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chrisg
07-15-2009, 02:07 PM
Hi all,
I'm looking for any advice you can provide on welding the front gear attach fittings. I've built my fittings and need to get them positioned and seated properly. I will probably use my gear legs (extended maule style) to help align them front to back and then a tape to make sure the width is correct. One thing I could use some tips on is heating and forming the cross tube (at that cluster) to get the fitting seated properly. I've seen some gear fitting plans that say to "heat and form tube to accomodate landing gear fitting". Any suggestions on how to best do that without effing it up?

I made the gear fitting out of 1.75" x 1.75" square tube 4130 (.120). That is what Eddie Trimmer uses for his gear STC. I may have extra available if someone else wants to make fittings for an experimental project.

Thanks![attachment=0:qepuzhr4]gear_fitting.jpg[/attachment:qepuzhr4]

Stephen
07-15-2009, 02:15 PM
On the Univair fittings that I welded on, there was a hole for a rosset weld, also a small curved plate to reinforce the joint. Not sure how you heat up the cluster prior to welding if you TIG, otherwise gas welding will do a good job heating the cluster. I tack welded it in place with gas then had it TIG welded.......the second time...

chrisg
07-15-2009, 04:28 PM
Stephen,
Was your installation similar to the attached drawing?

[attachment=0:3sx9yoky]LPC-1031.pdf[/attachment:3sx9yoky]

This has a single rosette weld on the fitting and a reinforcement plate out of .065.

JohnW
07-15-2009, 05:27 PM
Well, I TIG the fittings, but since I ALWAYS "normalize" the areas around any welding, there is always na O-A rollabout within "hose distance" of any welding. It just about always has Rosebud on the torch handle, and this is PERFECT for getting the ends of the cross tube nice and cherry red so that willingly "stand and receive" the judicious forming blows. But if all you have available is a welding tip (OO to 4), they work just satiafactorily.

Are you aware at all that there a a COUPLE different "front fittings" that Univair sells? One is the original PA-20 fitting, and the PA-22/20 conversion fitting is slightly different. The "legs" of the fittings are built at different angles standing off from the base...they are the same (as far as a "handed pair" is concerned. My point here is that you don't HAVE TO use your "ninety degree homebuilt fittings" (but they sure are nice!), you can "adjust" the offset, if it works to your convenience.

I would DEFINITELY recommend you go with the gear that you are putting on for alignment while tacking on the fittings!

Stephen
07-15-2009, 05:46 PM
Stephen,
Was your installation similar to the attached drawing?

[attachment=0:1g82i5uv]LPC-1031.pdf[/attachment:1g82i5uv]

This has a single rosette weld on the fitting and a reinforcement plate out of .065.


Yes, this is the exact drawing I have.

Lownslow
07-16-2009, 12:10 PM
I just welded mine on recently using the Univair conversion and drawings. It went extremely well with a few key considerations and my welder friend using TIG to do a superb job. To get the front fitting into center-line with the rear fitting I had to grind away the weld from the lower end of the cross-member tube on each side, allowing the bottom end of tube to be heated and formed to the bottom of the longeron (I did not take detailed pictures of the prep and welding to attach here, sorry).This allowed the gear fitting to be positioned with an acceptable surface to be mounted and within limits of centerline (per the drawing), but you want to be sure to re-weld this joint before installing and welding the gear fitting in place. You can see that I used measured 3/8 rod in place of bolts to aid in alignment. The Univair drawing shows positioning the gear fitting and reinforcement plate in the relationship to the lower longeron that is "ballpark" in getting the correct alignment and toe-in, but I would use a good (verified) straightedge to check and physically measure the exact toe-in. John W. had a great informational post on this in May, I believe. You must have "0" or up to 1.5 deg. toe in as I recall, but check the specs from John. Check and re-check the fit-up of fitting and reinforcement before tacking in the gear fitting. Tack in the gear fitting and then the reinforcement. Heat the reinforcement to mold it to the shape of the cluster and then finish weld. My $.02.

Lou S.

chrisg
07-16-2009, 08:48 PM
thanks that was really helpful information. I'm going to have a friend help me TIG them on this Sunday, so if anyone else has anymore ideas/experience I'd love to hear about it.

