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Thread: Model IV-1200 factory tube landing gear alignment discussion

  1. #11
    Senior Member HighWing's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    First regarding camber, I never worried about as my thinking was like Papua Pilot's sort of like camber yes while empty, but get in and presto - perfect alignment.

    Coincidentally, by first Model was also a 1993 model - delivered in March of 93.

    Grover,
    Your question has all the details of my experience. While I was in the build phase, Skystar issued a service bulletin regarding alignment of the early IV landing gear. Essentially it was to fasten the fuselage to the floor as an anchor point, then drop plumb lines and using chalk lines mark all the measuring points. I used a saw horse-like support under the lift strut attachments and a welded fixture that supported the tailwheel and was bolted to t
    he hangar floor for security and to counteract the bending forces. The geometry of the supports raised the main gear wheels for wheel removal to expose the axle. A square placed against the axle gave the alignment sighting against the square to a tape measure placed about 10 feet forward of the axle and aligned perpendicular to the center chalk line - both sides. A measurement between both axles gave the desired cross measurement. After the deviation was determined a piece of copper pipe was placed.over the axle to help preserve the threads and a long pipe was placed over that and the gear alignment began. As Grover suggested, it was the axle that bent rather than the gear structure and washers were strategically placed to bring the brake calipers in line with the axles. This procedure was as described in the service letter. I flew with the original bungee gear for a year or two without any issues, then switched to the Hammerhead gear. My take on the early Kitfox models and the number of ground-loops with corresponding high gear collapse rate had to do with either poor tooling alignment or poor welding technique resulting in a very poor quality bungee gear. When designing the cabane gear we once made, I used an original IV bungee gear to set longitudinal wheel positioning and that gear was extremely toed in - something like 3/8 inch at the length of the bungee arm.
    Lowell Fitt
    Goodyear, AZ


    My You Tube Channel

  2. #12

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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    Quote Originally Posted by GWright6970 View Post
    Auster,
    Good idea on rotating your tires to compensate for wear. Have you ever measured for toe in or out?

    Thank you for relating your experience!
    We did measure back when the plane was built. about ten years ago, and I think it was neutral but I will check again tomorrow when it is in the workshop. It isn't the easiest plane to keep straight on take-off or landing but I just put that down to it being a Kitfox and that I have to work a bit harder than in other taildraggers. Will report back.

  3. #13
    Senior Member efwd's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    Believe I recall you said you have a toe-in condition. If that's correct, then the handling characteristics you describe are precisely what you would expect with a toe-in condition from what I have read. I believe it is recommended to be neutral or slight toe-out for this reason. I bought shims from Kitfox. They aren't the cheapest peices of aluminum (less $$ than Grove) but my airplane tracks true down the runway. I believe I did the deed with two shims.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  4. #14
    Senior Member rv9ralph's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    Here is a picture of the nonstandard gear. Note the horizontal plate the axle is attached to. This in turn is attached to a plate on the gear weldement by 4 AN3 bolts, which allow adjustment for toe in/out.

    Ralph

    IMG_1236.jpg

  5. #15
    Senior Member GWright6970's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    Ralph,
    That is the way to do it! I wish ours was designed like yours! Thank you for posting this! Yeah, I'm envious!! LOL!!
    Grover Wright
    Flying a KF IV-1200
    ROTAX 912UL

  6. #16
    Senior Member GWright6970's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    Lowell,
    I must be blind, because I can't find either a Service Letter, nor a Service Bulletin on this issue. I will hopefully be finishing up my specialty Kitfox trailer in the next two weeks. You may find me at your front door again!

    Thank you Lowell, I would have never made it this far if it were not for your unselfish assistance and mentoring!
    Grover Wright
    Flying a KF IV-1200
    ROTAX 912UL

  7. #17
    Senior Member rv9ralph's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    Ralph,

    That is the way to do it! I wish ours was designed like yours!
    They are for sale.

    Ralph

  8. #18
    Senior Member t j's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    Back to the original question.

    The Model 4 standard tube landing gear should have neutral or slight positive (1/4 inch or so) camber when the fuselage is leveled. This is with the airplane empty or even with two 200 pounders sitting in the seat. The bungees will stretch to give it negative camber in a hard landing but only for a second.

    Using a six foot cheater on the axle to bend the gear or the axle to adjust toe in has been done by some builders. I chickened out when I tried to do that for fear of damaging the gear or the fuselage. I wish I had known about the option to install shims like Ralph did on his gear.

    Here's the thread on that. https://teamkitfox.com/Forums/thread...heel+alignment
    Last edited by t j; 01-25-2020 at 08:45 AM.
    Tom Jones
    Classic 4 builder

  9. #19
    Senior Member HighWing's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    Quote Originally Posted by GWright6970 View Post
    Lowell,
    I must be blind, because I can't find either a Service Letter, nor a Service Bulletin on this issue. I will hopefully be finishing up my specialty Kitfox trailer in the next two weeks. You may find me at your front door again!

    Thank you Lowell, I would have never made it this far if it were not for your unselfish assistance and mentoring!
    Definitely not blind, Just misled a bit. I did the search and found the original source. It was an article written by Kitfox Guru, Mark Budak and published in the Kitfox times of April 1996. I posted a link to a PDF of the Kitfox Times below and also in the sticky for the older documents. My approach to the correction deviates a bit, but the set-up and measurement description is pretty much the same.
    Attached Files Attached Files
    Lowell Fitt
    Goodyear, AZ


    My You Tube Channel

  10. #20
    Senior Member GWright6970's Avatar
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    Default Re: Model IV-1200 factory tube landing gear alignment discussion

    To all, my update:

    First, and most importantly, THANK YOU everyone for discussing this.

    All along, I have used the "Tom Jones" method of determining the values on toe in/out. I employed the cheater pipe on the axle method to align the left gear, but chickened out when the pipe appeared to be bending too much, and the Kitfox said "ouch." I then removed the axle, inserted the appropriate length into a section of 3/4" galvanized pipe representing the landing gear depth, and a different length of pipe over the portion of the axle representing the axle going through the wheel. I triple checked my Mark's on the axle end, showing me how it was to be bent. I then applied the "Tom Jones" sledgehammer to it. One hit was all it took! It bent the axle 1/4".... I reassembled the wheel, and presto, the 1/2" toe in has been removed. This then required the Lowell Fitt brake assembly realignment procedure with a couple washers.

    The wheel rotates free and aligned.

    Thank you Ralph for your fair offer to purchase your adjustable gear, in case I destroyed mine.

    Again, thank you everyone!
    Grover Wright
    Flying a KF IV-1200
    ROTAX 912UL

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