Today's Message Index:
----------------------
1. 10:22 AM - What Are The Odds (Sally Kilishek)
2. 12:10 PM - Re: Pitot/antenna (Phil Birkelbach)
3. 03:44 PM - Re: Re: Back-Up Battery ground (Pat Salvati)
4. 07:50 PM - Re: Pitot/antenna (Robert L. Nuckolls, III)
5. 09:24 PM - Re: What Are The Odds (Robert L. Nuckolls, III)
Message 1
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| Subject: | What Are The Odds |
Chuck:
Good question.
I'm an getting overvoltage light from the annunciator
panel, which uses one sensor to pick up buss voltage,
and getting a digital voltage readout from a separate
sensor on the EMS. Both concur on the overvoltage.
In terms of wiring, I think the following is true:
We're getting 12 volts to the regulator and the
connection from the regulator to the field terminal
is sound (since the alternator is charging).
The OVM-14 overvoltage device is working (alternator
cuts off when voltage goes over 15 volts).
I can't tell whether the regulator is not regulating
or is regulating at >15 volts.
George
Chuck Jensen wrote:
Are you measuring the voltage with a minimum of
two different
instruments? In short, are you sure it is the
voltage and not the
measuring device/indication?
Chuck Jensen
-----Original Message-----
From:
owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]
On Behalf Of Sally
Kilishek
Sent: Thursday, December 28, 2006 12:39 PM
Subject: AeroElectric-List: What Are The Odds
(Was Over Voltage)
--> <s_kilishek@yahoo.com>
Never to be deterred by experience, I installed
yet
another new VR749 regulator the other day. This
was
the fourth one. It worked fine for about 20
minutes,
then showed the same behavior as the other
three:
oscillations between overvoltage of 15+ volts
and
apparent cut off.
What are the odds that four consecutive
regulators
would be bad?
Is there anything else in a plane wired per Z22
that
could account for this behavior?
Temperatures here are in the 40s and 50s. Could
a
negative temperature coefficient be causing the
regulator set point to rise above 15 volts?
George
Dennis Haversham wrote:
I have the same regulator (VR 749) controlling a
100
amp Mazda
alternator. I'm running the engine on the
ground
while I finish the A/C
but I've experienced the same thing. High
voltage at
the battery...
Sally Kilishek wrote:
>
>I'm using a generic Ford regulator (Wells
VR749) and
a
>B&C OVM-14 overvoltage module wired as per Z-22
in my
>RV8.
>
>It worked fine for a short time, but after
about 4
>hours of flying, the overvoltage indicator
light
>started flickering. Bus voltage is rising
above 15
>volts (one time as high as 16 volts), then
dropping
>back below 15 volts and immediately rising
again.
>
>It looks to me like the regulator isn't
regulating
and
>that the OV module is cutting off the field
excitation
>until voltage drops below 15.
>
>I've replaced the regulator twice, but the
problem
>continues.
>
>Is there somewhere else I should be looking?
>
>George
>N57G
__________________________________________________
Message 2
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| Subject: | Re: Pitot/antenna |
That aft-end of the T could be closed with some small radially drilled
holes and used as the static port.
Godspeed,
Phil Birkelbach - Houston Texas
RV-7 N727WB
http://www.myrv7.com
Bill Boyd wrote:
> <sportav8r@gmail.com>
>
> No reason I see why we can't have the pitot shaped like an inverted-T
> rather than an L. That would allow more top (bottom) loading to be
> added, and the "hat" would not radiate, thus negating any directivity
> effects that would arise from the L-shape. The back of the T would be
> strictly antenna-related and not needed for Pitot, of course.
>
> I like it.
>
> -Bill B
>
> On 12/26/06, Robert L. Nuckolls, III <nuckollsr@cox.net> wrote:
>> <nuckollsr@cox.net>
>>
>> At 02:18 PM 12/26/2006 -0500, you wrote:
>>
>> <sportav8r@gmail.com>
>> >
>> >I wonder if we could prototype a helically-loaded "rubber duck" comm
>> >antenna and slip a polypropylene tube inside it with an L-bend at the
>> >end to act as a pitot; encase the whole thing in a streamlined radome.
