Today's Message Index:
----------------------
1. 12:42 AM - Re: Your email to Waterbirds (bill@waterbirds.com)
2. 05:55 AM - Re: Copper Bar vs "FAT" wire (Henry Trzeciakowski)
3. 07:47 AM - Re: Re: Copper Bar vs "FAT" wire (Robert L. Nuckolls, III)
4. 09:09 AM - Re: Re: Copper Bar vs "FAT" wire (Henry Trzeciakowski)
5. 09:32 AM - Re: Re: Copper Bar vs "FAT" wire (Ralph Finch)
6. 10:11 AM - Epoxy to Aluminum (Dennis Johnson)
7. 10:15 AM - Re: Re: Copper Bar vs "FAT" wire (Vernon Little)
8. 10:29 AM - Re: Re: Copper Bar vs "FAT" wire (dhall@donka.net)
9. 11:07 AM - Re: Epoxy to Aluminum (Charlie England)
10. 11:35 AM - Re: Re: Mechanical question (Tim Andres)
11. 12:00 PM - Mechanical question ()
12. 01:02 PM - Re: Epoxy to Aluminum (raymondj)
13. 01:34 PM - Strange Exp-Bus Problem (Peter Pengilly)
14. 03:07 PM - Re: Mechanical question (Speedy11@aol.com)
15. 05:56 PM - Re: Strange Exp-Bus Problem (RALPH HOOVER)
16. 11:27 PM - Re: Re: Copper Bar vs "FAT" wire (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Your email to Waterbirds |
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Message 2
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| Subject: | Re: Copper Bar vs "FAT" wire |
Bob:
I'm planning to use copper bar in lieu of "fat wire" in 2 areas:
1- from the Starter Contactor to Master Battery Contactor - 1/8" (.125)
thick
2- and from the Starter Contactor to the 60 amp Current Limiter - 1/16"
(.063)...
My question is: Is the thickness of the copper bar appropriate?
Thanks
Hank
Message 3
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| Subject: | Re: Copper Bar vs "FAT" wire |
At 08:58 AM 4/27/2008 -0700, you wrote:
><hammer408@comcast.net>
>
>Bob:
>
>I'm planning to use copper bar in lieu of "fat wire" in 2 areas:
>
>1- from the Starter Contactor to Master Battery Contactor - 1/8" (.125)
>thick
>
>2- and from the Starter Contactor to the 60 amp Current Limiter - 1/16"
>(.063)...
>
>My question is: Is the thickness of the copper bar appropriate?
>
>Thanks
>
>Hank
Those are PLENTY thick . . . if it's stuff you already
have laying around and don't mind working with copper
(machines like peanut butter) it will be find. If you're
of a mind to make the task a bit easier, .032" x 3/4"
brass strips like #243 found at:
http://www.udisco.com/hobbies/inv/KS.HTM
are much easier to work with.
Bob . . .
Message 4
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| Subject: | Re: Copper Bar vs "FAT" wire |
Bob:
I already have the copper bars and, if fact, they are cut and ready to bend
and install......they were a lottle hard to work with !!!!
I'm somewhat surprised that you suggest .032: isn't that a little thin,
considering these bars are replacing 4awg wire ????
----- Original Message -----
From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
Sent: Sunday, April 27, 2008 7:44 AM
Subject: Re: AeroElectric-List: Re: Copper Bar vs "FAT" wire
<nuckolls.bob@cox.net>
>
> At 08:58 AM 4/27/2008 -0700, you wrote:
>
> ><hammer408@comcast.net>
> >
> >Bob:
> >
> >I'm planning to use copper bar in lieu of "fat wire" in 2 areas:
> >
> >1- from the Starter Contactor to Master Battery Contactor - 1/8" (.125)
> >thick
> >
> >2- and from the Starter Contactor to the 60 amp Current Limiter - 1/16"
> >(.063)...
> >
> >My question is: Is the thickness of the copper bar appropriate?
> >
> >Thanks
> >
> >Hank
>
> Those are PLENTY thick . . . if it's stuff you already
> have laying around and don't mind working with copper
> (machines like peanut butter) it will be find. If you're
> of a mind to make the task a bit easier, .032" x 3/4"
> brass strips like #243 found at:
>
> http://www.udisco.com/hobbies/inv/KS.HTM
>
> are much easier to work with.
