School me: Cable Termination Hardware and install Techniques

[Bcone1381]

Control cables are terminated with either an Eye Splice (Nicopress Sleeve), or a Swaged fitting. FYI, Swaged Fittings are professional made by compressing the sleeve of the fitting onto the cable at a very high pressure with a special machine.

I have a few questions, but first the facts.
-The Eye Splice can be made with simple tools in the shop.
-The Swaged fitting is a special, made to order item, from dimensions provided by the builder.
-Most builders use Eye Splices.
-I like Swaged fittings.
-The cable length is adjusted to a small degree with a Turnbuckle to adjust tension.
-All cables must be made to an almost exact length to honer a 7 thread turnbuckle tolerance for initial installation of a cable given in AC43.13.
-The 7 thread tolerance provides a builder with only a 1/4" cable length tolerance.

My questions are;
-How did you measure the length of your cable runs?
-Is there any "Best Practice" or widely used method to accurately measure cable runs?
-Did anyone measure the cable run by threading Safety Wire through it?
-Do these tight tolerances demand that eye splices be made after the cables are installed to get the cable length exact?
-If one used a cable with a 3" stud fitting swaged onto it, would serious problems arise installing it, like learning that it can't be threaded from the strut thru the pulley, and into the wing or fuselage? In other words, is a naked cable end the only thing that can be threaded and installed?

Thanks for your input;

Brooks Cone
Patrol #303

cable ends jpg.png

[jim.mclaughlin924]

Brooks,
I like the swaged fittings. I borrow a rotary swaging tool from the local sailboat rigger for the weekend when I need to make up cables. Easy if you can find a tool, tough and expensive if you have to order.

[Battson]

If you are using swaged cables in the wings, then getting access to replace a worn out cable can require major disassembly of the aircraft. The carry through control cable is the worst to get at. If you use eye splices (or at least, if you replace worn cables with eye splices), then you can simply pull the new cable through, as you remove the old cable (by attaching them together).

[Steve W]

Not sure where or why your limiting yourself with only 1/4" tolerance with the turnbuckles. I just checked the distance on a -22 and got 1 and 1/4" of travel distance from three exposed threads to them both at the bottom of the barrel. Lots of room for adjustment if your close on the lengths. I use cable clamps to bring the length close to the required length.

[Bcone1381]

Steve,

I confess I am inexperienced. I appreciate seeing the turnbuckles have 1-1/4" of travel, thanks for the schooling there.

I got the idea of 1/4" tolerance from reading about turnbuckles in AC43.13. Page Chapter 7, section 9 says

When installing cable system turnbuckles.....it is essential that turnbuckle terminals be screwed into the barrel so that not more than three threads on the terminal are exposed. (See figure 7Â23A.) On initial installation, the turnbuckle terminals should not be screwed inside the turnbuckle barrel more than four threads.

The Key words I picked up on were 1) not more than three threads exposed... 2) On Initial Installation.... 3) ...Screwed inside....more than four threads. That makes a 7 thread tolerance with a turnbuckle thread pitch of 28 threads per inch, providing for 1/4" tolerance.

Is this tight tolerance is for the initial installation so that the turnbuckles have ample room to accommodate future cable to stretch? I assumed so. So, it would be a goal of mine to hit the AC43.13 target. But, I question my confidence of trying something unconventional at my experience level.

[Steve W]

Well, I'm an old dog and not too old to learn something new either. I've never seen the "four threads in" part before. I'm at a loss as to why. I just checked the barrel threads and they are good to the center hole. If u want to stay true to the manuel you would have a half inch of travel, quarter at each end.

[S Lathrop]

Steve,

I would think that you could get nearly spot on for length of cables by suing the electrical cable clamps on one end. My question, how much tension can you put on the cables by using the cable clamps on say one end of the cable? Can you get to the proper tension?

[Steve W]

You can get the cable fairly tight with the clamps but you don't want to tighten the clamps too much or you will kink the remaining cable. Course you would have the other end already pressed. It doesn't take very much tensioning to draw the cable tight from a snug point.

