Today's Message Index:
----------------------
1. 07:19 AM - Re: Flap motor draw for Rv-7A (Robert L. Nuckolls, III)
2. 08:57 AM - Re: FW: Zoo Sign In Dumas, TX, North of Amarillo (RScott)
3. 10:10 AM - Re: Flap motor draw for Rv-7A (Corrected) (Robert L. Nuckolls, III)
4. 11:55 AM - Downed EAA Plane (John Markey)
5. 12:07 PM - Re: Downed EAA Plane (Dj Merrill)
6. 12:23 PM - Slowing down the trim (jimbean6@verizon.net)
7. 12:44 PM - Re: Bob, Question on your WigWag flasher using a flasher relay (Robert L. Nuckolls, III)
8. 12:48 PM - Re: Downed EAA Plane (Kevin Horton)
9. 01:04 PM - Re: Downed EAA Plane (Robert L. Nuckolls, III)
10. 03:05 PM - Knuckolls Z-12 Power Grid Questions (Valin & Allyson Thorn)
11. 07:27 PM - Re: Knuckolls Z-12 Power Grid Questions (Robert L. Nuckolls, III)
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Subject: | Re: Flap motor draw for Rv-7A |
Some private emails on the flap motor thing
have prompted some further expansion on the
topic of powering and sizing motors . . .
Anyone know how many amps the flap motor draws on an RV-7A? I
don't see it listed on the motor itself or on any of the
documentation I've got and Van's doesn't know offhand either.
Up until now, we've only discussed the capabilities
and performance of DC motors as described in their
performance data. This discussion says NOTHING about
what the motor is expected to do as-installed in
the airplane.
Just because a motor has some particular nameplate
rating does not automatically set the operating point
as installed. Looking at the data plots I published
yesterday . . .
http://www.aeroelectric.com/Pictures/Curves/Speed-Torque-Current_Curve.jpg
. . . suppose your flap system extension from 0-10
degrees required only 4 oz in of torque from the
motor. During this portion of the stroke it would
draw about 2A and run at 6800 rpm. Assume from 10-
20 degrees, air loads are building on the panels
and the current averages 6 oz in. Now current rises
to about 2.5 amps and speed drops to 6600. From
20-30 degrees, the air loads are at max. Torque might
rise to 10 oz-in at end of stroke with the current
surging up to 3.5A
This may be typical of what an RV or many other
OBAM aircraft demand of their flap extension systems.
This does not amount to much power. Indeed if we
compare the effort required to extend flaps by hand
with a "Johnson Bar", the horsepower developed during
a 30 pound pull through a arc length of 2 feet over
say 10 seconds really isn't much. The motor's task
is no greater except that SOME flap systems may
incorporate some form of worm gear reduction which
can have an efficiency of 30% or worse.
But even then, the power needed to extend flaps
is small. A HP is 550 lb-ft of work per second.
Our 60 lb-ft in two seconds is only 30 lb-ft/second
or 1/20th HP. A really lousy mechanism efficiency
might push that up to 1/5th HP.
In the hypothetical extension scenario I cited
above, electrical power into the flap extension
system peaked just before the haulted at the
fully extended position. 3.5A x 14v = 49 watts.
49w / 746w/hp = 0.06 HP
If these numbers are in the same reality ball park
with the system in an RV, then it's easy to see
how motor ratings on the side of the motor can
be VERY misleading with respect to real performance
numbers. Van's has had no particular reason to
go get the real numbers. In the airframe/power-plant
integrator's world, detail of electrical system
performance become useful ONLY when things are not
working and some investigation is launched to fix
the problem. Even then, the investigators may come
out of the exercise only having UPsized some
obviously undersized component (motor, breaker,
attach hardware, etc) and may STILL be uninformed
as to the real numbers.
I hope this exchange has shed some light on the
difficulty of answering questions like the one
that started this thread. Unless somebody has
taken the time and tools to go measure the performance,
the answer's will always be shallow and tend toward
the conservative. Certainly, wiring and fusing the
flap motor cited in the data plots at say 10A and
wiring with commensurate wire will eliminate any
possibility of nuisance tripping.
