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Simple ideas in physics

 
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nuckolls.bob(at)aeroelect
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PostPosted: Sun Oct 14, 2018 5:02 am    Post subject: Simple ideas in physics Reply with quote

At 01:31 PM 10/13/2018, you wrote:
OMG!!!


If I had to put a number to it, 90% were due to bad contacts due to corrosion.
You can not visually inspect a ground connection. It must be undone, wire brushed,
NEW star lock washers replaced and tightened securely... Yes, tightened even
beyond specs.| Then, you can spray some chromate paint over the connection
for a bit more corrosion protection.

| I've never seen this kind of effort expended on a ground
| to the airframe. A bizjet has HUNDREDS of such grounds.

Barry - And this is a plane that you did design work on?| What about Ground Loops?
You do recall it was Ground Loops that initiated our rivalry .

All airplanes are rife with ground loops
of no consequence as long as
a potential victim's small signal path
does not intersect with an antagonistic
system's power path. Avoiding this condition
is a competent of 'system integration'.

*** Barry - This is an after thought - I'm coming back to this point after I re-read my remarks on 'That are being CURED...' I just realized I said use a New Star Washer. Well a Star Washer will NOT permit the type of joint you are theorizing about. AIR and MOISTURE will get under, around and between the Star Washer and the Ground Connection. So, that alone blows your NO AIR ACCESS theory out of the air and right onto the water. But, continue to read.
It is also a GREAT reason to use Chromate Paint or Dielectric Grease.

You will NEVER find a star washer used
in the current path on any production airplane I've
had contact with. They are used under the
heads/nuts of threaded fasteners on switch
and circuit breaker wiring as prophylactic
against fastener loosening . . . they are
never part of the joint's electrical integrity.


|Barry - Are you REALLY comparing a bizjet to what we fly?
|And how many hours a year does a bizjet fly compared to what we fly
|And what happens with the bizjet when it is not being flown?
|Stored in a heated hanger?

The examples I illustrated just happened
to be on a B400 . . . fabricated
by process specification that applies to
the fleet: Skippers to King Airs irrespective
of how often flown or where they are housed.

And what 'faying' surface are you talking about? Look up the definition of faying.
These are Grounding Points, not assembly points.

Okay . . .

[img]cid:.0[/img]


Preventing 'crevice corrosion' by exclusion of moisture
and air into GAS TIGHT joints is what we're talking
about here . . . and it is not unique to structural
joining.

<snip>

AND - IF your logic held water, why am I seeing so many BAD Grounds and Connections - That are being CURED *** by simply: Removing the Ground, Cleaning the Ground with a wire brush, installing a New Star Washer and Tightening the Nut?| How do you explain that!
And just for S&G, lets talk about SPARS, they should have a FAYED union, with heavy duty Nuts & Bolts or Large Size Rivets put together with tons of force - YET!| They corrode!!!

I cannot speak to your experiences. And yes,
I've never 'inspected' any airplane. I was
schooled in the art and physics of practical,
robust creations that meet design goals.

| A ground connection can look pretty bad on the surface
| of components but still maintain electrical integrity
| if assemble properly in the first place.|

Barry - That is a pretty damn big IF! See *** Barry

Not at all. How many threaded fasteners will
you find on any vehicle but especially on a complex
airplanes. What makes a joint to the airframe
unique over what might be many hundreds of
joints held in compression by threaded fasteners
elsewhere? Why are all such fasteners not painted
after assembly?

|
Wait a second Bob, aren't you the one the advocates the use of
Dielectric Grease on connections just to prevent corrosion?
I agree with the Dielectric Grease idea. Been doing it for decades.

| It sure doesn't hurt but recall that the purpose of
| the grease is to fill voids in the surfaces that did
| not get closed when the joint was made up in the
| first place. A void full of grease won't admit
| moisture+air.

| Here's a ground cluster in the nose of a Beechjet

Barry - I don't care about the Beachjet! One plane, out of 30 that I do or tens of thousands nationwide, is NOT statistical proof of your theory.
But, I will take pictures the next time I come across a ground/connection with with bad/failing continuity.
Hey Guys - Did you look at the picture in the link? It sure as hell looks like the area under the connectors was WIRE BRUSHED.

Yup . . . part of the process spec. If it were a single
terminal on a threaded fastener, the prepared area
would have been cleaned with a bonding brush . . .
also fitted with wire bristles.

[img]cid:.1[/img]

Standard aviation tooling for cleaning the area
in the made-up joint. Was awarded my own personal
boding brush in 1961 at Boeing.

This is not a statistical study nor is it my 'theory'. The
photo was offered as one example of hundreds of thousands
that went into production airplanes in Wichita over
the past 100 years.

And it sure looks like it was an AFTER THOUGHT!| If it was designed to be a bare area I would think the area would have a Nice Straight Lines and be chromate conversion to a Type 2, Class 3. <-- Yes, it is electrically conductive AND resists corrosion.
Guess the original design engineers forgot about that?

