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Thread: Control Cables Stainless vs Galvanised

  1. #1
    Steve Pierce's Avatar
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    Control Cables Stainless vs Galvanised

    I am rebuilding a set of Super Cub wings and was going to make new control cables but seem to remember an Advisory Circular or something about stainless steel cables wearing badly in Super Cubs. I like stainless because of rust etc. but wonder the pros and cons of each. Any comments would be greatly appreciated.

    Steve

  2. #2
    SuperCub MD's Avatar
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    Do not use SS cables on the ailerons or forward elevator cable in a Super Cub. Maybe 6 mo. ago? I was asked to give input on this to the powers that be, and doen't be suprised if there is a future AD against SS cables in Cubs. SS work hardens, and breaks anywhere it bends around a pulley in a Cub. The aileron cables, at the lower fuselage pulleys, the wing 90 degree bends behind the main spar, and especially the forward elevator where it makes a 180 around the pulley, are very suseptible to breaking. Flap cables at their bends also, but not as much, because they do not move as much, and have less tension.

  3. #3
    murph's Avatar
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    My mechanic that takes care of my Ag planes told me several years ago that he never uses stainless cables because of reasons cited above.
    murph

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    Tim's Avatar
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    Mark
    In your opinion how long would it be before the ss cable become hard. 1000 hours , or 3 or 4000 hours. I have ss cables on my 2+2 and you are makeing me nervous

    Tim
    2+2

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    Crash's Avatar
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    Stainless Cables

    Everyone I know uses stainless 7x19 cable and have for years without any problems. The truth is, 7x19 stainless steel cable is not entirely made out of stainless. Take a magnet and touch it to a 7x19 cable. It sticks...hmmm. Not hard, but it sticks non the less. There is some steel in there somewhere. You ought to see the galvinized factory cables on my 77' PA-18, they are rust balls. Now that scares the hell out of me. FAA and everone else involved in this better have some good proof such as labratory tests (same type of bend, same age, and x number of actions to compare SS vs galvinized) before they go off half cocked on this one. Crash

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    Tim's Avatar
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    Thanks Crash, my plane and cables have 700+ hours on them and I would hate to think I have to replace the cables. I gave them a close look today and don't see or feel any hard places or broken wires or anything else wrong. A guy I know just bought a Taylorcraft and I thought it had brown cables, a close look said rust, and it just had an annual. Go figure

    Tim
    2+2

  7. #7
    SuperCub MD's Avatar
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    I've found stainless cables that have begun to fray after just a 100 hours, and some seem to last longer. I could not say what the original soarce of the bad cables was, maybe there is just some bad stock being used out there? Stainless just seems to fray more anywhere it has to bend. You should always inspect these areas closely anyway, no matter what type of cable it is. I'm not a metalergist(sp), just telling you what I have found over the years.

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    Steve Pierce's Avatar
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    Thanks Mark. That is what I wanted to know. Experience is the best teacher as far as I'm concerned. If there is a question I'm going to go with galvanised. The old ones lasted this long so stay with tried and true.

    Thanks again.
    Steve

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    This is real good information. I have been running stainless for the last 9 years and they are holding up fine but you can bet I will be watching them more closely now.

    Thanks for the tip SuperCub MD.

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    T.J.'s Avatar
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    I have a tiny amount of fraying on my left lower aileron control cable. The aircraft has about 270 hours since total rebuild in 1996. How do I tell if the cable is made of SS or galvanised?

    As you can see from this thread, where I also discuss the issue, Univair sells both:

    http://www.supercub.org/phpBB2/viewtopic.php?t=1253

    Right now, this thread leaves me paralysed with indecision. Good info though. Just need to figure out some answers.

    Thanks,

    BCB

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    Lawn Dart's Avatar
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    BCB
    Simply put, just place a magnet on the cable. Stainless steel will have very little (if any at all) attraction to the magnet.

    PS Check your private messages!

