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Thread: rigging procedure

  1. #1
    Join Date
    Jun 2007
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    Bunker Hill, IL
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    264

    Default rigging procedure

    I am getting ready to rig my elevators for correct travel and cable tension, and I know I saw a detailed procedure somewhere, but I can't seem to find it. I only tinkered a little bit with it, but my problem sems to be that I only have 30 deg. of total travel with the horns contacting the bottom stop and ~1/4" from the top stop. I only spent about 20 minutes tonight, but I wanted to know the correct procedure for when I go to actually do it. Thanks.

  2. #2
    Join Date
    Sep 2005
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    Spokane Wa.
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    1,461

    Default

    OK, this is what I was talking about earlier. I had to call Tom Anderson on this one. You need to make sure you have the stops put on correctly. There is a differance in the stop lengths and it will get ya fouled up forever. I dont have the facts in front of me, but at least you have somewhere to start. I know they look like the same either way but they are not. Look real close!
    I will take a picture tomarrow and post it if some one else dont come across with the answer.
    Tom T.

  3. #3
    JohnW Guest

    Default

    Tom, "elevators", not "ailerons".

    Zac; you certainly have some weird problems! I suspect P.I.D.

    Take some pics to show what you got there, and how you are attempting to do this. And...don't you have an A&P or IA involved in this (or is you "experimental")?

    With nothing "attached" and the elevators attached to the stab (everything mounted on the airframe, of course) you will get 36 degrees elevator swing hard-stop to hard-stop. There is a 1/2" or so wide "plate" (maybe it's only 7/16", I don't recall for sure) welded between the upper longerons that the lower cable attach bracket (up stop) fitting strikes, and the lower elevator horn hits the forward cross tube between the upper longerons for the down stop. These stops are not "adjustable" (and they aren't located "top and bottom", they are "forward and aft" and both act off the lower part of the bellcrank), except that the steel bracket/stop at the aft end of the down elev cable can be [ORIGINALLY] ground to permit full travel, but if all this stuff was on this airplane, it should not require anything of the sort. This (grinding) is not a way to fix an incorrectly rigged system! WHY can't you hit the cross tube/forward, down, stop (what is with ~1/4" gap and where is this clearance)? Incorrect rigging forward is the usual culprit. If you have new cables, rod ends on the tiller/elevator drive shaft, et c then you have your work cut out for you.

    The elevators will hit these stops (they are the primary stops) at the ends of their travel, and rigging the forward part of the elev control system (under and between the seats) takes quite a lot of fiddling around to make this happen. You should have clearance on both the forward (down) and aft (up) yoke stops when you have the system correctly rigged. If you made your own cables, it is possible that you have attached the lower attach bracket in the aft nicopress on the WRONG CABLE (not hard to do, and don't ask me how I know!) and the cables are switched.
    Last edited by JohnW; 02-21-2009 at 11:56 AM.

  4. #4
    Join Date
    Jun 2007
    Location
    Bunker Hill, IL
    Posts
    264

    Default

    Quote Originally Posted by JohnW View Post
    Tom, "elevators", not "ailerons".

    Zac; you certainly have some weird problems! I suspect P.I.D.

    Take some pics to show what you got there, and how you are attempting to do this. And...don't you have an A&P or IA involved in this (or is you "experimental")?

    With nothing "attached" and the elevators attached to the stab (everything mounted on the airframe, of course) you will get 36 degrees elevator swing hard-stop to hard-stop. There is a 1/2" or so wide "plate" (maybe it's only 7/16", I don't recall for sure) welded between the upper longerons that the lower cable attach bracket (up stop) fitting strikes, and the lower elevator horn hits the forward cross tube between the upper longerons for the down stop. These stops are not "adjustable" (and they aren't located "top and bottom", they are "forward and aft" and both act off the lower part of the bellcrank), except that the steel bracket/stop at the aft end of the down elev cable can be [ORIGINALLY] ground to permit full travel, but if all this stuff was on this airplane, it should not require anything of the sort. This (grinding) is not a way to fix an incorrectly rigged system! WHY can't you hit the cross tube/forward, down, stop (what is with ~1/4" gap and where is this clearance)? Incorrect rigging forward is the usual culprit. If you have new cables, rod ends on the tiller/elevator drive shaft, et c then you have your work cut out for you.

