Today's Message Index:
----------------------
1. 04:21 AM - Re: LR3 regulator Amperage indications (Bill Schertz)
2. 06:42 AM - 12 Volt .vs. 24 Volt (Brooke Wolf)
3. 07:25 AM - Re: 12 Volt .vs. 24 Volt (Bruce Gray)
4. 08:33 AM - Re: 12 Volt .vs. 24 Volt (Peter Laurence)
5. 08:33 AM - Re: Re: EXP2BUS and non-functioning alternator (Ian)
6. 09:30 AM - Re: 12 Volt .vs. 24 Volt (David LLoyd)
7. 10:03 AM - Re: 12 Volt .vs. 24 Volt (ROGER & JEAN CURTIS)
8. 11:16 AM - Speaking of W-R/RBM/Stancore Contactors . . . (Robert L. Nuckolls, III)
9. 11:29 AM - Re: 12 Volt .vs. 24 Volt (Robert L. Nuckolls, III)
10. 11:53 AM - Re: 12 Volt .vs. 24 Volt (BobsV35B@aol.com)
11. 01:44 PM - Re: 12 Volt .vs. 24 Volt (Steve Thomas)
12. 02:40 PM - Re: 12 Volt .vs. 24 Volt (Bruce Gray)
13. 06:00 PM - Re: Modifying the Piper plug (woxofswa)
14. 06:12 PM - Re: 12 Volt .vs. 24 Volt (Rick Titsworth)
15. 07:25 PM - Re: 12 Volt vs. 24 Volt (Robert L. Nuckolls, III)
16. 07:26 PM - Re: Re: Modifying the Piper plug (Robert L. Nuckolls, III)
17. 08:38 PM - Re: 12 Volt vs. 24 Volt (joe motis)
Message 1
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Subject: | Re: LR3 regulator Amperage indications |
Bob,
I am now convinced that the variations were real. I inserted an ammeter into
the field line, while the engine was stopped. Got a reading of 3.5 amps.
Then took the plane out, fired it up with the ammeter in place, and when the
alternator switch was turned on, the current went to 3.5 amps for a very
short time, then dropped to zero. At that point, it stayed at zero, and the
battery would not charge.
Put plane back in hanger, and did some static measurements.
Voltage from LR-3 to field circuit breaker ~4.5 volts
Voltage at connector to alternator (black plug) ~4.5V
Resistance to ground through the leads that field current plugs into varies
(jumps around) and then often goes to open circuit.
Could the slip rings be contaminated or not in contact?
Comments?
Bill Schertz
KIS Cruiser #4045
N343BS
Phase I testing
----- Original Message -----
From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Sent: Friday, May 08, 2009 3:31 PM
Subject: Re: AeroElectric-List: LR3 regulator Amperage indications
> <nuckolls.bob@aeroelectric.com>
>
> At 10:33 AM 5/8/2009, you wrote:
>>Bob,
>>The heavy B lead comes off the B&C alternator, and passes through a sensor
>>supplied by Blue Mountain avionics, which I believe is a Hall effect
>>transducer, and then goes to the Batteries. The Voltage is measured at
>>the Main buss.
>>
>>I am enclosing the output from the last flight showing the variations.
>
> Those traces are almost certainly plagued with data sampling
> artifacts polluted by noise. There's no way that the "real"
> numbers are that trashy. Have you explored the R/C filtering
> I suggested? How many bits of resolution does the data
> acquisition system offer?
>
>
> Bob . . .
>
> ----------------------------------------)
> ( . . . a long habit of not thinking )
> ( a thing wrong, gives it a superficial )
> ( appearance of being right . . . )
> ( )
> ( -Thomas Paine 1776- )
> ----------------------------------------
>
>
>
Message 2
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Subject: | 12 Volt .vs. 24 Volt |
I have a feeling that this subject has been discussed before, but I
need help deciding on a voltage system for my Velocity. I intend a
robust electrical system to support a high end IFR panel. The highest
draw item will probably be an electric hydraulic pump which pulls
about 30 amps at 12 volts. I know a 24 volt will save some weight in
wiring because of the lower amperage. However, after reading Bob's
response to a Blue Mountain article
http://www.aeroelectric.com/articles/richter/response_1.pdf
the weight saved appears minimal. I don't know for sure, but I have a
feeling that the vast majority of OBAM airplanes are built around 12
volt systems. My question is, why do the likes of Cessna and Cirrus
build their single engine airplanes with 24 volt systems?
