Welding Front Gear Attach Fittings

[JohnW]

Hi,

This is a close copy of an earlier post I made at another site. When I read that someone has a tow-in/out suggestion I'm reminded that most , if not everyone, hasn't ever seen a print showing what's really called for, tow-in/out/straight, on these plane types. If I'm wrong about this, I'd like to read what the original plans call out.

Someone earlier in this thread mentions 1.5 degrees of tow-in, where'd that number come from?

Gentlemen; I am indeed "worked up" about the initial Post in this Thread, and I do not believe I have mistaken anything about what "which whom" was saying about "what". No apology is forthcoming.

[Edit 20Jul09 18:30 Eastern: I was remiss in calling Jim's Post "the initial Post in this Thread". It was the only Post ON PAGE THREE of this thread when I first read it, and I mistakenly thought that Jim had started a new Post.]

I read what Jim said, and my reading comprehension skills are frightfully intact. All in the same sentence, Jim scoffed at what amounts to MY information and made the wild accusation that [adding a touch more venom through my own "interpretational paraphrasing"] "whomsoever spouted such mindless pap likely never even looked at a print". My "(...mostly silly and almost impossible to comprehened nonsense...)" response is to what Jim said. Frankly, I don't care if it is terribly alienating. I'm not particularly here to make friends. My interest has always been "good, safe airplanes" of the ShortWing type. That's where I come from, and damn the torpedoes, full speed ahead.

Furthermore, I closely read what his referenced and excerpted (?) "artical" had to say, and found NO positive information related to mounting front gear fittings on a "Pacer" or (rears on) a TriPacer, correctly. I fully comprehend that the trike alignment is "diametrically opposite that of the taildragger" and specifies toe-OUT in the relevant Drawing. All I see there is "stone throwing". One of those stones bonked me on the forehead.

I did not ever say that changing caster was any kind or "solution" and I do not see how it can be said that I was offering it as any kind of "solution" to the matter of toe-in/out. Stephen, you read into my incomprehensible nonsense something that did not exist. I FULLY understand caster (castor), camber AND toe-in and their effects. Methinks it is you that needs to "go back" and read more closely (but your error is at least a simple, "honest" one). When the gear "flexes", the whole geometry changes. But the caster (/castor) is what it is and "we" cannot change it, willy nilly, without major re-work. Both Piper, and Univair (and the couple other "tailwheel solutions" that have been available over the years) only leave ONE option for the installer to mess up...toe-in. Pretty much, all the Shadetree Mechanics hit THAT nail right on the head (they mess it up, because they DON'T understand what they are working on, and they don't follow the directions). AS far as the guy with a "hot-wrench and a big bar" attempting to take the squirrel out of his takeoffs /landings, well that is another matter. Unintentional "adjustments" to castor, camber AND toe-in can easily be introduced. I HAVE [successfully] corrected handling problems that way, but I do NOT recommend it as the "preferred method". And... I do not "like it".

By providing "information" that it otherwise not "written on a tablet somewhere", MY intent was to help people NOT "mess up installation" and/or provide the "solution for nasty handling ShortWings". I did NOT say that this "prescription" is for Cessna 195s, SuperCubs, Citabrias, Funks, Stearmans. DC-3s or any other "type".

If anyone EVER finds this information to be ANYTHING other than "correct", I would appreciate their correcting me. But just grumbling "bull****" under the cheap guise of clearing your throat don't get it. Anyone with something POSITIVE to input is MORE THAN welcome to step up. Invited to, in fact. How about a couple people that HAVE "followed that ignorant advice"? What has been YOUR experience? Going "more than" 1.5 degrees in the appropriate direction will only become "detrimental to the handling" if taken to the extreme. What this "limit" is is the cutoff where "excessive tire wear" becomes a practical issue. However, "going past zero (neutral) in the wrong direction" is a HARD LIMIT, and airplanes get scary FAST when the gear is aligned this way. That is GUARANTEED to happen if you just "slap the gear on there and tack the fitting"; that is the nature of "what is there". You have to WORK a little bit to get it right. I've said it many times...I shoot for 3/4 of a degree toed IN and am pleased with however close I can get to that when the weld has cooled, and EVERY ONE has handled the way you would LIKE your ShortWing to handle on ANY surface. Feel free to argue with THAT with no "bullets" except "I don't believe it."

AS far as your links (Steve), Ed is on the right path. He's a thinker and as far as what I can get from what he wrote there, a conscientious mechanic. He probably is well finished, and got a good handling airplane out of his efforts.

Let the goosepile continue. Y'all can drive me away pretty easily, now. It's getting past ridiculous and I grow tired of people that don't read closely what is in front of them before the launch off into telling me I am unreasonable. Steve, I read your PM. Point taken (so...now what?).


ADDED: Stephen, you are barking up the wrong tree. You are right, no argument. But you are preaching the choir. See above. I fully admit that I misspoke "caster/castor" when the "artical" said "camber". Mea Culpa, and "so what?" Insert the correct word, and it STILL isn't relevant to Jim's "question"- although you ARE correct.

[Hillbilly]

Yes, I agree with HB. I was over celebrating one of those something-O birthdays last night. Oh, and thanx for the spelling lesson althought it's probably a bit late......good thing they never let me teach English. Like said "end of story" unless we want to talk about the tailwheels.