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    I just annualed a Husky with stainless cables. It had about 600 hours on it and almost every cable in the plane was frayed. However not at the pulleys but at every fairlead. Husky has a service bulletin out on it.
    Shawn

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    control cables stainless vs galvanized

    can any one tell me what the lengths of the four aileron cables are for a pa18 and how your measuring like inside of thimbles at the end for example? thanks

  15. #15
    Dave Calkins's Avatar
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    I prefer to build the cables in place. In other words, fabricate them on the a/c.

    Most guys will agree that this is the best way.

    If you don't know how to do this, or if you aren't credentialled to do it, Please don't.

    Dave Calkins.

  16. #16
    Dave Calkins's Avatar
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    PS.

    Stainless Steel cables are definitely softer than galvanized and won't wear for as long as galvanized. Also, the magnet trick doesn't work on SS as they do contain some ferrous material and will attract the magnet.

    The corrosion issue with galvanized is insignificant with an a/c that gets proper inspections. And the tougher material makes it worth the tradeoff.

    For those uninitiated, a broken strand is cause for replacement of the cable.

    In fact, the AC 43.13-1B lists criteria for cable inspection.

    50% wear of ONE STRAND is cause for replacement of the cable.

    This is very basic stuff, guys, and if you weren't aware, cable replacement is beyond the scope of preventive maintenance for which a pilot/owner is authorized to perform.......just in case you wanted to know.

    Dave.

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    SS cables

    I have SS cables on my cub and after reading these post I will be taking a closer look at them as of right now I have never had any visable wear.

    All SS is not created equal some has more carbon in it and that is why a magnet will stick to it, it will also make the cable more flexable. If people are having trouble with cables I wonder what they are made up of.

    I rebuilt my wings a few years back and at that time I had galvanized cables on it. During a close inspection when the cables had no tension on them it was easy to see the cables where shot due to corrosion. The wings had been rebuilt in 73 and the plane was new in 1960. I have no record of the planes cables ever being replaced. Is it possible those galvanized cables gave close to 40 years of service? If so I wonder why I change to SS.

    Cub_Driver

  18. #18
    bearsnack
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    stainless cables

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  19. #19
    Big AK's Avatar
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    WHOAAAAA!!!!!!

    consider all the dirt and debris that will stick to your paralketone/CPC mixture and the acceleration of wear it will cause in areas where the cable contacts pulleys, fairleads, and fabric exits.

    CAUTION!!!!! to those contemplating the above advice. It is my opinion that having clean cables is a better preventitive.

    DMC

  20. #20
    bearsnack
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    if your not on floats or around a salt water environment maybe you don't want to coat your cables. What would you rather have, dirty cables or corroded cables? The environment I work in we coat hardware and anything else that will corrode with paralketone on a weekly basis.
    Didn't mean to get you all stirred up there, buddy.
    Joe

  21. #21
    Crash's Avatar
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    Cables

    You guys are 20 miles from one another so I don't think the enviroment would have anything to do with it, just opinions. The cable is made with a lot of oil in it. I slosh the bulk cable around in some gas to get some of the outside oil off it. Just feeding them through fair leads and having them drag on the hanger floor picks up a lot of dirt. I like running them dry and replacing them at rebuild every twenty years, they won't rust that bad even if un protected. I jigged a set of cables for a PA-18 and will never do it again. Build them in place. Install the turnbuckle with two threads showing outside the barrel (two threads are legal by the FAA). Pull the cable semi-tight and slide the nicopress sleeve up to the thimble and clamp in place with medical hemostats (I sometimes cable up the whole airplane with hemosates to make sure everything has the right throw etc. before nicopressing). Nicopress the end of the sleeve closest to the thimble (I know this is not how some will tell you how to do it), slide a small piece of sheet metal between the cable tail and cable up to the nicopress sleeve (this is a shield to protect the cable). Use a 3" cut off saw and cut the tail off nice and square about 1/8" out from the end of the sleeve (shield the main cable from accidental cutting with the piece of sheetmetal). I have all the fancy cutters you can get and they all leave the end of the tail jagged, use a high speed cut off saw for a nice square cut. Nicopress the tail end of the sleeve then do the middle last. You should have a .020 ring at each end of the sleeve and two in the middle if you spaced your presses right. After you're done and tension the cable, the two threads will be inside the barrel, you will have plenty of adjustment as the cables stretch over time. If you start off too long, you will run out of turnbuckle at some point and have loose cables or flaps that do not extend all the way like they should. It's an art if you do it right or care. Your life hangs in the balance on the quality of your work. Crash

  22. #22
    PA12driver's Avatar
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    Good post Crash!

