Today's Message Index:
----------------------
1. 04:03 AM - Re: Re: "Broken and Garbled" (Additional data) (Chuck Jensen)
2. 05:35 AM - Alternator Failure ()
3. 06:13 AM - Re: 2-10 Switch (Dick Fisher)
4. 07:54 AM - Re: Another 60A alternator, internally regulated voltage regulator failure (Ken)
5. 11:41 AM - Re: Alternator Failure (Robert L. Nuckolls, III)
6. 11:46 AM - Re: $low$ handi-talkies (Robert L. Nuckolls, III)
7. 12:09 PM - Re: Alternator failures (Robert L. Nuckolls, III)
8. 12:53 PM - Re: Re: $low$ handi-talkies (Chuck Jensen)
9. 01:25 PM - Re: Re: $low$ handi-talkies (Robert L. Nuckolls, III)
10. 05:52 PM - Narco ADF with RG-62 Antenna (Matt Prather)
11. 06:35 PM - Re: Narco ADF with RG-62 Antenna (Robert L. Nuckolls, III)
12. 07:44 PM - Re: Narco ADF with RG-62 Antenna (Matt Prather)
13. 08:47 PM - Three Fat Wires on Starter Contactor Bolt: How? (r falstad)
14. 09:31 PM - Re: Three Fat Wires on Starter Contactor Bolt: How? (Robert L. Nuckolls, III)
15. 09:37 PM - Re: Three Fat Wires on Starter Contactor Bolt: How? (Robert L. Nuckolls, III)
Message 1
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Subject: | Re: "Broken and Garbled" (Additional data) |
Since I just happen to be in the market for a half-dozen walkie talkies
for a project, is there any concensus on the best, cheap unit....Cobra
MicroTalk? Motorola TalkAbout? Or, are they really all about the same.
I'm buying cheap as after a week, they are a Good-Will donation.
Chuck Jensen
-----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, March 07, 2007 1:32 AM
Subject: Re: AeroElectric-List: Re: "Broken and Garbled" (Additional
data)
--> <nuckollsr@cox.net>
I think it's one of those once-in-a-blue-moon or perhaps
in-our-fondest-wishes kinds of advertising. We see it a lot when
manufacturers talk about the wattage of their audio systems. The $low$
hand-helds have transmitters that run in the 100 mW range. Some $high$
transceivers for the $licensed$ service may be
allowed
to run more . . . I haven't dug out the rules on this.
But consider the 100 mW case by punching numbers into a path loss
calculator
at:
http://tinyurl.com/y9tte2
Use 0.1 watts, 14 km (about 10 mi) and 450 Mhz.
Use 0, 0 and -3 for transmit and receive antenna values
Use 0 for "other losses". Hit Calculate.
We see that this gives us a 4 microvolt signal at the
receiver end. A really good receiver can be barely
useful at about 1/10th this value or 0.4 microvolts.
This means that assuming the receivers in these $20 handhelds are
capable of 0.4 microvolt performance, we can tolerate 20 db of "other"
losses over a 10 mi course and still communicate.
It would be interesting to evaluate these radios in the lab
but the ones I have don't have coax connectors where the antennas go
such that one might easily evaluate real transmitter power output and
real receiver performance. Given the less-than-ideal antennas and poor
probability that the power and sensitivity numbers are equal to the
example cited, I doubt that the radios I've been using can be expected
to produce useful performance at the "advertised" ranges.
One can purchase much more expensive radios that operate
in this service. It's reasonable to expect some
improvements in performance, but it's still difficult to minimize
"other" losses in the communications path.
Most of the radios I've purchased were the $lowest$ I could find because
my path-lengths of interest ran from a few feet to perhaps 50 yards. I
often use them to communicate with a technician in the cockpit while I'm
working in the "hell-hole" of an airplane. The poorest performing was
good for perhaps 100 yards between vehicles on the highway and the last
set I bought are much better. They are usable out to 1 mile if the two
cars can see each other.