Happy birthday! (if'in it wuz yourn)

[Stephen]

John with a much clearer head this morning I understand and agree with your points in the last post. Not sure I read Jim's post the way you did, but I'm not you..You need a dog to kick....oops...that might be politically incorrect...or my flee bag dog might be reading this.......

"Happy birthday! (if'in it wuz yourn)"..... it wuz.....

With so many aftermarket PA22/20's, there are a number of poorly aligned main gear that should not be flying. If anyone learns something from these posts it is that a mechanic who knows proper gear alignment should check out the gear before anyone buys a PA22/20.

[chrisg]

I'm having some trouble getting the holes to align. How much (if any) can the longeron itself be deformed/flattened below the cluster? By instinct, I don't like the idea of flattening the longergon, but I don't have knowledge of such things. Stephen? Anyone?

[JohnW]

It's a good thing that whackin' away on structure with a hammer "bothers you"! But in THIS case, you HAVE TO heat the area and flatten it to get proper fitting alignment! Piper did the exact same thing on the Pacer (although the fitting with/from Univair's kit is formed at a SLIGHTLY different angle than Piper's).

Chris...do you understand completely that you can't just "line up the front and rear gear attach fittings" with something like a "un-threaded rod" of the proper diameter, and weld away, yeah??? There is quite a RANGE of where the gear fitting CAN BE and a very limited area of where it NEEDS TO BE, to insure against having toe-out. And because there is little "clearance" inside the fittings, you NEED TO have the gear in place when you tack weld the fitting. THAT is the time you should absolutely "set up" the location of the fitting(s)...with the gear right there (and...physically check the alignment of the axles). This is ALSO how and when you "know you got it flattened enough -but not too much"! [I recommend "dry assembling" for this part with "hardware store" bolts. The Real McCoys get pretty dicked up if you drive 'em in and out a few times (and you SHOULD be, before you actually get this thing up on it's sneakers for the last time). Save the cad plate goodies for the "final assembly"!] This is exactly WHY there are so many "lousy groundhandling" PA-22/20s that always seem to be for sale, out there. It LOOKS to be a whole bunch easier than it IS (that is why there is SO MUCH "to-do" about these fittings) and until you "find out for yourself", or have somebody forewarn you, you are pokin' a set bear trap. A lousy handling airplane is a REAL drag.

My sincere apologies if you DO realize all this...just making sure (lookin' out fer ya!).

As with ANY aircraft welding "fitment", you want as much close contacr with any two (or more) parts that you weld together." "Bridging" the welds on loose fitting alignments which have "unneccesary gappage" is really "bad luck".

[chrisg]

John,
I appreciate any and all advice...so, no worries. I'm not an A&P, nor am I super experienced with this type of work...but I'm attempting to build this experimental airplane because I want to learn more about the "nuts and bolts" behind the machine holding me up in the air. I do know that the gear should be really well aligned and that is why I'm asking so many questions.

I have several drawings that show the various gear attach fittings on the PA-22, PA-20, and PA-22/20 and they all show that the centerline of the fitting hole should be directly below (and in line with) the centerline of the longeron for 0 to 1.5 degree of toe-IN.

As mentioned earlier, the gear are not univair gear, they are a custom Maule style gear, but they line up the same. I am dry-fitting the gear using hardware store bolts and/or some 3/8" steel rod (see photo). My fittings match the dimensions of the univair straight fittings in my drawings, so that the center line of the hole will be 1 1/8" from the centerline of the longeron, but when the gear is attached to the rear fitting, my front fitting seems too tall. That is why I'm wondering if other people end up flattening the longeron some too.

The fitting will be tig welded by a friend ONLY after I've done my best (with helpful information from everyone here) to make sure they are properly aligned.

[attachment=1:2780pdr0]gear_leg_in_place.jpg[/attachment:2780pdr0]

[attachment=0:2780pdr0]front_fitting2.jpg[/attachment:2780pdr0]

[JohnW]

Good. Great! I've been a Card Carryin' EAA Member since 1976 (I know...no "record" there...but not too shabby), and it sounds to me like you got the right spirit. Looks like you got an "unusually UNtapered off" carrythrough there (I've seen 'em like that before; Piper "custom made" each and every airplane at that spot, and they're all "different"). Same where the upper longerons turn into the tailpost... Looks like you got a whole bunch of "Blacksmithing" to do, there!

Really. I'll bet you're havin' fun, aren'tcha?

[chrisg]

ok, so how much longeron deforming would y'all say is acceptable - 1/16", 1/8", more?

I think I could make it fit with 1/8" or a little less. Here is a better picture of the longeron and cluster...i'd be curious to know if anyone else thinks it looks fatter than preffered.

[attachment=0:2zra54we]front_gear_cluster.jpg[/attachment:2zra54we]

[Steve Pierce]

You could run a thin cut-off wheel through the cluster, parallel to the longeron, pull the longeron up and weld it back together but I think I would heat form and weld.

[Steve Pierce]

One second look your fitting looks way too tall to me. Is it per the drawing? I just installed this fitting I got from Univair, it is 3/4" from where it touches the longeron to the center of the hole.