    I have seen hundreds of sloppy, nicopress crimps, poorly tensioned cables (including some of mine) and more importantly many, many siezed pulleys that cause extreme wear on Cables. Also a lot of wear on cables against fairleads and interference with tubing and belcranks that are not always apparent with a brief inspection (often times it takes someone at he controls and someone with the light and mirror?

    Tim

    PS: I saw more damage to cables that were dirty and oily then clean and dry (especially in the Matsu "silt" valley)

    check closely the connections on the elevator horns on float planes!

  23. #23
    nanook's Avatar
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    cables

    I think one thing that wears cables out more than anything is leaving control surfaces unsecured to flutter away in the breeze. An airframe can have 200 hrs. on it and have frayed cables from the wind, it really accelerates the wear in a concentrated area. I personally have not seen the ss cables wear anymore than the galvanized under normal conditions. In corrosive areas, I'll use the stainless. Cessna has offered both types for well over 30yrs.(in the parts book) with no abnormal problems.

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  25. #25
    bearsnack
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    Paralketone

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  26. #26
    SuperCub MD's Avatar
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    Re: Cables

    (I know this is not how some will tell you how to do it),
    Well Crash, you asked for it. The correct (and not to mention legal) way to make a thimble eye splice is to make the center compression first, the one next to the thimble next, and the one farthest from the thimble last. This is because the sleeve grows a lot in length when it is compressed. A correctly crimped 1/8" sleeve should grow from 9/16" to 3/4" for example. By crimping the ends first, this normal expansion is not allowed, and the strength of the first two crimps,or the cable itself could be compromised.

    I bend the 4 sharp points of the thimble together a little so that initially they fit inside the sleeve a little. When the center of the sleeve is compressed, the sleeve expands up the thimble. When the thimble end is then compressed, it captures all the points and tightens the cable around the thimble, keeping everything tight and neat. The end of the cable is trimmed to the proper length, and the end crimp made. I can't see any advantage to doing it any other way.

    On a rebuild, when all the repairs and mods are done, and everything is ready for cover, I'll completely assemble the airframe and rig the plane. Then I will make up the cables like Crash discribes. Without cover on, it is easy to check pulley and guide alignments, correct movements, etc, and correct anything that is out of line.

    Inspecting older aircraft, a very common thing I find is badly, or incorrectly made cables. If you don't make a lot of cables, and you try making a set, you will probably screw up a few times. If you don't get it right, take the cable out and try again. Cable is cheap, and this is not a place to scrimp. Legally, newly made cables should have three threads exposed max, or four threads max in the turnbuckles when correctly tensioned. Get it right, or keep trying till you get it right.
    .

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    Back when I was a boy I was working for a company that had a C-210, While waiting for the boss to show for a flight, I was noticed that the aileron cables under the panel made a strange sound. I found that a control cable was not on the pully but was just running over the shank of the bolt. It was all rigged that way and I'm sure it was like that from the factory. Plane was about 10 years old, had never been damaged and had acouple of thousand hours on it.

    Don

  28. #28
    Lance's Avatar
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    After purchasing our cub I found an aileron cable, some how, over the top of the bolt on the fuel tank band. It was a stainless cable and one wire was frayed but the bolt was about 3/4 cut in half. No problems with our stainless cables so far. They probally have about 300 hours on them.

    I just finished doing an annual, along with my A&P, on our '75 180 with stainless cables and everyone of them looked good. 1155 TT.

  29. #29
    Dave Calkins's Avatar
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    Mark D., thanks for correcting Crash, I was afraid to bother mentioning the correct sequence for swaging nico sleeves.