Steve Pierce
07-19-2009, 08:39 AM
We just repaired a PA22/20 that ground looped. The bottom of each tube in that cluster ripped out with the fitting making it a lot harder to repair. I wonder how much stronger the half round plate makes that area?

Stephen
07-19-2009, 09:05 AM
We just repaired a PA22/20 that ground looped. The bottom of each tube in that cluster ripped out with the fitting making it a lot harder to repair. I wonder how much stronger the half round plate makes that area?

A few years back I had left it off, thinking that it really did not matter, my bracket attachment broke off taking out the right gear leg, on a landing on a rough field.

redbarron55
07-19-2009, 09:24 AM
When I repaired 11K many years ago it had been dropped in from about 50' ans the left gear attachment and cluster was heavily damaged. when I repaired the cluster I added gussets for every tube. This is the basic function of the semicircular piece. Adding gusetts per 43-13 is very good insurance in my opinion.

Steve Pierce
07-19-2009, 10:42 AM
The thing that I wonder about is that the Clipper and Pacer don't have the plate and i have not seen a problem. I wonder why it was added on the STC. The thing they didn't add on the PA22 to PA20 STC is the liner tubes in the rear longerons at the tail post. i would think that would be a major improvement over the .035" wall rear longerons.

Steve Pierce
07-19-2009, 12:13 PM
The ground loop.[attachment=0:24uwflp8]IMG_1152 (Medium).jpg[/attachment:24uwflp8]
The damage to the fitting area.[attachment=1:24uwflp8]DSC01437 (Medium).JPG[/attachment:24uwflp8]

Jim
07-19-2009, 06:16 PM
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.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~

Stephen 998 wrote:

.......I have never aligned the gear with tow-out. Where do you get this info from?

I read a recent artical at Oshkosh.

However, and this is a big one, there's a lot of information floating right around here that mentions the same thing, and opposing points. I'll post a few links below, but first I want to qualify what I initially wrote. I'm certainly not going to try to convince anyone of anything, I'd like to know the facts too. but, until someone produces evidence otherwise I'll stick with my own conclusions.

I've never written to Univair to ask them what they're currently using when assembling their landing gears for the PA 20 conversions, or for that matter if the legs are even comparable to what the PA 22s use for specs. There's a good chance that both planes use very different settings. We all know what a Tri would do if you raised its tail up and down a few feet while it was rolling along.

Then there's the matter of a specific planes camber angles which are also involved. Put your hands out in front of your face palms to palms and a few inches apart. Now move your wrists a little more away from each other than your finger tips. You're now holding in a camber angle which may or may not look like your plane. Are your tires closer together on top or on the bottoms? Not that it matters a lot, but as you raise or lower the tail with your particular camber angle your tow-in or tow-out will be greatly effected. This effect is also prominate when the bungees as working, as the gear spreads your camber angle changes. Tilt your finger tips away and you'll see that with the tail raised your tires are now pointing way different that they were before, and the tow-in/out doesn't make much difference in these real effects. Lower the tail and it's just the opposite of how it was pointing before. Using worn out bungees will also involve the camber angle tow-in/out effect, as well as a taxi with the control wheel in or out.

The artical previously mentioned wrote along the lines of;

The thinking behind needing toe-out instead of toe-in can be visualized by thinking of your plane swerving from a straight line.

If the plane starts to swerve left, the left wing will raise a little and weight will be transfered to the right tire. As the right tire now has more load it'll also have more authority. If it's towed-in it'll use its gained authority to turn left more which raises the left wing further, tightening your turn, then transferring more weight etc. I think it's referred to as tucking under.

With tow-out, adding weight to either tire will help stear the plane out of the swerve as it tends to straighten the swerve rather than contributing to the tire tucking under in a turn. The towed-out tire will pull in the direction that'll help lower a raised wing. You can't easily put weight on the right pointed tire while you're turning right, but you sure can while you're turning left.

We're not discussing problems like alleviating "wingtip in the ground", "skipping all over the runway", "tire will be pulled away from the rim", "ground loop in the other direction" or "wing-overs" getting fixed. For those you should.......well, that's a topic I won't to get into here.

