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Thread: Need help building control cables

  1. #1

    Default Need help building control cables

    I got my new control cable material today so I headed into the garage to start building.

    I quickly realized this will be a big pain as I had originally thought.

    I'm trying to make a test loop in the cable to see how this whole process goes. I started with the 1x7 cable because I knew it would be hard to work with. I'm having a bear of a time just trying to get it around the thimble and slide the sleeve up enough to crimp with my tool.

    There must be an easier way! How do you guys do it?

    Also, piper calls for three different crimp styles. The simplest is a single crimp that spans the entire sleeve. The other two are multiple crimps. Either two or three. It looks like my simple hand wrench style tool I got can do the three crimp one but it isn't wide enough to do a single. Would it be ok to do a triple crimp of everything or should I get a new tool or borrow the loaner from swpc.

    I'm quickly seeing why new cable sets are $800+.

    Thanks, Tim
    Attached Images Attached Images

  2. #2

    Default

    Here is my first attempt with the 7x16 cable. Much easier to work with.
    The tail seems a bit long. Is there a trick to cutting it shorter?

  3. #3
    rocket's Avatar
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    Default Re: Need help building control cables

    Tim,
    Whenever I decide that an aircraft needs all the cables to be replaced I order a whole set.
    If there is a problem with one cable that I can fabricate locally then I do. I deal with float planes mostly so I get to swedge a lot more cable then the average.
    I would not feel comfortable useing the hand tool shown in your picture but if it gages OK and test pulls fine then I should be airworthy...and would be fine for a float water rudder but perhaps not for a primary flight control.
    I would be sure to read AC43.13 a couple of times and then practice about ten times with loops that you can pull test at your work bench. Once you are satisfied with your test pieces you should be good to go.

    remember to use the plated (shinny silver) sleeves with stainless cable and stainless thimbles ONLY for stainless cable as the others can quickly cause some nasty corrosion.

    I like to soak the assembled cables in a vary thin parokeltone mixture , blue gas or stodderds solvent, and then let them dry before installing.

    I lay out the old cable in a bench between to screws or nails and build up the new cable right on top.

    When you practice make a note of how much the cable stretches or shrinks during the process so when you are making your real cables you can correct for this.

    Lets see...there must be a hundred other things that do not come to mind at the moment.

    Ok: Practice, practice practice, test pull a couple of samples, then get to it!

    I am guessing a good swedger , a vary good cable cutter, and all the cable and bits might run you about $400 bucks...all the sudden that $800 for that professionally assembled cable kit starts to look real good. Of course not as satisfying as rolling your own.

    I just noted that the soldered thimble instructions are not in AC43.13 any more...bummer.


    Rocket

  4. #4

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    Default Re: Need help building control cables

    All the instructions and requirements are clearly given in AC 43.13-1B Ch.1. Don't skip gauging each and every one of your crimps for the O.D. of the finished crimp, and... You NEED to "pull test" your cables before you call them "completed". I absolutely HATE that "tubing flair tool" for making Nicopress crimps and would drive 75 miles each way to "go home and get" my Nat'l Telephone Co. GCMP crimper tool if I only have to do ONE cable end!!! It was right up there with the best of tool investments I have ever made (and, they have only "inflated" in cost about seven percent in 35 years!). Got NO "hints" for you with that P.O.S. other than to give it to somebody you don't like and get yourself the REAL tool.

    The "three holer" crimps are perfectly legal (as long as you have THREE complete "swages" along the sleeve, all with definate "humps" on BOTH SIDES of each crimp (no "straight off the end" crimps.

    The sidebar picture of your "pilot crimp" should get just a little "critique", here. The "tail" is FINE. If you are using a REAL "cable cutoff tool" -and you SHOULD BE (they are a little under thirty bucks and work WONDERFULLY until you get to 1/4" cable, where you should then be getting the "Big Brother" of the standard sized cable cutter. They're right up there with the "real" Nicopress [Nat'l Tel Co] tool and work well and last "forever")- that is about as close as you can get anyway, and soon you will realize that if you trim the tail any shorter than that, the cable "untwists" at the crimp. No, that's good...REAL good. If you are persnickety about getting your socks snagged on your rudder cable connections, you can add a 1.5" piece of shrink wrap to the cable fittings, and after crimping, gauging and pull testing, you can then shrink it up over the sleeve and over and down the cable end. FORGET "wrapping it with Electrician's Vinyl Tape". That sux and it will soon be mysteriously "gone" somewhere! That is to say..."you're better off NOT BOTHERING in the first place". Either heat shrink it, or Fageddaboutit.