But understand that just because there's a 10 or
15A breaker protecting your hangar-mates flap
circuits doesn't say diddly-doo about what that
system really demands in terms of electrical
energy.
A pretty sharp cookie once opined,
"If you want to know, measure! When you can measure what you are
speaking about, and express it in numbers, you know something
about it, but when you cannot measure it, your knowledge is of
a meager kind." - Lord Kelvin 1824-1907
So after all this 'discussion' we're still unable
to answer the original question. Anyone got an
RV and a data acquisition system who would be
will to gather some real flight test data?
Bob . . .
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Subject: | Re: FW: Zoo Sign In Dumas, TX, North of Amarillo |
Message 3
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Subject: | Re: Flap motor draw for Rv-7A (Corrected) |
<nuckolls.bob@aeroelectric.com>
Some private emails on the flap motor thing
have prompted some further expansion on the
topic of powering and sizing motors . . .
Anyone know how many amps the flap motor draws on an RV-7A? I
don't see it listed on the motor itself or on any of the
documentation I've got and Van's doesn't know offhand either.
Up until now, we've only discussed the capabilities
and performance of DC motors as described in their
performance data. This discussion says NOTHING about
what the motor is expected to do as-installed in
the airplane.
Just because a motor has some particular nameplate
rating does not automatically set the operating point
as installed. Looking at the data plots I published
yesterday . . .
http://www.aeroelectric.com/Pictures/Curves/Speed-Torque-Current_Curve.jpg
. . . suppose your flap system extension from 0-10
degrees required only 4 oz in of torque from the
motor. During this portion of the stroke it would
draw about 2A and run at 6800 rpm. Assume from 10-
20 degrees, air loads are building on the panels
and the current averages 6 oz in. Now current rises
to about 2.5 amps and speed drops to 6600. From
20-30 degrees, the air loads are at max. Torque might
rise to 10 oz-in at end of stroke with the current
surging up to 3.5A
This may be typical of what an RV or many other
OBAM aircraft demand of their flap extension systems.
This does not amount to much power. Indeed if we
compare the effort required to extend flaps by hand
with a "Johnson Bar", the horsepower developed during
a 30 pound pull through a arc length of 2 feet over
say 10 seconds really isn't much. The motor's task
is no greater except that SOME flap systems may
incorporate some form of worm gear reduction which
can have an efficiency of 30% or worse.
But even then, the power needed to extend flaps
is small. A HP is 550 lb-ft of work per second.
Our 60 lb-ft in two seconds is only 30 lb-ft/second
or 1/20th HP. A really lousy mechanism efficiency
might push that up to 1/5th HP.
In the hypothetical extension scenario I cited
above, electrical power into the flap extension
system peaked just before the haulted at the
fully extended position. 3.5A x 14v = 49 watts.
49w / 746w/hp = 0.06 HP
If these numbers are in the same reality ball park
with the system in an RV, then it's easy to see
how motor ratings on the side of the motor can
be VERY misleading with respect to real performance
numbers. Van's has had no particular reason to
go get the real numbers. In the airframe/power-plant
integrator's world, detail of electrical system
performance become useful ONLY when things are not
working and some investigation is launched to fix
the problem. Even then, the investigators may come
out of the exercise only having UPsized some
obviously undersized component (motor, breaker,
attach hardware, etc) and may STILL be uninformed
as to the real numbers.
I hope this exchange has shed some light on the
difficulty of answering questions like the one
that started this thread. Unless somebody has
taken the time and tools to go measure the performance,
the answer's will always be shallow and tend toward
the conservative. Certainly, wiring and fusing the
flap motor cited in the data plots at something
like 10 A and commensurate wire sizing will eliminate any
possibility of nuisance tripping.
But understand that just because there's a 10 or
15A breaker protecting your hangar-mates flap
circuit doesn't say diddly-doo about what that
system really demands in terms of electrical
energy.
A pretty sharp cookie once opined,
"If you want to know, measure! When you can measure what you are
speaking about, and express it in numbers, you know something
about it, but when you cannot measure it, your knowledge is of
a meager kind." - Lord Kelvin 1824-1907
So after all this 'discussion' we're still unable
to answer the original question. Anyone got an
RV and a data acquisition system who would be
will to gather some real flight test data?