Who's to say all our planes are exactly the same in every possible alignment geometry even if we all had similar tow established?

I was trying to find the artical where this topic was discussed earlier when the guy said Univair sent him the specifics on their gear legs construction. I don't know if it was here in the last few years or over in the forums.

http://lists101.his.com/pipermail/sw...st/034960.html
http://lists101.his.com/pipermail/sw...st/034947.html

[Swpc] PA-22 wheel alignment
http://lists101.his.com/pipermail/sw...ect.html#start

I'd like to really know the difference between the legs on a 20 and the 22 as speced by the manufacturers. We've all got stories to tell that set us in our thinking, right or wrong.

You can also ask my wife about how often I don't know what the hell I'm talking about.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~

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

JohnW
07-19-2009, 09:13 PM
Well, Jim... funny you might be REMINDED of something...it certainly is NOT "everyone" that hasn't seen THOSE (not "the) print. I'm insulted. Where'd you get your assumption that you are the only one that "knows anything" for real? Do you EVEN have the SWPC Drawings CD? I have the CD AND Piper-made copies of the real McCoy (some of which are HUGE). Your doubt verifies that YOU haven't looked very closely at THOSE DRAWINGS. There is a DIMENSION on each that specifies the tolerance. Of course, without KNOWING what the angles relative to the ASSEMBLED AIRPLANE are (and confirming that each jig-built gear leg -Piper's OR Univair's- is within spec) as far as how the axles are "pointed" you don't have any place to start. See, YOU are the one that hasn't done your homework! GET THE ORIGINAL PLANS, dimbulb. Don't make as ass out of yourself "knocking" what little you DON'T EVEN know.

AS far as you buddy's "artical" (sic), whaaaaaaaaaaaa?

Bottom line: you can't find degrees on the drawings. You CAN (or...are assumed to be able to) follow the directions; compare the -20 and -22 drawings, and use your BRAIN to figure out what they are telling you. What you also won't find is "what angle the axle is supposed to be set on the OTHER END of the gearleg". Lemme tell ya...both Piper AND Univair build (built) their gear legs in jigs. THEY know what the "angles" are. All YOU have to know it whether your airplane is supposed to have "toe-in" or "toe-out", and what the limits are. Bot Piper and Univair GAVE YOU THAT, in the form of a 30" (plus or minus limit) call out. If that is all you can fathom, then that is as much of an Expert as you and your "artical writin' Buddies" are ever gonna be. That is precisely why Piper OR Univair won't tell anything about it to somebody that can't figure it out for themselves (and neither does).

If you got some smarts, you can "de-engineer" what makes a nice-handling airplane versus a rabbit-in-the- headlights airplane. Howsabout you get back to this Thread when YOU actually know what YOU are talking about? Don't just "come in here and start throwing stones". You may be able to figure out...I'm the one "throwing these numbers around" and I'll tell you no more than THIS: [I'm not blowing any more of my horns about this...] ask somebody that has SET UP THEIR AIRPLANE to "my numbers"; or someone that has checked their "rabbit" and found that they were skipping a 22/20 around that some idiot had missed the notation about exceeding the 30 inch dimension and who by-the-way never heated and flattened the place where the fitting welds on to... duh... ANd BYW, after they did that, have 'em check the measurement referred to on the drawings.

My "numbers" are hard won. AND, they are "confirmed", not only by empirical testing but by me walking down retired Piper Welders and Engineers and picking their brains. And picking it was. You WON'T find the "degrees" written down anywhere, even if you by miracle DID actually TRY to. Piper thought that if you were too damn dumb to follw the simple instructions on the print, you were not "good enough" to know the rest. So see if YOU can figure it out, SOMEHOW. I really want to know if you find out what I HAVE WRITTEN is wrong (I know it to not be). I got tired of hearing how Pacers are stupid to control on the ground. Well, them that ARE, are lousy because the guy that "made them that way" wasn't as damn smart as he THOUGHT he was! I am nothing but SORRY if you take "exception" at my trying to GIVE YOU what you appear to be too smart to accept. Walk your own path then. Let us know, when you DO "know something", okay? I thought I was doing people a FAVOR by telling them the WHY as well as the WHAT as to making a squirrely airplane into a baby carriage (or NOT making it a hazard to everyone on or near the runway), and I do not appreciate your negativity, when you really have NOTHING of your own to offer, in it's stead.

