Today's Message Index:
----------------------
1. 05:07 AM - Re: Flap Switch Protection (Bob Barrow)
2. 05:36 AM - RF connector ()
3. 06:32 AM - Re: Flap Switch Protection (Robert L. Nuckolls, III)
4. 06:56 AM - Re: Know Your Charging System article ()
5. 07:28 AM - Re: Know Your Charging System article (Walter Fellows)
6. 09:01 AM - Re: Know Your Charging System article (rampil)
7. 09:11 AM - Re: Re: Know Your Charging System article (Robert L. Nuckolls, III)
8. 10:18 AM - Re: RF connector (B Tomm)
9. 10:51 AM - Re: RF connector (Jeffrey Skiba)
10. 11:33 AM - Re: RF connector (B Tomm)
11. 11:35 AM - Re: Re: Know Your Charging System article (John Cleary)
12. 12:40 PM - Re: Know Your Charging System article (Robert L. Nuckolls, III)
13. 07:58 PM - Crowbar Application - off topic (Frank Davis)
14. 09:57 PM - Re: Crowbar Application - off topic (Robert McCallum)
Message 1
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| Subject: | Flap Switch Protection |
Bob, For my Vans RV7 flap actuation system I used your Drawing Flaps 4.2 wh
ich utilises two S704-1 Relays and two NO/NC limit switches.
Is this still your recommended system for a situation where one wants the m
otor to be positively turned off at the flaps full up and full down positio
n.
Incidentally, are the relays in Drawing Flaps 4.2 simply required as part o
f the circuit logic, or do they serve a dual function in protecting the tog
gle switch from damage.
Funny thing is that now I can't even find Drawing Flaps 4.2 on your site. I
s it still there.
Regards Bob Barrow
11 Feb 2008 18:20:52 -0600> To: aeroelectric-list@matronics.com> From: nuc
kolls.bob@cox.net> Subject: Re: AeroElectric-List: Flap Switch Protection>
lls.bob@cox.net>> > At 09:43 AM 2/11/2008 -0800, you wrote:> > >--> AeroEle
ctric-List message posted by: "Terry Frazier" > ><fraziernv@earthlink.net>>
>> >> >I'm using Van's electric flap motor with a on-off-(mom)on dpdt swit
ch. I'm> >looking for a protection config. for the switch similar to that u
sed on the> >battery/starter contactors. Found one diagram on the web using
two (Zeiner?)> >15V diodes opposing each other across the motor wires, but
I don't know the> >pedigree of the design. Is there a better way to do thi
s, and if not will a> >zeiner diode setup do what I'm trying to do - protec
t the switch?> > PM motors are not very "inductive" . . . the> switch used
to control this motor would not> benefit from a protective device like a tr
ansorb> or zener.> > > Bob . . .> > ---------------------------------------
-)> ( . . . a long habit of not thinking )> ( a thing wrong, gives it a sup
erficial )> ( appearance of being right . . . )> ( )> ( -Thomas Paine 1776-
========================> _
=====================> > >
_________________________________________________________________
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s
Message 2
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2/12/2008
Hello John, Are you looking for the push on BNC connector? Go to this Delta
RF page and look at the bottom center row center connectors:
http://www.deltarf.com/prodspecial.html
Since these are special connectors I don't know of any way to get Delta's
part number for them other than contacting Delta, describing what you want
with the aid of this page, and asking them for help.
Good luck.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
--------------------------------------------------
Time: 07:53:41 AM PST US
From: John Tvedte <johnt@comp-sol.com>
Subject: AeroElectric-List: RF connector -
Wondering if anyone knows the part # (I assume it's a Delta RF part) for Ga
rmin's P/N 162-0098.
It's a optional BNC connector that can be used on the SL30, etc - that repl
aces the std. issue clamp style.
Thanks,
John
Message 3
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| Subject: | Flap Switch Protection |
At 11:59 PM 2/12/2008 +1100, you wrote:
>Bob, For my Vans RV7 flap actuation system I used your Drawing Flaps 4.2
>which utilises two S704-1 Relays and two NO/NC limit switches.
>
>Is this still your recommended system for a situation where one wants the
>motor to be positively turned off at the flaps full up and full down position.
You may not need the limit switches. If the actuator
is fitted with a free-wheel mechanism at the extremes
of travel, then you simply rig the flap extension
mechanism such that flaps are fully extended and
fully stowed at the mechanical limits of the
actuator.
