Today's Message Index:
----------------------
1. 07:23 AM - Re: Flexible Wire for Pull Out Fuse Tray? (Valin & Allyson Thorn)
2. 09:02 AM - ammeter shunt (Ken Olson)
3. 10:23 AM - Re: ammeter shunt (Jeff Luckey)
4. 10:30 AM - Re: ammeter shunt (Joe Dubner)
5. 04:09 PM - Re: Starter Solenoid behavior with low Battery (John Morgensen)
6. 06:24 PM - Re: Starter Solenoid behavior with low Battery (Kelly McMullen)
Message 1
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Subject: | Flexible Wire for Pull Out Fuse Tray? |
Thanks Bob and all for the help.
In the webpage at your link provided, it shows the TKT Boeing
(Teflon/Kapton/Teflon) wire as safe and with the same Mil Spec ID (22759) as
I thought Tefzel wire has...?
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Wednesday, April 29, 2015 2:54 PM
Subject: Re: AeroElectric-List: Flexible Wire for Pull Out Fuse Tray?
<mailto:nuckolls.bob@aeroelectric.com> nuckolls.bob@aeroelectric.com>
At 15:16 2015-04-29, you wrote:
You can get a chunk of 10-3 drop
cord (SJ, SJO)and cut away the insulation to
acquire three, very flexible and robust
runs of 10AWG wire.
Bob, is that insulation "kosher" with respect to combustion by-products.
I thought that was the reason that Tefzel was the recommended
wire/insulation type.
It depends on who you talk too. There's one well
meaning and vocal faction out there that thinks
Tefzel is spawn of the devil . . .
<http://tinyurl.com/2f8uz> http://tinyurl.com/2f8uz
After you've spent some time in the test
lab letting the smoke out of things, you come
to realize that the flavor of smoke from any
combustible becomes a rather moot point.
Yeah, they do flame tests on insulation . . . by
plying it with a torch! After it appears sufficiently
antagonized that it should burn, you take away
the flame. If I recall the reasoning with any
accuracy, the flaming insulation should not propagate
along the wire, it should self extinguish in so
many seconds, it should not drip flaming
globs of insulation and . . . oh yeah . . .
should be minimally obnoxious to respiratory
system . . . the flavor of a fine pipe tobacco
being a design goal.
I've been present when wires were burned
either by accident or test. I've seen and smelled
lots of smoke . . . and there were no reminders
of grandpa's favorite pipe.
Most the flaming materials wienies seem to
think that there is increased risks for having
materials that will PROPAGATE or PROMOTE a fire
from any/un-named source . . . not many pilots I
know fly around with propane torches. Getting
a wire lit up by hard faulting to a battery is
exceedingly problematic unless the insulation is
VERY flammable . . . but wait, seems like those
fuses and circuit breakers are supposed to
keep things from going that far in the first
place. No . . .?
Airplanes have been wired with everything
from cotton covered rubber to super-exotic-
unobtanium for over a century. Yet in the annals
of aviation accidents, I'm aware of no incident
that was blamed on flammability of the insulation.
There may be some out there but they're a vanishingly
small proportion of totality of incidents.
INTEGRITY of insulation, yes. Swissair 111 wiring
sparked and set the airplane's cabin insulation
on fire. Look at the pictures of the 777 that
belly flopped in SFO. LOTS of stuff throughout
the cabin burned with some vigor . . . and I
doubt that anyone was reminded of their grandpa's
pipe in that incident either.
If the flaming materials wienies were really
taking their jobs seriously, then every new
requirement that strives for happy fires in the
cabin would have grounded the existing fleet
until sub-standard materials were replaced.
Hundreds of thousands of miles of 'sub-standard'
wire are airborne someplace over the planet
as we speak . . .
I suggest that the lowest risk path to personal
flight is grounded in good FMEA, craftsmanship,
and plan-b for highest risk failures. If
you've got serious smoke in the cockpit
that doesn't quit when you turn of the master
switch . . . well . . . the flavor of that
smoke is the least of your worries. I prefer to
design for no-fire as opposed to designing for
friendly fire.
Bob . . .
http://www.matronics.com/Navigator?AeroElectric-List
http://www.matronics.com/contribution
Message 2
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Hello,
I'm installing Dynon's Flight DEK D180. The instructions show the ammeter
shunt installed in one of three locations on the positive side of the
system. Taking a page from AeroElectric Connection book, I asked tech
support if I could install the shunt on the ground side of the battery. I'm
not getting a cogent answer. Is there any reason I cannot install the shunt
on the ground side or is there something going on in the inside the D180
"box" that won't allow this?
Thanks,
Ken
Message 3
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Subject: | Re: ammeter shunt |
Ken,
The current flow coming out of the positive terminal is equal to the flow g
oing back in to the negative terminal so the shunt really doesn't care.=C2
-
HOWEVER
Without seeing a diagram of your proposed installation, it's hard to provid
e more analysis, but here are some things to consider:
There are several legitimate places to put a shunt in an electrical system.
