Splicing to NASA Standards

Posted by 141drew Posted onMay 5, 2020 at 4:38 AM and filed under Projects
Updated onUpdated on Jun 1, 2021 at 1:26 PM

A friend of mine that works at NASA recently stumbled across an old standards manual for wire junctions. Essentially, these were the standards that NASA labs used from Gemini on up through the Shuttle era. And I thought some of you might find it as fascinating as I did. You can download the manual here.

However, if you aren’t a space nerd and don’t have the patience for the level of decoding required in the manual, there is an easy way out. Make magazine must have found the same document and actually did a video on soldering the NASA way. You can check it out above…

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Bad Habit

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Actually, looks like NASA just used Western Union's procedure. Ma Bell may have been a monopoly, but they sure did a great job of defining standards still in use today throughout many industries.
 
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Falcon67

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I had forgotten about the WU splice technique. That's robust for sure. Good splice for race car wiring if you have the room.
 
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cvairwerks

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The running lockstitch hasn't been an approved process for a lot of years now in DoD aircraft production. I think we had it outlawed at work back in the 90's. Everything is single position tied. A good string tie person can do the clove hitch to start the tie, on the backside of a bundle without even being able see what they are doing....blows the minds of the new kids at work when you do it.:bounce:

Also, for almost anything we build post F-16, solder isn't an approved process anymore. Crimp rules for production, but I prefer solder joints.
 
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ransil

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Did she use solid wire?

Sent from my SM-G960U1 using Tapatalk
 
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Lassen Forge

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Wow, that's how I was taught to solder wires together from dear old dad (who was a Ma Bell employee)... now I know where he got it.

My electronics teacher used to tell me it was overkill.

Now if I can find something to show me how to do the waxed twine wire harness bundle...
 
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Farmall450

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cvairwerks said:
The running lockstitch hasn't been an approved process for a lot of years now in DoD aircraft production. I think we had it outlawed at work back in the 90's. Everything is single position tied. A good string tie person can do the clove hitch to start the tie, on the backside of a bundle without even being able see what they are doing....blows the minds of the new kids at work when you do it.:bounce:

Also, for almost anything we build post F-16, solder isn't an approved process anymore. Crimp rules for production, but I prefer solder joints.
Click to expand...

Funny how things change...not necessarily for honest reasons.
 
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cvairwerks

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Lassen: AC21-99, Section 2, Chapter 8, Item 26 shows basic single point string tying a harness. Waxed cord is rarely used anymore, normally it's flat lacing cord these days. Some of the old antique restorations will use the wax cord, but most don't anymore. Running ties are no longer approved in what I deal with, spot ties only.
 
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Ryan

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A good string tie person can do the clove hitch to start the tie, on the backside of a bundle without even being able see what they are doing....blows the minds of the new kids at work when you do it.
Click to expand...

Can you explain this like I'm an idiot? Cuz, I am... and this sounds cool.
 
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cvairwerks

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Ryan: Think of having a section of a wire harness running in front of you... the knots have to be tied on the opposite side of the harness from you, and it has to be done while you are blindfolded.... We often have to do ties in areas on the aircraft where we have very limited access and at times, have to do it by feel, as we can't see because of everything in front of us. I've actually had to replace some ties, where I had to do the knots using a pair of hemostats instead of my fingers.:shocking:

For fun, try tying a regular shoelace knot with a piece of rope around your other half's waist, while you are standing behind her. The knot has to be where a belt buckle would normally be, and you can't look over her shoulder, then try tying a clove hitch....:bounce:
 
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Heel2toe

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Soldered connections are not an approved method in motorsports these days either and a proper mechanical crimp is the preferred method. Issues with cracks from vibration, excess solder increasing resistance and a big thing is the solder wicking up past the joint then causing the wire to become brittle in places that dont have proper strain relief.
 
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^&right

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This is very similar to how I was taught to splice 7 strand wire in the Army, but it started with trying a square knot.
 