>
>Incidentally, are the relays in Drawing Flaps 4.2 simply required as part
>of the circuit logic, or do they serve a dual function in protecting the
>toggle switch from damage.
The limit switches are not generally rated for
the kinds of stresses posed by the motor. Further,
we'd like to put a dead short on the motor when
OFF . . . this is dynamic braking that reduces
coasting.
>
>Funny thing is that now I can't even find Drawing Flaps 4.2 on your site.
>Is it still there.
See 4th page of
http://www.aeroelectric.com/PPS/Flight/Flaps/Flaps.pdf
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 4
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| Subject: | Re: Know Your Charging System article |
Bob Thanks for your typical detailed review of the
article. You make several good points, but I would like
to comment on "overload" v. longevity. You seem to
justify your opinion on certification of alternators (type
cert. planes), which is not relevant to alternator
service longevity.
Certification is fine, but no guarantee of longevity. For
example, Lycoming allows Cyl Head Temp (CHT) up to
500F, red line, but on the side, Lycoming tells pilots if
you want your engine to last, better keep CHT under
400F. Lyc doesn't make 2,000 hr TBO @ 500F or even
435F CHT. Lyc cert testing includes full pwr test, but
not for a full 2,000 hrs (I think its 20 hours). Bottom
line, a cert test is not the way to operate your engine.
Same with alternators, it may pass a FAA certification
test, but that is no guarantee of longevity, at least
past the test period.
I'm one that does subscribe to the unscientific myth that
running an alternator at full rated load will reduce its life.
More correctly stated running your alternator HOT all
the time reduces life. A Gent on this list, retired from the
automotive electrical engineering field, held the same
opinion, re-rating aside.
In a plane, the alternator is subject to external heat,
such as exhaust pipes. At high attitude the thin air
reduces cooling. The more power an alternator is
trying make, the hotter it runs. Combine all these
factors, YOU CAN COOK the alternator.
Clearly cooling is a big factor. If you have "forced
cooling" than yes you can run right up to rated power.
The issue is heat. That's why ND's have TWO fans.
HEAT has negative affects on semiconductors, brushes,
bearings and the voltage regulator (if on-board).
It's just common sense. Too much heat = bad.
Last, in the electronics industry, its well known there's a
direct correlation between semi-conductor life (like the
diodes in the rectifier) and temp. Chance of failure goes
up, time between failures goes down, statistically
with higher temps. I agree modern semiconductors are
amazingly robust devices, and they are better than past
components and will be better in the future.
I don't agree with the author's premise that alternators
in cars should last as long as ones in planes, all thing
being equal. In airplanes alternators tend to have less
cooling and more vibrations than in an auto application.
Also in the auto industry 80, 90, 100, 120 amp
alternators are now common for passenger cars, not
because they need all that power. It's because they are
de-rated and need to make power when the engine is
idling at low RPM and to KEEP THEM COOL.
To get more life from alternators increase cooling,
shield for head, reduce vibration and oversize the
alternator relative to max load (aka de-rating).
>From: "Robert L. Nuckolls, III" nuckolls.bob@cox.net
>Subject: Re: Know Your Charging System article
>
>> I recently ran across this article regarding aircraft
>> alternator operation and charging systems.
>>
>> http://www.nflite.com/ChargingSystem.html
>>
>> If you scroll down past the general explanations,
>> there is a section titled "Don't overload the system!".
>> The short story is that the author recommends
>> starting the engine with ALT field off so as to not
>> overload the charging system and/or put undue
>> strain on the diode rectifier. Is there anything to this
>> theory?
>>
>> Regards, Jay
>
> Yeah, that idea surfaces from time to time. It's
> been promulgated by a lot of folks who don't
> understand the physics of alternator performance.
>
>I've reviewed the article and posted some comments at:
http://www.aeroelectric.com/_temp/Know_Your_Charging_System.pdf
---------------------------------
Message 5
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| Subject: | Re: Know Your Charging System article |
Bob
Thanks for taking the time to read and comment on this article. It helps
with understanding the system. Have you written a description of the
electrical system that could be used with the drawings for a service manual
(including troubleshooting)? I understand your point about a good technician
not needing it but this is a less than perfect world and my experience is
that many good mechanics are not not that good with electrical systems. It
would also be helpful for the owner/builder to more efficiently diagnose
problems.
