Wire bracing

[TechMan]

Numerous problems occuring with Wire bracing whereby the wire is corroding inside the swages due to captured moisture.

 

Sometimes swages are covered neatly with heat shrink, making it impossible to inspect. Remove the heat shrink and if there is any sign of corrosion happening within the swage, do yourself a favour and replace the cable.

 

This is most important for wire braced aircraft, but can be applied to any cable that is in a aircraft.

 

Chris Kiehn

 

(giving this forum a try)

 

 

[Admin]

Sorry for my ignorance Chris but for my knowledge can you explain to me what a "swage" is?

 

 

[Wilfred]

Rigging Definitons

 

Term: Swage

 

Definition: Swaging is a method of affixing a tubular fitting to the end of a wire. The process cold works the tube by squeezing it hard enough that it forms into a part of the wire. The work is performed either by rolling dies or by squeezing tools such as the common Nicopress

 

basicly used to attach the terminals to your rigging cable

 

 

[Guest TOSGcentral]

Perhaps a bit of expansion on Turtle's comments?

 

There are two common uses for swaging:

 

1. You wrap the wire in a loop, usually around a protective gadget termed a 'thimble' (that is normally a grooved shaped piece of stainless steel in a tear-drop shape) and then clamp the loose end to the main wire shaft using a crushable 'tube' of what can be termed as a swage or ferrule.

 

2. You can extend a cable length by an in-line splice using TWO ferruls by laying both loose ends of the cable side by side and then clamping them together with the ferruls normally no closer than an inch apart.

 

Note that to preserve the overall design strength of the cable (in primary structure bracing or control system cables) an approved crushing tool has to be used that gives a measured crush such that the ferrul(s)strength is not compromised but the crush is powerful enough to make a suitably stong union.

 

These tools (like torque wrenches) go out of adjustment and periodically require calibrating.

 

Simply clobbering a ferrule/cable union with a hammer may give you a warm, fuzzy feeling when you give it a tug with your hands but can lead to very terminal situations if the cable is taken up to design loads and decides itself that the union was not really up to it!

 

Aye

 

Tony

 

 

[greggf]

It strikes me that the process of swageing, as described, is pretty feral.

 

As the cable is, effectively, just turned 180 degrees around the thimble, there is likely to be a fair bit of linear load carried through to the swage.

 

I thought, if the cable was wrapped 540 degrees around a modified end-fitting, and then swaged as before, the turn-and-a-half of termination should remove all but a bare trace of linear load from the swage. Ie. the swage would be holding the cable end adjacent to the cable under load, but there would be virtually zero load trying to pull the cable end from the swage.

 

Has this been tried?

 

 

[hiperlight]

Gregg, 'fork ends', 'eye ends' and turnbuckles are swaged onto the straight end of a cable. e.g. flying and landing wires. Done properly

 

the cable will fail before the swage lets go. You must have 'faith'.

 

I used to hand swage the 'fork ends' on the standing rigging on sailboats. I must admit that my 'faith' in hand swageing doesn't extend to flying (or even landing) wires on an aircraft. Proper hydraulic swageing is the way to go!

 

Bruce

 

 

[Guest TOSGcentral]

Hmmm! I will expand a bit on a couple of points you raised Gregg – that on the face of it seem practical enough.

 

A lot of the answer resides in practicality. Firstly, if the union is stronger than the actual cable, and you can make simple and light – then you have a winner!

 

In practice, the stranded stainless steel cable we use in control and bracing wires does not like being even taken around a 180 degree thimble. A bit of skill is required to get both a neat fit AND retain the desired cable length at the same time. Taking it around one and a half turns may be conceptually stronger but for what purpose if it is already strong enough?

 

We then have to consider what you intend to wrap the wire around? Take a simple rudder drive cable with a swaged loop on the end. We need this strong enough but also very simple as a very small D ring shackle will connect the cable to the rudder (usually). Importantly we need a hole to put the shackle in! The present system is clean, simple and works!