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smokeysevin

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Heel2toe said:
Soldered connections are not an approved method in motorsports these days either and a proper mechanical crimp is the preferred method. Issues with cracks from vibration, excess solder increasing resistance and a big thing is the solder wicking up past the joint then causing the wire to become brittle in places that dont have proper strain relief.
Click to expand...

Even knowing all that (I agree 100% with you both in the reason and the results), I still prefer to use tinned ends for connectors in marine/damp/powersports applications.

Too many times I have had to cut back huge lengths of wire where "sealed" connectors have allowed water to wick up the cable after prolonged use.

I could count on one hand the number of times I have had a solder joint cause a problem, I couldn't count the number of times I have had to replace part/all of a harness because of corrosion wicking.

Sean
 
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ZRX61

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cvairwerks said:
The running lockstitch hasn't been an approved process for a lot of years now in DoD aircraft production. I think we had it outlawed at work back in the 90's. Everything is single position tied. A good string tie person can do the clove hitch to start the tie, on the backside of a bundle without even being able see what they are doing....blows the minds of the new kids at work when you do it.:bounce:
Click to expand...


Was working on my ZRX11 last week & was going to replace two zip ties on some wires with string but couldn't find it. Only reason was the wires were going to the TPS on the #4 carb & are visible.
 
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sberry

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The wicking is theproblem. We spray penetrating, sometimes with the little straw on/in crimped fittings and wires and even wire nuts. If they are covered they really last a long time,, way better than a Shrinky thingy that has wicked water in.
 
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toplessHO

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12 cord is what the waxed lacing is called.
The old timers called it this because it has 12 strands.
The process is called lacing. I remember doing electrical panels also until time is money overcame the pride in workmanship.
Now I open up a panel and its an absolute nightmare to see what the new generation is calling good workmanship.
Heres an example I helped a neighbor with today. New panel put in by some jackleg
already shorted out one circuit when he opened the panel cover. Deadfront bowed to clear the cable coming in the top,that GE(the manufacturer) should have never supplied prepunched holes for.Absolute mess.
 

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EMD710

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boy this makes all the motorhome and bus builders bean counters cringe. those people use 5 **** connectors per foot it seems like!
 
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ddawg16

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sberry said:
The wicking is theproblem. We spray penetrating, sometimes with the little straw on/in crimped fittings and wires and even wire nuts. If they are covered they really last a long time,, way better than a Shrinky thingy that has wicked water in.
Click to expand...

That ^^ is the reason.

When soldering wires, you are not supposed to let solder wick up inside the insulation of the wire. It creates a stress point...and the wire can break right at the point of where the solder ends.

Crimp connections have come a long ways....but requires the right tool.
 
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Heel2toe

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^Thats what I meant by wicking. Of course moisture is always a concern from a corrosion perspective too.

And yes a proper mechanical crimp is how OEMs do it as it is very reliable. Of course it comes at a high entry cost to have the proper crimpers for the specific pins so at a homeowner level it can often be cost prohibitive.
 
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Bad Habit

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Lassen Forge said:
Wow, that's how I was taught to solder wires together from dear old dad (who was a Ma Bell employee)... now I know where he got it.

My electronics teacher used to tell me it was overkill.

Now if I can find something to show me how to do the waxed twine wire harness bundle...
Click to expand...
Kansas City Stitch or Chicago stitch? Still used in most Central Offices, they really frown on zipties. Think it's a little different than wire harnesses for aircraft, etc.
 

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Kevin54

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Her first mistake.....you never strip a wire like she did. Especially for something going into space. You are never supposed to cut completely through the coating because you can nick the wire. Secondly, you never use the strippers to pull the coating off of the wire. My wife worked on some Gemini and Apollo projects.
 