    Next, it's about impossible to reliably tell whether you have "carbon" or "stainless" cable there (Piper spec'd "carbon steel") but OF THE TWO, the carbon steel cable is rated at a higher tensile strength. To ME, that means "stainless MAY BE prettier 15 years from now, but CARBON IS STRONGER.,..forever". I'd risk a cup of coffee that what I'm seeing there is that you have "carbon" cable, in that picture, but repeat... I MAY be mistaken. Yes, Piper sold stainless cables for "seaplanes", but seaplanes were subjected to comparatively shorter "maintenance periods" and were replaced more often than "your Baby's"... which will probably "sleep" in an air conditioned/heated, humidity controlled hangar all year long, ...will. IF (caps on purpose) that is stainless cable, you have "avoided" probably the most-made error in "amateur aircraft maintenance"...carbon steel cables require the use of the BARE COPPER sleeves, and stainless cable requires the "silver" (cad plated copper) sleeves. See...It has to do with the Anodic Scale, and cadmium is further from stainless than copper, and copper is further from carbon than stainless. All this equates to "corrosion", down the road, and what is known as "Acceptable Methods, Techniques and Practices". If you got the plated sleeves and are using the carbon "wire aircraft rope", you need to get the COPPER sleeves. Your nicopresses will suffer from "early failure" if you use the wrong "piece/parts". Yeah, yeah...the "silver" cable and the "silver" sleeves just look so "right together". But really: if "carbon", then "copper". If "stainless", then "plated".

    Last tip (for THIS picture) is...your thimble isn't "far enough down inside the sleeve". It will (all to soon) be dangling around whatever fitting the cable is attached to (and that is one of the ugliest things you can find some sunny day). At the very least, you should "slightly TIP" the ends of the thimbles "in" before you put them in place to make the crimp. Then, when you "pull up" your "loops", you can get them as much as you can, "bareback", and then GENTLY "tap" then in place (I have this nifty brass hammer made out of a 1" dia copper [round] bar, mounted on an eight inch long piece of "re-bar" (aka: "rerod") with a 4" long "rubber hose" pushed on as a "handle". The "head end" is threaded and the "head" is tapped and they are screwed together. Don't "beat everything up"...just a couple of light taps will push the thimble into the sleeve JUST A LITTLE ways, and after crimping you will be Super-Pleased with they way they last FOREVER captured in place. On your "bigger cable sizes" (which we do not have much on these Little Girls, and you are NOT EQUIPPED for with that cut-rate crimping tool) you may even sometimes have to "clip" the very ends of the thimbles "back at 45 degrees" (using a decent pair of Dykes to "point" them) or the thimble will be pushed right off when you crimp the sleeve. This isn't usually necessary (nor, "desirable") on 1/8" cable, and depending on your "technique", not for 5/32 cable, either.

    Now, as far as the 1x7 vs the 7x7, you are definitely correct in your observation that the "flexible" control cable is MUCH easier to work with. Fortunately, the 7x7 is actually STRONGER than the 1x7, and MAY BE substituted for the 1x7. The reason Piper used 150-something inches (I forget...whatever it is) was that it represented a "cost savings" on the ONLY cable that wasn't subjected to "turning about a pulley". Four cents per airplane...and God-only knows HOW MANY airplanes over the years... made for some decent "Christmas Parties for the Troops" at Lock Haven/Bradaford/Ponca City. You and I have no such "Bean Counter requirements", and can be just that much "spendthriftylessness" than Piper. With the "proper, high-dollar" manufacturing equipment the Factory used, it made perfect "sense" to use 1x7 because it was just as easy to fabricate (uh..."manufacture"). But, it isn't "necessary" for "We-uns".

