Today's Message Index:
----------------------
1. 04:53 AM - : Re: Flap motor draw for Rv-7A (Fred Stucklen)
2. 07:13 AM - In search of the elegant solution (was: Z-12 considerations) (Robert L. Nuckolls, III)
3. 09:06 AM - Re: Flap motor draw for Rv-7A (Lapsley R. and Sandra E. Caldwell)
4. 11:31 AM - Re: Running Big Battery Wire Through Firewall (Robert L. Nuckolls, III)
5. 11:49 AM - Lamar solid state contactors (Robert L. Nuckolls, III)
6. 02:21 PM - Re: : Re: Flap motor draw for Rv-7A (thomas sargent)
7. 04:29 PM - Re: Knuckolls Z-12 Power Grid Questions (user9253)
8. 07:15 PM - Continued: Preferred Method for Redundant Power Sources to Single Input (jon@finleyweb.net)
Message 1
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| Subject: | Re: : Re: Flap motor draw for Rv-7A |
Interesting. I've tried 5 AMP fuses on three different RV's to date, and
all blew the fuses while
Trying to deploy the flaps during the first flight. Installing a 10 Amp
fuse always solved the problem.
Frederic Stucklen
RV-6A N925RV 2008 Hrs (Sold)
RV-6A N926RV 875 Hrs (Sold)
RV-7A N924RV 335 Hrs Flying
Time:
08:38:16 AM PST US
From:
"Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Subject:
Re: Flap motor draw for Rv-7A
At 07:13 AM 3/14/2010, you wrote:
My measured current for my RV-& with the model 92345 motor was 2.0
Amps when at the stop, ie stalled. I discount the theory that when
the lube is cold that the current could be higher since the motor has
an over ride clutch which slips at the end of travel and if the
mechanical load was higher in the middle of travel then at the stops
the clutch should slip. Of course the starting current could be
higher but I doubt if it would be briefly more than 4 amp.. I have
been using a 5 amp fuse without problems.
Thanks for taking the time to do some real
measurements and share them with us. I'm having
trouble visualizing the electrical and mechanical
features of your flap extension system.
Normally, a motor that is powered up but not
turning will draw some value of current limited
only by its internal resistance. This would be
close to the data sheet stall current . . . on
the order of 30A or more. In this case, we would
expect the supply protection device to operate.
This is another reason why the proper adjustment
of limit switches is important.
I seem to recall that the RV flap actuator
was a ball-screw with free-wheel clutches
at each end of travel. If this is the case,
then the current you measured wasn't a "stall"
current in the conventional sense, but an
motor unloaded value that is a by-product
of the free-wheeling mechanisms.
Drag of the free-wheeling clutches at ends of
a ball screw are relatively insensitive to
temperature variation as you've guessed.
Were these measurements taken in flight
- airloads on the flaps during extend cycle?
Bob . . .
Message 2
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| Subject: | In search of the elegant solution (was: Z-12 considerations) |
At 08:47 PM 3/14/2010, you wrote:
><thorn@starflight.aero>
>
>Thanks Bob,
>
>I was out of town on business when you came through Houston with
>your class so my wife attended without me (but I'm doing the electrical...?)
>So, I missed the previous debates, discussions on the AMS subject. I think
>you've convinced me that we don't need an AMS.
Yes, I recall meeting your wife and commiserating over
your absence!
>With the addition of a 43 lb electric A/C system in our little Lancair
>Legacy, we're working to trim some weight out. We've saved 17 lbs with an
>MT prop vs. the Hartzell. If it were not for the weight concern I'd
>probably opt for the dual alternator/dual battery system (or if I were going
>dual electronic ignition). It seems that the Z-12 power grid is an
>excellent, reliable architecture for us.
I agree.
>I'm not yet convinced that the Essential/Endurance Bus adds that much value.
Where does it DEVALUE? If you subscribe to the notion that
modern avionics have outlived the myths that promulgated
the AMS, then the task remaining is to craft a failure tolerant
system. The E-bus goes to that point. Further, it provides the
means by which electrical loads during an alternator-out configuration
can be predicted in advance. This is critical to an easily implemented
and well considered plan-B.
>Though, if I found myself IFR with electrical problems (aka panic:))
Why panic? That's the whole point of the plan-B exercise.
We KNOW that things are going to break. If one has plans
for every contingency, then where's the driver for panic?
>the idea of flipping a couple switches to reconfigure would probably
>look like genius... It seems, though, that it might improve
>reliability more for Z-12 to have dual parallel battery contactors.
>What do you think about that?
