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Thread: Moving the axle forward

  1. #11

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    Default Re: Moving the axle forward

    Quote Originally Posted by jiott View Post
    OK, that makes sense. So you have two opposite things occurring: More weight aft of the mains is destabilizing but a longer wheelbase is stabilizing. I can see why it may be hard to predict what the overall effect will be, as Chuck said.
    Back in my heyday building experimental airplanes, I saw a lot of guys who moved their gear forward to eliminate the nose-over tendency just to find they had created themselves a real monster to control. A good example, look at a sailplane, the wheel is just about on the cg. Did you ever hear of anyone ground looping a sailplane?
    Chuck Gruby
    Petal, Kit Fox III Flying

  2. #12
    Senior Member Dusty's Avatar
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    Default Re: Moving the axle forward

    Has anyone measured the position of the axle with the bungy to highwing cabane conversion? I suspect it may be slightly forward.
    No adverse handling!
    Better coordination between brakes elevator and throttle would be the best prevention from nose over!
    I don't have the power of a 912 but a rearward position for me would be better as I have trouble getting the tail up before rolling and need nearly 2/3 throttle hard breaking and stick forward progressively applied on landing to keep the tailwheel up in the rough.

  3. #13
    Senior Member Esser's Avatar
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    Default Re: Moving the axle forward

    Sailplanes have a rudder the size of a sheet of plywood too. Many times they have a skid or forward wheel to fall onto when the brakes are applied.

  4. #14

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    Default Re: Moving the axle forward

    I appreciate the replies and concerns about ground looping and nosing over.
    Most of the landings I do is a balance between the brakes and the elevator, to stop as short as possible to practice for the type of flying i enjoy.
    Take a look at minute 2:30 and 4:35 in the link below to see the type of flying I do (that is not me flying the cub) and why I want to move the gear forward to be able to brake sooner and harder.

    https://www.youtube.com/watch?v=ucdb0TKu3rks

    I was looking for structural advice regarding extending the Grove gear forward like the photo shows in post 1 as is commonly done on Cessna 140's to be able to brake harder and sooner.

  5. #15
    Super Moderator Av8r3400's Avatar
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    Default Re: Moving the axle forward

    The leverage would be somewhat greater trying to bend the side door trusses.

    This is what I did to strengthen this area on my IV project.



    I would suggest if this area hasn't been strengthened on your plane already, it needs to be. An old trick for the Avid guys to help their bungee truss under the seat, was to cut plywood triangles to fit snugly inside the truss webbing, then hysol them on place. This will work here as well if welding is not an option.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  6. #16

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    Default Re: Moving the axle forward

    Larry
    I am sure your "Swiss Cheese" reinforcement would take care of my longeron concerns with extended and forward swept Grove gear.
    How thick is that plate and any idea the weight added to make the reinforcement.
    What style of gear will that airplane get?
    Thanks
    Herman

  7. #17
    Super Moderator Av8r3400's Avatar
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    Default Re: Moving the axle forward

    That plane (the Mangy Fox) is getting a custom Grove spring that's 2" taller and 3" wider.

    The webbing is made from .032" sheet steel stitch welded in place. Overall weight of that mod was about 3 pounds.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  8. #18
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    Default Re: Moving the axle forward

    Larry are you planning on adding the wing slats, and practicing landing similar to the Super STOL guys. That definitely improves the strength of the landing gear & frame! I guess your planning on some smack down landings.
    Paul Zimmermann
    LSRM-A
    Garland, Texas

  9. #19
    Super Moderator Av8r3400's Avatar
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    Default Re: Moving the axle forward

    It won't be "just" any old Kitfox when I'm done with it...
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  10. #20
    Senior Member HighWing's Avatar
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    Default Re: Moving the axle forward

    Quote Originally Posted by Dusty View Post
    Has anyone measured the position of the axle with the bungy to highwing cabane conversion? I suspect it may be slightly forward.
    No adverse handling!
    Better coordination between brakes elevator and throttle would be the best prevention from nose over!
    I don't have the power of a 912 but a rearward position for me would be better as I have trouble getting the tail up before rolling and need nearly 2/3 throttle hard breaking and stick forward progressively applied on landing to keep the tailwheel up in the rough.
    Dùsty,
    That is an interesting question. When we designed that gear our intent was to give the airframe a 2" rise at the firewall and wider stance. The purpose of the rise was for better angle of attack on the take off run.

    This was all done while the airplane was in flying attitude so the gear when the fuselage is rotated back into three point does move forward a bit relative to the aft rotating fuselage. I just measured mine and when in level flight attitude the leading edge of the wing is about 2-3/4" forward of the center of the axle. When in three point, the wing leading edge is about 9-1/2" aft of the leading edge. It would seem that this would add a bit of weight at the tail wheel in three point attitude.

    The factory cabane gear has a profile that suggests they lengthened the gear leg while in three point while maintaining the fore/aft location of the axle. This is just supposition on my part, however.

    We have always maintained that installing our gear did not make the airplane a "Bush" plane, but was intended to make the airplane easier to handle on improved strips and to eliminate the need for periodic bungee replacement.

    It has long been my thought that the frequent stories of original bungee gear collapse in the early days was a design feature. The airframe was designed to be light weight and the gear, by design, the easier component to replace in case of stress damage in a hard landing. I think Larry is trending in the right direction. All the gear alternatives are quite robust. It is the air frame in the attachment area that typically remains the same while we ever increasingly challenge it. Again just one guy's opinion.
    Lowell Fitt
    Goodyear, AZ


    My You Tube Channel

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