>
> Bob . . .
>
>
Message 5
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| Subject: | Re: Copper Bar vs "FAT" wire |
I assume your motive for using a bar instead of wire is higher current
capacity -> lower resistance -> lower voltage drop and power loss.
I'm a hydraulic engineer for the California Dept. of Water Resources...and
years ago took a tour of our biggest lift station at the base of the
Tehachapi Mtns. A single lift of about 2,000 feet, 4,500 cfs pumping rate.
That requires a lot of power. I remember well the "wire" they use to carry
the current (which I think was about 1000 amps at 10-12kV): a tube a few
inches in diameter. The electrical engineer said current is carried on the
surface and the tube gave them the surface they needed.
Not suggesting you use a tube, but maybe braided multi-strand wire is better
than a single bar?
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Henry
Trzeciakowski
Sent: Sunday, April 27, 2008 8:58 AM
Subject: AeroElectric-List: Re: Copper Bar vs "FAT" wire
--> <hammer408@comcast.net>
Bob:
I'm planning to use copper bar in lieu of "fat wire" in 2 areas:
1- from the Starter Contactor to Master Battery Contactor - 1/8" (.125)
thick
2- and from the Starter Contactor to the 60 amp Current Limiter - 1/16"
(.063)...
My question is: Is the thickness of the copper bar appropriate?
Thanks
Hank
Message 6
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| Subject: | Epoxy to Aluminum |
Greetings,
As part of building a composite airplane, I studied everything I could
find about epoxies, materials, and adhesive bonding in general. I
concluded that I did not have the ability to make an epoxy bond to
aluminum that I could be confident that it wouldn't fail.
The problem is that aluminum begins oxidizing immediately after
cleaning. No matter how quick you are, unless you use extraordinary
measures, there will be aluminum oxide on the surface you are bonding.
Aluminum oxide has relatively low strength. The epoxy bonds well to the
aluminum oxide, but the aluminum oxide isn't stuck very well to the
underlying aluminum. After some number of hot/cold and wet/dry cycles,
the bond may weaken enough to fail.
Obviously, Boeing and others solved this problem long ago. However,
based on the great reference book, "Composite Basics," by Andrew
Marshall, their methods aren't practical for most of us homebuilders.
>From chapter 11, Marshall says, "Unfortunately, both the FPL etch and
the PAA treatments (the ones widely and successfully used in the
industry) involve extensive chemical control and a large investment in
equipment."
As an interesting aside, he describes an industry standard "wedge" test
where two .125" thick aluminum pieces are bonded together. After
curing, a wedge is driven into the end of the assembly, between the two
pieces of aluminum, which forces the bond to break at that point. A
mark is placed at the point where the fracture stops. The test piece is
then placed into a warm, wet chamber for one hour. The assembly is then
removed and the additional distance the crack propagated during the
warm/wet test is measured. If the crack grew less than three-fourths of
an inch, the bond is considered to be good for life. Marshall says that
if the aluminum was cleaned but not chemically treated, the assembly
will likely totally delaminate during the one hour test!
Since I didn't have the ability to duplicate Boeing's chemical treatment
process, I didn't make any bond to aluminum that would cause anything
more than inconvenience if it failed. Heat and humidity seem to be the
culprits, which might explain why some people report long lasting bonds
and others have failures.
Best,
Dennis
Message 7
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| Subject: | Re: Copper Bar vs "FAT" wire |
Actually, what you are referring to is "skin effect" and it only comes into
play at high frequencies. For DC loads in an aircraft, it's the total
cross-sectional area that determines the resistance.
For what it's worth, Brass has about 4 times the resistance of Copper (7 vs.
1.7 microhm-centimeters according the Handbook of Chemistry and Physics).
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ralph
Finch
Sent: April 27, 2008 9:29 AM
Subject: RE: AeroElectric-List: Re: Copper Bar vs "FAT" wire
--> <rgf@dcn.davis.ca.us>
I assume your motive for using a bar instead of wire is higher current
capacity -> lower resistance -> lower voltage drop and power loss.
I'm a hydraulic engineer for the California Dept. of Water Resources...and
years ago took a tour of our biggest lift station at the base of the
Tehachapi Mtns. A single lift of about 2,000 feet, 4,500 cfs pumping rate.