Idealized conditions are generally used when you're being seduced into
buying the critters. Real-world performance and non-idealized path loss
conditions are an all together different matter.
Bob . . .
Message 2
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Subject: | Alternator Failure |
Bob N. wrote:
"In other words, if I had a brand new
alternator and a charter to damage it in some way on the test
stand, what kinds of abuses might I heap upon the unsuspecting
device to bring about its untimely demise?"
Just for grins, here's a simple example applicable to the GM CS130 alternator (IR).
It is physically small but rated at 105 AMPS. It runs very hot at 40 AMPS
(Olds 98 'normal' load!) resulting in short diode life (without load and cooling
mods plus up-rated diodes). My re-built spare (kept in the trunk) came
with a tag attached to the alternator, "CAUTION: this alternator is NOT a battery
charger". In other words, do not "jump start" the vehicle because normal
running load plus a discharged battery will likely fail this alternator.
P.S. I have never come across this issue with non-GM cars. I have two 20+ year
Toyotas with original ND alternators (brushes replaced once).
Mike
Message 3
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Bob,
Thank you very much for the clear and concise answer
to my questions on the 2-10 switch. I am now able to
understand the functionality as depicted in your drawing.
Dick Fisher
sonex76@velocity.net
Message 4
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Subject: | Re: Another 60A alternator, internally regulated |
voltage regulator failure
For years I was skeptical too that a weak battery would hasten
alternator death. However eventually I developed a few thoughts on why
there may be some truth to this in automobiles.
1. Higher longer charging does tend to make the alternator run hotter
and some internal VR alternators are not well cooled. Any vehicle that
is started with jumper cables is about to ask for a serious effort from
its charging system.
2. Installing a new but partly charged battery may stress the alternator
even higher than ever as it charges the battery at max current for an
extended period. An old alternator just may not be up to the effort.
Maybe the brushes are worn or maybe the solid state devices get hotter
than they have for awhile. Certainly the cooling of old greasy/dirty
components is not as good as on a clean new unit. I'm not sure that a
test stand is going to successfully imitate the service environment that
I'm thinking of. This might explain death shortly after the new battery
is installed though.
3. Weak "maintenance free" batteries are sometimes low on electrolyte. I
think that further reduces their capacity to absorb any excess voltage
or current and might lead to more voltage excursions. Most people never
pop the caps off automobile batteries any more as it is often not
obvious how to do it, or that it can be done. It seems that my little
(8AH) AGM batteries will accept very little current initially when fully
discharged.
4. As a WAG another contribution might be abnormal operation while
fooling around with a weak battery. If I leave the ignition/key on with
my ND IR alternator on my aircraft without starting the engine, the
alternator does draw several amps of field current and it will heat up
quite noticeably with no cooling airflow.
Anyway my personal rule now is to change out any suspicious battery with
a new FULLY charged unit and I can sometimes send the vehicle to the
wreckers with the original alternator. I do run weak batteries in my
tractor but that has an external homemade VR that hangs out in the
breeze (like the alternator) and everything runs very very cool ;)
Ken
>> SNIP>
>> I had heard that a "weak" battery can damage the alternator/regulator
>> so this seamed to have validated that statement. For sure though,
>> from my observations, the battery appeared to go bad first then 2
>> hours later after a new battery was installed the regulator seems to
>> have failed.
>
>
> I'm skeptical of such claims. Consider how many batteries
> you've replaced in cars without having to replace the alternator
> too.
>
> I've "killed" a few alternators in various test situations
> but all failures involved either loss of cooling or mechanical
> issues such as bearing or shear-shaft failures.
>
> The way to "test" a weak-battery-kills-alternators hypothesis is
> to separate the two components and then craft a test plan designed
> to kill an alternator. In other words, if I had a brand new
> alternator and a charter to damage it in some way on the test
> stand, what kinds of abuses might I heap upon the unsuspecting
> device to bring about its untimely demise?
>
> Once such a test plan is devised, then deduce how battery
> behavior mimics any of the abuses you've crafted for the
> purpose of killing an alternator.
