Today's Message Index:
----------------------
1. 05:41 AM - Re: Starter guard ID (Robert L. Nuckolls, III)
2. 06:48 AM - Re: Electrical Education + Corrections (Thanx Richard!) (Robert L. Nuckolls, III)
3. 07:56 AM - Terminology Clarification ()
4. 11:03 AM - Re: Starter guard ID (Jim Jewell)
5. 11:30 AM - Turboprop and rocket engine alternators/generators (sjhdcl@kingston.net)
6. 11:41 AM - Re: Terminology Clarification (Robert L. Nuckolls, III)
7. 12:44 PM - Re: Turboprop and rocket engine alternators/generators (Brian Lloyd)
8. 01:21 PM - Got Lockwasher? (DAVID REEL)
9. 01:38 PM - Re: Turboprop and rocket engine alternators/ge (George Neal E Capt AU/PC)
10. 02:13 PM - Re: Turboprop and rocket engine alternators/generators (Matt Prather)
11. 03:14 PM - Contactor Torque (DAVID REEL)
12. 03:14 PM - Re: Turboprop and rocket engine alternators/generators (Greg Young)
13. 03:35 PM - Re: Got Lockwasher? (Robert L. Nuckolls, III)
14. 08:22 PM - Re: Contactor Torque (Robert L. Nuckolls, III)
15. 08:59 PM - Re: Turboprop and rocket engine alternators/generators (Pete & Farrell Rouse)
Message 1
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| Subject: | Re: Starter guard ID |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 07:27 PM 9/7/2004 -0700, you wrote:
>--> AeroElectric-List message posted by: Richard Riley <richard@riley.net>
>
>At 11:51 AM 9/7/04, you wrote:
>
> > If you're referring to the deep bezel that screws to the
> > mounting bushing of the pushbutton, see lower left corner
> > of last page of:
> >
> > http://www.hmcs.com.cn/Grayhill/Series_30_button.pdf
>
>That's the one. Any idea how I can get to page D-31 of that catalog to see
>the dimensions? I want to know how big to make the cup, so my finger will
>fit in it. I know, I can just measure my finger, but I figure if there's a
>standard I might as well find out what it is.
There are no standards I'm aware of. I've seen devices like this
in a variety of sizes. It's a matter of personal preferences. I searched
their webaite for access to the back pages of the catalog but no joy.
Bob . . .
---
Message 2
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| Subject: | RE: Electrical Education + Corrections (Thanx Richard!) |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
>Hello Bob Nuckolls,
>The slide switch at this URL
> http://ottoeng.com/control/slideswitch.htm
>has these listed electrical ratings at 28 V DC:
>
>Resistive: 5 Amp. Inductive: 3 Amp. Lamp: 1 Amp. Low level: 10 mAmp @30mv.
>
>Can you please help me better understand the significance of these
>ratings? The following questions come to my mind:
>
>1) Wouldnt an incandescent lamp (assumed) be a resistive load and have the
>same rating as given for the resistive circuit load?
A lamp IS a pure resistance (i.e., exhibits only very small capacitive or
inductive reactance components) however, lamp filaments have
a room temperature resistance that is a small fraction that of its
normal operating current. For example, a #327 lamp that draws .040A at
28v (700 ohms operating) has a room temperature resistance of about 70
ohms. This means that the instant contacts controlling this lamp close,
inrush current will be right at 10x or 400 mA. It falls to 40 mA in a
matter of milliseconds but the inrush is real, measurable and
demonstrably more stressful than a stable resistive load of 40 mA. This
particular manufacturer had de-rated his product by 5:1 for lamp loads .
. . some are more conservative and would de-rate 10:1.
>2) I understand the concept of higher initial inrush current affecting the
>lamp current rating, but wouldnt that apply to any resistive load and not
>just the lamp?
If it's a stabke resistor . . . of say 700 ohms, then make, carry and
break currents are constant at 40 mA irrespective of the measurement in
time.
Pitot heaters are another example of thermodynamics of unstable
"resistors".
A 100W pitot tube draws rated power at operating temperature (about 7.4
Amps at 100-125C). However, when you first turn it on, the low
temperature resistance value may be half the operating resistance for an
inrush current of 15 amps. We're dealing with a low reactance, nearly
pure resistance under all conditions . . . it's just a resistance value
that doesn't stand still!
>3) Why would the switch need a low level rating? If it can handle the
>larger current loads couldnt it easily handle any small current load?
