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Re: Welding Front Gear Attach Fittings
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.
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Re: Welding Front Gear Attach Fittings
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]
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Re: Welding Front Gear Attach Fittings
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.
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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.
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Someone earlier in this thread mentions 1.5 degrees of tow-in, where'd that number come from?
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Re: Welding Front Gear Attach Fittings
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?)
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Re: Welding Front Gear Attach Fittings
Originally Posted by
JohnW
..........(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.
"You can only tie the record for flying low."
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Re: Welding Front Gear Attach Fittings
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...
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Re: Welding Front Gear Attach Fittings
Allan, I think John is the only one who is worked up.
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Re: Welding Front Gear Attach Fittings
Originally Posted by
Steve Pierce
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...
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Re: Welding Front Gear Attach Fittings
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.
"You can only tie the record for flying low."
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