K

KayS

Well Known Member
good morning all,


yesterday the plan was to attach the RG400 coax cables that run from my lightspeed ignition brain box to the ignition coils top of the engine. the manual tells you to remove the coax's insulation and to crimp the supplied terminals, one to the core wire and one to the shielding material. so far ok.

apperantly i didn't use the right technique to remove and to twist the shielding material that is supposed to be crimped into the big terminal. i cut the shielding material lengthwise and then twisted it to fit into the terminal. thing ist that this part seemed very weak to me. i was easily able to "destroy" this part with very little force, it was basically falling apart.

could somebody tell me what i did miss here?


thanks much
Kay Stecklum
RV-7 still in progess
 
"Comb" or separate the braided strands; don't cut them. Also, you could use Bob Knuckles method of connecting grounds to shielded wire: basically fold the shield back a little, solder on a lead, cover with heat-shrink. Then attach terminal on the end of the longer lead wire.
 
Terminating the braid

The best way to expose the braid is to remove the outer teflon insulation carefully so as not damage the shield wire then using a small pick carefully make an opening in the braid right at the bottom where the outer insulation begins. Then open up the parting so that you can get a small needle nose into the opening and "fish" the center conductor out of the braid thru the opening. Now you have a whole uncut braid conductor to which you crimp the spade connector. Use a right angle spade female on the braid. and use a good COMPRESSION crimper per AC43-13
TB
 
TangoBravo said:
The best way to expose the braid is to remove the outer teflon insulation carefully so as not damage the shield wire then using a small pick carefully make an opening in the braid right at the bottom where the outer insulation begins. Then open up the parting so that you can get a small needle nose into the opening and "fish" the center conductor out of the braid thru the opening. Now you have a whole uncut braid conductor to which you crimp the spade connector. Use a right angle spade female on the braid. and use a good COMPRESSION crimper per AC43-13
TB
Click to expand...

This method works great on shielded wire, but not on coax. Sam (above) nailed it pretty well.
 
Good catch

I had one of my spades that was not crimped correctly come of the wire in flight on my RV-7 years ago.
 
Tango Brave is right ...

I use that technique on RG400 with 100% success. The "pick" I use is a small jeweler's (like an eyeglass type) screwdriver. You carefully pick a small hole thru both shield layers, bend the wire sharply at that point, and then extract the center conductor thru the hole in the shields. That gives you a VERY substantial piece of wire for the Lightspeed PGD terminals .... so much conductor, in fact, you have to use the big yellow terminals. The hard part is getting exactly the right amount of slack in those two wires .... like Baby Bear's porridge, it needs to be "just right". :D
 
I have developed an alternative

That I think works well to connect to the insulator jacket.

Strip the outside teflon insulation exactly like you are going to do a BNC connector except leave a 3 inch center conductor tail.

Take a piece of wire, say 16 gauge, 4 inches long and strip about 3/8". Place a ferrule from a BNC connector on the stripped section of coax insulator jacket. Splay the stripped end of the 16 gauge and slip this between the ferrule and the insulator jacket. Crimp the ferrule as you would for a BNC.

For extra security, I prepped this joint for solder before construction and was able to sweat solder into this joint without damaging the coax insulation.

Finish off with shrink wrap. You now have the center conductor and a 4" 16 gauge insulated picktail to terminate your connection. I used 90 degree spade connections. They make getting the lengths perfect less critical.

If you don't want to waste a BNC connector, go to the local electrical store and purchase a box of wire ferrules that are used for terminating multiple wires at household circuit breaker terminals. They are the perfect size, crimp just like a BNC ferrule and are made of copper so they solder easily.

A box of 50 is a few bucks. If interested, drop me your address and I will send you six or eight.
 
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Ok, thanks so much. i will try the suggested appoaches and see what works best. one thing that all of the advises have in common... don't cut the braided shield. think now i'm a bit smarter. :)

btw... what kind of crimper did you exactly use for the small terminals?
 
I recently installed a second LS Plasma III and from memory I decided not to use the LS supplied connector that crimps on to the centre conductor of the RG 400 (at the coil end) as it did not have the metal jacket at the end of the crimp area that squeezes on to the insulation.

Fin
9A
 
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prepared the wires yesterday as suggested and attached the terminals... looks good.

@fin: yep, i didn't like the small spade terminal also. what i did was to put on some heat shrink that covers the plastic part of the terminal and a 1/4" or so of the inner core insulation to support that area a little bit. should work now...

Kay Stecklum
RV-7 still in progess
 
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