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Author Topic: AMA and Arming Plugs  (Read 3727 times)

Mike Griffin

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AMA and Arming Plugs
« on: August 22, 2013, 05:38:44 PM »
I have tried to find this on the forums but have not been able to confirm it and may have just overlooked it.  I have heard that AMA now REQUIRES an Arming Switch in all full bodied electric powered CL planes.  Is this true and if it is, who or what was the driving force to get this passed as a requirement.  I also understand that electric powered profile planes are exempt from this rule...

Thanks

Mike

Offline Tim Wescott

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Re: AMA and Arming Plugs
« Reply #1 on: August 22, 2013, 05:53:56 PM »
First, there's a way that you can find answers to any and all questions like this: it's called The Rule Book.  It costs no money to get one, it's not hidden behind any combination or key locks, you don't need to kiss anyone's boots.  Just go to the AMA site and download the applicable sections: http://www.modelaircraft.org/events/compreg.aspx.  You probably want "General", "CL General", and "CL Aerobatics".

Second, to my knowledge, here's the skinny.  But you shouldn't believe what I say, because you shouldn't believe what anybody says about the rules (except the CD at a contest that you're competing in -- then you just say "uh huh" and either do what he says or withdraw).  You should read the rules, which happen to be written in English, so they're easy to understand.

http://www.modelaircraft.org/events/compreg.aspx

1: If you're just doing sport flying, the applicable rules are to be found in the Safety Guide.  The Safety Guide doesn't say anything about this.

2: If you're flying control line stunt, at a contest, then the rules say that any time the battery is connected to the ESC, the airplane must be restrained.  Failure to restrain a plane while the battery is connected results in you being disqualified for the flight.  That's it.

The rules say nothing at all about how you accomplish this.  You can do it by hanging onto the plane after you plug the battery in, whether it's profile or full-bodied, you can do it with an arming plug, whether it's profile or full-bodied, or you can have a big old-fashioned knife switch.  You just need to have the batteries mechanically disconnected from the ESC.

Practically, most people take this to mean that you need an arming switch on your full-bodied plane.  But that isn't what the rules say.

http://www.modelaircraft.org/events/compreg.aspx

Oh, and -- http://www.modelaircraft.org/events/compreg.aspx

And http://www.modelaircraft.org/events/compreg.aspx

and http://www.modelaircraft.org/events/compreg.aspx

and http://www.modelaircraft.org/events/compreg.aspx.

AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Mike Griffin

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Re: AMA and Arming Plugs
« Reply #2 on: August 22, 2013, 06:56:32 PM »
Tim is is my understanding that this has just happened therefore it would not be in the RULE BOOK yet.  I also have heard that PAMPA was instrumental in getting this through AMA. 

Mike

Offline Tim Wescott

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Re: AMA and Arming Plugs
« Reply #3 on: August 22, 2013, 07:01:31 PM »
Tim is is my understanding that this has just happened therefore it would not be in the RULE BOOK yet.  I also have heard that PAMPA was instrumental in getting this through AMA. 

Mike

It's in this year's CLPA regulations.  Brett Buck was instrumental in getting it passed -- you must have missed the abuse heaped upon him by the electric guys all last autumn in the Rules section here:

3.2 All aircraft that use electric propulsion shall have a positive arming device that, that when disarmed, mechanically prevents battery power from being applied to the motor. This may be (but is not limited to) a switch, the existing battery plug, or arming plug, but must be in series with the main power line(s) from the battery and mechanically disconnect the battery from the motor. Relying on the timer, timer start switch, flight programmer, or any other low-level logic signal for this function is specifically excluded. The model shall be restrained at all times while the system is armed, either by the pilot (including holding the handle before, during, or after an official flight), an assistant, or mechanical restraint device (e.g. stooge). The device must be disarmed after flight before the airplane is left unrestrained. Failing to restrain the model while still armed during an official flight attempt shall result in official flight with a score of 0. The system may be armed in the pits as long as it is restrained at all times.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Mike Griffin

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Re: AMA and Arming Plugs
« Reply #4 on: August 22, 2013, 09:25:59 PM »
OK Tim..thanks for posting that...

Mike

Offline Tim Wescott

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Re: AMA and Arming Plugs
« Reply #5 on: August 22, 2013, 09:31:51 PM »
Tim is is my understanding that this has just happened therefore it would not be in the RULE BOOK yet.  I also have heard that PAMPA was instrumental in getting this through AMA. 