That requires a lot of power. I remember well the "wire" they use to carry
the current (which I think was about 1000 amps at 10-12kV): a tube a few
inches in diameter. The electrical engineer said current is carried on the
surface and the tube gave them the surface they needed.
Not suggesting you use a tube, but maybe braided multi-strand wire is better
than a single bar?
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Henry
Trzeciakowski
Sent: Sunday, April 27, 2008 8:58 AM
Subject: AeroElectric-List: Re: Copper Bar vs "FAT" wire
--> <hammer408@comcast.net>
Bob:
I'm planning to use copper bar in lieu of "fat wire" in 2 areas:
1- from the Starter Contactor to Master Battery Contactor - 1/8" (.125)
thick
2- and from the Starter Contactor to the 60 amp Current Limiter - 1/16"
(.063)...
My question is: Is the thickness of the copper bar appropriate?
Thanks
Hank
Message 8
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| Subject: | Re: Copper Bar vs "FAT" wire |
I did the same thing. Van's recommends sandwiching (2) .063 strips, so
hopefully (1) .128 strip oughta be the same. I was using the same
thickness from master to starter to anl-60a to shunt, but it might be
worth a redo to change over to .063 between the starter, anl and shunt.
Here's my fwf wiring. The odd angle of the anl install was chosen to
keep the bolts accessible around the engine mount. Shaping the strip
was easy with a vice grip and hand seamer.
http://donka.net/gallery/view_photo.php?set_albumName=rv7wiring&id=DSC07591
Using the copper bar for these short runs was easier than fab'ing
cables at the time. I'm interested in feedback as well.
Don
Message 9
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| Subject: | Re: Epoxy to Aluminum |
Dennis Johnson wrote:
> Greetings,
>
> As part of building a composite airplane, I studied everything I could
> find about epoxies, materials, and adhesive bonding in general. I
> concluded that I did not have the ability to make an epoxy bond to
> aluminum that I could be confident that it wouldn't fail.
>
> The problem is that aluminum begins oxidizing immediately after
> cleaning. No matter how quick you are, unless you use
> extraordinary measures, there will be aluminum oxide on the surface
> you are bonding. Aluminum oxide has relatively low strength. The
> epoxy bonds well to the aluminum oxide, but the aluminum oxide isn't
> stuck very well to the underlying aluminum. After some number of
> hot/cold and wet/dry cycles, the bond may weaken enough to fail.
>
> Obviously, Boeing and others solved this problem long ago. However,
> based on the great reference book, "/Composite Basics/," by Andrew
> Marshall, their methods aren't practical for most of us homebuilders.
> From chapter 11, Marshall says, "Unfortunately, both the FPL etch and
> the PAA treatments (the ones widely and successfully used in the
> industry) involve extensive chemical control and a large investment in
> equipment."
>
> As an interesting aside, he describes an industry standard "wedge"
> test where two .125" thick aluminum pieces are bonded together. After
> curing, a wedge is driven into the end of the assembly, between the
> two pieces of aluminum, which forces the bond to break at that point.
> A mark is placed at the point where the fracture stops. The test
> piece is then placed into a warm, wet chamber for one hour. The
> assembly is then removed and the additional distance the crack
> propagated during the warm/wet test is measured. If the crack grew
> less than three-fourths of an inch, the bond is considered to be good
> for life. Marshall says that if the aluminum was cleaned but not
> chemically treated, the assembly will likely totally delaminate during
> the one hour test!
>
> Since I didn't have the ability to duplicate Boeing's chemical
> treatment process, I didn't make any bond to aluminum that would cause
> anything more than inconvenience if it failed. Heat and humidity seem
> to be the culprits, which might explain why some people report long
> lasting bonds and others have failures.
>
> Best,
> Dennis
When was the book written? There are some pretty impressive bonding
agents available now (not all are 'epoxy').
Even if you limit the discussion to epoxies, consider JB Weld. There are
*lots* of aluminum things flying around on homebuilts that were repaired
(or assembled) using JB Weld, including engine components.
The BD-4's original assembly method for the wing was to bond the
fiberglass wing ribs to the aluminum tube spar. Just about every one of
them leaked fuel through the poor quality 'glass rib/skin assemblies,
but I've never heard of a debonding event at the rib/spar joints. Note
that this joint was glued with what amounts to fuel sealant (commonly
called 'pro-seal'), not a true epoxy adhesive. It wasn't even designed
to be a structural adhesive.
