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Thread: Welding Front Gear Attach Fittings

  1. #41
    andya's Avatar
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    Default Re: Welding Front Gear Attach Fittings

    FWIW ie my $0.02, The "dogtracking" situation that John describes, as he says may not make it squirrely (if I read his statement right) but for the pilot that has the feel and visual acuity to know when his "seat of the pants" is absolutely aligned with the the direction of travel (fuselage CL aligned with direction of trave) at touchdown, the airplane will act as though it touched down in a slight crab. Not that this doesn't happen with a gear that is PERFECTLY aligned now and then but those landings will never result in a "squeeker" or a "whens did the wheels touch" type of landing. This is true of not only tailwheel types but of the training wheel types right up to the big birds with turbines.
    "Progress is our most important problem"

  2. #42

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    Default Re: Welding Front Gear Attach Fittings

    Yeah, that.

  3. #43
    chrisg's Avatar
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    Default Re: Welding Front Gear Attach Fittings

    Thanks again for all the great input!

    I should have been more specific in my last post. I didn't mean to imply that my distance "jig" for the front fittings was the end of my efforts to achieve proper alignment. I was really just talking about the distance between the fittings and not the centering. I will follow all the advice I've read here and try my darndest to get things perfectly aligned.

    Thanks!

  4. #44

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    Default Re: Welding Front Gear Attach Fittings

    Chris; Okay, then... if you "align" the gear using the gear itself to get the desired "angle of repose" of the welded (well, actually TACKED, because you have to tack the gear fitting in place, then REMOVE the gear leg itself in order to get "even" a small TIG stinger in there to actually weld it...) assembly, then the last thing you actually CARE about is the linear measurement between the fittings! FORGET the linear jig.

    See, Piper Engineers "fingered this all out" so that from a Production standpoint, you could simply take a gear leg (that was built up in a jig) off the gear leg pile, walk over to the frame that recently came from the welding shop (where they welded the fittings onto the frame using THEIR jig) and literally BOLT THE PARTS TOGETHER and the angle WAS right (within Production Tolerance limits)!

    Since what YOU (or ME, or whomever else ever finds himself welding gear fittings onto an airframe that MAY or MAY NOT retain it's "original, out of the jig fixture shape" -which is NOT likely after 50-60 years!) are working on is a "ONE OFF" assembly. You don't KNOW within acceptable tolerances whether the gear legs you are using is going to be "automatically aligned" if you simply "paint by numbers" and blindly follow [the INTENT OF] the print. Univair HAS TO take it for granted that THEIR PMA'd gear legs are going on a "perfect, as built" airframe (again, 50-60 years ago!) because they have no other starting point that the FAA would "accept" for their parts to "be put on". Everybody ASS/U/MEs that they will fit correctly IF you follow the directions (which heretofore hasn't exactly "been the case", if you were to explain WHY there are so many piss-poor handling conversions "making the rounds"). What YOU, and what I -and any other detail minded "installer" SHOULD be doing is confirming that WYSIWYG, no questions asked, no excuses manufactured, no Prisoners taken" that the results will be not only "all right:, when you have the ABILITY to make the airplane handle WONDERFULLY. You want it RIGHT, and you want it right THE FIRST TIME you touch down (never mind "fighting it into the sky" the first time). This "method" is how I have found repeatability in doing exactly that.

    By "offering" the WHOLE PROCESS from the beginning, it has been my hopes that anyone "mechanically inclined" enough that would undertake either "doing this task" or "reverse engineering" a bad handling airplane into a good one...would be able to accomplish same. Re-designing, altering the process, may be an admirable idea, and I am "open" to improvements on the METHOD I have detailed (several times). But I'm sticking with what I have "perfected" over a few DECADES of doing this on more than TWO DOZEN airplanes, until someone EXPERIENCED with a NUMBER of nice handling airplanes in their "resume" is willing to "step up" and straighten MY dumb ass out. I WOULD appreciate that, if and when it happens. This hasn't been "figured out from an armchair". It's been sweating into airplane after airplane, which I have PERSONALLY taken unto myself to FLY for the first time after completion, and hardass that I am when it comes to being "critical", I have no complaints with the results. THAT would be a "qualification" for showing me what could be done "better", or "easier".