On an unrelated matter, I notice that most of the type certified composite
aircraft (columbia, cirrus and diamond) have external antennas. Do you know
if this is a requirement for certification? Is there any reason that blind
antennas cannot be just as effective as external antennas?
Best Regards
Walter Fellows
On Feb 11, 2008 7:39 PM, Robert L. Nuckolls, III <nuckolls.bob@cox.net>
wrote:
> nuckolls.bob@cox.net>
>
> At 09:14 PM 2/9/2008 -0800, you wrote:
>
> >
> >I recently ran across this article regarding aircraft alternator
> operation
> >and charging systems.
> >
> >http://www.nflite.com/ChargingSystem.html
> >
> >If you scroll down past the general explanations, there is a section
> >titled "Don't overload the system!".
> >
> >The short story is that the author recommends starting the engine with
> ALT
> >field off so as to not overload the charging system and/or put undue
> >strain on the diode rectifier. Is there anything to this theory?
> >
> >Regards,
> >Jay
>
> Yeah, that idea surfaces from time to time. It's
> been promulgated by a lot of folks who don't
> understand the physics of alternator performance.
>
> I've reviewed the article and posted some comments
> at:
>
> http://www.aeroelectric.com/_temp/Know_Your_Charging_System.pdf
>
>
> Bob . . .
>
> ----------------------------------------)
> ( . . . a long habit of not thinking )
> ( a thing wrong, gives it a superficial )
> ( appearance of being right . . . )
> ( )
> ( -Thomas Paine 1776- )
> ----------------------------------------
>
>
Message 6
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| Subject: | Re: Know Your Charging System article |
Walter,
Many certified composite AC have a conductive layer in the composite
to reduce (possibly) the impact of a lightning strike. Might also reduce
P-static during IFR operatives
Conductive layer -> No RF passage
If you don't have a conductive layer, put your antennae inside and save
yourself a few knots. The antennae will not know the difference for most
intents and purposes
As for A&Ps knowing avionics or even power circuits, you are right,
there is an incredibly strong inverse correlation between memorization
of what size wrench to use on an AN-5 bolt and knowledge of how
ground loops form and how to reduce their effect!
Not a perfect correlation, but pretty darn good ;-)
I have met an exception or two out there
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=163678#163678
Message 7
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| Subject: | Re: Know Your Charging System article |
At 06:52 AM 2/12/2008 -0800, you wrote:
>Bob Thanks for your typical detailed review of the
>article. You make several good points, but I would like
>to comment on "overload" v. longevity. You seem to
>justify your opinion on certification of alternators (type
>cert. planes), which is not relevant to alternator
>service longevity.
No such thing. I'm saying that testing confirms
compliance with published limits. It says nothing about
the quality of the device. We DO a lot of testing
in the certified world . . . but precious little in
the OBAM world.
>
>Certification is fine, but no guarantee of longevity. For
>example, Lycoming allows Cyl Head Temp (CHT) up to
>500F, red line, but on the side, Lycoming tells pilots if
>you want your engine to last, better keep CHT under
>400F. Lyc doesn't make 2,000 hr TBO @ 500F or even
>435F CHT. Lyc cert testing includes full pwr test, but
>not for a full 2,000 hrs (I think its 20 hours). Bottom
>line, a cert test is not the way to operate your engine.
>
>Same with alternators, it may pass a FAA certification
>test, but that is no guarantee of longevity, at least
>past the test period.
>
>I'm one that does subscribe to the unscientific myth that
>running an alternator at full rated load will reduce its life.
>More correctly stated running your alternator HOT all
>the time reduces life. A Gent on this list, retired from the
>automotive electrical engineering field, held the same
>opinion, re-rating aside.
>
>In a plane, the alternator is subject to external heat,
>such as exhaust pipes. At high attitude the thin air
>reduces cooling. The more power an alternator is
>trying make, the hotter it runs. Combine all these
>factors, YOU CAN COOK the alternator.
Never said you couldn't . . . All I've said
is that the user of any product should have
a reasonable expectation of satisfactory
service life if the system integrator
respects operating limits cited in the
product's data sheets.
Are you suggesting that alternators in general
cannot be expected to deliver a satisfactory
service life unless de-rated or otherwise
papered in ways not cited by the manufacturer?
Are you saying that alternators last longer in
cars because the systems integrators have
built some form of pampering or de-rating
into their products?