FWIW,
Charlie
Message 10
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| Subject: | Re: Mechanical question |
I add my data point on them. Not to be contrary, but I have never had one
come off and indeed when I have misplaced one I found it very difficult to
remove. I wonder Stan, what kind of surface you were adhering to? Boeing,
Lockheed and Airbus use them, can't be all that bad.
Tim Andres
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Speedy11@aol.com
Sent: Saturday, April 26, 2008 7:26 PM
Subject: AeroElectric-List: Re: Mechanical question
Besides the aggravation of having to register to view their products, I find
their products not suitable for aviation. I have used their nutplates and
ty wrap anchors and found both to be unsuitable for use in my airplane.
Their adhesive does not adhere well. For example, of the nutplates I
installed (about 40), half came loose. Perhaps I didn't do a good job of
applying the adhesive, but I doubt I would have screwed up 20 of them. The
reasons I don't like using Click-Bond nutplates is because:
1. Nutplates are typically used in locations that are otherwise difficult to
access. When the nutplate comes unglued (it's a matter of time) you cannot
remove the screw to replace it because the nutplate spins with the screw.
The nutplates are shorter than normal riveted nutplates and thus they can
spin in a small space. If the nutplate location is not accessable, you have
to cut through panels to get to it.
2. If (when) a nutplate comes loose and frees itself from the screw (or
falls off while removing a screw), it can become FOD inside the airplane to
get jammed in (you name it) controls, cables, etc.
Ask me how I've learned these things.
Personally, I threw away my $100 worth of Click-Bond products. I didn't
give them to anyone because I didn't want anyone else to suffer the same
aggravations and fears I did. I use only normal nutplates or screws with
nuts.
Perhaps others have had better results with Click-Bond, but I am not
satisfied with them and cannot recommend them.
Stan Sutterfield
Do not archive
I'll take a look at the Click Bond website. I see you have to register
(Grrrrrrr!!!!)
to look at their products. Thanks for the tip. I have a hunch I'll wish
I'd known about them about 3,000 hours of airplane-building ago.
_____
Need a new ride? Check out the largest site for U.S. used car listings at
AOL Autos <http://autos.aol.com/used?NCID=aolcmp00300000002851> .
Message 11
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| Subject: | Mechanical question |
4/27/2008
Hello Stan, Take a look at Perforated Base Binding Nuts and Studs on page
3120 of the
http://www.mcmaster.com/
online catalog as alternatives to both Click Bond and EZ-Point hardware.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
--------------------------------------------------------
Time: 07:30:10 PM PST US
From: Speedy11@aol.com
Subject: AeroElectric-List: Re: Mechanical question
Besides the aggravation of having to register to view their products, I
find
their products not suitable for aviation. I have used their nutplates and
ty wrap anchors and found both to be unsuitable for use in my airplane.
Their
adhesive does not adhere well. For example, of the nutplates I installed
(about 40), half came loose. Perhaps I didn't do a good job of applying
the
adhesive, but I doubt I would have screwed up 20 of them. The reasons I
don't
like using Click-Bond nutplates is because:
1. Nutplates are typically used in locations that are otherwise difficult
to
access. When the nutplate comes unglued (it's a matter of time) you cannot
remove the screw to replace it because the nutplate spins with the screw.
The nutplates are shorter than normal riveted nutplates and thus they can
spin
in a small space. If the nutplate location is not accessable, you have to
cut through panels to get to it.
2. If (when) a nutplate comes loose and frees itself from the screw (or
falls off while removing a screw), it can become FOD inside the airplane to
get
jammed in (you name it) controls, cables, etc.
Ask me how I've learned these things.
Personally, I threw away my $100 worth of Click-Bond products. I didn't
give them to anyone because I didn't want anyone else to suffer the same
aggravations and fears I did. I use only normal nutplates or screws with
nuts.
Perhaps others have had better results with Click-Bond, but I am not
satisfied with them and cannot recommend them.
Stan Sutterfield
Message 12
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| Subject: | Re: Epoxy to Aluminum |
Greetings,
The following is intended for hardware mounting on boats.