    [edit] Heheheh...nice Post, Rocket! I took a call halfway through mine!

  5. #5

    Default

    Thank you guys! I do need to read through ac43.13 again. I got excited when my parts showed up and wanted to try things out.

    Let me get this correct. The 1x7 I got I can just throw away because they more flexible cable is fine? Man, wish I saw that one coming! I may just order that fancy nicopress swagger.. I'm in $300 for this stuff what's another $300 for the tool? I'm in not hurry to have this plane done so building cables is perfect. I managed to get one rudder cable made and all measurements fell perfectly in line with the blueprints. It took 4 hours but I didn't draw blood and only cussed a few times.

    I saw that piper used stainless on the seaplane and galvanized on all others. Since galvanized is coated in zinc and the sleeves I got are also coated in zinc I thought I was good. I'm pulling up ac43.13 to read again now. I saw that stainless Abel's seem to be more popular with people these days but ran across an FAA ac about the 737 breaking control cables even after they were inspected recently. Thy went on to say the galvanized coating added to the self lubricating properties and contributed to longer life. I like the sound of that.

    I do plan on pulling all cables to test for strength. How would you guys recommend I do that? Is there a break away gauge I can use or just have a helper read a pull scale that goes high enough. Off the top of my head I'm thinking the cables are only rated to 2,000 lbs so it shouldn't be too difficult.

    As for soaking the cables. Should that be done before assembly to remove the oil and grease?

    Thanks again guys!
    Tim

  6. #6
    rocket's Avatar
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    Default Re: Need help building control cables

    Tim,
    Stainless cables work harden then began to fray usually within a fairlead between a long unsupported run. Galvi cables last a long time.

    Cables are soaked in parlketon for corrosion resistance, thin with solvent to penetrate into cable.

    Galvi cables use bare copper sleeves and galvi or stainless thimbles. Just do not us use the bare coper sleeves with the stainless cable or the galvi thimbles in the stainless cable...bad.

    If you make all your cables with that little swedger your hands and forearms will be strong enough to pull test the cables. Think Popeye.


    7-146. CABLE PROOF LOADS. Cable terminals and splices should be tested for proper strength before installation. Gradually apply a test load equal to 60 percent of the cable-breaking strengths given in table 7-3 and table 7-4, for a period of 3 minutes. Place a suitable guard over the cable during the test to prevent injury to personnel in the event of cable failure

    Cable testing: So, 60% of 2000 lbs is 1200lbs. Now just pull that for three minutes! A long pipe with a pivot close to one end to give you some mechanical advantage works fine. You do not need anything fancy but note the smooth application of force and be prepared for a failure. A big fish scale and a twenty to one ratio on your pipe works fine.

    Rocket

  7. #7

    Default

    Thanks again rocket. I didn't even consider the fish scale on the other end of the lever... It was a long day at work yesterday.

  8. #8

    Default Re: Need help building control cables

    I'm having trouble finding this parlketon you talk about. Did you spell it correctly? What thiner do you use for soaking? I'm getting the bad boy nicopress tool. That hand thing sucks. If nothing else, this will be an adventure building these but then again, that's why I decided to tackle this project anyway.

    Tim

  9. #9
    rocket's Avatar
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    Default Re: Need help building control cables

    Tim,
    me, spell correctly, you have got to be kidding! Why do think I am an aircraft mechanic...and not a rocket scientist.


    http://www.aircraftspruce.com/catalo...aralketone.php


    Rocket
    Last edited by rocket; 02-19-2012 at 03:52 PM.

  10. #10

    Default

    Thanks again rocket! I was searching everywhere even using the mil-c spec number.

    Last question. These cables seem to be lubricated already. They seem a little dirty, just typical dust from the oil already on them. My final plan is clean the cables, build, then test to 60% for three min. Sound good?

    Lastly, ac43.13 shows 1x7 cable at 2100 lbs and 7x16 at 2,000. It was mentioned that I can substitute the easier to bend 7x16 cable for the rudder cable that is originally 1x7. That would mean I would loose a little strength. Is this really what others are doing? I'm thinking I'll just use the original since I already have it on hand but a back up plan besides two $200 premade cables would be nice.

    Tim

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