Nope, they considered it at length. Studied the
physics and then crafted an assembly line process
specification to share the findings of their
study with subsequent generations of airplane
builders.

| If the airplane is operated in a particularly
| wicked environs, like the sea coast, the surfaces
| on and around such joints will enjoy protection
| from accelerated corrosion but if the joint was
| properly made up in the first place, the service
| life of the joint is probably not extended much.

Barry - 'IF' - 'PROBABLY NOT' - Not the words the FAA or a customer wants to hear.

We're not talking about FAA or customers. These
are simple ideas in physics speaking to the
exclusion of moisture and oxygen into
contact-critical areas of an electrical
connection. Just as an AMP tool strives to
make a gas-tight connection between wire strands
and terminal, so do our fabrication practices
strive for moisture excluding interface in
the faying surfaces of a ground connection.

<snip>

Barry - I wish I was drunk so I can blame my "OMG" statement on alcohol.
Yes,| Bob, they are a 24 volt bulb in a 12 volt system.|
They have very heavy elements - you can take a magnifying glass and see that.
Yes, they are marked as 12 / 14 volts.
Where does my information come from?
It is published in the common sense handbook which fell off your desk.
PROOF - Take two bulbs.| Both of the same Wattage and same voltage.
Make sure one of the is the standard 12 volt Nav Marker Light.
Hook them up to an ample battery. At The Same Time.
Which one is brighter?
And one it is brighter by quite a bit.| NOT the Nav light!

I will offer you $100 for exemplar bulbs which
demonstrate the markings and characteristics
you cite. I will document, photograph, measure and
share my findings from your samples. Further, can you
share the ISBN for the "Handbook of Common Sense"?
I'd like to add a copy to my bookshelf.

<snip>


| Also discussed in Chapter 12. In fact, we suggested a
| keep-warm circuit to hold incandescent lamps at about
| 10% of nominal operating voltage when turned OFF. This
| keeps the tungsten filament ABOVE the brittle/ductile
| transition temperature making the bulb more resistant
| to both vibration and warm-up shock when turned ON.

Barry - TERRIFIC! But it becomes a moot point. I gather that was NOT
incorporated? Even though bizjets have an APU. And it certainly is not
what is done in our planes?
Stop talking around practicality. Do what works and does not cost the customer outrageous amounts of money.
Oh, wait! You did work for Beachcraft!!!
Great plane. Just don't expect a low co$t Annual or Repair Bill.
And I hope you never have to replace Hydraulic Landing Gear Manifold on a Beach Musketeer.
Apollo Mission 13 all over again.

You obviously have not read the book. The keep-warm
was never proposed for production aircraft. It's
value was most attractive to the OBAM aviation
community as a cost savings methodology for
extending the life of incandescent lamps based
on the simple physics describing the behavior
of tungsten filaments. You can get your own
copy at no charge:

http://www.aeroelectric.com/Book/AEC_R12A.pdf



| Yeah, the air around the airplane can carry a host
| of antagonistic stressed into vulnerable locations,
| like the metal parts of a lamp socket. Dielectric grease
| on the shell and tip of a lamp base is a good thing.

So, what happens is the filament breaks but stays in contact with
the âpostâ. I have shave seen the problem happen twice and both
times it was at the mounting post of the filament.
The low current of the DMM checks the bulb as good. But when
operational voltage and CURRENT is applied the break heats up and opens.

| So does the bulb come back on when it cools only to
| immediately go dark again?

Barry - I don't know! My eyes can not detect something that happens in micro seconds.
The bulbs did NOT show any coming to life, EXCEPT for resistance through the filament.|
Twice I have seen this - I am not an electron so I can not see what is happening inside the bulb.| |
I only know:
1 - The bulb shows continuity/resistance.
2 - The bulb does not SHOW me any light.
3 - When a new bulb is inserted the system works.

I don't think I emptied the 55 gal trash can as yet... If I can find the bulb I'll mail it to you.

I'd be delighted to receive it. Will reimburse your
expenses. I used to study remnants of light bulbs
from car wrecks to see if we could ascertain whether
or not the bulb was illuminated when the major impact
forces were impressed on the bulb.

Once such study helped secure a family's recovery after
loss of a daughter squashed in her VW bug
by an 18-wheeler. Your example of filament behavior
is new and I'd love to add it to my library of
knowledge.


Bob, you are just not following the K.I.S.S. M.E. principal. If it works why fight it!

Bob, I like our banter. It is just your single minded logic that escapes me.
I would buy you a drink should we ever meet. I hope we do.
Wow! Twice in one email I referenced alcohol, you must think me a drunk?

Not at all. But I do think you misunderstand
what goes on here. There cannot be any rivalry. This
is not a political arena and I seek no 'approvals'.
We study properties of materials and management of
energy founded in science. I.e the repeatable
experiment based on simple-ideas in physics.

This is a class-room with roots that go back to the Compuserve
AVSIG forum in 1988. The first volumes of the AeroElectric
Connection were published about that time too. It has
be updated 11 times and over 10,000 copies sold. If there
is bad-science in there, I need to know about it so that
it can be corrected with the next update.


Bob . . .


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