After proper dry preparation per the manual, West System epoxy technical
manual ( catalogue number 002-950, 1994) on page 9, item 5, in bonding
hardware ( continued from page 8) says: "Coat the bottom contact surface of
the hardware with unthickened epoxy.Wire brush or sand the wet epoxy into
the surface with 50 grit sandpaper. Sanding the base with, coated with
epoxy, will expose the epoxy directly to fresh metal with no chance for the
metal to oxidize."
Raymond Julian
Kettle River, MN
"Hope for the best,
but prepare for the worst."
----- Original Message -----
From: "Dennis Johnson" <pinetownd@volcano.net>
Sent: Sunday, April 27, 2008 12:06 PM
Subject: AeroElectric-List: Epoxy to Aluminum
Greetings,
As part of building a composite airplane, I studied everything I could find
about epoxies, materials, and adhesive bonding in general. I concluded that
I did not have the ability to make an epoxy bond to aluminum that I could be
confident that it wouldn't fail.
The problem is that aluminum begins oxidizing immediately after cleaning.
No matter how quick you are, unless you use extraordinary measures, there
will be aluminum oxide on the surface you are bonding. Aluminum oxide has
relatively low strength. The epoxy bonds well to the aluminum oxide, but
the aluminum oxide isn't stuck very well to the underlying aluminum. After
some number of hot/cold and wet/dry cycles, the bond may weaken enough to
fail.
Obviously, Boeing and others solved this problem long ago. However, based
on the great reference book, "Composite Basics," by Andrew Marshall, their
methods aren't practical for most of us homebuilders. >From chapter 11,
Marshall says, "Unfortunately, both the FPL etch and the PAA treatments (the
ones widely and successfully used in the industry) involve extensive
chemical control and a large investment in equipment."
As an interesting aside, he describes an industry standard "wedge" test
where two .125" thick aluminum pieces are bonded together. After curing, a
wedge is driven into the end of the assembly, between the two pieces of
aluminum, which forces the bond to break at that point. A mark is placed at
the point where the fracture stops. The test piece is then placed into a
warm, wet chamber for one hour. The assembly is then removed and the
additional distance the crack propagated during the warm/wet test is
measured. If the crack grew less than three-fourths of an inch, the bond is
considered to be good for life. Marshall says that if the aluminum was
cleaned but not chemically treated, the assembly will likely totally
delaminate during the one hour test!
Since I didn't have the ability to duplicate Boeing's chemical treatment
process, I didn't make any bond to aluminum that would cause anything more
than inconvenience if it failed. Heat and humidity seem to be the culprits,
which might explain why some people report long lasting bonds and others
have failures.
Best,
Dennis
--------------------------------------------------------------------------------
Checked by AVG.
3:01 PM
Message 13
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| Subject: | Strange Exp-Bus Problem |
Hi,
The last few times I have flown I have had a few strange 'brown-outs'.
It is most noticeable over the intercom as a short kind of shhuukkk
sound. Occasionally the radio (KX-135A) re-cycles and goes through its
re-boot routine. Initially I thought it was the master solenoid, but
thinking some more, I concluded that if the master solenoid were to
momentarily lose contact then the alternator would hold everything up.
The interrupts are usually of very short duration, such that I don't
notice most of the services blink, or by the time I have looked inside
everything is back on again. Sometimes it happens once every 5 or 10
minutes, sometimes not for a half hour or more.
I have an Exp-Bus DC load centre - I know that there has been some less
than complementary comments here about these devices (and I would not
fit one to an airplane I built, but I bought this one and I don't want
to rip it out). I'm now thinking that I am suffering some strange very
intermittent failure of this device (that I can't reproduce on the
ground).
Does anyone have any experience of the Exp-bus, or could suggest what
the fault might be?
Regards, Peter
Message 14
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| Subject: | Re: Mechanical question |
Very Cool! Thanks for pointing them out to me.
Stan
Do not archive
Take a look at Perforated Base Binding Nuts and Studs on page
3120 of the
http://www.mcmaster.com
**************Need a new ride? Check out the largest site for U.S. used car
listings at AOL Autos.