>
>Clearly cooling is a big factor. If you have "forced
>cooling" than yes you can run right up to rated power.
>The issue is heat. That's why ND's have TWO fans.
>
>HEAT has negative affects on semiconductors, brushes,
>bearings and the voltage regulator (if on-board).
>It's just common sense. Too much heat = bad.
>
>Last, in the electronics industry, its well known there's a
>direct correlation between semi-conductor life (like the
>diodes in the rectifier) and temp. Chance of failure goes
>up, time between failures goes down, statistically
>with higher temps. I agree modern semiconductors are
>amazingly robust devices, and they are better than past
>components and will be better in the future.
>
>I don't agree with the author's premise that alternators
>in cars should last as long as ones in planes, all thing
>being equal. In airplanes alternators tend to have less
>cooling and more vibrations than in an auto application.
>Also in the auto industry 80, 90, 100, 120 amp
>alternators are now common for passenger cars, not
>because they need all that power. It's because they are
>de-rated and need to make power when the engine is
>idling at low RPM and to KEEP THEM COOL.
"tend to have less cooling" . . . are you telling
me that the system integrator purposefully ignored
or accidently overlooked the manufacturer's operating
limits? Or perhaps you believe published limits
are bogus or inaccurate?
What's KEEP THEM COOL mean? Do you have temperature
limits to recommend? Where measured? How does one KNOW
they are doing a good thing? Should I consider
offering a new product: "Alternator Over-Temp
Warning Module"?
>
>To get more life from alternators increase cooling,
>shield for head, reduce vibration and oversize the
>alternator relative to max load (aka de-rating).
. . .or do good engineering to confirm your
design is golden before you hand the keys
to the customer. I don't see where we disagree.
The end goal is the same whether you're building
your airplane in the garage or on a factory floor.
The tests are the same whether you're doing
a FAR cert plan or a 40-hour fly off on your
homebuilt.
If one doesn't KNOW by means of purposeful
MEASUREMENT that the system is golden,
then yes, the alternative is subscription
to any doctrine of faith or uncertainty one
wishes. The author of the article was speaking
about certified aircraft and offering a LOT of
slightly organized, sometimes accurate
information sprinkled with too many
inferences and baseless deductions. In
many cases, the deductions were demonstrably
wrong.
The bottom line is that one may choose to
understand and act on that understanding
or "go with the flow" of what ever advice
passes by. The problem is navigating an
ocean of advice.
Walking past the front of one of those
so-called health and nutrition centers in
a shopping mall, I've oft fantasized about
walking into the store and saying, "Give me
one of everything."
No doubt the clerk would be surprised and
possibly even curious as to why I would
make such a request. I'd then offer, "Would
you agree that all the products in this
store are offered to be helpful and are
free of hazard?"
"Of course."
"0kay, if one wishes to exploit the benefits
offered, then the easy approach is to take
one of everything."
"But that would be too much . . . what malady
or health issue are you wanting to address?"
"Oh, I'm okay . . . or at least I feel okay
right now, but since you can't practice
medicine by offering cures, then 100% of
the products in this store are considered
a hedge against suffering some future malady."
"Sure."
"Okay, what's your advice for preventing
if not mitigating any or all future
suffering?"
Here's where we discover that the store
is stocked with thousands of competing
ideas and advice where less than 1% of
ingredients in all products would be
truly useful to the target customer.
In this case the target customer is ignorant
of the mechanism by which any product
offers benefit. The customer is concerned
about lots of things. Every tenth add on TV
and in magazines is for some kind of pill. Every
devotee of the store's doctrine and dogma
willing to extoll the virtues of a variety
of offered products. Thousands of hopeful
customers drag their various worries to
the store hoping their faith in the church
of bottle-driven health will be rewarded.
The article is question is the technological
equivalent of the 10,000 bottle health
and nutrition store. It's my mission to
filter the 99% noise and useless (but
mostly harmless) data so that folks can
exploit what's left over to advance their
understanding and the utility of their project.
Are you suggesting that the readers of this
List de-rate their alternators and subscribe
to every maintenance and operating procedure
offered in every article written about their
electrical system? Would you agree that
some filtering of advice is called for? What
filtering mechanism do you recommend?
