Today's Message Index:
----------------------
1. 07:08 AM - Contactor and Crowbar Ratings (Craig Winkelmann)
2. 07:28 AM - Of pop rivets and lock nuts . . . (Robert L. Nuckolls, III)
3. 07:35 AM - Re: Contactor and Crowbar Ratings (Robert L. Nuckolls, III)
4. 07:53 AM - Re: Is a pop rivet acceptable for a ground attachment? (LarryMcFarland)
5. 09:14 AM - Alternator excitation - suggested wiring? (mikef)
6. 06:55 PM - Re: Contactor and Crowbar Ratings (Craig Winkelmann)
7. 07:56 PM - Re: Alternator excitation - suggested wiring? (Robert L. Nuckolls, III)
8. 08:21 PM - Re: Re: Contactor and Crowbar Ratings (Robert L. Nuckolls, III)
9. 08:27 PM - Alternator excitation - suggested wiring? (Robert L. Nuckolls, III)
10. 08:35 PM - Re: Re: Contactor and Crowbar Ratings (Bob McCallum)
11. 09:19 PM - Re: Is a pop rivet acceptable for a ground attachment? (Ralph Finch)
Message 1
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| Subject: | Contactor and Crowbar Ratings |
Bob:
I looked at the contactors made by Eaton that are 337 approved for Cessna Aircraft.
Eaton P/N PW6041H215. rated for 28 volts continuous which is good for my
24 volt experimental aircraft. My question is about the crowbar circuit for
overvoltage protection of the ground relay. The ones I see B&C and aeroelectric
carry are rated at 12 VDC and 24 VDC. Shouldn't they be 15 VDC and 28 VDC
to allow for battery charging thru the ground power port? If so, can the ones
you sell be modified for this?
Craig
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=243982#243982
Message 2
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| Subject: | Of pop rivets and lock nuts . . . |
Yesterday I offered a short list of simple ideas that
went to the task of getting life-of-the-airplane
joints between a wire and the airframe. Specifically,
how to get a wire "grounded" in a way that it stays
grounded.
Discussions here on the List have considered the goals
of achieving low resistance, high-longevity connection
between two conductors in a variety contexts. Some
tasks call for temporary or "service" connections
between two wires. In this case, we look to the products
offered by skilled designers and manufacturers of
connectors. They spend a LOT of time figuring out
the simple ideas that keep two mechanically independent
pins in low resistance contact with each other in
spite of moisture, vibration, temperature cycles,
electron flow, etc., etc.
These same designers have reasonable expectations
that users of their products will understand that
while we purchased their product for it's 'temporary'
connection features, the user still has to make the
'permanent' connections between pins and wires.
There are further considerations for supporting the
joint adjacent to the transition between 'permanent'
and 'flexible' segments of the assembly.
When we purchase crimp tools appropriate to the
well considered-components (like PIDG terminals)
then much of the process sensitive actions are
taken care of . . . as long as we follow instructions.
We have a further interest in being able to evaluate
the end-product of our labors. Did we use the right
components/tools? Was the wire properly inserted?
Was the crimp fully seated? etc. etc.
Understanding and acknowledging the skill of folks
who supply us with terminals, crimp tools, and
connectors illuminates a need for the OBAM aircraft
builder to consider his/her part in maintaining the
overall strength of the chain . . .
Emacs!
No matter how 'good' the rest of the chain's links
might be, inattention to detail at any point negates
the integrity of the whole.
Yesterday I offered a means by which a properly installed
terminal can be electrically and mechanically attached
to the airframe for the purpose of effecting a good
ground connection. I suggested that a combination of
10-32 screw, washer and lock nut would apply mate-up
forces would produce a very satisfactory joint in
terms of performance and longevity. I suggested that
a little silicone grease in the interface would be
a further hedge against ingress of moisture.