Thanks...Brooke
Message 3
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Subject: | 12 Volt .vs. 24 Volt |
Similarity of construction.
Bruce
Glasair III (28v)
www.Glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Brooke Wolf
Sent: Monday, May 18, 2009 9:40 AM
Subject: AeroElectric-List: 12 Volt .vs. 24 Volt
I have a feeling that this subject has been discussed before, but I
need help deciding on a voltage system for my Velocity. I intend a
robust electrical system to support a high end IFR panel. The highest
draw item will probably be an electric hydraulic pump which pulls
about 30 amps at 12 volts. I know a 24 volt will save some weight in
wiring because of the lower amperage. However, after reading Bob's
response to a Blue Mountain article
http://www.aeroelectric.com/articles/richter/response_1.pdf
the weight saved appears minimal. I don't know for sure, but I have a
feeling that the vast majority of OBAM airplanes are built around 12
volt systems. My question is, why do the likes of Cessna and Cirrus
build their single engine airplanes with 24 volt systems?
Thanks...Brooke
Message 4
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Subject: | 12 Volt .vs. 24 Volt |
>
I have a feeling that this subject has been discussed before, but I
need help deciding on a voltage system for my Velocity. I intend a
robust electrical system to support a high end IFR panel. The highest
draw item will probably be an electric hydraulic pump which pulls
about 30 amps at 12 volts. I know a 24 volt will save some weight in
wiring because of the lower amperage. However, after reading Bob's
response to a Blue Mountain article
http://www.aeroelectric.com/articles/richter/response_1.pdf
the weight saved appears minimal. I don't know for sure, but I have a
feeling that the vast majority of OBAM airplanes are built around 12
volt systems. My question is, why do the likes of Cessna and Cirrus
build their single engine airplanes with 24 volt systems?
Thanks...Brooke
I wired a Velocity XL RG for a friend as a 12v system. Dual B&C alternators
and Regulators.
No issues for over four years and five hundred hours.
Peter
Message 5
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Subject: | Re: EXP2BUS and non-functioning alternator |
Bob,
I have the installation manual (attached) but it doesn't have a
conventional circuit diagram. There is a logical layout in Figure 7,
and a physical layout in Figure 3 (the IRF4905 is at J17) and a photo on
the front page, which also shows it's location.
There is evidence that the track leading from the Source pin on the
IRF4905 has overheated, but I have yet to check it for continuity (meter
is at the airport).
Ian
On Sun, 2009-05-17 at 21:31 -0500, Robert L. Nuckolls, III wrote:
>
> At 05:08 PM 5/16/2009, you wrote:
> >
> >I discovered that the IG lead to the alternator was only producing
> >12V when measured disconnected. As soon as a load was applied that
> >went down to 1.5V. It turns out that some filings had got under
> >the legs of an IRF4905 Mosfet and seemed to have shorted the pins.
> >
> >So, new question: Does anyone know how to test whether the cleaned
> >up IRF4905 still works, and what the pinouts might be. There are
> >three legs, but nothing I've read tells me what leg does what.
>
> See:
>
> http://www.irf.com/product-info/datasheets/data/irf4905s.pdf
>
>
> >Would I have to remove the IRF4905 from the board to test it's output?
>
> I wouldn't think so . . . but I'm mystified as to how
> an IRF4905 might be used to control an alternator. This
> is a really husky device. Far larger than necessary
> to effect control of the IG lead of an alternator. Do
> you have a schematic of the EXP2BUS product? I wasn't
> able to find anything useful on the website.
>
>
> 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: 12 Volt .vs. 24 Volt |
Why 24 v. systems.... in the commercial world it is usually about costs and
profits. Less copper used, less cost.
David
----- Original Message -----
From: "Bruce Gray" <Bruce@Glasair.org>
Sent: Monday, May 18, 2009 7:01 AM
Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt
>
> Similarity of construction.