    The elevators will hit these stops (they are the primary stops) at the ends of their travel, and rigging the forward part of the elev control system (under and between the seats) takes quite a lot of fiddling around to make this happen. You should have clearance on both the forward (down) and aft (up) yoke stops when you have the system correctly rigged. If you made your own cables, it is possible that you have attached the lower attach bracket in the aft nicopress on the WRONG CABLE (not hard to do, and don't ask me how I know!) and the cables are switched.
    JohnW,
    My father is the A&P/IA. I did make up new stainless cables, but I did one at a time, and put the cable end hardware back on the new cables exactly as they came off. I had the stabilizers leveled (not accounting for the different size tubing yet) and was only measuring total travel (not UP travel vs. DOWN travel) and got approx. 30 deg. The ~1/4" was approx. how far my lower bracket is from hitting the elevator UP stop. When I push the yokes forward(elevator DOWN), It hits the primary stops first and will hit the stops under the panel, only if I continue to push it after it hits the rear stops. The end hardware and stabilizers were original for my airplane, but the elevators were purchased from a salvage yard. I was mostly looking for "where to start" rigging, before I spent much time on it. I will look more closely at what I have actually got going on, then "report" my findings, maybe with some pictures.

  5. #5
    JohnW Guest

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    Okay! The it should suffice to say that you SHOULDN'T need to change the rod end on the push-pull tube where it attaches to the bottom of the tiller (UNLESS, of course, the "last guy" had the rigging all screwed up. This is VERY common, sad but true).

    There is no practical way to actually "do this" but if the tiller is not attached to the P/P tube, the bottom elevator horn (the fitting, aft) should hit the aft bracket AND the forward cross-tube. You'll see...this will give you the full 36 degree "throw". Once verified that the stops are dead nutz, you really have little need for measuring the up/down throws any more, other than to "hit the stops" when the rigging is right. Then, you do whatever you have to to get the stops on the {pilot's side} yoke to provide whatever clearance you can get (but these are "secondary stops", and are only to prevent you from "overloading" the cable system by really honking on the yoke, possibly bending or breaking something). This can be really frustrating (and it shouldn't be, but it is), and especially so if the airplane is 3/4 to all "assembled" (that is PRECISELY why I advocate doing "dry-assembling everything and perfecting all the rigging BEFORE recover and only just having to "put the bolts in" when the time comes!!!)

    The "not practical" part is that you need to have the bolt in the tiller-to-P/P rod end in order to check anything! But clearly, you can SEE what you have to do AS IF you had proved the throws are correct (hits both elevator horn stops) and THEN you can confirm that your angularity using your inclinometer, or Pro360, or whatever, is correct. If, at THAT time, you find that your throws are out of limits, all you can really do is "file the lower stop fitting in place to get more travel. But if somebody at some time filed this bracket/fitting to get "more up elevator travel" (BECAUSE the system was rigged wrong!), then you have to replace the bracket/fitting with a new, slightly longer one (that sux).

    At least nine out of ten (and PROBABLY ninety-eight out of a hundred) airplanes CAN be properly rigged, with enough fartin' around with the adjustments that Piper DID provide. Too bad that (in MY experience) as much as 70% of these airplanes are not properly rigged!!! But, I will go on to say that if the elevators are properly rigged AND the pilot would just TRIM PROPERLY for landing, there is enough "stock elevator travel/authority" to land on the tailwheel first, every time (or...drag the tail skid, for the nose-pushers out there that learned to land in a Cessner). Grinding the stop is POOR maintenance practice (unless it is a new fitting... and even then, if SHOULD BE correct within tolerances, but MAY be "tweaked" if found to be necessary...the first time!). If and when you find your turnbuckle adjustments are going out of limits (providing you "hit the money" for length when you made up the cables"), it's time to start messin' with the stuff "up front".