Bob . . .
Message 4
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Subject: | Downed EAA Plane |
EAAer Lands Safely on Interstate in New Mexico
By Patrick Panzera
=C2-
=C2-
Jon Finley with Subar-Sonic, his Quickie Q-2 that won the COPPERSTATE 2008
Best Alternative Engine award.
March 8, 2010 =94 A Quickie Q-2, owned and piloted by Jonathan (Jon)
Finley (EAA 394580), made an emergency landing Saturday morning, March 6, o
n Interstate Highway 25, parallel to Mid Valley airpark (E98) in Los Lunas,
New Mexico. Jon=99s plane is powered with a direct-drive, Subaru aut
omobile conversion and was featured in the March 2009 issue of Experimenter
, EAA=99s homebuilder e-newsletter.
=C2-
[snip]
=C2-
By noon, Subar-Sonic was back in the hangar and still not willing to start.
Initial troubleshooting indicates that the problem may be due to a single
nut coming loose and getting into some electronics. =9CThe problem ap
pears to have been a nut in the cockpit (no, not this nut),=9D he jok
ed =9CLast time I looked at it was some 300 hours ago. Somewhere in t
hat timeframe it worked its way off the bolt and fell onto a printed circui
t board which seems to have defeated all of my built-in redundancy.
=C2-
=9CAt least that is the theory at the moment, and I can=99t fin
d anything else wrong. I won=99t know for sure for at least several d
ays but will let ya=99ll know when I know,=9D Jon told us.=0A
=0A=0A
Message 5
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Subject: | Re: Downed EAA Plane |
On 3/13/2010 2:26 PM, John Markey wrote:
> At least that is the theory at the moment, and I cant find anything
> else wrong. I wont know for sure for at least several days but will let
> yall know when I know, Jon told us.
Jon followed up later with:
Hi all,
I have confirmed the cause of my power failure last weekend. Long story
short - it was builder error. When you install a locknut on a bolt, you
MUST ensure that there is at least a thread or two coming all the way
thru the nut. If not, it will eventually vibrate free. I am guessing
that I did not look at these nuts after installation due to the
difficulty of seeing anything in this area. No excuse - get a mirror or
whatever is required and visually confirm this type of thing.
Longer story: To mount my EFI controller (computer in a metal box), I
mounted two bolts on the underside of my header tank, two holes in the
controller box, and then put locknuts on each of these bolts. One of
these nuts (and washer) came off the bolt and got down into the
electronics. I assume they bounced around in there for awhile before
finding the ideal location to cause a short which shut everything down.
I have changed my mounting method and now have nutplates inside this "box".
Please; learn from other's mistakes cause you don't have enough time to
make them all yourself!!
Jon Finley
Message 6
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Subject: | Slowing down the trim |
We all know that the usual trim setup used in the RV's and others is very touchy.
Early in building my RV-8 I built and installed a 9 volt power supply intending
to power the headsets with it.
Foolish boy, that doesn't work.
Since the 9 volts was already there I tried it on the trim motor, leaving the trim
indicator supply at 14 volts.
Everything has been working fine with the trim just running slower, a good thing.
I realize that most people will not want to bother installing a separate 9 volt
supply but it does work.
For those interested the shack 5 amp regulator has a schematic and parts list on
the back of the package.
Contact me off-line for my trim schematic. It is in autocad format.
Jim Bean
jimbean6@verizon.net
RV-8 81110 80 hours.
Message 7
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Subject: | Re: Bob, Question on your WigWag flasher using a |
flasher relay
At 10:00 AM 3/12/2010, you wrote:
>
>Bob,
>
>On page 3.0 of your diagram on the single switch solution to a wig
>wag using the flasher relay.....
>
>You state that we can use a 15 amp breaker and 16awg wire for up
>to 2ea 100w lamps.
>
>Is this correct or a typo? Since when not in wigwag mode the full
>combined current will flow thru one 16awg wire, this seams to breaks
>some rules????