For myself, I find comfort in reliance
upon experience of myself and my
colleagues where understanding and
observation of published limits confirmed
with good measurement are the path to
electrical system Nirvana. Service life
then becomes a quality/performance issue
that drives a search for manufacturers who
excel at conducting business in an honorable way.
Bob . . .
Message 8
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I was researching this a few weeks ago. I believe the Delta part number is
4205018N995-000. The supplier I found them at has a $25 minimum order and
no stock. Perhaps we could do a group buy. Does anybody need one, two...?
Bevan
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
bakerocb@cox.net
Sent: Tuesday, February 12, 2008 5:34 AM
Subject: AeroElectric-List: RF connector
2/12/2008
Hello John, Are you looking for the push on BNC connector? Go to this Delta
RF page and look at the bottom center row center connectors:
http://www.deltarf.com/prodspecial.html
Since these are special connectors I don't know of any way to get Delta's
part number for them other than contacting Delta, describing what you want
with the aid of this page, and asking them for help.
Good luck.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
--------------------------------------------------
Time: 07:53:41 AM PST US
From: John Tvedte <johnt@comp-sol.com>
Subject: AeroElectric-List: RF connector -
Wondering if anyone knows the part # (I assume it's a Delta RF part) for Ga
rmin's P/N 162-0098.
It's a optional BNC connector that can be used on the SL30, etc - that repl
aces the std. issue clamp style.
Thanks,
John
Message 9
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I might what is the cost for one ?
> -->
AeroElectric-List message posted by: "B Tomm"
<fvalarm@rapidnet.net>
>
> I was researching this
a few weeks ago. I believe the Delta part number
> is
>
4205018N995-000. The supplier I found them at has a $25 minimum order and
> no stock. Perhaps we could do a group buy. Does anybody need
one,
> two...?
>
> Bevan
>
>
-----Original Message-----
>
From:
owner-aeroelectric-list-server@matronics.com
>
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
> bakerocb@cox.net
> Sent: Tuesday, February 12, 2008 5:34
AM
> To: aeroelectric-list@matronics.com; johnt@comp-sol.com
> Subject: AeroElectric-List: RF connector
>
>
>
> 2/12/2008
>
> Hello John, Are you
looking for the push on BNC connector? Go to this
> Delta
> RF page and look at the bottom center row center connectors:
>
> http://www.deltarf.com/prodspecial.html
>
> Since these are special connectors I don't know of any way to get
Delta's
> part number for them other than contacting Delta,
describing what you want
> with the aid of this page, and asking
them for help.
>
> Good luck.
>
> 'OC'
Says: "The best investment we can make is the effort to gather and
> understand knowledge."
>
>
--------------------------------------------------
>
>
Time: 07:53:41 AM PST US
>
From: John Tvedte
<johnt@comp-sol.com>
> Subject: AeroElectric-List: RF
connector -
>
> Wondering if anyone knows the part # (I
assume it's a Delta RF part) for
> Ga
> rmin's P/N
162-0098.
>
> It's a optional BNC connector that can be
used on the SL30, etc - that
> repl
> aces the std.
issue clamp style.
>
> Thanks,
>
>
John
>
>
>
>
>
>
>
>
>
>
>
List Features Navigator to browse
such as List Un/Subscription,
Download, 7-Day Browse, Chat, FAQ,
much more:
http://www.matronics.com/Navigator?AeroElectric-List
>
>
available via the Web Forums!
http://forums.matronics.com
>
>
generous support!
--> http://www.matronics.com/contribution
>
>
>
>
>
Message 10
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I'm not sure. I sent an email this morning for clarification and have not
heard back yet.
Bevan
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jeffrey
Skiba
Sent: Tuesday, February 12, 2008 10:39 AM
Subject: RE: AeroElectric-List: RF connector
I might what is the cost for one ?
>
> I was researching this a few weeks ago. I believe the Delta part number
> is
> 4205018N995-000. The supplier I found them at has a $25 minimum order and
> no stock. Perhaps we could do a group buy. Does anybody need one,
> two...?
>
> Bevan
>
> -----Original Message-----
>
From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
> bakerocb@cox.net
> Sent: Tuesday, February 12, 2008 5:34 AM
> To: aeroelectric-list@matronics.com; johnt@comp-sol.com
> Subject: AeroElectric-List: RF connector
>
>
> 2/12/2008
>
> Hello John, Are you looking for the push on BNC connector? Go to this
> Delta
> RF page and look at the bottom center row center connectors:
>
> http://www.deltarf.com/prodspecial.html
>
> Since these are special connectors I don't know of any way to get Delta's
> part number for them other than contacting Delta, describing what you want
> with the aid of this page, and asking them for help.
