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Thread: Welding Front Gear Attach Fittings

  1. #1
    chrisg's Avatar
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    Default Welding Front Gear Attach Fittings

    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]

  2. #2
    Stephen's Avatar
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    Default Re: Welding Front Gear Attach Fittings

    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...
    "You can only tie the record for flying low."

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

    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.

  4. #4

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    Default Re: Welding Front Gear Attach Fittings

    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!

  5. #5
    Stephen's Avatar
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    Default Re: Welding Front Gear Attach Fittings

    Quote Originally Posted by chrisg
    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.
    "You can only tie the record for flying low."

  6. #6
    Lownslow's Avatar
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    Default Re: Welding Front Gear Attach Fittings

    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.

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    chrisg's Avatar
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    Default Re: Welding Front Gear Attach Fittings

    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.

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    Administrator Steve Pierce's Avatar
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    Default Re: Welding Front Gear Attach Fittings

    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?

  9. #9
    Stephen's Avatar
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    Default Re: Welding Front Gear Attach Fittings

    Quote Originally Posted by Steve Pierce
    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.
    "You can only tie the record for flying low."

  10. #10

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    Default Re: Welding Front Gear Attach Fittings

    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.

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