Sorry for being pissy at first.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Mike Griffin

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Re: AMA and Arming Plugs
« Reply #6 on: August 22, 2013, 09:47:11 PM »
No offense taken..  :)

Mike

Offline Tim Wescott

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Re: AMA and Arming Plugs
« Reply #7 on: August 23, 2013, 08:20:34 AM »
Hi Tim:

I think you meant to write: ...you must have missed the abuse heaped upon him by SOME OF THE electric guys all last autumn in the Rules section here:

I, for one, was in total agreement with this rule proposal. Safety is always the first thing we should address, no matter what the propulsion mode. Please do not ascribe any abuse that may have been "heaped upon" Brett to those of us who agreed with him. I'm a member of the CLACB (Control Line Aerobatics Contest Board) and most enthusiastically supported Brett's proposal.

Hey, I know what you meant, but it was important to me to have this clarified... ;)

Later - Bob Hunt   

That's certainly what I should have written!  You're right -- there was the usual vocal minority that were opposed to it, with a bunch of folks who thought it was a good idea.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Fred Cronenwett

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Re: AMA and Arming Plugs
« Reply #8 on: August 24, 2013, 10:54:27 AM »
I have a CL scale model where I have to take the wing off to install the batteries, then put the wing on. If I didn't have an arming plug the model would be armed at all times until I was ready to fly.

model is listed in "List my setup", page 3  - http://stunthanger.com/smf/index.php?topic=12044.100

So I use a homemade version of this on the RV-4 so that I can arm the model when I am ready to fly. Works great and allows me to install the batteries, put the wing back on and then when I am ready to fly install the arming plug and get it airborne. this way there is no possibility of the system turning on accidently before I am ready.

My local hobby shop did not know what an arming plug was...

http://www.hobby-lobby.com/armsafe_kit_14_guage_1037033_prd1.htm?pSearchQueryId=4459480

Fred Cronenwett
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James_Mynes

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Re: AMA and Arming Plugs
« Reply #9 on: August 24, 2013, 01:52:09 PM »
I have a CL scale model where I have to take the wing off to install the batteries, then put the wing on. If I didn't have an arming plug the model would be armed at all times until I was ready to fly.

model is listed in "List my setup", page 3  - http://stunthanger.com/smf/index.php?topic=12044.100

So I use a homemade version of this on the RV-4 so that I can arm the model when I am ready to fly. Works great and allows me to install the batteries, put the wing back on and then when I am ready to fly install the arming plug and get it airborne. this way there is no possibility of the system turning on accidently before I am ready.

My local hobby shop did not know what an arming plug was...

http://www.hobby-lobby.com/armsafe_kit_14_guage_1037033_prd1.htm?pSearchQueryId=4459480

Fred Cronenwett

I know the description says it can handle 50 amps continuous, 75 burst, but 14 guage wire just seems like it's small for this application. They offer a 10 guage version which might be the way to go.

Offline Tim Wescott

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Re: AMA and Arming Plugs
« Reply #10 on: August 24, 2013, 02:27:48 PM »
I know the description says it can handle 50 amps continuous, 75 burst, but 14 guage wire just seems like it's small for this application. They offer a 10 guage version which might be the way to go.

The 1964 ARRL Handbook rates 14 gauge wire for 32 amps in open air, 17 amps if it's bundled in a big cable.  They give 55A and 33A to 10 gauge.

In an engineering context, rating current carrying capacity of wiring is a big stinking mess: what size you want for what current varies depending on how hot you can let it get because of things around it, how hot you can let it get because of its own insulation burning up, how hot the environment is, how much voltage drop you can stand, etc.

There is no right answer -- but fatter wire means less loss and less heat, and that's always good (at least as long as your aircraft can get off the ground).
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Fred Underwood

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Re: AMA and Arming Plugs
« Reply #11 on: August 24, 2013, 03:13:11 PM »
What voltage is that amperage for?  AC or DC?  Line/wire length?  I have considered calculators and tried 24V DC and 14 awg could handle 50 amp and drop about 1% to "heat" and up to 3% tolerated if I understand correctly???

http://www.bdbatteries.com/wirerules.php

http://www.supercircuits.com/resources/tools/voltage-drop-calculator
Fred
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Offline Tim Wescott

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Re: AMA and Arming Plugs
« Reply #12 on: August 24, 2013, 03:55:07 PM »
What voltage is that amperage for?  AC or DC?  Line/wire length?  I have considered calculators and tried 24V DC and 14 awg could handle 50 amp and drop about 1% to "heat" and up to 3% tolerated if I understand correctly???

http://www.bdbatteries.com/wirerules.php

http://www.supercircuits.com/resources/tools/voltage-drop-calculator

That BD site is feeding you a total mishmash of worthwhile, useful facts, and total BS.  Using stranded vs. solid wire has nothing to do with whether the current is AC or DC, and AC does not magically help the "electrons move" (in fact, AC exhibits the so-called "skin effect" which inhibits the current flow, as conductors and frequencies get large).