>
> Bruce
> Glasair III (28v)
> www.Glasair.org
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
> Brooke Wolf
> Sent: Monday, May 18, 2009 9:40 AM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: 12 Volt .vs. 24 Volt
>
>
> I have a feeling that this subject has been discussed before, but I
> need help deciding on a voltage system for my Velocity. I intend a
> robust electrical system to support a high end IFR panel. The highest
> draw item will probably be an electric hydraulic pump which pulls
> about 30 amps at 12 volts. I know a 24 volt will save some weight in
> wiring because of the lower amperage. However, after reading Bob's
> response to a Blue Mountain article
>
> http://www.aeroelectric.com/articles/richter/response_1.pdf
>
> the weight saved appears minimal. I don't know for sure, but I have a
> feeling that the vast majority of OBAM airplanes are built around 12
> volt systems. My question is, why do the likes of Cessna and Cirrus
> build their single engine airplanes with 24 volt systems?
>
> Thanks...Brooke
>
>
>
Message 7
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Subject: | 12 Volt .vs. 24 Volt |
Similarity of construction.
(Please elaborate!)
Bruce
Glasair III (28v)
www.Glasair.org
I have a feeling that this subject has been discussed before, but I
need help deciding on a voltage system for my Velocity. I intend a
robust electrical system to support a high end IFR panel. The highest
draw item will probably be an electric hydraulic pump which pulls
about 30 amps at 12 volts. I know a 24 volt will save some weight in
wiring because of the lower amperage. However, after reading Bob's
response to a Blue Mountain article
http://www.aeroelectric.com/articles/richter/response_1.pdf
the weight saved appears minimal. I don't know for sure, but I have a
feeling that the vast majority of OBAM airplanes are built around 12
volt systems. My question is, why do the likes of Cessna and Cirrus
build their single engine airplanes with 24 volt systems?
Thanks...Brooke
Message 8
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Subject: | Speaking of W-R/RBM/Stancore Contactors . . . |
FYI . . .
I've become aware of a failure internal to a 3-terminal
White-Rogers/RBM Controls contactor that shorted the coil
stud to the contactor's floating conductor ring. This caused
the contactor to "buzz" and ultimately burned the wire between
the contactor and the battery master switch. Artifacts of
arcing are visible in:
http://aeroelectric.com/Pictures/Failures/W-R_RBM_3-Terminal_2s.jpg
The solder lug that attaches to the coil wire is oriented UP
toward the conductor ring and then formed over for clearance.
At first blush, I would suspect that this solder lug was
improperly assembled at the factory . . . it could have
been laid over 90-degrees and still provided for coil
lead termination with MUCH more clearance to the fat
copper conductor ring.
To understand the internal construction of this
product I'll refer the readers to images at:
http://www.aeroelectric.com/Pictures/Contactors/S701-1a.jpg
http://www.aeroelectric.com/Pictures/Contactors/S701-1b.jpg
http://www.aeroelectric.com/Pictures/Contactors/S701-1c.jpg
http://www.aeroelectric.com/Pictures/Contactors/S701-1d.jpg
http://www.aeroelectric.com/Pictures/Contactors/S701-1e.jpg
http://www.aeroelectric.com/Pictures/Contactors/S701-1f.jpg
These photos are for a later configuration of the 3 and 4-
terminal contactors. The tiny coil wire is not even
visible and ample clearances are maintained between coil
terminal hardware and conductor ring by a molded nylon terminal
housing.
The 'Connection (and to the best of my knowledge B&C) has
never sold contactors with the earlier terminal
configuration. The failed contactor had a date code of 9515;
15th week of 1995). Every 4-terminal device I've torn down
featured later configuration for coil terminals visible in
photos above. It's also a fair bet that older versions of
the contactor described in the failure analysis were assembled
with more attention to detail for positioning the solder
lug.
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: | Re: 12 Volt .vs. 24 Volt |
At 10:44 AM 5/18/2009, you wrote:
>
>Why 24 v. systems.... in the commercial world it is usually about
>costs and profits. Less copper used, less cost.
>David
>
Close. When I went to work for Cessna in '64, we had
14v airplanes (150, 172) and 28v airplanes (182, 206,
210). When you need to run high-energy electro-whizzies
you can get more WATTS of engine driven power from
essentially the same WEIGHT of system if it's 28v.