>
> Good luck.
>
> 'OC' Says: "The best investment we can make is the effort to gather and
> understand knowledge."
>
> --------------------------------------------------
>
> Time: 07:53:41 AM PST US
>
From: John Tvedte <johnt@comp-sol.com>
> Subject: AeroElectric-List: RF connector -
>
> Wondering if anyone knows the part # (I assume it's a Delta RF part) for
> Ga
> rmin's P/N 162-0098.
>
> It's a optional BNC connector that can be used on the SL30, etc - that
> repl
> aces the std. issue clamp style.
>
> Thanks,
>
> John
>
>
>
>
>
>
>
>
>
> http://www.matronics.com/Navigator?AeroElectric-List
> http://forums.matronics.com
> --> http://www.matronics.com/contribution
>
>
>
>
Message 11
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| Subject: | Re: Know Your Charging System article |
Bob's response
-----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, 13 February 2008 4:08 AM
Subject: Re: AeroElectric-List: Re: Know Your Charging System article
<nuckolls.bob@cox.net>
At 06:52 AM 2/12/2008 -0800, you wrote:
>Bob Thanks for your typical detailed review of the
>article. You make several good points, but I would like
>to comment on "overload" v. longevity. You seem to
>justify your opinion on certification of alternators (type
>cert. planes), which is not relevant to alternator
>service longevity.
No such thing. I'm saying that testing confirms
compliance with published limits. It says nothing about
the quality of the device. We DO a lot of testing
in the certified world . . . but precious little in
the OBAM world.
>
>Certification is fine, but no guarantee of longevity. For
>example, Lycoming allows Cyl Head Temp (CHT) up to
>500F, red line, but on the side, Lycoming tells pilots if
>you want your engine to last, better keep CHT under
>400F. Lyc doesn't make 2,000 hr TBO @ 500F or even
>435F CHT. Lyc cert testing includes full pwr test, but
>not for a full 2,000 hrs (I think its 20 hours). Bottom
>line, a cert test is not the way to operate your engine.
>
>Same with alternators, it may pass a FAA certification
>test, but that is no guarantee of longevity, at least
>past the test period.
>
>I'm one that does subscribe to the unscientific myth that
>running an alternator at full rated load will reduce its life.
>More correctly stated running your alternator HOT all
>the time reduces life. A Gent on this list, retired from the
>automotive electrical engineering field, held the same
>opinion, re-rating aside.
>
>In a plane, the alternator is subject to external heat,
>such as exhaust pipes. At high attitude the thin air
>reduces cooling. The more power an alternator is
>trying make, the hotter it runs. Combine all these
>factors, YOU CAN COOK the alternator.
Never said you couldn't . . . All I've said
is that the user of any product should have
a reasonable expectation of satisfactory
service life if the system integrator
respects operating limits cited in the
product's data sheets.
Are you suggesting that alternators in general
cannot be expected to deliver a satisfactory
service life unless de-rated or otherwise
papered in ways not cited by the manufacturer?
Are you saying that alternators last longer in
cars because the systems integrators have
built some form of pampering or de-rating
into their products?
>
>Clearly cooling is a big factor. If you have "forced
>cooling" than yes you can run right up to rated power.
>The issue is heat. That's why ND's have TWO fans.
>
>HEAT has negative affects on semiconductors, brushes,
>bearings and the voltage regulator (if on-board).
>It's just common sense. Too much heat = bad.
>
>Last, in the electronics industry, its well known there's a
>direct correlation between semi-conductor life (like the
>diodes in the rectifier) and temp. Chance of failure goes
>up, time between failures goes down, statistically
>with higher temps. I agree modern semiconductors are
>amazingly robust devices, and they are better than past
>components and will be better in the future.
>
>I don't agree with the author's premise that alternators
>in cars should last as long as ones in planes, all thing
>being equal. In airplanes alternators tend to have less
>cooling and more vibrations than in an auto application.
>Also in the auto industry 80, 90, 100, 120 amp
>alternators are now common for passenger cars, not
>because they need all that power. It's because they are
>de-rated and need to make power when the engine is
>idling at low RPM and to KEEP THEM COOL.