They may be drawing the AC vs. DC distinction because usually when folks encounter something called "AC" it's house wiring, and it's 120 volt or higher, and when they encounter something called "DC" it's in a car or from a battery, and it's 24 volts or below.  The distinction is important, but it's important because of the voltages involved far more than because the current is direct or alternating.

Stranded wire doesn't conduct electricity better.  It generally conducts electricity worse, it costs more, and it's harder to connect to.  Stranded wire is used because it can flex; you either use it because you don't want it to break under vibration, or because you need it to flex so you can fit stuff together, or both.  You use solid wire when you can, because if you're going to put it in and leave it forever, then it's cheaper and easier to use.

You use stranded wire in a situation where there is vibration or movement, such as in a car, boat or airplane, or a cord or cable that needs to move.  You use solid wire in a situation where there isn't movement, and the application is cost-sensitive, such as house wiring.  Basically, you use stranded wire where you want the wire to flex; except in some oddball electronic applications there is only slight electrical difference between stranded and solid wire.

The ARRL Handbook recommendations are mostly put together so that when you build a ham shack using those guidelines, it does not burst into flame.  They're assuming that you're going to wire it, then leave it alone for years while the mice nibble the insulation and pee on the wire.

The biggest concerns that you should have when wiring an airplane is heat (because you don't want it to burst into flame), voltage loss (because you want to fly the plane, not heat the air), mechanical longevity (because you don't want the airplane stopping in midair, or bursting into flame from a short-circuit), and ease of installation (because you want to jam all that wire in there).

The Supercircuits calculator is good from the voltage drop standpoint, but doesn't tell you much about heating, and tells you nothing about mechanical robustness.

The BP site tells you that they'll sell you "welding wire", whatever the heck that is, which presumably is flexible and mechanically robust, but may be a bit big for your model plane.

As long as your 14 gauge wire isn't getting so hot that its causing problems, and as long as you're happy with losing some of your oomph to the wire, then you're fine.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Fred Underwood

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Re: AMA and Arming Plugs
« Reply #13 on: August 24, 2013, 04:21:05 PM »
Those sites were simple calculators.  I am trying to understand, not convince you, or argue.  Many of the batteries come with 14 awg and as the C rating goes up they jump to 12 awg...  I had also noted some sites stated that under 3% loss did not seem to cause much heat, again short runs.  I was getting around 1% loss.  I believe the ESC has 14 awg for a 50 amp. I also looked at RC heli site, on a fairly short thread where experience they discussed wire size, and wire resistance.  I am finishing an electric and looking at arming plugs.

http://rc.runryder.com/helicopter/t685208p1/

My reason for asking and wanting to understand was your statement below that seems far different than I can find for DC.

The 1964 ARRL Handbook rates 14 gauge wire for 32 amps in open air, 17 amps if it's bundled in a big cable.  They give 55A and 33A to 10 gauge.

In an engineering context, rating current carrying capacity of wiring is a big stinking mess: what size you want for what current varies depending on how hot you can let it get because of things around it, how hot you can let it get because of its own insulation burning up, how hot the environment is, how much voltage drop you can stand, etc.

There is no right answer -- but fatter wire means less loss and less heat, and that's always good (at least as long as your aircraft can get off the ground).

Is the 32 amps AC 120v, or DC voltage? 

Thanks 
Fred
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Offline Tim Wescott

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Re: AMA and Arming Plugs
« Reply #14 on: August 24, 2013, 04:37:30 PM »
The criteria that the ARRL would have used would have been temperature rise, with a good safety factor thrown in to account for the fact that it's a house that would burn down instead of a toy airplane, and the fact that ham shacks often come equipped with mice.

Add to that the fact that wing loading is not usually a consideration in a ham shack, and you've probably accounted for the difference.