This was a best-we-know-how-to-do alternative to
the use of the pop-rivet joint that raised a list
member's curiosity as to potential loss of joint
integrity. There is some value in expanding this
discussion
The driven rivet can be both electrically and
mechanically robust. A #4 (.125) rivet set in a
#30 (.128) hole swells up during the driving process
to apply great pressure (tons per square inch)
against the walls of the hole. Further, sheets of
aluminum assembled with aluminum rivets offer no
risk for effects of dissimilar metals in presence
of moisture/oxygen for electrolytic corrosion. It's
fair to say that an aluminum grounding tab for a
rear mounted battery installed with 4-6 properly
driven rivets has a life-of-the-airplane shot for
performing as intended.
The pop-rivet is a hollow fastener that also
swells in the hole . . . and like it's driven cousin,
applies some forces in tension that holds the
parts together. But unless you use un-plated,
aluminum pop-rivets, there are dissimilar metal
issues (Yeah, you can get monel rivets too).
Further, since the device is hollow, it
cannot generate and maintain the mate-up forces
offered by it's driven cousins. In the case that
prompted this thread, the finished joint was loose
enough to allow the mated up parts to move under
ordinary manipulation with the fingers.
One might deduce from this observation that attaching
the battery ground tab with pop-rivets is
problematic . . . even if the mounted bracket can't
spin on the fastener.
Yesterday, I suggested a 10-32 screw for the works-
good-lasts-a-long-time joint. How much smaller can
we go without serious degradation of the joint?
For grounding of medium wires, say 14AWG or lighter,
an 8-32 is probably fine. Grounding small wires
(20-22AWG) can be tied down with 6-32 hardware.
In all cases, bringing clean surfaces together
with forces equal to the capabilities of the fastener
is required. The use of all-metal lock washers makes
the screw look more like a rivet. The addition of
moisture ingress protection is also a useful ingredient
in this recipe for success.
This little dissertation is not intended to demean
the lowly pop-rivet. Keep in mind that John Thorpe's
very successful T-18 was assembled with "pulled" or
"pop" rivets. See:
http://tinyurl.com/pdhszb
When use within their performance limits, the pop-rivet
has a role to perform in many plays. However, making
up lasts-a-long-time, gas-tight joints for airframe
grounds just isn't one of them.
Bob . . .
Message 3
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| Subject: | Re: Contactor and Crowbar Ratings |
At 09:06 AM 5/14/2009, you wrote:
><capav8r@gmail.com>
>
>Bob:
>
>I looked at the contactors made by Eaton that are 337 approved for
>Cessna Aircraft. Eaton P/N PW6041H215.
When you can find these, get a grip on your
wallet. While these are the cream of the crop
for DC contactors, they're quite pricey.
> . . . rated for 28 volts continuous which is good for my 24 volt
> experimental aircraft. My question is about the crowbar circuit
> for overvoltage protection of the ground relay. The ones I see B&C
> and aeroelectric carry are rated at 12 VDC and 24 VDC. Shouldn't
> they be 15 VDC and 28 VDC to allow for battery charging thru the
> ground power port? If so, can the ones you sell be modified for this?
No, generally speaking 12/14 and 24/28 are
interchangeable with respect to functionality.
The low-cost 12/24v RBM/Stancore/W-R and Cole-Hersee
battery contactors offered by B&C and others
are quite suited to our task.
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: Is a pop rivet acceptable for a ground attachment? |
Ralph,
I used an A5 pop for securing a ring lug to ground my tanks and there
are a few hundred providing
ground from the firewall back to the batteries without any problems.
Perhaps a A5 would be better
than an A4, but that's it.
Larry McFarland 601HDS at www.macsmachine.com
Ralph Finch wrote:
>
> I am grounding a gizmotron (Dynon pitot heater controller) to a wing rib
> with a Fast-On Tab. I used a pop rivet to attach the Tab to the rib, but
> then it occurred to me this might not be acceptable. The Tab can rotate
> around the rivet, though not freely or loosely. I'm not concerned about the
> mechanical properties as much as the electrical. Maybe a tighter connection
> is required?
>
> Having been wrong about almost everything electrical in the past, I thought
> I'd post here and get a definitive answer.