(http://autos.aol.com/used?NCID=aolcmp00300000002851)
Message 15
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| Subject: | Strange Exp-Bus Problem |
Peter,
This is just a shot in the dark as I have no experience with the EXP
buss. I do have considerable experience with failed solder joints on PC
boards used in automotive applications. Look carefully at the solder joints
for a fracture either through the solder or at the junction of the solder
and heavy objects like relays. A magnifying glass helps.
PS if this doesn't help on the EXP Buss keep it in mind for Bosch relays as
used on Volvo, Saab and many others. 10 minutes may save you enough to fill
a gas tank twice:) I've fixed flakey auto instrument panels this way also
and that's way more than a couple tanks of gas!!
Ralph & Laura Hoover
RV7A N527LR
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Peter
Pengilly
Sent: Sunday, April 27, 2008 4:30 PM
Subject: AeroElectric-List: Strange Exp-Bus Problem
<peter@sportingaero.com>
Hi,
The last few times I have flown I have had a few strange 'brown-outs'.
It is most noticeable over the intercom as a short kind of shhuukkk
sound. Occasionally the radio (KX-135A) re-cycles and goes through its
re-boot routine. Initially I thought it was the master solenoid, but
thinking some more, I concluded that if the master solenoid were to
momentarily lose contact then the alternator would hold everything up.
The interrupts are usually of very short duration, such that I don't
notice most of the services blink, or by the time I have looked inside
everything is back on again. Sometimes it happens once every 5 or 10
minutes, sometimes not for a half hour or more.
I have an Exp-Bus DC load centre - I know that there has been some less
than complementary comments here about these devices (and I would not
fit one to an airplane I built, but I bought this one and I don't want
to rip it out). I'm now thinking that I am suffering some strange very
intermittent failure of this device (that I can't reproduce on the
ground).
Does anyone have any experience of the Exp-bus, or could suggest what
the fault might be?
Regards, Peter
Message 16
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| Subject: | Re: Copper Bar vs "FAT" wire |
At 12:12 PM 4/27/2008 -0700, you wrote:
><hammer408@comcast.net>
>
>Bob:
>
>I already have the copper bars and, if fact, they are cut and ready to bend
>and install......they were a lottle hard to work with !!!!
>
>I'm somewhat surprised that you suggest .032: isn't that a little thin,
>considering these bars are replacing 4awg wire ????
Yeah . . . I stuck my foot in it. I was tangled up
in some numbers recalled from a different case
and blew it.
For COPPER thin sheet conductors, the resistance is
Micro-ohms/inch = .69/(t * w)
where t = thickness in inches and w = width in
inches.
So a copper bus bar .75" wide by .062" thick is on
the order of 15 micro-ohms/inch and from the big bus
bar tables in the sky at:
http://www.stormcopper.com/design/ampacity.htm
will exhibit a 30C rise at 145 amps. A strap
with 3" of length between studs would have a
resistance of about 45 micro-ohms. A 250 average
amps cranking current would drop 250 x 45
11,250 microvolts or 11.2 millivolts. Power
lost in this jumper would be .0112v * 250A
2.8 watts. If you had a 250 amp, 50mV shunt
in series with the starter for the purpose of
measuring its current draw, it would toss off
4x the voltage at 12.5 watts!
Note also that the same .062" x .75" strap
has a cross section of 0.046 square inches.
The minor diameter of a 5/16 stud is on the
order of 0.25" for a cross section of 0.049
square inches. So a 0.062 x .75 strap is
equivalent to the contactor studs it
attaches to.
In practice, this short bus will benefit from
heat-sinking by the mounting studs and
from relatively short duty cycle so you won't
experience the calculated 30C rise that can be
expected in long conductors allowed to achieve
a stabilized temperature.
As another Lister pointed out, brass has a higher
resistance than copper. A quick measurement of
some stuff in my metals bin from K&S Engineering
shows their brass alloy to be about 4x the
resistance of equivalent copper sheet. So, the
same stud-to-stud strap of .062 x .75 brass strip
would drop about 45 millivolts . . . on the same
order as a shunt . . . but unnecessarily high.
When I get the drive stand running, I'll be
strapping some high current contactors in the same
manner as those on your airplanes and I'll get some
actual drops and temperature rises for the various
materials available to us. In the mean time,
the K&S metals 16142 0.060 copper sheet is the
better material from which to fabricate stud
jumpers than the brass strip cited earlier.
Bob . . .
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