>
> I'd be interested in anyone's ideas as to how you might go
> about it. Alternators are inherently self current limiting.
> Given sufficient cooling air, you cannot "overload" one to
> destruction. Alternator diodes are robust and will withstand
> reverse voltage transients many times greater than system voltage.
> It's the regulators that are most vulnerable to a load-dump
> event and that's been demonstrated by several builders using
> Van's (and perhaps other) alternators combined with b-lead
> contactor controls.
>
> I'm not suggesting that battery condition might not be a bit-player
> in a scenario that's hard on alternators. For example:
> I can see how the "weak battery" thing might have morphed into
> a cause/effect for alternator failure where someone knows that
> having a battery be disconnected from the alternator at the same
> time all loads are removed causes a potentially hazardous
> over-shoot. One might deduce that a "weak" battery has
> lost its ability to mitigate a load-dump events thereby
> placing the alternator at-risk.
>
> If this hypothesis were in play for your situation, the alternator
> seems most likely to have failed while the "weak" battery was
> in place. Certainly having a "strong" new battery in place totally
> eliminates the risk for hazardous transients during ordinary
> system load reductions.
>
> This could be hypothetically thrashed for days but without very
> specific test data, we'll never know how your tandem failures
> may or may not have been related.
>
>
>> My current battery voltage is really good, even after the voltage
>> regulator failure stress on the battery.
>
>
> The momentary abuses heaped on your battery were of limited duration
> and will have the net effect of reducing your battery's service
> life by some small fraction. By the way, once your alternator is
> turned ON after engine start, are you able to turn it OFF from
> the pilot's controls while the engine is running?
>
> Bob . . .
Message 5
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Subject: | Re: Alternator Failure |
At 08:34 AM 1/7/2007 -0500, you wrote:
>
>Bob N. wrote:
> "In other words, if I had a brand new
> alternator and a charter to damage it in some way on the test
> stand, what kinds of abuses might I heap upon the unsuspecting
> device to bring about its untimely demise?"
>
>Just for grins, here's a simple example applicable to the GM CS130
>alternator (IR). It is physically small but rated at 105 AMPS. It runs
>very hot at 40 AMPS (Olds 98 'normal' load!) resulting in short diode life
>(without load and cooling mods plus up-rated diodes). My re-built spare
>(kept in the trunk) came with a tag attached to the alternator, "CAUTION:
>this alternator is NOT a battery charger". In other words, do not "jump
>start" the vehicle because normal running load plus a discharged battery
>will likely fail this alternator.
Hmmmm . . . how often do you get a manufacturer to
ADMIT his product isn't designed to live in the real
world in which it is expected to function? As you
noted early on, this alternator was probably starved
for cooling and the folks that sold it to you were
admitting that you couldn't expect it to survive a
situation that should be and is a piece of cake for
other systems.
>P.S. I have never come across this issue with non-GM cars. I have two 20+
>year Toyotas with original ND alternators (brushes replaced once).
One of the tests we have to do when installing
an new alternator on an airplane is to accomplish
extended best-angle climbs with the alternator loaded
to it's nameplate rating. We then extrapolate that
data to worst case, hot day situations to deduce
whether or not the alternator is adequately cooled.
For a manufacturer to offer the caveat you cited
does not speak well of their sense of responsibility
as engineers.
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
---------------------------------------------------------
Message 6
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Subject: | RE: $low$ handi-talkies |
At 07:03 AM 1/7/2007 -0500, you wrote:
>
>Since I just happen to be in the market for a half-dozen walkie talkies
>for a project, is there any concensus on the best, cheap unit....Cobra
>MicroTalk? Motorola TalkAbout? Or, are they really all about the same.
>I'm buying cheap as after a week, they are a Good-Will donation.
As long as you're not expecting them to function at
more than a fraction of advertised range, go for
the $low$ versions. Buy one pair and try them out
in the most demanding situation you can anticipate
before you buy the rest.
Bob . . .