>
> Ralph Finch
> Davis, CA
> RV-9A QB-SA
>
>
>
Message 5
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| Subject: | Alternator excitation - suggested wiring? |
I have a question about wiring my alternator. My question is primarily about the
excitation/ignition-on connection. I've found lots of articles about alternators,
and info on this list. But most other articles talk about internally regulated
versions. So far I can't quite get my head about the excitation question.
I can surely experiment with the connections, and plan to do so this weekend.
I'm just hoping to get a better understanding before diving in too deep with
a running engine and spinning prop.
My alternator has three connections, one for field, one for 12v excitation, and
the B lead. I have the B&C LR3C regulator, overall electrical is a Z19. The alternator
was built by a local high performance shop, after talking through the
needs of my aircraft. Good bearings and grease, precise tolerances, etc. All
those things Bob talks about in his book. The instructions that came with it
say:
"Alternator has isolated field wires. Either one can be the IGNITION ON 12 volt
supply wire. The other to the FIELD CONNECTION on the regulator. The regulator
case must be grounded. "
So what I was planning to do is run a small wire from the B lead on the alternator
to one of the alternator's connections, making it the IGNITION ON connection.
Then connect the other tab to the Field connection on the regulator. That
way when I turn on the Master Switch to middle position (batt) it sends 12 volts
to the IGNITION ON connection. The hope being that is supplies the alternator
with that 12 volt IGNITION ON voltage.
I already know that turning the Master Switch to BATT position (or Alt) sends power
all the way to the B lead.
What I am not sure about is: do I need to keep that excitation/Ignition on voltage
running all the time the engine is running (would it hurt anything if I did)?
Or should it be shut off after the engine is started and alternator is producing
power?
My Master Switch is exactly as in the Z19, so it controls the on/off of the regulator
already.
It is this question of excitation that I am unclear about. Lots of articles talked
about the need for an ignition on light as a mandatory component in making
some alternators actually operate.
Thanks in advance,
Mike
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=244022#244022
Message 6
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| Subject: | Re: Contactor and Crowbar Ratings |
Bob:
Spoke with Bill at B&C. Their 24 volt crowbar trips at 32 VDC. That is OK.
However, I am having difficulty finding a contactor for a 24 VDC application.
The Stancor ones have a coil voltage of 24 VDC or 36 VDC. However, 28 VDC exceeds
the coil voltage of the 24 VDC unit so it can't work. Also, their 36 VDC
contactors will not work because of the coil voltage being too high to activate
it. Bottom line is I need a contactor with a coil voltage rating of 28 VDC.
Other than the Eaton unit (which you are correct is costly) I am running out
of luck. Any ideas?
Craig
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=244076#244076
Message 7
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| Subject: | Re: Alternator excitation - suggested wiring? |
>My alternator has three connections, one for field, one for 12v
>excitation, and the B lead. I have the B&C LR3C regulator, overall
>electrical is a Z19. The alternator was built by a local high
>performance shop, after talking through the needs of my aircraft.
>Good bearings and grease, precise tolerances, etc. All those things
>Bob talks about in his book. The instructions that came with it say:
>
>"Alternator has isolated field wires. Either one can be the IGNITION
>ON 12 volt supply wire. The other to the FIELD CONNECTION on the
>regulator. The regulator case must be grounded. "
>
> Okay, the connections described are for
> a "pull-down" regulator . . . typical of
> the built in regulators. The LR3 is
> a "pull-up" style device. This means
> that one of your free field leads goes
> to GROUND instead of 12v excitation. The
> other field terminal connect to the FIELD
> lead of the LR3.
>
>So what I was planning to do is run a small wire from the B lead on
>the alternator to one of the alternator's connections, making it the
>IGNITION ON connection.
>
> No, that's what you do for the "pull down"
> regulator architecture. Take one field lead
> to ground.
>
>Then connect the other tab to the Field connection on the regulator.
>
> Yes.