"tend to have less cooling" . . . are you telling
me that the system integrator purposefully ignored
or accidently overlooked the manufacturer's operating
limits? Or perhaps you believe published limits
are bogus or inaccurate?
What's KEEP THEM COOL mean? Do you have temperature
limits to recommend? Where measured? How does one KNOW
they are doing a good thing? Should I consider
offering a new product: "Alternator Over-Temp
Warning Module"?
>
>To get more life from alternators increase cooling,
>shield for head, reduce vibration and oversize the
>alternator relative to max load (aka de-rating).
. . .or do good engineering to confirm your
design is golden before you hand the keys
to the customer. I don't see where we disagree.
The end goal is the same whether you're building
your airplane in the garage or on a factory floor.
The tests are the same whether you're doing
a FAR cert plan or a 40-hour fly off on your
homebuilt.
If one doesn't KNOW by means of purposeful
MEASUREMENT that the system is golden,
then yes, the alternative is subscription
to any doctrine of faith or uncertainty one
wishes. The author of the article was speaking
about certified aircraft and offering a LOT of
slightly organized, sometimes accurate
information sprinkled with too many
inferences and baseless deductions. In
many cases, the deductions were demonstrably
wrong.
The bottom line is that one may choose to
understand and act on that understanding
or "go with the flow" of what ever advice
passes by. The problem is navigating an
ocean of advice.
Walking past the front of one of those
so-called health and nutrition centers in
a shopping mall, I've oft fantasized about
walking into the store and saying, "Give me
one of everything."
No doubt the clerk would be surprised and
possibly even curious as to why I would
make such a request. I'd then offer, "Would
you agree that all the products in this
store are offered to be helpful and are
free of hazard?"
"Of course."
"0kay, if one wishes to exploit the benefits
offered, then the easy approach is to take
one of everything."
"But that would be too much . . . what malady
or health issue are you wanting to address?"
"Oh, I'm okay . . . or at least I feel okay
right now, but since you can't practice
medicine by offering cures, then 100% of
the products in this store are considered
a hedge against suffering some future malady."
"Sure."
"Okay, what's your advice for preventing
if not mitigating any or all future
suffering?"
Here's where we discover that the store
is stocked with thousands of competing
ideas and advice where less than 1% of
ingredients in all products would be
truly useful to the target customer.
In this case the target customer is ignorant
of the mechanism by which any product
offers benefit. The customer is concerned
about lots of things. Every tenth add on TV
and in magazines is for some kind of pill. Every
devotee of the store's doctrine and dogma
willing to extoll the virtues of a variety
of offered products. Thousands of hopeful
customers drag their various worries to
the store hoping their faith in the church
of bottle-driven health will be rewarded.
The article is question is the technological
equivalent of the 10,000 bottle health
and nutrition store. It's my mission to
filter the 99% noise and useless (but
mostly harmless) data so that folks can
exploit what's left over to advance their
understanding and the utility of their project.
Are you suggesting that the readers of this
List de-rate their alternators and subscribe
to every maintenance and operating procedure
offered in every article written about their
electrical system? Would you agree that
some filtering of advice is called for? What
filtering mechanism do you recommend?
For myself, I find comfort in reliance
upon experience of myself and my
colleagues where understanding and
observation of published limits confirmed
with good measurement are the path to
electrical system Nirvana. Service life
then becomes a quality/performance issue
that drives a search for manufacturers who
excel at conducting business in an honorable way.
Bob . . .
9:31 AM
9:31 AM
Message 12
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| Subject: | Re: Know Your Charging System article |
At 07:23 AM 2/12/2008 -0800, you wrote:
>Bob
>
>Thanks for taking the time to read and comment on this article. It helps
>with understanding the system. Have you written a description of the
>electrical system that could be used with the drawings for a service
>manual (including troubleshooting)? I understand your point about a good
>technician not needing it but this is a less than perfect world and my
>experience is that many good mechanics are not not that good with
>electrical systems. It would also be helpful for the owner/builder to more
>efficiently diagnose problems.
See the website at
http://aeroelectric.com/
where the AeroElectric Connection textbook
is offered in addition to numerous writings
downloadable from the website. In particular,
check out Appendix Z from the text where
you'll find numerous exemplar alternator
installations and a troubleshooting procedure
in the notes section. Note 8 as I recall.