    I am the FIRST to have said that "this" is ONE METHOD of getting a sweet handling airplane due to "correct" gear alignment. ONE method. There may be MORE methods, and some may be "easier", "faster", or "more prone to producing acceptable results"...and ya know, I would LOVE to hear it (them). What I CANNOT even remotely TOLERATE is someone coming along and saying "what makes you think you are right?". Not because I think "my way or the highway", or that I'm the "only one" that could accomplish this (while there ARE people that LOVE that kind of STUPIDITY just for the sake of tweaking someone)... when they have never DONE THE TASK themselves, and in some cases can't even understand what is being explained to them on a theorethical level (...another unintelligible garbage rap...). If you wanna "improve the system", might I respectfully request that you "attempt it" as written from the beginning? If you have any epiphanies along the way, I'd love to hear them.

    Try it "my" way. We can discuss ideas/improvements later...AFTER you fly the finished project, I will MOST graciously accept your accolades. AND suggestions.

  5. #45

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    Default Re: Welding Front Gear Attach Fittings

    Just curious, on PA 20's (and 22/20's) is toe in and toe out measured tail low or with the tail in the level flight attitude? I am actually building a stretched pacer with gearl legs like a producer and have heard of it being measured both ways. I dont actually understand why it would make a difference if it is tail low or high but I am told it does. I have built a jig which will hold my axles and fuselage in a zero/zero alignment but may need to re-think the tail position (which is set tail high right now).This has been a great thread and I have learned a lot. Thanks to all who have provided input so far.

    Brad

  6. #46

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    Default Re: Welding Front Gear Attach Fittings

    Quote Originally Posted by stretchedpacer
    Just curious, on PA 20's (and 22/20's) is toe in and toe out measured tail low or with the tail in the level flight attitude? I am actually building a stretched pacer with gearl legs like a producer and have heard of it being measured both ways. I dont actually understand why it would make a difference if it is tail low or high but I am told it does. I have built a jig which will hold my axles and fuselage in a zero/zero alignment but may need to re-think the tail position (which is set tail high right now).This has been a great thread and I have learned a lot. Thanks to all who have provided input so far.

    Brad
    I cant answer your question but think of it like this, If you had 1 degree toe in in level attitude and you were able to let the tail down 90 degrees
    your 1 degree toe would become 1 degree negative camber. hope this helps. -Hillbilly

  7. #47

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    Default Re: Welding Front Gear Attach Fittings

    What You See Is What You Get. The specifications as found on the Piper drawing (the original source of the item of discussion) HAVE TO BE considered to be "as drawn" unless otherwise noted. There is NO "note" that the aircraft is "tail low" at any point in looking for information on any Drawing UNLESS that drawing specifically DEFINES a condition "otherwise". The view on the drawing is drawn with the Horizontal Reference Line of the aircraft PARALLEL to "level", in the real world. This is a BASIC Mechanical Drawing (or Drafting) "condition", and there is absolutely NO REASON to entertain the "thought" that the airplane should be ANYTHING other than "leveled" when referencing the Drawings. Duhhh, because THAT IS THE WAY IT IS DRAWN. While a Drawing MAY BE MADE at any OTHER "angle" to plumb, or level...it would need to be SPECIFIED as such, or the drawing is unusable. Piper took this question OFF THE TABLE when they "unnecessarily" (unecessary because they didn't HAVE TO do that) verified "level" by INCLUDING the HRL (hor. ref. line) ON THE DRAWING. Whomsoever might "say it's tail low" should be avoided when looking for someone that may be of "assistance" as a source of "expert information" (that's as POLITELY as I can say it, and it kills me to pull that punch).

    Example: measure the "full length [firewall to tailpost (and all stations in between)"] of the fuselage -as the drawing calls out the "distances"- with the airframe LEVEL ("as drawn") and then set the frame at the "angle of repose" of the "completed taildragger" (or at a 45 degree up angle agaist a wall) and then measure it again. Unless you "make reference to the horizontal reference line" by measuring at a "corrected angle" (..that returns you to "level", as the drawing clearly indicates -IF you realize what you are LOOKING AT...) all your measurements would be wrong. They would be "short". You would HAVE TO measure "along the HRL" in order to get the correct measurements. What you are doing if you haven't set the "level" is to CORRECT FOR not being level by measuring along the HRL! This is SO BASIC that it is easy to understand how easily it could be overlooked that that is what you are "doing". It's a "forehead slapper", for sure. But, you do things the way the drawing was drawn, or -again- the drawing is useless.

  8. #48

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    Default Re: Welding Front Gear Attach Fittings

    Toe-in means the turn will be assisted or wont be resisted by the angle of the wheels. Too much Toe-in means it will over-steer and tend to grab a little, and too much Toe-out that it will be harder to turn or under-steer. On my Tripacer to Pacer conversion with the almost the same Experimental Wings I will set it up with a bit closer to strait than standard Toe-in. This should mean the tyres wont wear out so quickly on the hard stuff because we tend to taxi strait most of the time.

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