Message 7
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Subject: | Re: Alternator failures |
At 10:54 AM 1/7/2007 -0500, you wrote:
>
>For years I was skeptical too that a weak battery would hasten alternator
>death. However eventually I developed a few thoughts on why there may be
>some truth to this in automobiles.
>
>1. Higher longer charging does tend to make the alternator run hotter and
>some internal VR alternators are not well cooled. Any vehicle that is
>started with jumper cables is about to ask for a serious effort from its
>charging system.
So after getting the car started. Let it stand at
curb idle for ten minutes or so with minimal accessories
turned on. This little pre-charge should have the
battery boosted beyond it's max-recharge current
draw.
>2. Installing a new but partly charged battery may stress the alternator
>even higher than ever as it charges the battery at max current for an
>extended period. An old alternator just may not be up to the effort. Maybe
>the brushes are worn or maybe the solid state devices get hotter than they
>have for awhile. Certainly the cooling of old greasy/dirty components is
>not as good as on a clean new unit. I'm not sure that a test stand is
>going to successfully imitate the service environment that I'm thinking
>of. This might explain death shortly after the new battery is installed though.
>
>3. Weak "maintenance free" batteries are sometimes low on electrolyte. I
>think that further reduces their capacity to absorb any excess voltage or
>current and might lead to more voltage excursions. Most people never pop
>the caps off automobile batteries any more as it is often not obvious how
>to do it, or that it can be done. It seems that my little (8AH) AGM
>batteries will accept very little current initially when fully discharged.
An RG battery is sealed and should not be opened over
the service life of the battery. The do-called "maintenance
free" he's referring to is a class of vented, flooded battery
which will run without service as long as they are not
abused. But this is a separate issue not related to the
thread and generally not applicable since I doubt that
anyone would put such a battery in their airplane.
>4. As a WAG another contribution might be abnormal operation while fooling
>around with a weak battery. If I leave the ignition/key on with my ND IR
>alternator on my aircraft without starting the engine, the alternator does
>draw several amps of field current and it will heat up quite noticeably
>with no cooling airflow.
Yup. All externally regulated alternators will do this.
They've been commanded by a regulator (full field output
voltage) to raise the bus voltage will the shaft is not
turning. Hence, full field current of about 3A x 12v dissipates
36 watts of unproductive heat within the machine. Some
modern IR alternators sense the ac voltage from the
stator windings and won't allow the regulator to come alive
until it senses that the shaft is turning. Apparently the
one you have does not have this feature. But when
the field is fully excited this 36 watt dissipation
is a fraction of that which the alternator would dump
under full load.
Consider a 60A machine putting out 14V (840 watts)
running about 75% efficient. This means that
at full load it rejects about 280 watts of heat.
>Anyway my personal rule now is to change out any suspicious battery with a
>new FULLY charged unit and I can sometimes send the vehicle to the
>wreckers with the original alternator. I do run weak batteries in my
>tractor but that has an external homemade VR that hangs out in the breeze
>(like the alternator) and everything runs very very cool ;)
You've suggested that IR alternators are, as a class of product,
more vulnerable to cooling starvation than ER alternators. I have
no personal observations that might support this idea. All
alternators are energy conversion devices that run at less than
100% efficiency. This means that when operated at name-plate rated
loads, they will have some heat to reject. An alternator cannot
be loaded to more than a few percent above name plate rating.
I.e. unlike generators, you cannot get the machine to dump
out say 2x rated load. They're magnetically current limited
so it all comes down to cooling. The smaller and more compact
the alternator, the more difficult it is to get air to flow
to vital areas . . . but this is still an INSTALLATION issue
and not one we should have to address by how we install
or deal with dead batteries.
It may well be that many poorly installed alternators
have been saved from early demise by any number of hat-dances
performed to various tunes. But in the final analysis,
you cannot expect ANY alternator to function to nameplate
ratings under all conditions if you don't provide for
adequate cooling.
Bob . . .
Message 8
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Subject: | RE: $low$ handi-talkies |
Good advice Bob, but Larry McDonald, off-line, suggested even better.