But as quantities of all airplanes sold dwindled,
it was economically more efficient to simply install
the same hardware in all aircraft. The alternators
were the same size and weight, batteries could be
sized to the task for total energy stored. Common
landing lights, nav lights, strobe kits, etc made
for fewer line items of electrical goodies in
inventory and more wider applicability of fewer
parts for field spares.
It had nothing to do with any practical level
of weight savings. We kinda like 14v stuff in the
OBAM market: unlike the uniquely aircraft
"pallet of paints" for 28V hardware, 14V automotive
hardware is stocked in thousands of varieties and
sources virtually everywhere on the planet.
The "improved performance" and "lighter weight"
canards are difficult to measure/prove without
carefully detailed studies with slice-n-dice
instrumentation. For us get-in-n-go airplane
drivers, the 14 vs. 28 volt differences are
not readily observable. So the big driver is
simply cost of ownership in terms of $acquisition$
and $time$ to maintain. 14v has it hands down.
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: 12 Volt .vs. 24 Volt |
Good Afternoon,
Definitely NOT 'Lectric Bob here!
I DO like twenty-four volt systems. I also agree that any weight saving is
probably minimal on an overall basis, nevertheless, I do subscribe to the
theory that ounces count.
Twenty-four volts allows us to use lighter weight starters, alternators,
wires, even relays. The trouble is that most twenty-four volt units weigh as
much as their twelve volt counterparts. If you want to take full advantage
of a twenty-four volt system you also have to use lighter components. If
thirty amps at twelve volts will handle all of your aircraft requirements,
all you need is fifteen amps with a twenty-four volt system. How many fifteen
amp alternators do you see available?
If you go ahead and use a thirty amp twenty-four volt alternator, you have
not taken full advantage of the weight saving capabilities of the
twenty-four volt regime.
Cessna went to twenty-four volts for everything from the 152 on up many
years ago. It was cheaper and lighter for the whole fleet and only having to
deal with twenty-four volt components made inventory control a lot easier.
Commonality of parts and all of the economies that breeds!
If you want to be able to jump start your airplane form a twelve volt car,
twenty-four volts may not be for you.
Personally, If I ever have the feeling that I need a jump start for my
airplane, I would also determine that I had made some sort of error in managing
my flying machine.
If I leave the master on and deplete the battery, I will pull the battery,
have it properly serviced, and chalk the experience up to my own stupidity.
(I have, unfortunately for me, had to do that more than once.)
What I have NOT done, however, is jump start my airplane! If I need the
battery at all, I want it to be fully charged and properly serviced before I
fly.
Happy Skies
Old Bob
AKA
Bob Siegfried
Ancient Aviator
628 West 86th Street
Downers Grove, IL 60516
630 985-8502
Stearman N3977A
Brookeridge Air Park LL22
In a message dated 5/18/2009 12:07:06 P.M. Central Daylight Time,
mrspudandcompany@verizon.net writes:
Similarity of construction.
(Please elaborate!)
Bruce
Glasair III (28v)
www.Glasair.org
I have a feeling that this subject has been discussed before, but I
need help deciding on a voltage system for my Velocity. I intend a
robust electrical system to support a high end IFR panel. The highest
draw item will probably be an electric hydraulic pump which pulls
about 30 amps at 12 volts. I know a 24 volt will save some weight in
wiring because of the lower amperage. However, after reading Bob's
response to a Blue Mountain article
http://www.aeroelectric.com/articles/richter/response_1.pdf
the weight saved appears minimal. I don't know for sure, but I have a
feeling that the vast majority of OBAM airplanes are built around 12
volt systems. My question is, why do the likes of Cessna and Cirrus
build their single engine airplanes with 24 volt systems?
Thanks...Brooke
**************A Good Credit Score is 700 or Above. See Yours in Just 2 Easy
Steps!
=Mayfooter51809NO115)
Message 11
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Subject: | Re: 12 Volt .vs. 24 Volt |
And don't forget to add that you can save much more weight in the
operation of your aircraft by going on a diet! Drop 10 to 15 pounds
off your personal frame and it will make up for many many incremental
weight saving devices in your airframe.