    Bottom Gun, just for fun, take another look at the aileron cables in the cabin roof of your 180, the ones you can see after you unzip the headliner. If you don't have Cessna shoulder harnesses, you can just unzip the headliner and look right at 'em.

    So take your gust lock out and then turn the yoke to determine which way the cables move, then check the cables where they've been running over those smallish white nylon pulleys. You'll need a flashlight, and you'll have to twist the cable with you fingers to see the side of them that runs on the pulley.

    If you don't find any wear (shiny area, or frays), then you're the winner. 90% of the Cessna's I look at have problems with the cables in this area. How this is NOT an AD escapes my puny mind.

    Good Luck. DAVE

  30. #30
    Lance's Avatar
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    Thanks for the tip. I just looked at them, I will go back and double check. Will let you know.

    Lance

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    Crash's Avatar
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    Mark Reply

    Mark

    I believe my method for makng nicopress splices is both legal and as strong as the one you describe. The "typical" installation as described on the "FAA Methods and Techniques" manual is just that -- typical, and not mandatory.

    In the section on thimble to eye splices they describe the "3-1-2" sequence of pressing, and the label under the diagram describes it as the "typical" procedure. I read that as not necessarily the "only" way to do it. They do require that your nicopress tool be in good condition and pressing fully. They also require that a sleeve gauge pass over the presses to make sure they are pressed all the way. These two items are required as I read it.

    My A&P /I&A (30 years rebuilding Cubs) reccommended the "2-3-1" crimping order I use and since he oversees my work and signs off my plane as airworthy, I will use his crimping order. I came up with the cut off procedure for the tails. I also form the points of the thimble (as you do) so it will go up into the sleeve about half the length of the points. If you press the middle first, then the thimble end, it pushs the sleeve too far up onto the thimble in my opinion. I have also seen it cock the loop off to one side.

    I do thank you for giving my son an idea for a science fair project called "The Weak Link in Aircraft Control Cables". We used a portable 4,000 pound shop crane and did some pull tests on 1/8", 7x19 galvenized control cable with a eye-to-fork turnbuckle, thimble, and nicopressed sleeve as is used on a PA-18 aileron horn.

    See photos at:
    ftp://ftp.supercub.org/upload/Crash1
    (password is cub)

    We did the first pull test and found the weakest link in the connection was the eye end of the turnbuckle; it snapped before the cable broke. We then nicopressed the ends without a turnbuckle installed to see if the end of the cable would slip and open before the cable snapped. I did one end with the "3-1-2" sequence like you describe, and the other end using the "2-3-1" sequence I described in my previous post.

    As the tension increased with each pump of the handle, I started to hear strands of the cable break but nothing appeared, then POW. The crane almost did a back flip as the cable snapped. Upon close examination I found that the "Mark Darth / FAA 3-1-2" splice started breaking strands down inside the nicopress sleeve and snapped with only a few strands sticking outside the sleeve. The "2-3-1" splice had all the cable and showed no strands broken, hmmm.... If this was Thanksgiving and we were pulling the turkey's wishbone, you just lost.

    I know this is not a conclusive test, done in a laboratory, and I should do it several times to prove my point. It tells me, though, that your theory is not necessarily correct about my splice not being as strong as yours. Either way, it's a moot point because the splice isn't the weakest link anyway. I don't think the sequence of compressing the sleeve has anything to do with the strength of the splice. The weakest points in a PA-18 control system in my opinion are, in order:

    1) The aileron horn to aileron connection. The aileron horn (riveted to the aileron with aluminum rivets) will pull out of the aileron before anything else would let go.

    2) The turnbuckle ends - they will snap before the cable will break.

    3) The cable, which will break before the thimble loop and nicopress sleeve will slip or open up (at least with the "Crash Splice").

    P.S. I measured the length of the sleeves on your "3-1-2" crimping method and my "2-3-1" crimping method and they were the same length when finished. Take care. Crash

  32. #32
    SuperCub MD's Avatar
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    I love it Crash, hope the science fair goes well. Wish I could get to the pictures, but I'm too computer stupid.

