leadouts and line ends - how does the 'recommended' method actually work

[Chris Gilbert IRL-1638]

Guys,

Please don't take this as needing advice on how to make leadouts/line ends or which method is better.
I don't need a lecture on stress risers, and I'm sure I've seen stronger thread than than wire used in some line ends.

It seems we have two methods of making leadouts/line ends - wrap and crimp

Wrapping:

We can use thread or wire for the wrapping (depends on where you look on the web)
we can use CA/Solder/Epoxy or nothing (ok heatshrink) to 'secure' the wrapping.

Crimp:
Fewer options here, we wither crimp or swage, and we may or may not use epoxy to eliminate stress risers.

OK, standing back from all of that, it looks like the fundamental mechanism at work in the line ends/leadouts is the same.

In my minds eye I see a belay at work in my leadouts/line ends, but I'm a simple flyer, not a mechanical engineer, though I have dangled, and been dangled from the end of a climbing rope a few times (maybe I hit my head once too often)

What is the mechanism behind the lead out/line end form (not construction) that we use, since it seems that in spite of large amounts of heat and smoke the actual method of creating that termination is not of any particular importance

It seems to me that the usual heat and smoke generated when leadouts and line ends are discussed have not ever explained the theory (even in laymans terms) of how the recommended termination actually works.

Chris

[peabody]

hi Chris...
I believe that wrapping line ends with anything but (metal) wire would NOT be proper (read insurable). I'm also quite sure that you will learn of countless horror stories where wrapped lead-outs were soldiered or CY'ed ....makes 'em too brittle.

I also believe that the majority of folks that use crimped ends DO NOT follow the AMA suggestions as to path of the wire and most, too, use tubing that is too big.

Done properly, each method works just fine....but conversely, if done improperly, failure is almost assured.

Have fun!

[john e. holliday]

I would never recomend any body using crimps.  Take a good look at them.  You are almost cutting the cable if crimped too hard.  Swagging is a different story.  It is used in industry as well as real aircraft.  If done right it is a great termination for cable.  Do not use on solid wire.  The terminations at the end of the leadouts and flying lines is very important.  If not done properly, you may lose a good aircraft.  I don't know how to explain the mechanics of swagging other than it grips a lot more cable than crimping. 

Wrapping was my choice of temination for years before I was introduced to swagging.  Carl Shoup is the culprit that showed it to me.  I came home and tried to make the tool  he showed me.  I wound up getting the tools from him as well as his tool for making line clips.  So far no failures, knock on wood(my head).  Some where I posted about doing the swagging and another post on wrapping.   The only time I ever soldered a connection was in an F2C plane on the leadouts.  Then there is a way I wrap those in which I have to solder for my feeling of safety.  You also don't flex the leadout as much as you do on other control line aircraft.  Anyway I probably haven't ansered your question, but, I say stay away from crimping.

[Brian Massey]

My vote goes with swagging also. I learned the technique from fishing, and never had it fail up to and including a  252 lb Yellowfin Tuna. I say bring on the 40 lb pull test! If you do choose crimp, it can be done safely but you have to be much more careful; I've crimped and never had one fail either.

Brian

[Jim Thomerson]

I think the problem is not with the wrap, or crimp, or swage coming loose, but rather setting up a stress riser where the control line or leadout flexes in a very small area until it breaks.  I wrap lines, and run the wrap up the line for three or four turns past where the AMA diagram shows.  I hope I am softening the stress point.  On leadouts, I usually crimp, using tubing and round nosed pliers.  I think the leadouts are big enough that I don't damage them.  I do the crimps about 1/8 in in from the end of the tubing, again hoping to soften the stress point.  I've never had a leadout break, but have had lines break a couple of times.  I've also had cables on the handle break from flexing. 

[dale gleason]

I think the mechanism in the wrapped termnination is simply a "noose" whereby anything that slips is limited in how far it can slip. dg

[Dwayne]

Where do I get a swagging tool small enough for our purpose?
Thanks
Dwayne

[W.D. Roland]

Where do I get a swagging tool small enough for our purpose?
Thanks
Dwayne

I would have to dig to find the info but a good tool can be had from who ever I bought my bulk lines from.
He also has the eyelets and proper size tubing.
Howard Rush turned me on to him.

Not sure of what the swagging would look like compared to this tool.
This tool puts basically put a crimp down the length of the tube.

In the past younger, dumber and broke I would use cutting pliers across the tube and only remember one that broke.

What I like about this tool is that it squeezes on the length of the cable so that the entire length of the crimp is tight on a length of line(x3).
With the tubing and lines sizes matching the tool this seems to be the best I have seen.

3 passes of line through the tube and crimp in center of length will leave the end of the tubing uncrimped to help reduce the stress riser.

Will look and see if I can find info on where to get and post, if not we can always ring Howard.


Du bro had a simple crimp tool way back yonder when.

David

[john e. holliday]

MBS Model Supply used to have the crimping tool along with the furrels(tubing).  The swagging tool is from Carl Shoup.  He is in the members section for the e-mail or PM.  He also has a tool for making the line clips.   Lee Machine Shop in the vendors corner has a tool for making line cips also.