Steve
________________________________________________________________________
On May 18, 2009, at 11:23 AM, Robert L. Nuckolls, III wrote:
> The "improved performance" and "lighter weight"
> canards are difficult to measure/prove without
> carefully detailed studies with slice-n-dice
> instrumentation. For us get-in-n-go airplane
> drivers, the 14 vs. 28 volt differences are
> not readily observable. So the big driver is
> simply cost of ownership in terms of $acquisition$
> and $time$ to maintain. 14v has it hands down.
>
>
> Bob . . .
Message 12
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Subject: | 12 Volt .vs. 24 Volt |
Sorry, poor choice of words on my part. What I meant was "Commonality of
Manufacturing". It easier for the factory to use one battery, one relay,
one bulb, one starter, across the entire line than a mixed bag for each
different aircraft.
Where 28v has 14v beat is in delivery of power. I remember flying my 14v
C177RG at night with everything, including all the lights turned on.
When I reached for the gear lever and flipped it down, everything went
dim! Just about every 14v RG airplane I've flown does that. Not the 28v
ones, just the 14v. Power, when you need it, you need it!
Bruce
www.Glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]
Sent: Monday, May 18, 2009 10:58 AM
Subject: RE: AeroElectric-List: 12 Volt .vs. 24 Volt
Similarity of construction.
(Please elaborate!)
Bruce
Glasair III (28v)
www.Glasair.org
I have a feeling that this subject has been discussed before, but I
need help deciding on a voltage system for my Velocity. I intend a
robust electrical system to support a high end IFR panel. The highest
draw item will probably be an electric hydraulic pump which pulls
about 30 amps at 12 volts. I know a 24 volt will save some weight in
wiring because of the lower amperage. However, after reading Bob's
response to a Blue Mountain article
http://www.aeroelectric.com/articles/richter/response_1.pdf
the weight saved appears minimal. I don't know for sure, but I have a
feeling that the vast majority of OBAM airplanes are built around 12
volt systems. My question is, why do the likes of Cessna and Cirrus
build their single engine airplanes with 24 volt systems?
Thanks...Brooke
Message 13
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Subject: | Re: Modifying the Piper plug |
Bob,
I am going to mount the receptacle close to the battery and run a #4awg right to
the battery ground. As such, would the brass plate washer still be advised?
Thanks for all your help.
--------
Myron Nelson
Mesa, AZ
Emp completed, legacy build fuse in progress
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=244565#244565
Message 14
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Subject: | 12 Volt .vs. 24 Volt |
If you're thinking heated prop, Elec air conditioning, Elec cabin heat,
heated seals, or other high-energy goodies, then a 24V system/alternator
offers twice the "power" for roughly the same system weight as a 12v
alternator. It's not the (potential) smaller wire savings that is
significant/relevant, rather it's twice the available power from the same
weight alternator, contactors, etc (i.e. the heavy items).
This is also perhaps a consideration if you're planning on a small backup
(B&C type) alternator. The 24v version again has twice the available
"power" as the 12v (same weight/package) - i.e. more things you can drive on
the E-bus.
It used to be that 24V goodies were hard to come by. However, an evening
with an aircraft spruce (or west marine) catalog will revel that many common
items are now available 12v or 24v (14/28) for the same price. More over,
most modern avionics items now operate over the entire 12-28 range.
With some "shopping", perhaps the only items that needs converting down to
12v is the cigarette lighter port and Ray Allen trim tab servos.
.02
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Monday, May 18, 2009 2:24 PM
Subject: Re: AeroElectric-List: 12 Volt .vs. 24 Volt
<nuckolls.bob@aeroelectric.com>
At 10:44 AM 5/18/2009, you wrote:
<skywagon@charter.net>
>
>Why 24 v. systems.... in the commercial world it is usually about
>costs and profits. Less copper used, less cost.
>David
>
Message 15
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Subject: | 12 Volt vs. 24 Volt |
At 08:06 PM 5/18/2009, you wrote:
<rtitsworth@mindspring.com>
If you're thinking heated prop, Elec air conditioning, Elec cabin heat,
heated seals, or other high-energy goodies, then a 24V system/alternator
offers twice the "power" for roughly the same system weight as a 12v
alternator. It's not the (potential) smaller wire savings that is
significant/relevant, rather it's twice the available power from the same
weight alternator, contactors, etc (i.e. the heavy items).