And...I'm gonna give to a free hint or two (if you might deign to accept them)...don't listen to people that talk with their hands, they got nothin' they know is CORRECT to put forth through their lips. Also...while camber is an interesting discussion, it has NOTHING WHATSOEVER to do with were you weld the gear attach fittings on. Camber is "built into" the position of the axle by the designer (remember "jigs"), and the "changing of toe-in due to castor" was taken into consideration when the people that DO "specify" this stuff designed it. Including "production stackup". You artical author's wife is correct. Impressive (not), but it doesn't actually SAY anything, does it? Lastly, Always remember that "A little bit of knowlege is a DANGEROUS thing." (why would you go out of your way to be so negative when you have no information of your own to even discuss?)

Steve Pierce
07-19-2009, 10:07 PM
John, What the heck? :oops:

The old posts from the SWPC List.

http://lists101.his.com/pipermail/swpc/ ... 34960.html (http://lists101.his.com/pipermail/swpc/2006-August/034960.html)

http://lists101.his.com/pipermail/swpc/ ... 34947.html (http://lists101.his.com/pipermail/swpc/2006-August/034947.html)

I believe the Pacer should be straight or slightly toed in and that the Tri-Pacer should be straight or maybe slightly towed out. I have not verified this with the Tri-Pacer fuselage drawing but will.

Stephen
07-20-2009, 02:21 AM
..........(mostly silly and almost impossible to comprehened nonsense deleted)......... Also...while camber is an interesting discussion, it has NOTHING WHATSOEVER to do with were you weld the gear attach fittings on. Camber is "built into" the position of the axle by the designer (remember "jigs"), and the "changing of toe-in due to castor" was taken into consideration when the people that DO "specify" this stuff designed it.....more silly nonsense deleted...


JohnW, please explain how changing CASTER (which I do not think is adjustable on our Pacers) will change toe-in???? Methinks you need to review what Caster is.

I agree with Steve on the alignment....based on personal mis-experience.

Hillbilly
07-20-2009, 06:34 AM
its CASTER not CASTOR, and I think everyone is a tad too worked up because a caster angle cannot exist on a non pivotable (ie. steerable) wheel. end of story.

So class, lets all take a deep breath and shake hands with the fellow to your left...

Steve Pierce
07-20-2009, 06:40 AM
Allan, I think John is the only one who is worked up.

Hillbilly
07-20-2009, 06:42 AM
Allan, I think John is the only one who is worked up.

I wasnt addressing anyone in particular Steve, I've just set a bad example in the past so I thought I nag them for a time out...

Stephen
07-20-2009, 08:18 AM
Caster angle is the angular displacement from the vertical axis of the suspension of a steered wheel in a car, bicycle or other vehicle, measured in the longitudinal direction. It is the angle between the pivot line (in a car - an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint) and vertical. Car racers sometimes adjust caster angle to optimize their car's handling characteristics in particular driving situations[attachment=0:2eradwmd]600px-Caster_angle_svg.png[/attachment:2eradwmd]


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.

JohnW
07-20-2009, 08:22 AM
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
07-20-2009, 10:44 AM
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
07-20-2009, 11:36 AM
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
07-20-2009, 03:34 PM
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
07-20-2009, 05:41 PM
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
07-20-2009, 06:17 PM
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
07-20-2009, 09:55 PM
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
07-20-2009, 11:07 PM
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
07-21-2009, 06:45 AM
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
07-21-2009, 07:53 AM
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.

chrisg
07-21-2009, 12:31 PM
Steve,
Thanks the the info and photo! Yup, the distance from top of fitting (where it touches the longeron) to the center of hole is 3/4". I've already done some heat forming on the cross-tube (where it connects to the longeron), but it sounds like I need to heat form the longeron as well. How much can I safely flatten the bottom of that longeron (i.e. how far would you be comfortable flattening the bottom)? My inexperienced guess is that 1/8" is as far as a person would want to go.