>
>That way when I turn on the Master Switch to middle position (batt)
>it sends 12 volts to the IGNITION ON connection. The hope being
>that is supplies the alternator with that 12 volt IGNITION ON voltage.
>
> Technically, once modified for legacy
> functionality as an externally regulated
> alternator, there is no more "IGN" terminal.
> Just F1, F2, B and GND (case).
>
>
>I already know that turning the Master Switch to BATT position (or
>Alt) sends power all the way to the B lead.
>
> Yes . . . through your b-lead protection
> device. ANL, MANL or other fat fuse.
>
>What I am not sure about is: do I need to keep that
>excitation/Ignition on voltage running all the time the engine is
>running (would it hurt anything if I did)? Or should it be shut off
>after the engine is started and alternator is producing power?
>
> If wired per Z-19 (or any other Z-figure, the
> DC PWR MASTER switch has control over the
> alternator.
>
>My Master Switch is exactly as in the Z19, so it controls the on/off
>of the regulator already.
>
> Then it controls the alternator too. If the
> regulator is unpowered, the altenrator is OFF.
>
>It is this question of excitation that I am unclear about. Lots of
>articles talked about the need for an ignition on light as a
>mandatory component in making some alternators actually operate.
>
> This is only for some (in fact a few) alternators
> with built in regulators. This feature no longer
> applies to your situation.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 8
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| Subject: | Re: Contactor and Crowbar Ratings |
At 08:53 PM 5/14/2009, you wrote:
><capav8r@gmail.com>
>
>Bob:
>
>Spoke with Bill at B&C. Their 24 volt crowbar trips at 32 VDC. That is OK.
Yes . . . the nominal trip range for 14v ov protection
is 16.2 to 16.5 volts. 28v aircraft it's 32.4 to 33 volts.
>However, I am having difficulty finding a contactor for a 24 VDC
>application. The Stancor ones have a coil voltage of 24 VDC or 36
>VDC. However, 28 VDC exceeds the coil voltage of the 24 VDC unit so
>it can't work. Also, their 36 VDC contactors will not work because
>of the coil voltage being too high to activate it. Bottom line is I
>need a contactor with a coil voltage rating of 28 VDC. Other than
>the Eaton unit (which you are correct is costly) I am running out of
>luck. Any ideas?
I can tell you that the 70 series, continuous duty contactors
have been used in 14 and 28 volt aircraft with good
service histories. Yes, they run warm. But in airplanes,
the ambient temperatures for most operating conditions
are lower that max rated for 12v operation which tends
to offset the effects of the extra heating.
The 70-903 contactor has a resistance of 60 ohms
operating at room temperature. If you're worried
about it, you could put a 6 ohm, 1W resistor in
series with the coil to "cool" it off by about
10% of applied voltage . . . but I think you're
okay without it. These contactors have been around
since about WWII. While they're not "Space Rated"
contactors, they've proven to be of good value
in a failure tolerant airplane.
Even the $high$ contactors have bad days
http://tinyurl.com/qmk6gm
If you're loosing sleep over it, consider the
these EV200 series contactors. They feature
automatic coil current reduction after pull-in
to reduce continuous power to keep the contactor
energized. However, they're about 6X the price
of the 70 series device and do generate some
noise that has been a problem for a few builders.
See:
http://tinyurl.com/qazl8t
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 9
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| Subject: | Alternator excitation - suggested wiring? |
My alternator has three connections, one for
field, one for 12v excitation, and the B lead.
I have the B&C LR3C regulator, overall electrical
is a Z19. The alternator was built by a local
high performance shop, after talking through the
needs of my aircraft. Good bearings and grease,
precise tolerances, etc. All those things Bob talks
about in his book. The instructions that came with it say:
"Alternator has isolated field wires. Either one
can be the IGNITION ON 12 volt supply wire. The other
to the FIELD CONNECTION on the regulator. The regulator
case must be grounded. "
Okay, the connections described are for
a "pull-down" regulator . . . typical of
the built in regulators. The LR3 is
a "pull-up" style device. This means
that one of your free field leads goes
to GROUND instead of 12v excitation. The
other field terminal connect to the FIELD
lead of the LR3.