Some manufacturers will clad their silver alloy switch contacts with
gold. Gold does not tarnish with age and environment and is a superior
contact material when currents are low (less than 100 ma). However, if
you expect to use a gold clad switch for small signal switching, do not
test it at the full current ratings. We had a batch of gold-clad relays
pass a receiving inspection test at max loads only to have them fail
when used in small signal applications at a later time. The high test
current burns off the gold and converts the relay into a power only
device.
In the case of the OTTO grip switch, gold contacts are optional for using
the switch at very low power levels.
Examples of low signal applications include audio and navigation
signals. Suppose this switch were used to drive inputs to a solid state
trim controller where contact currents never exceeded a few milliamps .
. . you'd definitely want gold cladding on the contacts to insure
predictable operation over the life of the switch. However, if one
purchases a working used switch with hopes of using it in a low-level
application, you want to ask how the switch was used in its first
life . . . the gold may be gone by now.
Another example of unique combinations of load versus contact
behavior is illustrated here. A sub-minature switch is used
to sense full travel of a mechanism and illuminate a pair of lamps.
http://www.aeroelectric.com/Pictures/sm_switch_cutaway.jpg
With as few as 200 hours on the airframe, these contacts
in series with the switch would go open and the lights would
not come on. Here you see the "failed" contacts.
http://www.aeroelectric.com/Pictures/openckt.jpg
Turns out that there was not enough energy flowing through
these contacts to keep them clean (0.08A) but the lamp inrush
current was too high (1.0A) for gold contacts. So
we wired up this little series circuit as a "contact saver".
http://www.aeroelectric.com/Pictures/ContactSaver.jpg
http://www.aeroelectric.com/Pictures/ContactSaver_2.jpg
Changing contacts to gold and installing the "contact saver"
produced the following changes to system operation:
http://www.aeroelectric.com/Pictures/ContactSaver_1.jpg
Note that contacts are closed and stable before the
contact saver triggers. The contacts don't have to
switch the 1A inrush of the pair of lamps and the gold
plating insures contact performance in spite of
low operating currents.
This is a case where failure of a $2 switch wasn't
really a "failure" but a mis-application of hardware.
None-the-less, it triggers a kilodollar maintenance
event on an airplane that takes the airplane out of
service for at least half a day. Clearly the cost-benefit
ratio of adding the contact saver and modifying switch
material was attractive.
>4) Is the inductive circuit current rating lower than the resistive
>circuit rating because of the voltage spike caused by opening the
switch?
Yes, although this is easily mitigated as you suggest
below . . .
>5) Couldn't that inductive circuit current rating for the switch be higher
>if one used a diode connected to ground across the inductive coil in the
>circuit?
You betcha . . . An inductive load with a spike catcher is about the
easiest load there is for set of contacts to control. Inductors have a
delayed build up of current so contacts have a chance to stop bouncing
before currents reach max load. A spike catcher diode eliminates 95% of
arcing on contact opening. See:
http://www.aeroelectric.com/articles/spikecatcher.pdf
>6) Would those current load ratings improve, be less, or the same if the
>switch were used in a 12 V DC circuit instead of a 28 V DC circuit?
Slightly improved but not enough to make much difference to you. Keep in
mind that all ratings for switches and relays are predicated on
laboratory tests where expected "life" of the contacts are given tens of
thousands of operations. If you're selecting a switch for a tool of some
kind, then maintenance issues have a significant return-on-investment
calculation predicated on cost of part, replacement labor and
downtime costs for the tool. These are useful exercises when designing
air transport category and military aircraft. Switches in your airplane
are going to die of environmental and effects of age before they'll
succumb to service stresses.
See: http://www.aeroelectric.com/articles/swtchrat.pdf
>
>Many thanks for your help from an electrical neophyte.
>
My pleasure sir.
I've been jousting with switch and relay contact issues at RAC for
several years. I've run across a number of useful documents on the 'net
that I'll recommend for others
Applying Precision Switches
http://content.honeywell.com/sensing/prodinfo/basicswitches/technical/010172.pdf
Low Energy Switching
http://content.honeywell.com/sensing/prodinfo/basicswitches/technical/001008_3.pdf
Here's a fairly lucid description of switch/relay operation and a
description of various contact materials. There are a few errors in
this piece but nothing serious . . .
http://www.naisweb.com/e/relaye/mech_eng/mech_eng_rtia/idapm4w.html
Bob . . .
---
Message 3
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| Subject: | Terminology Clarification |
--> AeroElectric-List message posted by: <bakerocb@cox.net>
Previous posting by Bob Nuckolls:
<<The Microair has a ptt intercom . . . sometimes called
a "hot mic" intercom. I prefer this style for noisy
airplanes. No vox adjustment hence no "pecking" of the
audio gate on ambient noise . . . no clipping of first
word.>>
9/8/204
Hello Bob, In my past experience the term hot mike meant just that every utterance,
breathing, lip smacking, throat clearing, etc. (usually when wearing an
oxygen mask) continuously went out over the intercom with no other action than
making the mouth noise required. No breaking of squelch, no pushing of button
required.