Steve Pierce
07-21-2009, 12:39 PM
Hard to say, you don't want any cracking etc but the doubler over the cluster should help if you do induce any stress.

Steve Pierce
07-22-2009, 07:44 AM
We had to rebuild everything to the gear fitting so were able to put it right where it needed to be. I hadn't noticed the gusset until y'all brought it up and low and behold it was on the left side and the fitting that got ripped out. I guess I never noticed it before between the Clippers, stock Pacer and the PA22/20 conversions I had worked on not having the gusset. Thanks for bring it up, I learned something. ;)

Stephen
07-23-2009, 11:43 AM
y'all????? somekind of new puter lingo????

Steve Pierce
07-23-2009, 12:47 PM
You need to come down south for a while and we'll teacha how ta talk.

Lownslow
07-23-2009, 02:42 PM
My post on this subject referred to John's previous post, in which he provided details of the front gear fitting set-up to achieve an acceptable angle to centerline (caster), also in which he gave detailed reference of where the information was obtained. I think he delivered the "straight poop" for those of us that were willing to listen. Perhaps everyone has now reached an understanding of where each other's respectful expectations lie, and will allow this forum to continue to be educational and fun. John, I would like to have a beer with you some day, but I'll have to remember to lay off the momma jokes.

As they say in New Orleans, "Le se bon ton roulette" (I don't want to go there, but I like what they say).

Amen??


Lou S.

chrisg
07-28-2009, 06:35 PM
JohnW, Stephen, Steve, (and anyone else who knows or cares),
What do you think of this technique to make sure the distances between the front and rear fittings are the same? I've taken a 4' x 1" x 1/4" length of flat steel and drilled holes to match my rear fittings. Then I moved them to the front fittings. I had to put a little pressure on the gear to move the front fittings towards each other to get them to fit my "jig" (i.e. moved them from tow-out to straight).

Is this a reasonable approach?

[attachment=0:31adrwal]gear_alignment1.jpg[/attachment:31adrwal]

Lownslow
07-28-2009, 08:44 PM
On my conversion, I became aware of the more detailed critical positioning requirements through John after I had already welded the fittings into place (per Univair drawings). With the gear in place, I measured my caster with a true straight-edge right off the gear axles, after I leveled up the fuselage. I measured forward and aft a given distance from a point of reference on the axle with the straight-edge on the wheel hub, marking the floor. I then measured between the forward reference marks from each side and then between rear reference marks made on the floor. Equal measurements indicate 0 toe-in or toe-out. Shorter forward measurement indicates to-in. I took the differential measurement and converted to degrees using the measured longitudinal distance on each side between the fore and aft reference marks as the measured diameter of a circle. To me, this is a pretty accurate measurement of "where the rubber meets the road". In my case I measured .95 degrees toe-in, which makes me extremely pleased. This is just my experience. I recognize John as the "authority" on this subject. I have just put the cover on my fuselage and am months away from a high speed taxi and me having that beer with John.

Lou S.

jay heil
07-28-2009, 09:20 PM
by chrisg Tue Jul 28, 2009 5:35 pm

JohnW, Stephen, Steve, (and anyone else who knows or cares),
What do you think of this technique to make sure the distances between the front and rear fittings are the same? I've taken a 4' x 1" x 1/4" length of flat steel and drilled holes to match my rear fittings. Then I moved them to the front fittings. I had to put a little pressure on the gear to move the front fittings towards each other to get them to fit my "jig" (i.e. moved them from tow-out to straight).