Looked up Carls e-mail:   shoupentstatorrepair  at  prodigy  dot  net    .    Remember he is a busy man.   

[Brian Massey]

Where do I get a swagging tool small enough for our purpose?
Thanks
Dwayne

A well supplied fishing tackle store sells them.

Brian

[dale gleason]

What was the question?   dg

[Robert Zambelli]

Available from  www.savacable.com
Number T-185.

Bob Z.

[don Burke]

To answer the original question.  A non-soldered wrapped end provides a flexible termination of the wire.  The solid ferrule works just like soldering and provides a stress riser right where you don't want it.  They work just fine in a pure push-pull application.  In normal use control lines don't get any bending, but ground handling can do a lot.  Not worth the risk of failure for me.  IMO crimped or swaged although used in aerospace is NOT for cables or wires that may be subjected to bending, OK inside the wing at the bellcrank. 

[Chris Gilbert IRL-1638]

I'd mark that as 1 possible and "what was the question again"? Just as well we're not sitting any exams/tests folks.

If we were flying bricks on strings I'd be happy to say that the knots we used on the string work because of the friction of the string on itself through the knot.

But we don't fly bricks on strings, we fly works of art connected to the pilot by steel cables. If we were for example to use knots we'd have trouble finding a suitable knot because of the lack of friction on the steel lines.

So, how does the approved termination method actually work, what are the mechanics of it?

[Dick Pacini]

So, how does the approved termination method actually work, what are the mechanics of it?

Geez, how do your shoes stay tied and why should it be an issue?  Laces tied in bows or knots,  velcro straps, snaps...all have the same purpose...to keep the shoe secured to your foot.

The line is wrapped smoothly around a small eyelet, thimble, grommet...whatever you want to call it.  That forms a point of connection that evenly spreads the load over the length of braided cable following the circumference of the eyelet.  The excess cable is secured by a swagged tube or by wrapping/doubling back/wrapping with fine copper wire.  Either method works by preventing the cable from slipping and releasing its hold on the eyelet.  That's it.  Not rocket science, just basic Yankee ingenuity at work.

As an aside, I never used cable leadouts.  I always used solids as shown to me by Jack Sheeks in the 60's.  They were easy to make and I never had to worry about them wearing through or slipping.

[Brian Massey]

As an aside, I never used cable leadouts.  I always used solids as shown to me by Jack Sheeks in the 60's.  They were easy to make and I never had to worry about them wearing through or slipping.

Amoungst several old planes from the 60's sits a Ringmaster with solid leadouts. I often look at that and wonder why I don't do it again. What are the drawbacks of solid leadouts?

Brian

[Jim Thomerson]

When you hit solid leadouts on the van door when unloading your airplane, they bend,  If you can straighten out the bend and make them still work, you may have a weak spot in the leadout. 

[Jim Treace]

When you hit solid leadouts on the van door when unloading your airplane, they bend,  If you can straighten out the bend and make them still work, you may have a weak spot in the leadout. 

Here in Florida I fish offshore quite a bit and we completely rely on our crimped connections. Properly applied and frequently checked, never had one fail. I have gone to crimping my lead outs.
Also, if you need to remove minor kinks from solid lines, Du Bro fishing sells a great little wire straightener device. Use it all the time on solid fishing wire. Don't see why it wouldn't work on CL leads as well. http://www.shopatron.com/products/category/101.2.314.409.0.0.0
Jim

[Bill Little]

To the original question of what makes it work, I would say pressure and friction.  By folding the wire back, wrapping and then folding it back over itself again and wrapping, we are squeezing the wire into a tight series of anti slip turns.  The wrapping wire providing the pressure.

Same concept with the swadge since it is passed back and forth between the tube.

A mechanical connection in either case which provides pressure and friction to prevent the line from unwrapping.



Mongo

[FLOYD CARTER]

We have had two line failures recently at our field.  One was a Chinese crimp at the bellcrank.  The other was my unique leadout wrap, which was really a bad idea.  Now, I use only the approved AMA line wrap (back on itself and wrapped with #27 copper wire).

Floyd

[Bill Little]

I have had probably 4 line failures over the past 47 years.  3 were when I was young and kept using lines until they finally broke....... not on purpose, just did.

The last one wasn't really *mine*, it was Aaron's.  He had a stranded LO saw through an unbushed aluminum BC.  The plane was built as a Product review for Stunt news and nothing was altered/replaced during the build.  It took a lot of flights to actually do it, and he saved the plane for the most part.  Only popped a LG out of the wing and a crack to the bottom of the fuselage.

I truly am the *Blind Hog* when it comes to this stuff.

Big Bear

[W.D. Roland]

Never did find contact for where I bought my line stuff. Howard Rush ?? You turned me on to him.

Did get a picture of crimp tool and crimped lead outs.

Also is pic of some Dad made in 76 or so on a combat airplane. the shiny thing is the tool used. The tool came with Sullivan lead out kits and was used in pliers.

Apologies for cheap camera( expensive Kodak)

David