If that's what you want to do, by all means. But you'd probably
be flying one of a few dozen aircraft in the history of aviation
that was so equipped.
There are tens of thousands of airplanes that have successfully
launched and recovered into IMC with less reliable equipment,
heavier electrical loads and wired like a 1965 C-172.
Accidents having root cause in electrical system failure are
already exceedingly rare . . . and many if not most of those
could have been mitigated if not avoided by understanding
(well considered plan-B) and good preventative maintenance
(batteries, belts, attach brackets, etc) on the part of the
owner. Z-12 or any other z-figure offers a recipe for
success that has been filtered through years of
discussion and actual practice on thousands of airplanes.
Rather than stirring in new ingredients, it would seem
a better plan to deduce ways in which the architecture
fall short of mitigating demonstrable risks.
Then there's the matter of WHERE to put things and
HOW to wire them all up. Risks to your future in-flight
comfort will be driven more by the processes by which
you carry out the plan than the ingredients that go
into the plan. This idea is supported by the numerous
dark-n-stormy night stories we've studied here on the
list. We've also been privy to information from the
gleaned from the wreckage of several airplanes. NONE
of those events were forced by the failure of
single pieces of of properly installed hardware.
Bob . . .
Message 3
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| Subject: | Re: Flap motor draw for Rv-7A |
I guess I did not make myself clear. I believe the clutch in the RV-7 is a friction
clutch. In other words the motor never stalls, but the clutch slips. Thus
max steady state current draw is set by the breakaway torque not any air loads.
Of course the current draw varies with temp, but I will still claim the peak current
will be the starting current. That too varies with temp. I would futher
claim that the peak starting current will occur if the flap is at the stop,
and you attempt to restart the flaps in that same direction, thus starting the
flap motor at max torque. However this would be a transient and mat not blow
the fuse. It does not blow my 5 amp fuse, admittedly at benign temps.
Since I do not have a environmental chamber at home I will be unable to meet your
request to measure at -5 deg.
Roger
Time: 06:52:10 PM PST US
From: "William Gill"<wgill10@comcast.net>
Subject: Re: AeroElectric-List: Re: Flap motor draw for Rv-7A
You can surmise all you want about cold temps and related current draw,
but there is a relationship. Don't think so, test at -5F and report.
Otherwise, you're smply guessing.
From: Lapsley R. and Sandra E. Caldwell
To:aeroelectric-list@matronics.com
Sent: Sunday, March 14, 2010 7:13 AM
Subject: AeroElectric-List: Re: Flap motor draw for Rv-7A
My measured current for my RV-& with the model 92345 motor was 2.0
Amps when at the stop, ie stalled. I discount the theory that when the
lube is cold that the current could be higher since the motor has an
over ride clutch which slips at the end of travel and if the mechanical
load was higher in the middle of travel then at the stops the clutch
should slip. Of course the starting current could be higher but I doubt
if it would be briefly more than 4 amp.. I have been using a 5 amp
fuse without problems.
Roger
Message 4
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| Subject: | Running Big Battery Wire Through Firewall |
At 08:37 AM 3/10/2010, you wrote:
>
>David,
>
>I can tell you there is more than one way to skin a cat, but if you look
>at one of the gazillion Piper Cherokees out there, the cable runs from
>under the back seat along the left panel through the generally dry
>rotted grand-daddy grommet to the contactor mounted on the firewall.
>Size does matter but for 2 or 4 GA that won't make a difference. Good
>enough for Piper...
I don't think I've yet seen a commercial-off-the-shelf firewall
feedthru where the insulating material would have stood off
Jack Thermin's "puff the magic dragon" test. Electrically
and mechanically, these critters function as advertised.
The price is low and they seem adequately robust.
However, if one subscribes to the notion of protecting
firewall integrity with processes like . . .
http://www.aeroelectric.com/articles/Firewall_Penetration/firewall.html
then devices like . . .
Emacs!
and . . .
Emacs!
Are incompatible with the design goal cited in the
article. So if your design goals include attention
to details of fire-wall integrity, then perhaps
single fat-wires are best brought through grommets
with fire-shields and application of fire-putty
per Tony B's writings.
Bob . . .
Message 5
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| Subject: | Lamar solid state contactors |
I've been in communication with folks at Lamar and
was updated on their plans and current offerings
for solid state contactors.
I'm going to be receiving an engineering data package
on the product line. They'll be sending me
some samples to play with as soon as I get a few
more boxes unpacked in M.L.
I've been both competitor and collaborator with
these folks (and their corporate ancestors) for
many years. In my experience they're both capable
and forthright in their dealings with the aircraft
industry.