If one has to PTT (or break a squelch level) in order to communicate over the intercom
it would not be considered hot mike.
A typical installation would have 3 modes: A) Hot mike -- selected ON or OFF by
a separate switch. B) A PTT button with the first stage being intercom only (used
for intercom communication when the hot mike switch is in the OFF position)
and C) The second PTT stage being radio transmission activation.
In the tactical jets the PTT button was on the throttle. In the helos the PTT button
was really a Pull-To-Talk trigger button on the cyclic switch. Many's the
time when I pulled that trigger button on the cyclic and wished to hell that
I had multiple .50 cals firing forward out of my helo just like in the good old
days prior to forced transition.
OC
Message 4
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| Subject: | Re: Starter guard ID |
--> AeroElectric-List message posted by: "Jim Jewell" <jjewell@telus.net>
Hi Richard,
I made my own start button guard.
I made the inside diameter.of the bezel small enough (about 5/16" deep and
9/16" ID) and deep enough that I could not make the switch make electrical
contact with the bezel just caught on the first threads of the switch
itself.
I then adjusted the depth of the button until I could reach the start
position without undue discomfort. In this position it will be difficult to
hit the button without the full intention of actuating the starter.
The dimensions I suggested above
suited the switch I bought. My local electronic supply house had a small
variety to pick from.
Happy finishing,
Jim in Kelowna
----- Original Message -----
From: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
Subject: Re: AeroElectric-List: Starter guard ID
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <b.nuckolls@cox.net>
>
> At 07:27 PM 9/7/2004 -0700, you wrote:
>
>>--> AeroElectric-List message posted by: Richard Riley <richard@riley.net>
>>
>>At 11:51 AM 9/7/04, you wrote:
>>
>> > If you're referring to the deep bezel that screws to the
>> > mounting bushing of the pushbutton, see lower left corner
>> > of last page of:
>> >
>> > http://www.hmcs.com.cn/Grayhill/Series_30_button.pdf
>>
>>That's the one. Any idea how I can get to page D-31 of that catalog to
>>see
>>the dimensions? I want to know how big to make the cup, so my finger will
>>fit in it. I know, I can just measure my finger, but I figure if there's
>>a
>>standard I might as well find out what it is.
>
> There are no standards I'm aware of. I've seen devices like this
> in a variety of sizes. It's a matter of personal preferences. I searched
> their webaite for access to the back pages of the catalog but no joy.
>
> Bob . . .
>
>
> ---
>
>
>
Message 5
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| Subject: | Turboprop and rocket engine alternators/generators |
--> AeroElectric-List message posted by: sjhdcl@kingston.net
Bob,
Can you point me in a direction to find out more about alternator and
generator applications on turboprops, jets, rocket propulsion, etc.
A typical reciprocating engine has a belt driven or geared alternator
onboard. Specically I'm looking for info on how rocket engines produce the
required electrical needs and backups.
Thank you
Steve
RV
Message 6
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| Subject: | Re: Terminology Clarification |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 10:56 AM 9/8/2004 -0400, you wrote:
>--> AeroElectric-List message posted by: <bakerocb@cox.net>
>
>Previous posting by Bob Nuckolls:
>
><<The Microair has a ptt intercom . . . sometimes called
>a "hot mic" intercom. I prefer this style for noisy
>airplanes. No vox adjustment hence no "pecking" of the
>audio gate on ambient noise . . . no clipping of first
>word.>>
>
>9/8/204
>
>Hello Bob, In my past experience the term hot mike meant just that every
>utterance, breathing, lip smacking, throat clearing, etc. (usually when
>wearing an oxygen mask) continuously went out over the intercom with no
>other action than making the mouth noise required. No breaking of squelch,
>no pushing of button required.
Correct.
>If one has to PTT (or break a squelch level) in order to communicate over
>the intercom it would not be considered hot mike.
Depends on how you wire it. in the manual I produced for
this radio at http://www.aeroelectric.com/Catalog/avionics/760imB.pdf
I suggest a ptt version on page 2.1 of wiring diagrams and
then show an optional hot mic version that can be selected off
on page 2.2
>A typical installation would have 3 modes: A) Hot mike -- selected ON or
>OFF by a separate switch. B) A PTT button with the first stage being
>intercom only (used for intercom communication when the hot mike switch is
>in the OFF position) and C) The second PTT stage being radio transmission
>activation.
