the event . . . but
the overt evidence of failure in craftsmanship
does raise valid questions.
So if one chooses to explore departures from
published instructions, any such departure needs
to be considered carefully. It's not difficult,
just rigorous. Get on the List and let's talk
about it. Bundle all the concerns together and
develop a plan to morph an experiment into a
recipe for success.
But if you don't want to be an explorer or
crafter of new recipes, that's fine too. The
vast majority of our brothers building OBAM
aircraft are not explorers and the last thing
they want to do is experiment. This venue for
acquiring a personally owned aircraft recognizes
that too. Most never frequent this List and
don't need to . . . their relationship with
their airplane's electrical system is no
different than the average spam can driver
in a 172 . . . and that's okay.
Bob . . .
Message 15
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Subject: | Larger D-Sub pins |
Thanks Bob,
Good idea. I think I'll go ahead and make a parallel wire loom now, then
replace it with a PCB later (when I have more time) ... after all, we never
really stop working on our boys toys do we !! :)
Thanks Bruce,
My circuit tracks out to a TCW Safety Trim and TCW Intelligent Flap
Controller, so the flaps can't be oversped (i.e. they can't be extended
above 95kts) and my stick grip start button is off to the right where it's
out of the way of my fat fingers A taildragger F1 Rocket is capable of
dragging itself across the ground (braked) at about 2000 RPM and is
relatively easy to tip over, so I want one hand on the throttle and one hand
holding the stick right back during start. All of the copilot stick
functions can be turned off by the pilot to avoid back seat embarrassments.
Cheers, Stu
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Friday, January 27, 2012 4:25 AM
Subject: RE: AeroElectric-List: Larger D-Sub pins
At 06:24 AM 1/26/2012, you wrote:
Thanks for your help everyone.
I thought it would also be more convenient to use 18AWG pins for this
reason (but I haven't tried removing them).
Hmmm . . . hadn't thought about that. I'm not sure they
CAN be removed with the legacy extraction tools.
Given the complexity of your stick grip wiring I think
I would give serious thought to building an etched
circuit board for the relay-deck and stick-grip-junction-
box.
Your mating connectors then solder to the board. The
board can mount the relays and perhaps a speed adjustment
system. the mating connectors get 'really clean' with
respect to materials and techniques.
Express PCB has free software and really reasonable
prices on double-sided, plated-thru boards laid
up and ordered via your computer.
Emacs!
Bob . . .
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