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Tefzel cables and d-sub connectors

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Terry Phillips

Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT

Posted: Wed Nov 21, 2007 6:55 am Post subject: Tefzel cables and d-sub connectors

I am have reached the point in my building where I have to address some electrical design issues. I need to install the servo for the R.A. Allen electric elevator trim tab. The servo has 5 leads, and is supplied with a length of 5-conductor Belden 8445 cable to connect to the controls in the cockpit. A check on the Internet shows that this cable is PVC insulated with 5 22AWG wires. I have a several questions.



1. I was planning to use Tefzel insulated cable as much as possible. Is it worthwhile to  replace R.A. Allen's PVC insulated cable with Tefzel insulated cable?



2. For this application cable would be better than 5 individual wires, because the wires must pass outside the skin from the elevator to the fuselage. After looking around on the Internet, I was unable to find a 5-conductor cable with Tefzel wire insulation and a Tefzel jacket. I did find a company, TPC Wire, 



http://www.tpcwire.com/tpc/pdf/03_TrOxCable_6.pdf, 



that sells 100 ft lengths of shielded cable with Tefzel wire insulation and a polyurethane exterior cover that should work (part no. 61506). They don't have 5 conductor cable, but the 6 conductor cable would not be much heavier. Does such a cable look like a reasonable substitute? Are there other sources for Tefzel insulated cable that I should consider?



3. The servo instructions suggest soldering the cable conductors to the servo leads and wrapping the joints with electrical tape. I was originally planning to use butt splice crimp connectors instead of soldering. I'm now considering using a 9 conductor d-sub plug. Are the d-sub plugs a good choice for a remote location, like the elevator? 



4. If one uses a d-sub, should the plug itself be secured to the elevator (how?) or would cable ties or an adel clamps on the cable provide adequate support.



5. Also, since TPC Wire has a $100 minumum order, it behooves me to buy cable for other uses in the airplane in this one order. E.g., power for the nav lights, headlights, etc. One use that I'm considering is to buy some 24 conductor cable to pass through the firewall to carry engine instrument signals. Which brings me back to the d-sub connectors. Would d-subs be reasonable replacement for the terminal strips that I have seen used to connect engine instruments to wires passing through the firewall? Can d-subs handle engine compartment temperatures? Will thermocouple leads crimped into d-sub pins work OK? Are d-subs robust enough to endure the correction of wiring goofs?

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_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings.

rv10(at)sinkrate.com
Guest

Posted: Wed Nov 21, 2007 8:10 am Post subject: Tefzel cables and d-sub connectors

Terry,



Bob has a decent webpage that covers your question #3 below.



http://www.aeroelectric.com/articles/macservo/macservo.html



There is another good article on "Soldering D-Sub Connectors" that can be

found here:



http://www.aeroelectric.com/articles/dsubs/d_solder.html

-Ben Westfall



--

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kuffel(at)cyberport.net
Guest

Posted: Wed Nov 21, 2007 4:46 pm Post subject: Tefzel cables and d-sub connectors

Terry,



I have a small amount of Belden 89503 plenum cable.  3-pair 

twisted with overall foil shield & drain wire, 24 AWG and Teflon 

FEP insulation.  Flame and smoke resistant, good to 200 degrees C.



If this is acceptable for your use let me know the length from 

your trim motor to your trim switch.  I'll add 5 feet, cut off a 

hunk and drop it off in Corvallis.  I am driving through Hamilton 

Wed Dec 5 and coming back the next day.



do not archive



Tom Kuffel

Whitefish, MT

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nuckolls.bob(at)cox.net
Guest

Posted: Wed Nov 21, 2007 7:44 pm Post subject: Tefzel cables and d-sub connectors

At 06:55 AM 11/21/2007 -0800, you wrote:



 	  Quote: 	
		  



I am have reached the point in my building where I have to address some 

electrical design issues. I need to install the servo for the R.A. Allen 

electric elevator trim tab. The servo has 5 leads, and is supplied with a 

length of 5-conductor Belden 8445 cable to connect to the controls in the 

cockpit. A check on the Internet shows that this cable is PVC insulated 

with 5 22AWG wires. I have a several questions.



1. I was planning to use Tefzel insulated cable as much as possible. Is it 

worthwhile to  replace R.A. Allen's PVC insulated cable with Tefzel 

insulated cable?


	




   See:



http://aeroelectric.com/articles/macservo/macservo.html

 	  Quote: 	
		  2. For this application cable would be better than 5 individual wires, 

because the wires must pass outside the skin from the elevator to the 

fuselage. After looking around on the Internet, I was unable to find a 

5-conductor cable with Tefzel wire insulation and a Tefzel jacket. I did 

find a company, TPC Wire,



http://www.tpcwire.com/tpc/pdf/03_TrOxCable_6.pdf,



that sells 100 ft lengths of shielded cable with Tefzel wire insulation 

and a polyurethane exterior cover that should work (part no. 61506). They 

don't have 5 conductor cable, but the 6 conductor cable would not be much 

heavier. Does such a cable look like a reasonable substitute? Are there 

other sources for Tefzel insulated cable that I should consider?


	


    Run individual 22AWG wires from the connector forward.

    The connector as described is light enough to simply

    be covered with heat shrink and supported by the cable

    assembly, no need to mount it separately. There's no

    good reason to treat your trim actuator wires any

    differently than a bundle of wires that carry nav,

    strobe and antenna wires to the back of the airplane.