He suggested that I spend a few dollars more to get a little better
quality units, then donate them to the troops in Afhganistan and Iraq
when I'm done--necessary it seems since we are buying so many billion
dollar bombers and nuclear submarines that we can't afford to provide
walkie talkies to our troops to keep them safe. Excellent idea and
consider it done.
Chuck Jensen
Do not Archive
-----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, March 07, 2007 2:41 PM
Subject: AeroElectric-List: RE: $low$ handi-talkies
--> <nuckollsr@cox.net>
At 07:03 AM 1/7/2007 -0500, you wrote:
>--> <cjensen@dts9000.com>
>
>Since I just happen to be in the market for a half-dozen walkie talkies
>for a project, is there any concensus on the best, cheap unit....Cobra
>MicroTalk? Motorola TalkAbout? Or, are they really all about the
>same. I'm buying cheap as after a week, they are a Good-Will donation.
As long as you're not expecting them to function at
more than a fraction of advertised range, go for
the $low$ versions. Buy one pair and try them out
in the most demanding situation you can anticipate
before you buy the rest.
Bob . . .
Message 9
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Subject: | RE: $low$ handi-talkies |
At 03:51 PM 1/7/2007 -0500, you wrote:
>
>Good advice Bob, but Larry McDonald, off-line, suggested even better.
>He suggested that I spend a few dollars more to get a little better
>quality units, then donate them to the troops in Afhganistan and Iraq
>when I'm done--necessary it seems since we are buying so many billion
>dollar bombers and nuclear submarines that we can't afford to provide
>walkie talkies to our troops to keep them safe. Excellent idea and
>consider it done.
Wasn't aware of that. Do you have an address for a "pipe"
that would put any such donations in the right hands?
Bob . . .
Message 10
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Subject: | Narco ADF with RG-62 Antenna |
Hey Listers,
My airplane has a Narco 141 ADF (which works only marginally). I was
under the panel inspecting things and noticed that it's wired with RG-62
coax. I didn't recognize that number so I looked it up. I found that
it's 93ohm impedance cable. Does anybody know if that's the right stuff
for this ADF? I had thought 50ohm was the defacto standard for avionics.
I am wondering if having the wrong cable might be causing the substandard
performance..
Other question.. Does anyone have a diagnostic manual or install manual
for this ADF?
Regards,
Matt-
Message 11
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Subject: | Re: Narco ADF with RG-62 Antenna |
At 06:49 PM 1/7/2007 -0700, you wrote:
>
>Hey Listers,
>
>My airplane has a Narco 141 ADF (which works only marginally). I was
>under the panel inspecting things and noticed that it's wired with RG-62
>coax. I didn't recognize that number so I looked it up. I found that
>it's 93ohm impedance cable. Does anybody know if that's the right stuff
>for this ADF? I had thought 50ohm was the defacto standard for avionics.
>I am wondering if having the wrong cable might be causing the substandard
>performance..
>
>Other question.. Does anyone have a diagnostic manual or install manual
>for this ADF?
Yeah, that's the right stuff. It's a special lo-capacity
coax used in low frequency radio receivers. Not easy to find
and not fun to work with either as I recall but it's been
many moons.
The only data I have on it is the pinout diagrams I've published
at:
http://www.aeroelectric.com/Installation_Data/Narco_140-141_ADF.pdf
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
---------------------------------------------------------
Message 12
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Subject: | Re: Narco ADF with RG-62 Antenna |
Okee doke.. The pinout is interesting, but doesn't have everything I was
looking for.
Thanks anyway (times two).
Matt-
> <nuckollsr@cox.net>
>
> At 06:49 PM 1/7/2007 -0700, you wrote:
>
>> <mprather@spro.net>
>>
>>Hey Listers,
>>
>>My airplane has a Narco 141 ADF (which works only marginally). I was
>>under the panel inspecting things and noticed that it's wired with RG-62
>>coax. I didn't recognize that number so I looked it up. I found that
>>it's 93ohm impedance cable. Does anybody know if that's the right stuff
>>for this ADF? I had thought 50ohm was the defacto standard for avionics.