Sure, one could do that too by making the toggle switch on page 2.2
have three positions: OFF, HOT MIC, and wiring the PTT switches
into the third position.
Bob . . .
---
Message 7
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| Subject: | Re: Turboprop and rocket engine alternators/generators |
--> AeroElectric-List message posted by: Brian Lloyd <brianl@lloyd.com>
On Sep 8, 2004, at 2:29 PM, sjhdcl@kingston.net wrote:
> --> AeroElectric-List message posted by: sjhdcl@kingston.net
>
> Bob,
>
> Can you point me in a direction to find out more about alternator and
> generator applications on turboprops, jets, rocket propulsion, etc.
>
> A typical reciprocating engine has a belt driven or geared alternator
> onboard. Specically I'm looking for info on how rocket engines produce
> the
> required electrical needs and backups.
They use batteries for short-term flights and fuel cells for long-term
flights mostly. They could do it using magnetohydrodynamics but a
secondary APU-like turbine would probably be a better solution. The
problem is that it consumes fuel that would be better used to provide
delta-V.
TANSTAAFL
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
+1.340.998.9447 St. Thomas, VI 00802
Message 8
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"aeroelectric-list" <aeroelectric-list@matronics.com>
--> AeroElectric-List message posted by: "DAVID REEL" <dreel@cox.net>
I need one switch locking washer, you know, the kind with tabs that prevent switch
rotation in the mounting hole, to complete my panel installation. If anyone
out there bought a dozen when they were in the same situation & could mail
me one, drop me an email & I'll send you back a buck.
Do not archive.
Dave Reel - RV8A
Message 9
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| Subject: | Turboprop and rocket engine alternators/ge |
nerators
--> AeroElectric-List message posted by: George Neal E Capt AU/PC <Neal.George@MAXWELL.AF.MIL>
Steve -
The rocket engines that I'm familiar with don't require much electrical
power.
In a previous assignment with the 1st Space Launch Squadron at Cape
Canaveral, I was one of the Air Force Launch Crew Commanders in the Delta
program. The various Delta platforms that we use to launch orbital
payloads all use batteries for electrical power during the powered flight
phase. The payloads (satellites) use a variety of batteries, solar arrays
and fuel cells. The primary mission of the 1st SLS is to launch GPS
satellites. Between GPS missions, we also launched a number of NASA and
commercial missions, including the MARS missions and the GENESIS bird that
made such a nice hole in the desert this morning.
Delta II uses hydraulics to gimbal the 1st and 2nd stage thrust chambers and
a combination of fuel-fired and nitrogen-gas stabilizers for steering. Up
to 9 strap-on solid-fuel boosters with fixed thrust chambers. Delta III
added thrust vectoring to 3 of its 9 solid-fuel boosters, also hydraulically
gimbaled. If memory serves, the hydraulic pumps were electrically powered.
The biggest power hog in the system was probably the main engine fuel pump,
which was a turbine pump spun by exhaust gas from a separate combustion
chamber, also burning hypergols.
Delta II has a total powered-flight time of about 30 minutes, not counting
second-stage coast times. GPS flies in a semi-synchronous orbit at about
220 nm altitude, and takes the longest of Delta's payloads to get to its
assigned testing orbit. Seems like 30 hours of battery time is more than
enough. My memory is rusting.
My first assignment was as a Missile Combat Crew Commander for the 320th
Missile Squadron. Minuteman III and Peacekeeper also use batteries for
electrical power during flight. Long-term electrical power was not a
concern with these systems :).
I have a video that one of my squadron mates from 1-SLS produced that I'd be
happy to share. It's basically a montage of us standing up and launching a
Delta II mission, complete with rocket-cam video. If one of our
web-competent listers will offer to post it, I'll dig it out.
Do not archive.
Neal
>Specically I'm looking for info on how rocket engines produce the
required electrical needs and backups. Steve<
Message 10
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| Subject: | Re: Turboprop and rocket engine alternators/generators |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
It strikes me that I have seen both gear and belt driven alternators
on gas turbine/turboprops. I assume the same can be said of turbofans
and turbojets, but at the moment, I can't visualize where the power
takeoff would be located. It can't be too hard since they use electric
motors to spool up.
Regards,
Matt-
VE N34RD, C150 N714BK
> --> AeroElectric-List message posted by: sjhdcl@kingston.net
>
> Bob,
>
> Can you point me in a direction to find out more about alternator and
> generator applications on turboprops, jets, rocket propulsion, etc.
>
> A typical reciprocating engine has a belt driven or geared alternator
> onboard. Specically I'm looking for info on how rocket engines produce
> the required electrical needs and backups.