 	  Quote: 	
		  3. The servo instructions suggest soldering the cable conductors to the 

servo leads and wrapping the joints with electrical tape.


	


    It was my first view of a behind the panel rat's nest

    of odd pieces of wire and way too much electrical tape

    that prompted me to write the first edition of the

    'Connection 21 years ago.



 	  Quote: 	
		    I was originally planning to use butt splice crimp connectors instead of 

 soldering. I'm now considering using a 9 conductor d-sub plug. Are the 

 d-sub plugs a good choice for a remote location, like the elevator?


	


    Yup, that works. There are some smaller, classier

    connectors you could consider too . . . but they're

    more expensive, take special tools and don't do

    any better job than a d-sub.

 	  Quote: 	
		  4. If one uses a d-sub, should the plug itself be secured to the elevator 

(how?) or would cable ties or an adel clamps on the cable provide adequate 

support.


	


   Float it on the cable.

 	  Quote: 	
		  5. Also, since TPC Wire has a $100 minumum order, it behooves me to buy 

cable for other uses in the airplane in this one order. E.g., power for 

the nav lights, headlights, etc. One use that I'm considering is to buy 

some 24 conductor cable to pass through the firewall to carry engine 

instrument signals.


	


   Please don't do this. In over 30 years of

   systems design and integration I've never seen

   a practical need for multi-conductor bundles

   other than those called out as shielded

   for the purpose of protecting a signal path.



   Build your bundles one wire at a time.

 	  Quote: 	
		    Which brings me back to the d-sub connectors. Would d-subs be reasonable 

 replacement for the terminal strips that I have seen used to connect 

 engine instruments to wires passing through the firewall?


	




    Sure.



 	  Quote: 	
		    Can d-subs handle engine compartment temperatures?


	


    Yes.



 	  Quote: 	
		    Will thermocouple leads crimped into d-sub pins work OK?


	




    Yes. Been doing it for years.



 	  Quote: 	
		    Are d-subs robust enough to endure the correction of wiring goofs?


	




    Depends on how clumsy you are. I've got connectors

    in my data acquisition systems where some pins have

    been removed/replaced over a dozen times. Be nice to

    them and they'll do well for you for a long time.



    Terminal strips are labor intensive, drive up

    parts count, use threaded (ugh) fasteners. Crimped

    joints into machined pins/terminals are far less

    troublesome for maintenance and cost of ownership.



    Bob . . .

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Terry Phillips

Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT

Posted: Sun Nov 25, 2007 4:39 pm Post subject: Re: Tefzel cables and d-sub connectors

Thanks to all who responded both on and off line. I have a much more clear picture of what to do now. I will definitely be using d-subs extensively. I think they can really save some precious space in the engine compartment, while providing a reliable connection. 



I do have 2 questions about using the DB-9 in the elevator. 



It seems to me that it would be easier to fab a nice little mount for the DB-9 inside the elevator than it would be to modify the DB-9 to Bob's ultralight configuration (that could be more easily supported by the wiring.) Would a std DB-9 with a shrink cover provide adequate protection from moisture?



Bob's write up uses soldered pins. I have ordered a crimp tool and a supply of crimp pins from SteinAir. Would crimp pins be adequate in the elevator?



Thank you again for the help.



Terry

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_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings.

nuckolls.bob(at)cox.net
Guest

Posted: Sun Nov 25, 2007 5:56 pm Post subject: Tefzel cables and d-sub connectors

At 04:39 PM 11/25/2007 -0800, you wrote:



 	  Quote: 	
		  



Thanks to all who responded both on and off line. I have a much more clear 

picture of what to do now. I will definitely be using d-subs extensively. 

I think they can really save some precious space in the engine 

compartment, while providing a reliable connection.



I do have 2 questions about using the DB-9 in the elevator.



It seems to me that it would be easier to fab a nice little mount for the 

DB-9 inside the elevator than it would be to modify the DB-9 to Bob's 

ultralight configuration (that could be more easily supported by the 

wiring.) Would a std DB-9 with a shrink cover provide adequate protection 

from moisture?



Bob's write up uses soldered pins. I have ordered a crimp tool and a 

supply of crimp pins from SteinAir. Would crimp pins be adequate in the 

elevator?



Thank you again for the help.


	


    Two things. It depends on what size holes that

    the terminated cable needs to pass, the "minaturized"

    d-sub is optimized to go through the smallest possible

    hole. Obviously, you can forego trimming if you'd

    rather mount the connector on some form of bracket.



    The solder cup connector is recommended for the actuator

    side . . . Ray-Allen (and MAC before them) is/was

    really pedantic about their tefzel covered cat hair

    wires.



    I hit them up in the booth at OSH several years running

    to suggest that the motor wires should be different

    colors so that I could publish drawings that would

    let a builder wire it up right the first time by

    knowing in advance which wire was (+)extend and

    (+)retract. Finally, the stuff was too small

    for the neophyte and really too small as an "airframe"

    wire. Even if you choose to use crimped pins, double

    the strip length to increase amount of wire inside the

    pin -AND- support at the back with E6000 to give these

    small wires extra support.



    I've put several Ray-Allen actuators into test

    fixtures and the first thing I do is install

    a "soldered and glued" connector as shown to

    give me a robust interface to 'real' wires

    on the other side of the mated connectors.



    Bob . . .

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