>>I am wondering if having the wrong cable might be causing the substandard
>>performance..
>>
>>Other question.. Does anyone have a diagnostic manual or install manual
>>for this ADF?
>
> Yeah, that's the right stuff. It's a special lo-capacity
> coax used in low frequency radio receivers. Not easy to find
> and not fun to work with either as I recall but it's been
> many moons.
>
> The only data I have on it is the pinout diagrams I've published
> at:
>
> http://www.aeroelectric.com/Installation_Data/Narco_140-141_ADF.pdf
>
> Bob . . .
>
> ---------------------------------------------------------
> < What is so wonderful about scientific truth...is that >
> < the authority which determines whether there can be >
> < debate or not does not reside in some fraternity of >
> < scientists; nor is it divine. The authority rests >
> < with experiment. >
> < --Lawrence M. Krauss >
> ---------------------------------------------------------
>
>
Message 13
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Subject: | Three Fat Wires on Starter Contactor Bolt: How? |
Folks,
I'm building a GlaStar with the battery behind the baggage compartment.
I've run (2) 2 AWG cables from the firewall to the battery area. I
intend to terminate the (8 AWG) "B" alternator lead on the battery side
of the starter contactor as it is shown on Z-11. I also want to run
another 8 AWG from the same starter contactor bolt to the fuse panel to
avoid running another fat wire all the way to the back.
But the starter contactor bolt isn't long enough to capture three lugs
with lock washer and nut. I could gain some room by putting a thinner
nut next to the contactor body but I'm afraid to start wrenching on that
nut for fear of screwing up the contactor internals. I have two
possible approaches and am looking for comments or alternatives.
First, crimp the two 8 AWG wires into a single lug (I have a good
crimper for big lugs and will fill the cavity with solder). The space
on the contactor bolt will be tight but should be feasible. I could
gain even more room by using a metal stop nut and eliminating the lock
washer. Second, fabricate a short buss bar out of heavy gauge brass and
attach that to the contactor bolt and fasten the three lugs to the buss
bar. My concern here is properly insulating and securing the buss bar.
Any shorts here and I'd have a flying arc welder under my cowling.
Would that dippable plastic coating material (Plasti-Kote?) work? How
about the fuseable silicon tape?
(I've already used an uninsulated piece of brass to tie my ammeter shunt
into the negative side. The brass bolt through the "forest-of-tabs"
also captures the ground strap to the engine crankcase and one end of
the brass bar. The ammeter shunt is attached to the other end of the
brass bar and my 2 AWG negative return cable is attached to the other
end of the ammeter shunt.)
Unrelated question: Is Ultra Tef-Gel conductive? I've been using it on
some electrical connections on the assumption that it is conductive. If
it isn't, I've got some rework to do.
Best regards,
Bob
Message 14
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Subject: | Re: Three Fat Wires on Starter Contactor Bolt: How? |
At 10:37 PM 1/7/2007 -0600, you wrote:
>Folks,
>
>I'm building a GlaStar with the battery behind the baggage
>compartment. I've run (2) 2 AWG cables from the firewall to the battery
>area. I intend to terminate the (8 AWG) "B" alternator lead on the
>battery side of the starter contactor as it is shown on Z-11. I also want
>to run another 8 AWG from the same starter contactor bolt to the fuse
>panel to avoid running another fat wire all the way to the back.
>
>But the starter contactor bolt isn't long enough to capture three lugs
>with lock washer and nut. I could gain some room by putting a thinner nut
>next to the contactor body but I'm afraid to start wrenching on that nut
>for fear of screwing up the contactor internals. I have two possible
>approaches and am looking for comments or alternatives.
>
>First, crimp the two 8 AWG wires into a single lug (I have a good crimper
>for big lugs and will fill the cavity with solder). The space on the
>contactor bolt will be tight but should be feasible. I could gain even
>more room by using a metal stop nut and eliminating the lock
>washer. Second, fabricate a short buss bar out of heavy gauge brass and
>attach that to the contactor bolt and fasten the three lugs to the buss
>bar. My concern here is properly insulating and securing the buss
>bar. Any shorts here and I'd have a flying arc welder under my
>cowling. Would that dippable plastic coating material (Plasti-Kote?)