    When I make up cables, I reference AC43.13, chapter this, paragraph that, which discribes the middle first crimp as my "Approved Technical Data". Everything I do or inspect and sign off must be done in accordance with some sort of approved data, it's all about the paperwork. No matter how you do it, it will take anyone some time to figure out how to make nice tight eyes.

    Truth is, these cables are one of the strongest parts of the airframe, and if they were pulled hard, the airplane would probably tear in half before the cable broke. I think on Super Cub ailerons, the upper wind strut pulley bracket or the balance cable pulley bracket up in the wing would probably fail before anything else.

    I've found cables in planes that just had one crimp in the middle of the sleeve, or just one on each end where three are required, and they were holding just fine. I added the extra crimps to make them "legal". If I knew you were going to do testing, I would have been curious to know if a single or double crimped sleeve would slide before the cable broke.

  33. #33
    Steve Pierce's Avatar
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    Piper used one big crimp originally.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  34. #34
    SuperCub MD's Avatar
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    I have wondered what Pipers tool was to make that one long smooth crimp, must have been big. There are still a lot of those cables flying.

    The ones I'm talking about finding are obviously not original cables, and just have one or two small crimps where three should be.

    On the early Cubs, they also used two small crimps for a while. There is a old AD on it to check the dimension of the crimps, and use three crimps when making a replacement cable. Still see some of these old two crimp cables everyonce in a while.

    Before crimps, they hand braided the cable ends, or were wire wrapped and soldered. Always wanted to try hand braiding them, it looks nice when done corectly, but I think a lot of bloody fingers would be involved in the learning curve.

  35. #35
    Crash's Avatar
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    Cable Splices

    Piper was the first aircraft manufacturer to employ the Nicopress method of cable splicing. Walter C. Jamouneau was cheif Piper engineer (J-2, J-3, J-4, J-5) one day he noticed the phone company installing a telephone pole behind the factory. The telephone guy was installing the guy wires and using a big tool to squeaze sleeves onto the guy wires to secure them to the anchors. He went down and checked out the process and adopted it for aircraft cables. The FAA didn't invent it. Most of the FAA inspectors have probably never made a Nicopress splice, never fired up a TIG welder or ever bent a piece of sheetmetal. They inspect out of a manual and couldn't tell you why they suggest pressing the sleeves in a certin order (even though it is weaker). Crash

  36. #36
    Dave Calkins's Avatar
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    Nevermind. I had plenty to say, but it'd sound like an argument.

    No offense, I'll keep doing it my way....The typical way.

    Not to say Crash is wrong. It's just that any means of repair or alteration other than those "acceptable" or "approved" must have substantiating data "approved" by an FAA ASI. This is what's know as a "field approval".

    DAVE

    ....probably said too much again. no offense.

  37. #37
    Steve Pierce's Avatar
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    Joe Fleeman has won many awards at OSH with J-3's and a J-5 in recent years. They were featured in EAA Vintage or Sport Aviation. He made a die for the bearing press to replicate these single crimps. I have some very old nicropress tools marked with something to do with the phone company.
    Steve Pierce

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    FlipFlop's Avatar
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    Quote Originally Posted by SuperCub MD
    Before crimps, they hand braided the cable ends, or were wire wrapped and soldered. Always wanted to try hand braiding them, it looks nice when done corectly, but I think a lot of bloody fingers would be involved in the learning curve.
    When I did my A&P practical in 1968, I had to braid a cable for the examiner (FAA)... Haven't done one since...

  39. #39
    FlipFlop's Avatar
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    Re: Cable Splices

    Quote Originally Posted by Crash
    The FAA didn't invent it. Most of the FAA inspectors have probably never made a Nicopress splice, never fired up a TIG welder or ever bent a piece of sheetmetal. They inspect out of a manual and couldn't tell you why they suggest pressing the sleeves in a certin order (even though it is weaker). Crash
    Then again, some have...

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