Which reminds me of advice I've offered in
years past but worth repeating again: The
first task for crafting your electrical system
is to craft a load analysis. If your maximum
cruising load is expected to exceed 1000 watts,
then PERHAPS a 28v system is called for.
In the past 20 years, I've been directly
involved in crafting only two 28v OBAM
aircraft. One was a LongEz where the owner
wanted to fly a lot in the northern climes.
A 100 amp, 28v alternator was included to
over about 200 watts of energy to run the
airplane . . . and 2,000 watts for toe
heaters!
The other was a Lancair IV with electrically
driven air conditioning. But even this system
pretty low duty cycle. For all the weight, cost
and complexity of an air conditioner, it operates
an average of 30 minutes per flight cycle in
hot weather. The rest of the time, it was dead
weight.
The 14/28 debate really isn't a debate if you
need the energy. But with continuing advances
in LED lighting, LCD under glass instruments,
etc the energy required to run the vast majority
of the OBAM fleet has been going down. It's a
rare airplane that needs more than 500 watts
(40A at 14v) continuous running loads. Up to
twice that load is easily carried by modern
automotive alternators. There are a lot of
cars coming off the line these days with 100+
amp alternators on them.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 16
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Subject: | Re: Modifying the Piper plug |
At 07:58 PM 5/18/2009, you wrote:
>
>Bob,
>
>I am going to mount the receptacle close to the battery and run a
>#4awg right to the battery ground. As such, would the brass plate
>washer still be advised?
Some kind of backing plate is called for.
You need the structural benefits of the
backing plate to double up the skin and
improve conductivity of the pot-metal
jack-housing to cranking currents. But if
you want to make it out of aluminum, that's
okay too . . . in fact probably better.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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Subject: | Re: 12 Volt vs. 24 Volt |
As more and varied low current draw devices become available, do you see PV
in the equation?
On Mon, May 18, 2009 at 7:23 PM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> nuckolls.bob@aeroelectric.com>
>
> At 08:06 PM 5/18/2009, you wrote:
> rtitsworth@mindspring.com>
>
> If you're thinking heated prop, Elec air conditioning, Elec cabin heat,
> heated seals, or other high-energy goodies, then a 24V system/alternator
> offers twice the "power" for roughly the same system weight as a 12v
> alternator. It's not the (potential) smaller wire savings that is
> significant/relevant, rather it's twice the available power from the same
> weight alternator, contactors, etc (i.e. the heavy items).
>
> Which reminds me of advice I've offered in
> years past but worth repeating again: The
> first task for crafting your electrical system
> is to craft a load analysis. If your maximum
> cruising load is expected to exceed 1000 watts,
> then PERHAPS a 28v system is called for.
>
> In the past 20 years, I've been directly
> involved in crafting only two 28v OBAM
> aircraft. One was a LongEz where the owner
> wanted to fly a lot in the northern climes.
> A 100 amp, 28v alternator was included to
> over about 200 watts of energy to run the
> airplane . . . and 2,000 watts for toe
> heaters!
>
> The other was a Lancair IV with electrically
> driven air conditioning. But even this system
> pretty low duty cycle. For all the weight, cost
> and complexity of an air conditioner, it operates
> an average of 30 minutes per flight cycle in
> hot weather. The rest of the time, it was dead
> weight.
>
> The 14/28 debate really isn't a debate if you
> need the energy. But with continuing advances
> in LED lighting, LCD under glass instruments,
> etc the energy required to run the vast majority
> of the OBAM fleet has been going down. It's a
> rare airplane that needs more than 500 watts
> (40A at 14v) continuous running loads. Up to
> twice that load is easily carried by modern
> automotive alternators. There are a lot of
> cars coming off the line these days with 100+
> amp alternators on them.
>
>
> Bob . . .
>
> ----------------------------------------)
> ( . . . a long habit of not thinking )
> ( a thing wrong, gives it a superficial )
> ( appearance of being right . . . )
> ( )
> ( -Thomas Paine 1776- )
> ----------------------------------------
>
>
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