Good catch. Those drawings were done so long ago
that I don't now recall the reasoning behind
the suggestions. Obviously, not finely tuned.
I'll get them fixed in the not too distant future.
Thanks for the heads-up.
Bob . . .
Message 8
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Subject: | Re: Downed EAA Plane |
On 2010-03-13, at 15:05 , Dj Merrill wrote:
>
> On 3/13/2010 2:26 PM, John Markey wrote:
>
>> At least that is the theory at the moment, and I cant find anything
>> else wrong. I wont know for sure for at least several days but will let
>> yall know when I know, Jon told us.
>
> Jon followed up later with:
>
> Hi all,
>
> I have confirmed the cause of my power failure last weekend. Long story
> short - it was builder error. When you install a locknut on a bolt, you
> MUST ensure that there is at least a thread or two coming all the way
> thru the nut. If not, it will eventually vibrate free. I am guessing
> that I did not look at these nuts after installation due to the
> difficulty of seeing anything in this area. No excuse - get a mirror or
> whatever is required and visually confirm this type of thing.
>
> Longer story: To mount my EFI controller (computer in a metal box), I
> mounted two bolts on the underside of my header tank, two holes in the
> controller box, and then put locknuts on each of these bolts. One of
> these nuts (and washer) came off the bolt and got down into the
> electronics. I assume they bounced around in there for awhile before
> finding the ideal location to cause a short which shut everything down.
>
> I have changed my mounting method and now have nutplates inside this "box".
>
> Please; learn from other's mistakes cause you don't have enough time to
> make them all yourself!!
>
> Jon Finley
I'd also suggest that if a single short can lead to an engine failure that he should
review his system design. Even if he wishes to assume that this short cannot
physically occur, this occurrence suggests there are possibly other single
failures than can kill all power to critical components.
--
Kevin Horton
RV-8
Ottawa, Canada
http://www.kilohotel.com/rv8
Message 9
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Subject: | Re: Downed EAA Plane |
Jon followed up later with:
Hi all,
I have confirmed the cause of my power failure last weekend. Long story
short - it was builder error. When you install a locknut on a bolt, you
MUST ensure that there is at least a thread or two coming all the way
thru the nut. If not, it will eventually vibrate free.
<snip>
I have changed my mounting method and now have nutplates inside this "box".
Please; learn from other's mistakes cause you don't have enough time to
make them all yourself!!
I would like to follow up with the idea that
on a TC aircraft, there are NO plain nuts or
combinations of plain nuts and lockwashers used.
Non-locking, threaded fasteners are often supplied
on accessories from the outside world . . .
http://www.aeroelectric.com/Pictures/Contactors/Kilovac_EV200_contactor.jpg
http://www.aeroelectric.com/Pictures/Contactors/s701-2.jpg
http://aeroelectric.com/Pictures/Switches/Toggle_Switch_with_Mold-Captured_Terminals.jpg
http://aeroelectric.com/Pictures/Switches/Flap_Switch.jpg
Every time the system integrator picks up such
devices, there's supposed to be an evaluation of
risk due to "loose hardware". If the risks are
deemed great enough, non-locking fasteners will
be replaced with locking devices -or- doped with
Loc-tite on final assembly.
The tree-visible-threads rule has much more to do
with strength of the assembled fastener (indicates
that the screw is long enough) than with anti-
loosening. The same rule applies to all threaded
fasteners including the locking style nuts and
nutplates.
Where locking threads are not possible or practical,
consider still longer screws with a jamb-nut installed
on top of the structural nut. Further, a thread locker
that can be easily disassembled can go a long way
toward insuring joint integrity. Super-glue works
nice. It's thin and wicks into an already assembled
set of threads.
Bob . . .
Message 10
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Subject: | Knuckolls Z-12 Power Grid Questions |
First for Bob K., I don't know what the experimental aircraft community
would do without all you've done to educate and guide us with your books,
classes, and ongoing advice on this forum. Thank you so much.
Hello AeroElectric gang,
My wife and I are building a Lancair Legacy and I've been working on wiring
diagrams to help with electrical system planning since they help capture the
layout of components, wiring, and connectors in the approximate topology of
the airplane.