>work? How about the fuseable silicon tape?
>
>(I've already used an uninsulated piece of brass to tie my ammeter shunt
>into the negative side. The brass bolt through the "forest-of-tabs" also
>captures the ground strap to the engine crankcase and one end of the brass
>bar. The ammeter shunt is attached to the other end of the brass bar and
>my 2 AWG negative return cable is attached to the other end of the ammeter
>shunt.)
>
>Unrelated question: Is Ultra Tef-Gel conductive? I've been using it on
>some electrical connections on the assumption that it is conductive. If
>it isn't, I've got some rework to do.
>
>Best regards,
>
>Bob
>
>
><http://www.matronics.com/Navigator?AeroElectric-List>http://www.matronics.com/Navigator?AeroElectric-List
>
>
>-- incoming mail is certified Virus Free.
>Checked by AVG.
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
---------------------------------------------------------
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Subject: | Re: Three Fat Wires on Starter Contactor Bolt: How? |
At 10:37 PM 1/7/2007 -0600, you wrote:
>Folks,
>
>I'm building a GlaStar with the battery behind the baggage
>compartment. I've run (2) 2 AWG cables from the firewall to the battery
>area. I intend to terminate the (8 AWG) "B" alternator lead on the
>battery side of the starter contactor as it is shown on Z-11. I also want
>to run another 8 AWG from the same starter contactor bolt to the fuse
>panel to avoid running another fat wire all the way to the back.
>
>But the starter contactor bolt isn't long enough to capture three lugs
>with lock washer and nut. I could gain some room by putting a thinner nut
>next to the contactor body but I'm afraid to start wrenching on that nut
>for fear of screwing up the contactor internals. I have two possible
>approaches and am looking for comments or alternatives.
>
>First, crimp the two 8 AWG wires into a single lug (I have a good crimper
>for big lugs and will fill the cavity with solder).
that will work.
> The space on the contactor bolt will be tight but should be feasible. I
> could gain even more room by using a metal stop nut and eliminating the
> lock washer. Second, fabricate a short buss bar out of heavy gauge brass
> and attach that to the contactor bolt and fasten the three lugs to the
> buss bar.
that probably works better.
> My concern here is properly insulating and securing the buss bar. Any
> shorts here and I'd have a flying arc welder under my cowling. Would
> that dippable plastic coating material (Plasti-Kote?) work? How about
> the fuseable silicon tape?
See pictures at:
http://www.aeroelectric.com/Pictures/Wiring_Technique/Firewall_Ckt_Protection.jpg
http://www.aeroelectric.com/Pictures/Wiring_Technique/Contactor_Interconnect/Contactor_Strap_3.jpg
This is the engine side of firewall on Model 36 Bonanza. LOTS
of exposed, high current conductors. What's going go get into them?
You've got a propeller spinning up front that will make hamburger out
of you in a heartbeat . . . but we don't put wire cages around them.
It's perfectly okay to have "open hazards" as long as you've
done the necessary homework to keep things from falling into them.
>
>(I've already used an uninsulated piece of brass to tie my ammeter shunt
>into the negative side. The brass bolt through the "forest-of-tabs" also
>captures the ground strap to the engine crankcase and one end of the brass
>bar. The ammeter shunt is attached to the other end of the brass bar and
>my 2 AWG negative return cable is attached to the other end of the ammeter
>shunt.)
>
>Unrelated question: Is Ultra Tef-Gel conductive? I've been using it on
>some electrical connections on the assumption that it is conductive. If
>it isn't, I've got some rework to do.
No, it's an anti-seize compound and not conductive. However, in
a properly bolted or crimped joint, compression forces in the
metal-to-metal joints would extrude any Tef-Gel out of the joint.
Don't worry about it.
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
---------------------------------------------------------
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