>> >Interesting excercise. Bandwidth would inevitably suffer from the
>> >physical shortening versus a quarter wave. A lossy loading coil would
>> >give some feeble de-ice heat during Tx (just kidding.) A lot of work
>> >to shave a half knot of speed penalty, but a fun excercise
>> >nonetheless. If I weren't busy with other projects, it's just the
>> >kind of thing I'd try.
>> >
>> >Come to think of it, a full size transponder antenna would easily fit
>> >in a very modest blade pitot housing...
>>
>> Cool! Hadn't considered that.
>>
>> Hmmm . . . maybe better yet, slice metal pitot tube into
>> horizontal and vertical portions (right across
>> the knee joint). Materials that traverse the joint wound
>> have to be non-conductor -OR- fabricated in a way
>> that provides loading components for the comm antenna.
>>
>> Now the horizontal portion becomes more of a minimally
>> radiating top-hat and the vertical mast enjoys majority
>> current flow in the right polarity.
>>
>> THAT could work! Except for the inevitable distortion
>> in pattern that arises from a leading edge location
>> on wing, it might function rather well.
>>
>> If I can get an IR&D activity spun up next year, I'll toss
>> that out on the table to see if some RF-inquisitive guys
>> might like to go mock that up in the lab. It would be an
>> easily crafted experiment.
>>
>> Bob . . .
>>
>>
>>
>>
>>
>>
>
>
Message 3
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| Subject: | Re: Back-Up Battery ground |
Touche'
Message 4
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| Subject: | Re: Pitot/antenna |
At 02:08 PM 12/29/2006 -0600, you wrote:
>
>That aft-end of the T could be closed with some small radially drilled
>holes and used as the static port.
That kind of rings a bell for something I've seen before
although I'm sure the pitot-static tube was not also an
antenna. Great thought! I'll add that to the mix. A pitot-static
tube that is also a reasonably efficient antenna. I believe
that's doable.
Bob . . .
Message 5
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| Subject: | Re: What Are The Odds |
At 10:16 AM 12/29/2006 -0800, you wrote:
>
>Chuck:
>
>Good question.
>
>I'm an getting overvoltage light from the annunciator
>panel, which uses one sensor to pick up buss voltage,
>and getting a digital voltage readout from a separate
>sensor on the EMS. Both concur on the overvoltage.
>
>In terms of wiring, I think the following is true:
>
>We're getting 12 volts to the regulator and the
>connection from the regulator to the field terminal
>is sound (since the alternator is charging).
"Getting 12 volts" is not especially definitive. Do
the specific votlage measurement cited below . . .
>The OVM-14 overvoltage device is working (alternator
>cuts off when voltage goes over 15 volts).
How does it "cut off"? The OVM-14 is supposed to trip
the field supply breaker. If the breaker does not trip,
the OVM-14 is not a part of this trouble-shooting
task . . .
>I can't tell whether the regulator is not regulating
>or is regulating at >15 volts.
Easy. Use a voltmeter to measure between the A/S terminals
and regulator case. THIS is the point where the regulator
believes it is seeing bus voltage. You may find that it
it sitting happily at 14.2 volts while voltage
drops in wiring BETWEEN the A/S terminals and the BUS
are cause for an artificially raising of regulation set-point.
Take one of your regulators and install some short leads
on it as illustrated below. Install right on the back of
the alternator and see what the bus voltage does while
the engine is running and you vary loads by turning things
on and off. These experiments totally bypass all other
ship's wiring.
http://www.aeroelectric.com/Pictures/Regulators/Alternator_Test_1.jpg
http://www.aeroelectric.com/Pictures/Regulators/Ford_Test_Reg.jpg
I think you'll find that the alternator and regulator
are fine . . . there's some bug in installation.
Conduct the experiments cited above and report back the
results. We can begin to divide the probabilities-list into
manageable partitions.
Bob . . .
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