    I pretty much disagree with the "apparent benefit" from making new cables from stainless steel, unless the airplane is going on floats and will see a LOT of "salt water duty". The SS cables are not as strong as the galvanized carbon steel "standard" cable (not that they should EVER even see anything CLOSE to two thousand pounds applied to them!!!), but you absolutely HAVE TO use the correct nicopress sleeves with stainless cable, or you WILL be finding cracked nicopress sleeves at a later date!!! Who wants to change out a couple year old cable in a "flying airplane"??? Not me! But I HAVE! Note that there was a Piper S.B. about inspecting and removing SS cables on the PA-18 and -22. "Modern carbon steel cables will stay looking JUST FINE for 25 to 30 years anyway, and no matter HOW LONG the fabric will last, airplanes should be stripped "regularly" anyway, to have the tubing and other "hard to see" places inspected. So, let the NEXT GUY put new carbon steel cables on, screw 'im! Most of your "rusted out", crappy cables on these airplanes were there because somebody "cheaped out" and re-used cables that were already thirty years oldwhen THEY used them again! I STILL find original Piper cables in ShortWings, and they haven't built a TriPacer in 49 years (nor Colts in 45 -or MAYBE 46!!!).

  6. #6
    Join Date
    Jun 2007
    Location
    Bunker Hill, IL
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    264

    Default

    Okay, today, I unhooked the push-pull rod from the steering column, and I CAN get the full travel that way. However, when I hook it back up, It just barely hits the rear stop first on DOWNWARD travel, but is approx. 4 deg. from hitting the UP stop, as it hits the secondary stop first. I did adjust the push-pull rod some, but ended up with it back where it was. I'm out of ideas.

  7. #7
    JoeC Guest

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    Are you sure you have the bungee cables in the right place? They ARE of different lenth.
    Joe

  8. #8
    JohnW Guest

    Default

    Yeah, the bungee cables are different length, but if they are wrong, all that happens is that one cable sags way too much (rendering the "spring effect" useless). It still should TRAVEL stop to stop.

    First, rig the cable turnbuckles in the "right direction" (loosen one, tighten the other) to offset the surfaces as much as you can and still have the turnbuckles "legal". If that isn't enough, lengthen or shorten the rod end (thread in or out) on the fwd end of the P/P rod.

    You CAN'T get everything rigged right if the cables are either switched, or "incorrectly made" (long, or short). You more than likely "copied the old ones", and there is NO guarantee that the last guy made them right! Check them out against the Cable Drawing on the Drawings CD within plus/minus specs. Get the p/n for both cables either from the PM or off the Drawings, and look up those dash numbers for proper length.

    Again, WHEN YOU ARE DONE, the secondary stops (under the panel, on the "square tube") will NOT make contact. They just "stop you from crunching anything" when the elevator hits the primary stops.

    Duhhhhh, I don't THINK you can install the P/P rod/bellcrank ass'y upside down, but they ARE different "lengths" on the bellcrank. Worth checking on...

    You are making progress. I tol'ja this can be frustrating...persevere. Walk away from it when you hafta, and come back to it "fresh". This is why most of them are WRONG.

  9. #9
    Join Date
    Sep 2005
    Location
    Spokane Wa.
    Posts
    1,461

    Default

    Quote Originally Posted by Tom T. View Post
    OK, this is what I was talking about earlier. I had to call Tom Anderson on this one. You need to make sure you have the stops put on correctly. There is a differance in the stop lengths and it will get ya fouled up forever. I dont have the facts in front of me, but at least you have somewhere to start. I know they look like the same either way but they are not. Look real close!
    I will take a picture tomarrow and post it if some one else dont come across with the answer.
    OOPS! OK, JW, I'll put this one away for later!!
    Tom T.

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