If anyone on the List is waiting for ME to accomplish
anything specific in terms of evaluating the Smartswitch,
you may be wasting your time. After my conversation
this morning I judge that there is very low risk
for integrating the Lamar devices offered by
Aircraft Spruce into your project.
Bob . . .
Message 6
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| Subject: | Re: : Re: Flap motor draw for Rv-7A |
Fred:
I have a 5 amp fuse on mine too. I haven't flown yet, so all the operation
of the flaps has been in the hangar, but I have not yet blown a fuse.
Do these things really use a clutch? I thought it was a screw that just
runs off the end of the threaded portion of the shaft at either end and the
n
re-engages when you reverse it. I don't know where I got that notion. I
could easily be wrong. I'm just point out that min/max flap extension may
not be high current events.
On Mon, Mar 15, 2010 at 4:29 AM, Fred Stucklen <wstucklen1@cox.net> wrote:
> Interesting I=99ve tried 5 AMP fuses on three different
RV=99s to date, and
> all blew the fuses while
>
> Trying to deploy the flaps during the first flight. Installing a 10 Amp
> fuse always solved the problem
>
>
> *Frederic Stucklen*
>
--
Tom Sargent
Message 7
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| Subject: | Re: Knuckolls Z-12 Power Grid Questions |
> "On the avionics contactor relay, I thought the diode was for if it was switching
inductive loads to prevent back EMF. Is a diode still recommended for an
avionics bus with resistive loads? Do I misunderstand the diodes role here?"
A relay has two (or more) circuits. The coil is one circuit and the relay contacts
are in another circuit. The two circuits can be completely isolated from
each other. The purpose of a diode connected across a relay (or contactor) coil
is to protect the controlling switch from high voltage spark generated by
the relay coil when it is shut off by the switch. That high voltage has nothing
to do with the load on the relay contacts, whether that load is inductive or
resistive. In fact, a relay coil will produce a high voltage when it is shut
off, even if nothing at all is connected to the relay contacts. The bigger
the coil, the bigger the spark. A relay coil will not make as big of a spark
as a contactor coil. Connecting a diode across a relay coil will prolong the
life of the switch that controls it. The diode arrow should point towards positive.
> "Thanks for pointing out that the avionics relay is a single point failure. What
do you guys think about getting one fault tolerant by having two avionics
bus relays/switches in parallel - maybe one passing power from the Battery Bus
and one from the System Bus?"
Yes, that will work. What you are proposing is similar to the E-Bus. And it is
similar to what I proposed in my previous post, although I might not have explained
it clearly. Even if you do use two relays, the diode must still be used
to prevent high current from flowing from the avionics bus (AKA E-Bus) to the
system bus.
> "I'm not yet convinced that the Essential/Endurance Bus adds that much value."
The important feature of an E-Bus is that is has two independent current paths.
It would be easy to turn your avionics bus into an E-Bus by adding the alternate
feed path from the battery bus and a diode to prevent back-feeding the system
bus.
> "It seems, though, that it might improve reliability more for Z-12 to have dual
parallel battery contactors."
Yes, that will work, but will cost more and weigh more than using a relay and diode
along with an E-Bus that will accomplish the same thing.
It can be satisfying to design one's own electrical system. However, there could
be failure modes that you might not be aware of. The big advantage of using
one of Bob's drawings is that they have been proven over time and scrutinized
by many eyes. Any bugs have been worked out. Your schematic looks great in
colors. After a couple of minor changes, it will be similar to Z-11.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=290394#290394
Attachments:
http://forums.matronics.com//files/e_bus_106.jpg
Message 8
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| Subject: | Continued: Preferred Method for Redundant Power Sources |
to Single Input
=0AHi Bob,=0A =0ARegarding this archive thread: [http://forums.matronics.c
om/viewtopic.php?p=272463#272463] http://forums.matronics.com/viewtopic.p
hp?p=272463#272463=0A =0AI am interested to know the answer to the final
question. It was also the first question that came into my head after readi
ng your response. I'm not sure whether or not the answer matters but suspec
t that knowing the answer will answer that question!! ;-) =0A =0AGordon
Smith wrote:=0A"In this case when the two always-on sources differ by a vol
t or two, for whatever reason, Do the sources provide power proportionally
to their voltage or will it be a 100% feed from the highest voltage source?
" =0A =0AThanks!=0A =0AJon Finley=0AN314JF - Q2 - Subaru EJ-22=0A[http://ww
w.finleyweb.net/Q2Subaru.aspx] http://www.finleyweb.net/Q2Subaru.aspx
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