[Bcone1381]

Steve, I missed your comment about using cable clamps to tighten things up. That trick makes sense, and helps a great deal.

[JimParker256]

I guess I'm a bit slow tonight... What kind of cable clamps are we talking about?

[Bcone1381]

Jim, I assume Steve was using something like this.

[Mark Goldberg]

I have used vice grips with tape on the jaws for this also. Mark

[jaredyates]

I have used this style. Whether you use Mark's method, this one, or Collin's (below), some type of temporary clamp will make life much easier.

[Steve W]

Yep. I use the tiny ones. 1/4 nuts. Thread the cable through the sleeve, thimble and back through the sleeve again, draw the cable tight, clamp, snug the sleeve up against the thimble and make the center press in the sleeve. Of course you already have a piece of thick shrink tube on the cable. Disassemble and cut the extra cable off with a dremel cut off disc. Don't forget to wrap the center of the cut tight with masking tape (2-3 wraps) preventing the cable from unravelling. You can bend the remaining cable out of the way so you don't nick it with the disc. You can use a small piece of flat steel between the two cables in case your afraid you might cut the remaining cable. Cut quickly to prevent heat which will release the masking tape. Finish the other two presses keeping the thimble straight and shrink the tube for a clean looking job.

[jaredyates]

I use the dremel method, and the small piece of flat steel that I use for shielding the good cable happens to also be the "go/no-go" gauge that I use to measure the completed crimps.

[Zzz]

I think making cables is one of the funnest parts of building, but I've only done a few, so take my advice with a grain of salt.

Swaged are nice as they're more aesthetically pleasing, and theoretically won't catch on anything because of the clean tapered swage, but for everything else, Nicopress works great. I ordered pre-made swaged cables from Spruce for my rudder pedals and for the rudder horn.

I've only done my flap and elevator cables, and didn't use any clamps. I made up one end, connected it to the turnbuckle with the turnbuckle near the limits of long travel. Then I ran the cable to the other end of the run and cut it long, giving you enough to grab and pull on. Then I run the tag end through the sleeve and thimble and just pulled it as taught as I could, marking the estimated cut point with a sharpee, which is about 1/4" extended through the sleeve. My early ones I had like an 1" long tag, but now I think much shorter is better. I see some people cut it so it's almost flush to the sleeve but I like a little tag extending. Plus you need a little to hold/secure it. I don't think AC43.13 specifies this.

Then I cut the cable using a hack method my dad taught me: Wrap the cable at the cut tightly with masking tape and mark your cut point with a fine sharpee. Use a sharp edge like a cold chisel or splitting maul on end, and firmly smack the cable against it with a small sledge hammer. It shears it rather cleanly. They make a cable cutter tool too that's probably a lot easier but I got good results with this method so I never bothered.

Slide 2 pieces of shrink tubing onto the cable. One for the far end and one for this new end. Assemble your sleeve and thimble. I like to put my nicopress tool in the vise, clamped onto one of the jaws. Then follow the instructions, guidance, and spec for the sleeve size you're using from AC43.13. The order of compressions is important for how the sleeve elongates. Leave a little space inside the loop for the thimble, as it will tighten up as the sleeve elongates. When you're done, slide your shrink tubing into place over the tag end and shrink it. Some people criticize this saying it can trap water, but I chose to do it.

Do several practice ones. The consumable materials are cheap. Get a good Loos and Co nicopress tool.

[Collin Campbell]

I like the split bolt used in electrical work to hold the cables.

Collin

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[Bcone1381]

These posts help a great deal answering questions I have asked, and those I did not even know I should have. My understanding is....

-The purpose of Masking Tape is to prevent the tag end of the wire rope from unraveling while its being cut. I think the tape is never removed, and the Shrink Tube is installed and shrunk over it.
-Steve, you install your eye splice, press it, and cut it in position, and have no need to precisely measure each cable run that way.
-Zane, you surely must remove your cable before you whack it with a maul, but your instructions leave me with doubts.

So, the standard practice seems to avoid precise measurement of cable run lengths.