Here is some background for our electrical system design goals and
requirements. For propulsion/engine reliability, we will fly with dual
magnetos though we will likely replace one with electronic ignition in the
future for improved efficiency and starting. We are designing for IFR
flight. We're planning on a Garmin G900X integrated avionics system. We
have an all electric air conditioning system (hot, humid Houston) that sits
behind the seats that steady state can pull about 50A continuous. To
support all this we have a 28V system with a primary 100A alternator and an
auxiliary 20A alternator.
For the power grid, we're using Knuckolls' Z-12 design (main alt, aux alt,
one battery) but without the Endurance Bus. In the event of an alternator
failure, I prefer to selectively load shed to reduce power demands based on
the current flight situation. We'll be ganging up two 12V Odyssey PC-680 17
AHr batteries to serve as one battery.
I have a couple questions I'd appreciate help with.
First, related to the E-Bus deletion, If we should find ourselves flying
along and the battery goes dead but the alternators are still working, I
want to still have power to the Battery Bus. So I've connected the
Main/System Bus to the Battery Bus with a diode in line to keep power from
flowing to the Main Bus when the battery contactor switch is off. Is this
the right way to provide this? Should this failure mode be protected for?
How likely is it with good maintenance practices that the battery would fail
in flight?
Second, with a carbon fiber/epoxy composite airframe, what are the options
for achieving a "common ground" for the system? Is it okay to have the
ground bus at the firewall, with a thru bolt to connect both sides, and then
run a jumper to a ground bus on the instrument panel where everything on the
panel is connected? Does this count as a common ground that will avoid
"electrical ground loops"?
Third, I'd like to have a battery ammeter to see it's charge and discharge
status. I've indicated a 100 mV/200A ammeter shunt. Should it be larger to
be able to see really high load cases like engine start?
I've attached a draft of our wiring diagram if that helps understand my
questions. Also, I'd appreciate hearing if anyone sees mistakes in it.
Thanks,
Valin Thorn
Lancair Legacy project
Houston, Texas USA
Message 11
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Subject: | Re: Knuckolls Z-12 Power Grid Questions |
At 05:02 PM 3/13/2010, you wrote:
First for Bob K., I don't know what the experimental aircraft
community would do without all you've done to educate and guide us
with your books, classes, and ongoing advice on this forum. Thank you so much.
You're welcome. I'm pleased that you find the work useful!
<snip>
Here is some background for our electrical system design goals and
requirements. dual magnetos. Garmin G900X.
All electric air conditioning at 50A continuous. 28V system. 100A
alternator. 20A aux alternator. Two 12V Odyssey PC-680 17 AHr
batteries in series.
First, related to the E-Bus deletion, If we should find ourselves
flying along and the battery goes dead . . .
So I've connected the Main/System Bus to the Battery Bus with a diode
in line to keep power from flowing to the Main Bus when the battery
contactor switch is off. Is this the right way to provide this?
Should this failure mode be protected for? How likely is it with
good maintenance practices that the battery would fail in flight?
Battery failure for devices favored with good
preventative maintenance is exceedingly rare.
We generally don't include battery failure as
a component of a failure mode effects analysis.
Second, with a carbon fiber/epoxy composite airframe, what are the
options for achieving a "common ground" for the system? Is it okay
to have the ground bus at the firewall, with a thru bolt to connect
both sides, and then run a jumper to a ground bus on the instrument
panel where everything on the panel is connected? Does this count as
a common ground that will avoid "electrical ground loops"?
Yes. See figure Z15 View A at:
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z15K1.pdf
Third, I'd like to have a battery ammeter to see it's charge and
discharge status. I've indicated a 100 mV/200A ammeter
shunt. Should it be larger to be able to see really high load cases
like engine start?
Please don't do this. This was instrumentation of choice
for automobiles and some airplanes for years but needs
to go away. The readings presented are not useful for
managing an airplane in flight and are subject to a lot
of variability in interpretation. This configuration is
going to be removed from the 'Connection at Rev 13.
Active notification of Low Voltage, alternator load meters
and what ever voltmeters are built into your panel instrumentation
are more than adequate to the task.
Bob . . .
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