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kursplat

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still quite a few WU splices in the power lines in los angeles. i don't think anyone has ever seen one that failed. when they get cut out for any reason, someone usually want's to take it home. we still use the waxed string too. main purpose is for tying off the paper insulation in lead cable when making a splice
 

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laser3kw

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Kevin54 said:
Her first mistake.....you never strip a wire like she did. Especially for something going into space. You are never supposed to cut completely through the coating because you can nick the wire. Secondly, you never use the strippers to pull the coating off of the wire. My wife worked on some Gemini and Apollo projects.
Click to expand...

Cool! :thumbup:
 
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kald

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Heel2toe said:
Soldered connections are not an approved method in motorsports these days either and a proper mechanical crimp is the preferred method. Issues with cracks from vibration, excess solder increasing resistance and a big thing is the solder wicking up past the joint then causing the wire to become brittle in places that dont have proper strain relief.
Click to expand...
How would excess solder increase resistance?
 
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MBfreak

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My input from High Power/Voltage, Nuclear and Railroad industries.

For control and power cables nothing but crimping with calibrated and tested crimp tools operated by licensed people.
For really high current ( > 15000 A) cables and bus ducts TIG welding by licensed welders.
Tubular aluminium busbars in and outdoor, some welding but mostly clamps.

The railroad industry here does not permit screw terminal blocks, must be push in!
Forbidden everywhere else in high power electrical control wiring?
Go figure.
Soldering? Never.
Only on PCB , never on wires or cables.

Ola
 
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Heel2toe

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kald said:
How would excess solder increase resistance?
Click to expand...

Sorry, I guess I shouldn't say excess solder per se. Lets go back to basics for a second. The electrical conductivity of solder is less than that of copper, of course it depends on the type of solder used but regardless of that its not as conductive as copper.

A proper soldered connection should have a mechanical bond, i.e twisting of wires, linesman splice etc etc. This mechanical bond gives it strength and is what should be transferring the current and then the solder is sorta the glue if you will to keep it together.

When someone isnt that competent at soldering, often times too much solder is used and there isnt a proper mechanical bond thus the resistance is increased. From there you get heat which can melt the solder and eventually you have a failed connection.

At the end of the day a poor crimp also *****. But there is a huge difference from a standard universal pick your color barrel crimp connected like a **** connector for example vs a Delphi/Molex style more specialized crimping tool. OEMs use crimps exclusively but those tools are almost always cost prohibitive but good results can be had with cheaper crimpers.
 
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ddawg16 said:
I personally don't like splices. When possible I replace the wire
Click to expand...

That's the right answer. They should be avoided at just about all cost. Every termination adds resistance to the wire. They can be a system trouble shooting nightmare when they've been added as a repair because they're not shown on diagrams.... so you don't know that you're even searching for one when trouble shooting. On an airplane a wire can be hundreds of inches long and buried deep within the airplane. Also like other repairs, splices can require additional in-service inspections.
 
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theoldwizard1

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The original Western Union splice did not involve soldering.

Aircraft guys help me out. I though soldering was verboten especially on stranded wire. The place were the solder wicking stop became a high failure point.

In the automotive world (at least 10-15 years ago), they just twisted the bare copper strands over each other, (I think) the minimum was 1.5 turns. Back then they were still using adhesive impregnated cloth tape (friction tape, 3M 1755), with some kind of outer covering.

Observation - That procedure is a problem for "field" repairs. If the repair is from a break/nick, you will have to cut part of that section out and install a much longer piece of wire in order to do all of the twists. 18 gauge (or larger diameter) tinned, stranded wire is difficult to twist with just your fingers.
 
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cvairwerks

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Wiz: It depends on what is being done. On the F-16, almost everything is soldered. The exception was our flight test harnesses. Almost everything on them was crimped. Within those, all shields and interconnects known as wireties, were either solder or solder sleeves. F-35, nothing but shields have solder sleeves, everything else is crimped. All of the crimp dies and pin/socket positioners are considered calibrated tools and have to be checked every so often.
 
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