 

Going on to Hiperlight’s comments. Fair enough! Hand swaging is quite safe and a totally accepted practice – if you have the right gear! The Nicopress system is probably one of the better ones but the supreme hydraulic press is really for the factories. It is not much use 300 km the other side of the Black Stump, you have just lost your stud bull, and a cable gives way!

 

The Nicopress tool is not cheap at around $100 dollars a pop for something you seldom use, plus you have to have a stock of the right swages and thimbles. However the tool is entirely driven by Armstrong power and Mk1 eyeball. The arms compress the big pliers while the eyeball checks that two cunningly designed lugs come together that ensures a correct crush. 5 min job and forget about it!

 

That is assuming the tool is within calibration so when the lugs come together you do have the correct crush!

 

Aye,

 

Tony

 

 

[hiperlight]

Tony,

 

The swageing tool I used on sailboat rigging is like a double action

 

bolt cutter with the appropriate swageing jaws. Is that similar to the

 

nicopress tool you mentioned?

 

The problem I have using that type of swageing tool is that several

 

bites are necessary for fixing fork ends etc. OK for fitting thimbles

 

but it is impossible to get a really professional looking swage on a

 

long sleeve. Probably strong enough but psychologically worrying. But

 

then you have the practical experience with aircraft rigging.

 

Bruce

 

 

[Guest TOSGcentral]

Yup - that is the tool.

 

I agree with your points. I will normally take three bites - an initial

 

crush to locate things and check my tensions & length etc, then a

 

fixing crush to do the job, then a last one to ensure that the lugs are

 

freely connected and I have full tool tension.

 

And yup - I do not like the appearance either! You get about an eighth

 

of an inch horribly splayed out each side of a central crush on the

 

ferrul. This can be hidden by shrink wrap to tidy up the job but is

 

nowhere near as neat as the hydraulic press jobs

 

T.

 

 

[pylon500]

When terminating (the technical term)cable ends, yes the Nicopress sleeve (usually copper) crushes the loop ends of the cable at a higher strength than the cable itself.To

 

get a neat fit around the Thimble when using Nicopress, if you have the

 

standard tool, you should be able to do three squeezes on the ferrule.With

 

the cable threaded around the thimble and fed back into the ferrule,

 

arrange to have about one and a half cable diameters protruding from

 

the ferrule, and the ferrule pushed tightly against the thimble, set

 

the first swage in the middle.You will notice that the ferrule will 'grow' in length, this helps to tighten the loop.Swage

 

again near the thimble, leaving a small amount of the ferrule

 

protruding, to both tighten the loop and leave a tapered oppening for

 

the cables to enter the swage (don't pinch on the edge)Finally, swage the remaining amount of ferrule (also not on the edge) to leave about half a cable diameter protruding from the swage.If you have a wide jaw swager, start away from the thimble first, then set near the thimble.Things to consider;NEVER swage at the same place on the ferrule twice.Don't try to swage onto plastic coated cable, if you get a ferrule that fits, you've got the wrong one!Putting heat shrink over a swage is ill advised as it will hold moisture and promote corrosion.For more detail goto;http://bosunsupplies.com/NicopressSwage.cfmOr if you can read German, (some good diagrams);http://www.schmidtler.de/html/ht_technik/seile.htmAs for EYE and FORKends, these should never be set with a Nicopress tool Any

 

kinks in the swage tube can form a stress raiser and start cracking

 

strands, use the correct rotary swage tool or full length hydraulic

 

press swage.(I have seen a system that used full length jaws powered by a pneumatic hammer, it seemed to work once you got the hang of it)End tonights lesson.Arthur.ps, I don't know why I can't use most of the site shortcuts?

 

 

[pylon500]

Cable update;While manouvering our aircraft into the

 

hangar the other night, a loud bang was heard which we thought was the

 

tailwheel turning.We then noticed one of the tail wires

 

appeared loose, and on inspection found the cable swage had corroded

 

away under it's heat shrink cover!After all heat shrink was removed, it was found this wire was the only one with an aluminium swage?New cable with propper nickel plated copper swages fitted.

 

Arthur.

 

 

 

[Guest ozzie]

Aluminium swage????

