XPost: sci.electronics.design, sci.electronics.misc   
   From: mocha@mailexcite.com   
      
   > On 20/07/2022 07:53, Mike Mocha wrote:   
   >>   
   >> Hey all,   
   >>   
   >> Just curious what you think about this.  The photos at the link are   
   >> showing large gauge wire used on a vintage 600 VDC rail vehicle.  We're   
   >> talking 1930's electric streetcar technology.  Basically 600 VDC   
   >> connected to a knife switch, then to a rotating manual controller which   
   >> you partially see in the photo.  The rotation of it sets up the series   
   >> and parallel stages to the traction motors.   
   >>   
   >> We see this weird rubber beading occurring on the outside of the older   
   >> wire insulation.  I'm not sure what that insulation is made of or how   
   >> old it is.  This only seems to occur on the older wires.  The newer   
   >> NFPA compliant wires don't have this symptom.   
   >>   
   >> What is it and what causes it?  Any theories?  Thanks.   
   >>   
   >> https://imgur.com/a/OqHQV8U   
   >>   
   > Looks like heat damage to me!   
   > Possibly caused by resistance heating in a tarnished/corroded   
   > connection?  I would disassemble, clean, grease and remake the   
   > connections.   
   > Replace any damaged cable along the way:  If I am right, there will be   
   > some. If I am wrong, there may not be :-)   
   >   
   > HTH, Chris   
      
   Thanks for all the responses.  I guess that makes sense about it being tar   
   over some kind of fiber wrap.  Maybe it's time for us to upgrade to   
   something more NFPA 130 compliant!!   
      
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