AC or DC, 2 volts or 200, the temperature rise in a given piece of wire with 50 amps going through it is the same.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Fred Underwood

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Re: AMA and Arming Plugs
« Reply #15 on: August 24, 2013, 08:48:06 PM »
Add to that only say a foot of wire, not a house full, and a wind tunnel not a wall.  Perhaps why I see 14 awg on some batteries and ESC.
Fred
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Offline roy cherry

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Re: AMA and Arming Plugs
« Reply #16 on: August 30, 2013, 02:04:57 PM »
hi you u. s. a. guys if i fly at a comp in the states  is it legal to put my model in the circul have it restrained then put the battery in the model then give the signal to start then turn on the switch to the timer  this is the system we are most likly to adopt in the united kingdom   as an aside i stll use a stooge when flying  alone  cheers for now roy cherry

Offline Brett Buck

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Re: AMA and Arming Plugs
« Reply #17 on: August 30, 2013, 07:50:03 PM »
I have tried to find this on the forums but have not been able to confirm it and may have just overlooked it.  I have heard that AMA now REQUIRES an Arming Switch in all full bodied electric powered CL planes.  Is this true and if it is, who or what was the driving force to get this passed as a requirement.  I also understand that electric powered profile planes are exempt from this rule...

    There is no requirement for an arming plug or switch per se. You can just not hook up the battery until you are ready to fly. It specifically says "existing battery plug" is adequate. Profile models are not exempt.

    You can connect the battery, insert the arming plug, or turn on the *mechanical* switch, at any time, but someone has to hold on to the model from then until it is disconnected. Meaning you can't connect everything up and then count on the timer or start switch to keep it from running.

    Note that any form electronic switch (transistor switch, etc) IS NOT OK, you have to break the main power connection to the battery.

   I wrote the rule with assistance from others, and it passed in the last cycle. It was extensively discussed here last summer.
     
     Brett

Offline Brett Buck

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Re: AMA and Arming Plugs
« Reply #18 on: August 30, 2013, 08:04:46 PM »
Stranded wire doesn't conduct electricity better.  It generally conducts electricity worse, it costs more, and it's harder to connect to.  Stranded wire is used because it can flex; you either use it because you don't want it to break under vibration, or because you need it to flex so you can fit stuff together, or both.  You use solid wire when you can, because if you're going to put it in and leave it forever, then it's cheaper and easier to use.

  I think it might be more like oversimplified at the BD site than wrong. Litz wire certainly does conduct RF frequencies better, and it is stranded. Of course it does nearly nothing at 60 hz.

   Even with that, even at 60 hz, you reach a diameter of about 1/2" and you stop improving the current capability due to skin effect.

   Stranded wire is used in high-reliability applications because it is more robust to vibration. Solid wire is pretty notorious for cracking, stranded can have some strands break but keep going. One of the few changes they made to captured V2 rockets was to make new wiring harnesses out of stranded wire instead of solid because the solid wire German harnesses were failing at a very high rate due to cracking.

   The other bit about using AC for power transmission "because it helps push the electrons along better" is certainly bullcrap. AC is used because it's easy to convert the voltage with little loss. It's actually worse for long-distance transmission due to corona loss and our buddy skin effect again. A lot of the really super-long transmission lines are actually very high voltage DC because the loss from up-converting the voltage and turning it back to AC at the end is less than the corona loss with AC. It also allows safe connections between grids, since you don't have to match the phase.  Imagine the fun you might have hooking the Hoover dam to the Niagara Falls  powerplant 180 degrees out of phase!

     Brett

Offline Tim Wescott

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Re: AMA and Arming Plugs
« Reply #19 on: August 30, 2013, 08:19:31 PM »
  I think it might be more like oversimplified at the BD site than wrong. Litz wire certainly does conduct RF frequencies better, and it is stranded. Of course it does nearly nothing at 60 hz.

Litz wire has strands, but if they're not insulated from one another it's not litz wire: uninsulated stranded wire just acts like bumpy solid wire.  It's not at all the same thing as the stranded wire that you want to use in a vibration-prone environment.  I didn't mention it because I thought it was more of a side issue.

(For the curious: http://en.wikipedia.org/wiki/Litz_wire.  Litz wire is used in some radio circuits.  Some high-performance switching power supplies also use a form of it, with multiple strands of insulated wire used to wind the inductors.  Some motors do the same thing, using multiple strands of magnet wire to form the windings.)
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.


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