 

 

[greggf]

Extract from a previous contribution (about 5 up in this thread)

 

>Putting heat shrink over a swage is ill advised as it will hold moisture and promote >corrosion.>For more detail goto;>http://bosunsupplies.com/NicopressSwage.cfm>Or if you can read German, (some good diagrams);>http://www.schmidtler.de/html/ht_technik/seile.htm

 

I suggest that the heat shrink did more harm than the "aluminium" swage.

 

I'm trying a new technique on my drifter. Well, new for me, anyway.

 

First I thoroughly cleaned all visible surface ageing (verdigris)

 

off the swaged cables by scrubbing them with detergent solution and a

 

brass wire brush. Then rinsed thoroughly in clean water and let them

 

dry all day in the hot sun.

 

Then I sprayed them thoroughly with

 

an automotive underbody sealant wax. I was careful to ensure as

 

complete a coverage as I could achieve. This leaves a brown translucent

 

waxy layer over the metal. When the wax was "dry" (doesn't completely harden) I coated the cables and fittings with Lanox, as I usually do.

 

I'll report on success or otherwise in months to come. Problem is, I live and fly in a very salty warm humid atmosphere (beautiful Port Macquarie).

 

 

[Guest micgrace]

How did that foreign part sneak in??

 

Aluminium + steel &

 

water = corrosion. Point to bear in mind if using stainless rivets

 

against aluminium too. Can be used though with appropriate cad primer.

 

Must have come from the local hardware and was disguised??

 

You just never know what shows up.

 

Micgrace :)

 

 

[Guest micgrace]

Just asuggestion. A simple wipe over with some auto polish will do.

 

Micgrace :)

 

 

[Guest Fred Bear]

You will find that swages of all kind have a definite service "life."

 

As the Techman will no doubt advise, the aircraft service manual

 

contains vital information on the care and handling of your aircraft

 

and maintenance. The swage and or cable as displayed in the photo

 

above, probably should have been relpaced quite some time ago, possibly

 

years. Depending on the aircraft type, the result of above photo could

 

have killed somebody, or a number of people, not to mention doing

 

damage to life and property on the ground.

 

An aircraft is an important piece of machinery and must be maintanted as if your life depended on it.

 

Please people if you can carefully look after your machines. I've seen

 

too many good people pass on over time for aircraft accidents and it's

 

not a good feeling.

 

Clem.

 

 

[Guest micgrace]

:)

 

Yup - that is the tool.

 

I agree with your points. I will normally take three bites - an initial

 

crush to locate things and check my tensions & length etc, then a

 

fixing crush to do the job, then a last one to ensure that the lugs are

 

freely connected and I have full tool tension.

 

And yup - I do not like the appearance either! You get about an eighth

 

of an inch horribly splayed out each side of a central crush on the

 

ferrul. This can be hidden by shrink wrap to tidy up the job but is

 

nowhere near as neat as the hydraulic press jobs

 

T.

FAA have an advisory and probably some more ADs as well. Worth

 

getting a copy for ALL repairs. I think the current one is AC143-1B

 

Aircraft maintence & repair. Also online. (monster file)

 

I

 

was taught to do the outside crush first. i.e. the free end, not the

 

thimble end, then the thimble end, then the central. This certainly

 

looked the part. Bit of heat shrink on the pineapple, and a bit

 

previously fed down the cable before looping the cable to capture the

 

pineapple end, but not over the swage.

 

The theory being the central crush took the major load regardless.

 

I seen a 6' bolt cutter with removable jaws modified by an engineering shop. This seemed to work a treat.

 

Micgrace

 

 

[Guest Ken deVos]

Has anyone had a problem with the 'swaged' cables connected to the spring that centres the rudder in a Jab LSA55?

 

Not much of a problem if the thing goes feral on the ground or even in the cruise, but my encounter was just after the landing flare and with no spare underwear at hand!

 

Not sure what was worse, the loud bang, the fright induced ballooning, veering off the RW centreline and eventualtouchdown on the taxiway, facing the unavoidable audience, or simply having my PPL passenger tell me "this would never happen in a Piper!".

 

Cheers

 

Ken.