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Thread: Avionics Wiring Harness: A Tutorial

  1. #11

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    Default Re: Avionics Wiring Harness: A Tutorial

    I'd like to add that Aircraft Tool Supply has many of the electrical tools you may need (and many others) for very reasonable prices.

    https://aircraft-tool.com/shop/searc...ORY=Electrical
    Mike
    Building the JaMFox N677JM
    Kitfox 5 Vixen
    KRNM

  2. #12
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    Default Re: Avionics Wiring Harness: A Tutorial

    3. D-SUB CRIMPER

    You can spend many hundreds of dollars on tooling to crimp d-sub pins and sockets, but itís definitely not necessary. Note that weíre going to be using turned contacts, not stamped-and-formed (Iíll explain why in Part 2). This means you want the 4-way indent type of crimper with a rounded head, not the type with replaceable dies in jaws that hinge open. I use a clone of the Greenlee or Paladin PA1460 that I got on Amazon for $27, and it works perfectly.
    This is super useful information. I currently have a Daniels AFM8 on my ebay watch list. I used one previously when I installed the COM and TXP equipment in my Citabria and the T-6 (under supervision of course). It is also mentioned in the aircraft electrical book I bought, so I thought it was required equipment. That Daniels AFM8 is $250-ish used, and it doesn't come with the "positioner" which is an easy $55-80 each. With the Daniels tool you don't adjust anything, it just works flawlessly.

    Now with your recommendation I would say that for 1/10 the cost I can fiddle around adjusting for a moment or two.
    Kitfox 5 (under construction)
    Citabria (sold)
    Commercial SE/ME, CFII

  3. #13
    Administrator DesertFox4's Avatar
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    Default Re: Avionics Wiring Harness: A Tutorial

    I purchased several wiring tools from SteinAir one of our site sponsors up in Minnesota. Check out their website but they have lots more than is on their site also especially avionics.


    DesertFox4
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  4. #14
    Senior Member jiott's Avatar
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    Default Re: Avionics Wiring Harness: A Tutorial

    I got all my wiring tools from SteinAir; very happy with them.
    The wire stripper was the most expensive, but is also the most used and lots of time saved.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  5. #15

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    Default Re: Avionics Wiring Harness: A Tutorial

    Quote Originally Posted by Eric Page View Post
    Thanks, everyone; I'm glad it's well received. On the 'net you never know when someone will shoot you full of holes!


    Keep in mind that I'm not an electrical engineer (or any other kind, for that matter). I'm a bit murky as well, but here goes...

    As I understand it, twisting helps to mitigate the effects of electromagnetic interference. It places the two wires the same average distance from any source of interference, which means the noise induced in the pair will be the same on both wires (called "common mode"). That's easier for a receiving circuit to filter out because it's looking for a difference between the pair, and any noise that's common to both isn't a difference, so it isn't detected.

    Apparently it also reduces the pair's ability to transmit interference as well, but I can't begin to explain that.
    I am an EE so I'll give it a go. The reason to twist the wire with its ground is to average out the induced voltage. Any stray AC magnetic field will induce a voltage in a loop of wire. Make the wires very close together and minimize the size of the loop. Twist the wires and they spend 1/4 the time facing the field and 1/4 away. Averages out to 0. And 1/2 the time they are at right angles to the field so the induced voltage is also 0. Note this is most effective for low frequency. At high frequency (RF, ignition impulse noise) the field can couple onto the wire pair like an antenna. The solution is a shield that is terminated only at one end: at the power ground of the instrument. Thus the shielded twisted pair.

    Similar situation with transmitted EMI. The generated magnetic field follows the wire (right hand rule) and gets bigger with the size of the loop. Minimize the loop size. Twist the wires and the magnetic field goes + and -. Averages out to 0.

    Hope this helps.
    Last edited by napierm; 07-19-2021 at 04:44 PM.
    Building a KF IV Classic

  6. #16

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    Default Re: Avionics Wiring Harness: A Tutorial

    The problem I have with these crimpers is that there isn't a calibrated adjustment for the depth of crimp. If they are adjustable at all then you could use set of pin gauges (go/no go) to set them. The crimp depth is set for the size of terminal as well as the wire gauge.


    "3. D-SUB CRIMPER

    You can spend many hundreds of dollars on tooling to crimp d-sub pins and sockets, but itís definitely not necessary. Note that weíre going to be using turned contacts, not stamped-and-formed (Iíll explain why in Part 2). This means you want the 4-way indent type of crimper with a rounded head, not the type with replaceable dies in jaws that hinge open. I use a clone of the Greenlee or Paladin PA1460 that I got on Amazon for $27, and it works perfectly.
    "

    Quote Originally Posted by alexM View Post
    This is super useful information. I currently have a Daniels AFM8 on my ebay watch list. I used one previously when I installed the COM and TXP equipment in my Citabria and the T-6 (under supervision of course). It is also mentioned in the aircraft electrical book I bought, so I thought it was required equipment. That Daniels AFM8 is $250-ish used, and it doesn't come with the "positioner" which is an easy $55-80 each. With the Daniels tool you don't adjust anything, it just works flawlessly.

    Now with your recommendation I would say that for 1/10 the cost I can fiddle around adjusting for a moment or two.
    Building a KF IV Classic

  7. #17
    Senior Member efwd's Avatar
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    Default Re: Avionics Wiring Harness: A Tutorial

    That has clarified many questions I have had and resolved to just never ask. Thanks for posting that Napierm.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  8. #18
    Senior Member Eric Page's Avatar
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    Default Re: Avionics Wiring Harness: A Tutorial

    Quote Originally Posted by napierm View Post
    The problem I have with these crimpers is that there isn't a calibrated adjustment for the depth of crimp. If they are adjustable at all then you could use set of pin gauges (go/no go) to set them. The crimp depth is set for the size of terminal as well as the wire gauge.
    Well, I'm not sure what to say about that except that I've pull tested the crimps that mine makes on standard density d-sub contacts with 22AWG wire and found them to be plenty strong enough. How strong? I didn't put a scale on it, but given that the backshell provides strain relief I'm not at all worried about wires pulling loose from their contacts.

    B&C sell the Paladin PA1460 ($49) and SteinAir sell a crimper ($38) identical the one that I use. I'll bet a lot of E-AB aircraft have been successfully wired with them.

    I wish I had the budget to buy NASA-spec tooling for every task, but sadly I'm just not that builder. I sure envy the guys who do.
    Eric Page
    Building Kitfox 5 Safari
    Member: EAA, AOPA, ALPA
    ATP: MEL / Comm: SEL, Glider / ATCS: CTO
    Map of Landings

  9. #19
    tdldedcd's Avatar
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    Default Re: Avionics Wiring Harness: A Tutorial

    Eric, great post. Thanks for taking the time to put together such a complete and in-depth description for wiring. I'm not quite there yet, but will be referring to your post regularly once I start.
    Todd Downing
    SS7 458LK
    Building
    G3X
    915is, Airmaster prop

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