>
> Thank you
> Steve
> RV
>
>
Message 11
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| Subject: | Contactor Torque |
--> AeroElectric-List message posted by: "DAVID REEL" <dreel@cox.net>
I've seen a number of messages regarding ruining the cole-Hersee contactors by
over-torque but the messages never state a correct torque. Presuming one holds
the bottom nut to prevent rotating the terminal, what would be the torque to
apply? The terminals are 5/16-24 thread but are not cadmium plated & who knows
what metal is being used. Looks like copper on the one I got from Vans. Cole-Hersee
hasn't replied to my emails so I'm wondering if someone on the list
knows.
Dave Reel - RV8A
Message 12
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| Subject: | Turboprop and rocket engine alternators/generators |
--> AeroElectric-List message posted by: "Greg Young" <gyoung@cs-sol.com>
You're not too far off, most use starter-generators. They're attached to the
gearbox which is typically under the engine. That's why nacelles for most
low/no-bypass turbines have a bulge on the underside.
Greg
> It strikes me that I have seen both gear and belt driven
> alternators on gas turbine/turboprops. I assume the same can
> be said of turbofans and turbojets, but at the moment, I
> can't visualize where the power
> takeoff would be located. It can't be too hard since they
> use electric
> motors to spool up.
>
Message 13
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| Subject: | Re: Got Lockwasher? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 04:24 PM 9/8/2004 -0400, you wrote:
>--> AeroElectric-List message posted by: "DAVID REEL" <dreel@cox.net>
>
>I need one switch locking washer, you know, the kind with tabs that
>prevent switch rotation in the mounting hole, to complete my panel
>installation. If anyone out there bought a dozen when they were in the
>same situation & could mail me one, drop me an email & I'll send you back
>a buck.
If you can't put your hands on one . . . B&C stocks them and
would probably drop one in an envelope to you for the price of
a phone call.
Bob . . .
---
Message 14
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| Subject: | Re: Contactor Torque |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 06:16 PM 9/8/2004 -0400, you wrote:
>--> AeroElectric-List message posted by: "DAVID REEL" <dreel@cox.net>
>
>I've seen a number of messages regarding ruining the cole-Hersee
>contactors by over-torque but the messages never state a correct
>torque. Presuming one holds the bottom nut to prevent rotating the
>terminal, what would be the torque to apply? The terminals are 5/16-24
>thread but are not cadmium plated & who knows what metal is being
>used. Looks like copper on the one I got from Vans. Cole-Hersee hasn't
>replied to my emails so I'm wondering if someone on the list knows.
"Over torque" of the threads isn't the biggest risk, it's twisting
the studs in their plastic insulators. You can avoid this with
the two-wrench approach to tightening. You need to counter-torque
the nut next to the housing while tightening the top nut down on
the terminals. The studs are hard copper. AC43-13 calls out 60-85
inch-pounds for 24,000 psi steel bolts. 50-60 in-lb would be fine
for the contactor studs . . . which is not a lot of force at the
end of a 12" wrench . . . about 5 pounds. Your nut should have
an internal tooth, phosphor-bronze or beryllium-copper lockwasher
under it.
Bob . . .
---
Message 15
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| Subject: | Turboprop and rocket engine alternators/generators |
--> AeroElectric-List message posted by: "Pete & Farrell Rouse" <pete-farrell@kc.rr.com>
To All,
The accessory gear case of the turbine engine is where the starter and other
accessories are located. On the TFE731, the starter is a starter/generator
and does double duty.
The accessory gear case is usually driven off of the high speed spool. On
most engines that I've worked on, it is located at the bottom of the engine,
just behind the fan case or particle separator.
Turbofan engines use electric and air turbine starters; each has its own
drawbacks. I have spent many a day trying to figure out what the start
system was doing on the engine I was working on....
Pete Rouse
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Matt
Prather
Subject: Re: AeroElectric-List: Turboprop and rocket engine
alternators/generators
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
It strikes me that I have seen both gear and belt driven alternators
on gas turbine/turboprops. I assume the same can be said of turbofans
and turbojets, but at the moment, I can't visualize where the power
takeoff would be located. It can't be too hard since they use electric
motors to spool up.
Regards,
Matt-
VE N34RD, C150 N714BK
> --> AeroElectric-List message posted by: sjhdcl@kingston.net
>
> Bob,
>
> Can you point me in a direction to find out more about alternator and
> generator applications on turboprops, jets, rocket propulsion, etc.
>
> A typical reciprocating engine has a belt driven or geared alternator
> onboard. Specically I'm looking for info on how rocket engines produce
> the required electrical needs and backups.
>
> Thank you
> Steve
> RV
>
>
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