>On an unrelated matter, I notice that most of the type certified composite
>aircraft (columbia, cirrus and diamond) have external antennas. Do you
>know if this is a requirement for certification? Is there any reason that
>blind antennas cannot be just as effective as external antennas?
It's a matter of degrees. ANYTHING one puts between
the antenna and a signal source has an effect on
performance. From the standpoint of producing an
installation on a TSO'd system that yields predictable
airplane to airplane performance, it's best that the
antenna be mounted outside.
That's not to say that some ambitious air-framer
would be told not to cover the antenna up but
it adds to the certification workload to prove
that the degradation is acceptable. Hence,
most folks don't do it.
Bob . . .
Message 13
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| Subject: | Crowbar Application - off topic |
I have a large air compressor plumbed into outlets around my shop, I
try to remember to turn the compressor off at the circuit breaker when I
leave the shop, but some times I forget. Recently, after forgetting, an
air line came loose dropping the air tank pressure below the compressor
turn on point (about 90 psi). The compressor could not keep up with the
air loss and ran continuously.
To prevent reoccurrences I came up with a crowbar circuit to shut the
compressor off in this situation, thanks to learning about crowbars from
the Z Figures. I wired a DPST 110V relay with the N/O contacts going to
the two hot legs of the 220V service and the fixed terminals to ground.
Energizing this relay put a dead short to ground on both hot leg and
opens the circuit breaker. Probably very high current through the
contacts for a very short time, but I haven't welded the contacts shut yet.
One side of t he relay coil goes to ground. The other side of the coil
goes to one leg of the 220v line (which is 110v above ground) through an
adjustable pressure switch (from McMaster-Carr) and a SPST switch in
series. The pressure switch is set to close below about 85psi. The
STSP switch is opened to allow compressor start up and is manually
closed to arm the system above 90psi. If the pressure drops below 85psi
with the system armed the circuit breaker opens, shuts off the
compressor, and removes voltage from the relay. It works well, but I'm
not sure how a building inspector would feel about it.
Message 14
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| Subject: | Re: Crowbar Application - off topic |
Frank
Why not use a DPDT or DPST-N/C relay instead, and wire the contacts in
series with the compressor supply instead of shorting it to ground? That way
when the pressure drops low enough the compressor simply shuts off rather
than shorting out. When you are using large quantities of air of course you
have to defeat this system however just as you would with your scheme.
Sounds very inconvenient. Shorting the hydro line to ground isn't a
particularly good idea and is asking for trouble, probably sooner than
later. An alternative is to wire your DPST relay such that the compressor
supply is through this relay and then wire the relay coil to the lighting
circuit in your shop. You turn out the lights when you leave and the
compressor is automatically shut down. While you're in the shop working, the
compressor runs as intended, no dangerous shorts or other complications
involved and no extra circuits to arm or disarm as required.
Bob McC
----- Original Message -----
From: "Frank Davis" <ffdavis@earthlink.net>
Sent: Tuesday, February 12, 2008 10:54 PM
Subject: AeroElectric-List: Crowbar Application - off topic
<ffdavis@earthlink.net>
>
> I have a large air compressor plumbed into outlets around my shop, I
> try to remember to turn the compressor off at the circuit breaker when I
> leave the shop, but some times I forget. Recently, after forgetting, an
> air line came loose dropping the air tank pressure below the compressor
> turn on point (about 90 psi). The compressor could not keep up with the
> air loss and ran continuously.
>
> To prevent reoccurrences I came up with a crowbar circuit to shut the
> compressor off in this situation, thanks to learning about crowbars from
> the Z Figures. I wired a DPST 110V relay with the N/O contacts going to
> the two hot legs of the 220V service and the fixed terminals to ground.
> Energizing this relay put a dead short to ground on both hot leg and
> opens the circuit breaker. Probably very high current through the
> contacts for a very short time, but I haven't welded the contacts shut
yet.
>
> One side of t he relay coil goes to ground. The other side of the coil
> goes to one leg of the 220v line (which is 110v above ground) through an
> adjustable pressure switch (from McMaster-Carr) and a SPST switch in
> series. The pressure switch is set to close below about 85psi. The
> STSP switch is opened to allow compressor start up and is manually
> closed to arm the system above 90psi. If the pressure drops below 85psi
> with the system armed the circuit breaker opens, shuts off the
> compressor, and removes voltage from the relay. It works well, but I'm
> not sure how a building inspector would feel about it.
>
>
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