=C2- If you are considering, for lack of a better term, a "battery" shunt
, which measures current flow into & out of the battery, consider this.
The starter circuit is not typically run thru the shunt. So when wiring a s
hunt in the conventional way, it is usually put down-stream of the starter.
=C2-
If you put the shunt in the big negative wire, it will see starter current.
=C2- Something you probably do not want.
There are other issues with ground return paths that might get complicated.
.. ( and require a lot of typing ;)
Now the big question: Why are you considering this?
-Jeff
On Thursday, April 30, 2015 9:16 AM, Ken Olson <klolson@wwestsky.net>
wrote:
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}#yiv3599908948 div.yiv3599908948Section1 {}-->Hello, I=99m installin
g Dynon=99s Flight DEK D180. Theinstructions show the ammeter shunt i
nstalled in one of three locations on thepositive side of the system. Takin
g a page from AeroElectric Connection book, Iasked tech support if I could
install the shunt on the ground side of thebattery. I=99m not getting
a cogent answer. Is there any reason I cannotinstall the shunt on the grou
nd side or is there something going on in the insidethe D180 =9Cbox
=9D that won=99t allow this? Thanks, Ken
Message 4
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Subject: | Re: ammeter shunt |
Ken,
Short and simple: Don't do it. Here's why:
1. You didn't mention what type of airplane you have but there's a good chance
it has a starter. The starter current will have to go through it. Chances are
also good that the shunt isn't rated for more than 50-100A.
2. The shunt will be a additional point of failure for the battery system (like
the battery ground cable, but in addition to it). Flight without a battery
ground connection will be a lot "less good" than flight without, say, an
alternator B-lead connection.
I've been very satisfied with the ammeter shunt located in my RV-8A's alternator
B-lead output. It shows only the output of the alternator, which is what I care
about (although I can appreciate that you may feel differently). The downside
of this location is the requirement for protection of the wires from the shunt
to the instrument but that's easily handled with fusible links.
--
Joe
Independence, OR
Ken Olson wrote, On 4/30/2015 09:01:
> Hello,
>
> I'm installing Dynon's Flight DEK D180. The instructions show the ammeter
> shunt installed in one of three locations on the positive side of the
> system. Taking a page from AeroElectric Connection book, I asked tech
> support if I could install the shunt on the ground side of the battery. I'm
> not getting a cogent answer. Is there any reason I cannot install the shunt
> on the ground side or is there something going on in the inside the D180
> "box" that won't allow this?
>
> Thanks,
>
> Ken
>
>
Message 5
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Subject: | Re: Starter Solenoid behavior with low Battery |
I arrived at the 10 volt figure by the hasty assumption that the Skytec
trouble shooting guide says that a voltage of less than 10 is not a
starter problem.
My symptoms are a, "bump and continue" where the prop hangs for a second
and then continues. It starts but I thought it should be better.
john
On 4/29/2015 9:26 AM, Robert L. Nuckolls, III wrote:
>
> <http://www.skytecair.com/Wiring_diag.htm>The starter barely gets 10
> volts after the master contactor and the
> starter contactor in series. By eliminating the starter contactor, you
> would have a hot wire to the starter whenever the master is on. Is this
> a good idea or suicide
>
>
> How do you arrive at that voltage level. What do you
> believe voltage drop across the starter contactor
> to be?
>
> Bob . . .
>
Message 6
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Subject: | Re: Starter Solenoid behavior with low Battery |
That is very typical behavior of the Skytec PM models, if the battery,
wiring and relays are not all up to spec. It just can't generate the
torque to overcome the first compression stroke of the engine unless it
is getting enough current. As discussed many times, relatively low
resistance in each connection adds up in a hurry when you are drawing
over 150 amps. Each connection needs to be torqued to spec after
disassembly, cleaning to bare metal and reassembly. Ground connections
for battery, engine block and firewall are all common suspects, as well
as the positive side connections.
On 4/30/2015 4:08 PM, John Morgensen wrote:
> I arrived at the 10 volt figure by the hasty assumption that the
> Skytec trouble shooting guide says that a voltage of less than 10 is
> not a starter problem.
>
> My symptoms are a, "bump and continue" where the prop hangs for a
> second and then continues. It starts but I thought it should be better.
>
> john
>
> On 4/29/2015 9:26 AM, Robert L. Nuckolls, III wrote:
>>
>> <http://www.skytecair.com/Wiring_diag.htm>The starter barely gets 10
>> volts after the master contactor and the
>> starter contactor in series. By eliminating the starter contactor, you
>> would have a hot wire to the starter whenever the master is on. Is this
>> a good idea or suicide
>>
>>
>>
>> How do you arrive at that voltage level. What do you
>> believe voltage drop across the starter contactor
>> to be?
>>
>> Bob . . .
>>
>
> *
>
>
> *
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