So what I was planning to do is run a small wire
from the B lead on the alternator to one of the
alternator's connections, making it the IGNITION ON
connection.
No, that's what you do for the "pull down"
regulator architecture. Take one field lead
to ground.
Then connect the other tab to the Field connection on
the regulator.
Yes.
That way when I turn on the Master Switch to middle position
(batt) it sends 12 volts to the IGNITION ON connection.
No, just the B-lead terminal. The field supply
delivered through the regulator is still cold until
you take the DC PWR MASTER all the way up.
The hope being that is supplies the alternator with that
12 volt IGNITION ON voltage.
Technically, once modified for legacy
functionality as an externally regulated
alternator, there is no more "IGN" terminal.
Just F1, F2, B and GND (case).
I already know that turning the Master Switch to
BATT position (or Alt) sends power all the way to the B lead.
Yes . . . through your b-lead protection
device. ANL, MANL or other fat fuse.
What I am not sure about is: do I need to keep that excitation
/Ignition on voltage running all the time the engine is running
(would it hurt anything if I did)? Or should it be shut off after
the engine is started and alternator is producing power?
If wired per Z-19 (or any other Z-figure, the
DC PWR MASTER switch has control over the
alternator. Start BATT only, once engine is
running, bring alternator on line. Reverse
process at ramp idle before parking the airplane.
My Master Switch is exactly as in the Z19, so it controls
the on/off of the regulator already.
Then it controls the alternator too. If the
regulator is unpowered, the alternator is OFF.
It is this question of excitation that I am unclear about. Lots
of articles talked about the need for an ignition on light as
a mandatory component in making some alternators actually operate.
This is only for some (in fact very few) alternators
with built in regulators. This feature no longer
applies to your situation.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 10
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| Subject: | Re: Contactor and Crowbar Ratings |
As Bob N stated in his earlier reply 24 and 28 volt components are
interchangeable. (They are the same thing from a practical/functional point
of view) just as 12 and 14 volt components are. Items such as contactors,
relays, motors, light bulbs etc are just not that voltage sensitive that
they are affected by the normal swing of system voltages. Your 24 volt
(nominal) system may experience actual measured voltages from a low of say
20 (maybe less) to a high of 28, 29 (maybe more) but all of the nominally
rated 24 volt components will function just fine. It's like your house
current at home. It may be 110,112, 115,120,125, 130 Volts or thereabouts if
you actually measure it, but you don't use different toasters, washing
machines, light switches etc for these different values. Standard 120 volt
rated devices are close enough. Similarly 24 volt devices are fine for any
voltage likely to be present in a 24 /28 volt aircraft.
Another Bob
Bob McC
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-
> server@matronics.com] On Behalf Of Craig Winkelmann
> Sent: Thursday, May 14, 2009 9:54 PM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Re: Contactor and Crowbar Ratings
>
<capav8r@gmail.com>
>
> Bob:
>
> Spoke with Bill at B&C. Their 24 volt crowbar trips at 32 VDC. That is
OK.
>
> However, I am having difficulty finding a contactor for a 24 VDC
application. The
> Stancor ones have a coil voltage of 24 VDC or 36 VDC. However, 28 VDC
exceeds the coil
> voltage of the 24 VDC unit so it can't work. Also, their 36 VDC
contactors will not work
> because of the coil voltage being too high to activate it. Bottom line is
I need a
> contactor with a coil voltage rating of 28 VDC. Other than the Eaton unit
(which you are
> correct is costly) I am running out of luck. Any ideas?
>
> Craig
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=244076#244076
>
>
>
>
>
>
>
> _-
> =====================================================
> =====
> _-
> =====================================================
> =====
> _-
> =====================================================
> =====
> _-
> =====================================================
> =====
>
>
Message 11
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| Subject: | Is a pop rivet acceptable for a ground attachment? |
I replaced two ground wires using pop rivets with solid driven rivets. Much
tighter connection and it makes me feel better anyway.
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