Is this a reasonable approach?


to chrisg: that should be a good way of making sure the distances are equal but you also need to have some referance to have the front gear exactly inline with the rear lets say for instance you have them position equal distance aprt but have them 1/8th inch right or left now you probably have way to much toe in on one and toe out on the other while still having the gear fittings the same distance as the rear also I think if you were using univairs directions it says equal distance as the rear is the "width limit "if you have your toe in built into your gear your fine but this should leave you with "0" as your toe angle which is probably fine but John likes a little toe in and you wont get toe in with your method will you??? now I am not sure what it is I always used to say 1/2 gegree toe in is great and it makes sense to me to have that but awhile ago some people were having this discussion over on the supercub site and one guy mentioned the the annual inspection form for a supercub states that you are supposed to check your gear alignment and it should be set to 0 degrees toe in so I thought I wonder i what the pa20 annual insp form says??? well the one we have is combined for PA 22 and PA 20 so that part is a little confusing but it does say that both PA 22 and PA 20 should have 0 degrees toe in 0 degrees toe out so I dunno you kind of have a little conflicting information there the prints show 0 as the linit so you make sure you dont have toe out so if it is at 0 its at the limit in my mind if your limits are say 1 degree toe in and 0 toe in if you shoot for the middle it seems 1/2 degree is what you aim for ok so Im just rambling here but your method does need somthing to make sure those front gear fittings which are the same distance apart as the rear are also centered on the rear---------also is there any toe in built into your gear?

JohnW
07-29-2009, 08:19 AM
Chris, Jay's got a handle on this, I'm not gonna repeat what said. The part about "guaranteeing zero" is correct, and while a SLIGHT "out of square" doesn't necessarily mean the airplane will absolutely be squirrelly, there is this thought in MY mind that even if the airplane DOESN'T "jump around with a mind of it's own", there will still be SOME issue with what is known as "dogtracking" if the gear doesn't point "straight down the centerline of the airframe" (that would be the definition, I would think). This -even if the airplane is quite "comfortable" going down the runway "hanging it's butt out sideways to WHATEVER degree- CAN'T be good on tires and adds cycles and frequencies to the structure! Does that MATTER? I say....sure it does!

Every job on an airplane is a job worth doing to the best of "your" abilities. Any number of ways, it always "pays off" in the long run. I don't mean AT ALL to sound "snotty", but damn, Man...it ain't like levelling the airframe and dropping a few plumb lines to the floor is any kind of sweat producing WORK (except, you might smell the faint odor of a slipping V-belt as your mind may get a bit of a workload applied to it. Surely the amp draw can go "up". This is GOOD for you!). Unless you find the centerline of the airframe AND physically CHECK the actual direction the axles point in relation to that... then all you are doing is HOPING you "get what you want". No accusation, but you might consider if "working so hard to avoid a little work" just wastes your time, and is therefore "unprofitable". I do NOT see this as a "viable method" for getting what you want.

You know...others MAY...there is a thread here referring to a guy who built his own retract with electrically driven gear that APPARENTLY thought his BATTERY was a "backup" if he had an electric problem!!! Jeesh! Now what if he had a simple bad electric motor, or a copper TERMINAL broke off at it's lug???!!??? HOW was he planning to get the gear down THEN? Seems like not putting in a hand crank, or provision for free fall might border on "terminal stupidity" (IF that was the case!).

I surely haven't perused the SuperCub drawings for what THEY speak to about requiring absolute "0" toe-in. But I HAVE done exactly that in regards to the ShortWings (and I cannot believe that a very slight toe-IN condition isn't not only "acceptable" on the SuperCubs, but actually "preferred". Then, too...I haven't read that requirement alleged, myself (and I AM a bit of a stickler for "and", "or", "must", "shall", "should", "may" and a BUNCH of other "qualifiers" that most people seem to think are inconsequential to the meaning of a "requirement").

Bottom line is... while I am a long-time-running EAA Member, I don't buy "other people's homebuilts" exactly for the reason that I have NO WAY of knowing what any individual person might THINK is "satisfactory". At least with certificated airplanes, there is SOME "reasonable oversight" (read: someone with a brain AND "no interest in" the economics of building and selling ready-made airplanes to say "Hey. Wait a minute, here..."). You can do what ever you think is right. That's the whole beauty of Amateur Built.

andya
07-29-2009, 08:42 AM
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.

JohnW
07-29-2009, 10:16 AM
Yeah, that.

chrisg
07-29-2009, 12:50 PM
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!

JohnW
07-29-2009, 01:32 PM
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.

stretchedpacer
07-29-2009, 10:18 PM
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

Hillbilly
07-29-2009, 10:46 PM
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

JohnW
07-30-2009, 07:54 AM
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.