[Milsurplus] Wire harness questions

[Jim Whartenby]

Just a follow up on the tinning and soldering of PVC jacket wire to crimp style connector socket pins.
Set the solder pot to 500 degrees F and used a 600 degree tip on the Weller WTCPT soldering iron.  Mechanical wire stripper caused no noticeable nicks but some scraping of the wire strands was noted.  Each wire was dipped in solder paste before going to the solder pot.  No issues with charing or melting of the PVC insulation was noted.  Traces of rosin residue was seen on the PVC jacket but was easily wiped off.
After tinning, the wire was cut to final length.  The connector pin was held in a machinist vice so that heat could be applied to the connector pin while the wire was inserted.  A small bit of solder made a bridge between the iron tip and connector pin to fully heat the pin before the wire was inserted.  20 AWG wire was a snug fit into the connector and sometimes required a little rotation to fully seat the wire into the pin.  Other then this, soldering over a hundred connections went smoothly.
Only a few solder connections failed a pull test and re-tinning the wire and a second go around made a strong solder connection.Jim

      From: Michael Hanz <aaf-radio-1 at aafradio.org>
 To: Jim Whartenby <antqradio at sbcglobal.net>; Milsurplus at mailman.qth.net 
 Sent: Monday, May 28, 2018 7:36 AM
 Subject: Re: [Milsurplus] Wire harness questions
   
 On 5/27/2018 6:16 PM, Jim Whartenby wrote:
 
  Plan to use some white PVC 18 AWG wire to make up several wire harnesses for various mil-radio projects.  The wire more or less chose me since a spool of about 4000 feet was just about free.  The wire is marked Style 1007 or 1569 which is rated at 105 deg C and is 16 strands of 30 AWG. 
  Can I use the Ideal "T" Stripper tool or should I go with a thermal wire stripper?  Both are available but mechanical stripping seems so much faster.  The T-Stripper does an excellent job, I see no wire nicks where the tool cuts the insulation.  
 
 I think you just answered the question, Jim - whatever works!  :-)
 
 
  Plan to use braided insulation to protect the wire harness.  Do I need to lace the wire bundle before I put the braid weave over the completed harness?  I still have most of the roll of waxed nylon lacing that I got some 50 years ago when I was a member of USAF.  The stuff never seems to go bad!  
 
 I'm not sure why you would need to lace it if you are using sleeving.  Lacing it will make the wire bundle more stiff to route around the equipment if that's what you want, but I just slide the bundle into the sleeving/conduit/whatever and forget it.  Heh...when you're upside down under the equipment you might appreciate a bit of flexibility.
 
 
  Plan to use a solder pot to tin the wire.  How often does one replace the solder?  I know that tinning gold plated parts contaminates the solder pot but is there any issue with standard tinned wire?  
 
 I've used both, but frankly the solder pot is more trouble than it's worth.  You have to keep cleaning the oxidation dross off of the surface, and for me it's easier to tin the wire with the iron just before insertion, or even not to tin it at all unless the wire is oxidized - just shove it into the solder cup and hold it there with some kind of tweezer assembly, then solder it in place.  Pretinning may add enough diameter to make it difficult to get the wire in the solder pot.  Using PVC, you'll find the insulation melts very quickly, so any heat you can keep away from it earlier will help.  If the cable isn't going to be an open wire version with original WWII aircraft wire (i.e. using a cover or conduit,) I have tended to use teflon insulated wire to avoid the melting problem.  Using a 2%-3% silver bearing solder will help.  (Tektronix was right...)  Also, using some 1/2"-3/4"pieces of fiberglass or teflon sleeving over each wire will keep the chance of later contact between melted insulation on wires down to a minimum.  (Shrink tubing can also be used but interferes with your plan to keep later options open...it's tough to cut off after shrinking.)
 
 
  The connectors I have for the project are crimp contact mainly because they were available.  But I plan to solder them so I can make any needed changes as the project progresses.  I think I have the proper tools to insert and remove the contacts from the connector shell.  Any issues doing it this way?  
 
 Seems entirely reasonable.
 
      73,
  - Mike  KC4TOS
 

   
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