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G-Force Landin Gear Help

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  • G-Force Landin Gear Help

    Hi Lads,

    I've tired to get help for a couple of weeks there and elswhere overt the internet... in vain
    does it means that g-force landing gear gyros have disapeared with larry neal or simply that not enough people have read my help messages ?

    I have read all I could read about this gear in the butterfly section of this forum and foud out that very few datas and even less experience were discussed and I am wondering why

    I would like to speak with people who flew giros fitted with the g force landings gear to know what it is like in the real world because i doubt that 25 ft stops and drop are possible for normal pilots

    generally speaking, I don't know if it is rigth but I fear that the new shape of the forum has reduced traffic ?

    regards

    jean michel

  • #2
    On sait que accélération = Vitesse / tempsou en abrégé : a = V/t
    La distance x parcourue, quand l’accélération a est constante, est donnée par la formule x = ½ a . t2
    D’où on tire que t = √(2x /a)
    En remplaçant cette valeur dans l’équation a = V/t, on trouve : a = V / (√(2x /a)
    De là, on obtient a = V2 /2x

    Ainsi, pour amener la composante verticale de descente planée de 4,5 m/s à 0 en 0,4m de course verticale, il faudra que l'’atterrisseur impose une décélération constante de : a = 4,52 / (2 *0.4) = 25 m/s2soit 2,5 g, puisque g vaut environ 10 m/s2 . Attention, ne pas oublier d'ajouter 1g pour tenir compte de la gravitation de notre monde réel, soit 3,5 g
    Et pour la chute d'une autorotation verticale (environ -8 m/s ) stoppée en 0,4 m/s de course il faudra une décélération verticale de a = 82 / (2 *0.4) = 80 m/s2soit 8 g (+1g)
    Last edited by Jean - Claude; 09-29-2017, 11:21 AM.

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    • #3
      Jc
      thx a lot for the formulas
      this gear has been used Îd love to speak with guy who used it
      cheers
      jmi

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      • #4
        I fly a friend's G-force equipped Butterfly now and then. I don't care for the particular model of this gear on his machine. It presents the possibility of a forward-then-sideways capsize, as the nosewheel does not have a long-stroke leg as the mains do. I tie the gear off in the retracted position.

        There's no reason why a properly-designed long-stroke gear that allows vertical descents from any height won't work. There are films on YouTube of Cierva-derived machines with this ability. The necessary gear travel to reduce the G's to about 2 is in the vicinity of 2.5-3.0 feet. The nose gear will need to be energy-dissipating as well, unless you revert to taildragger gear.

        People insist on using swing axles, double swing axles, inward-inclined struts, springy compression gizmos that store energy instead of converting it to heat, and other unhelpful elements.. Fixed outriggers with purely vertical travel would be much better. Just copy Cierva and Pitcairn.

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        • #5
          Cessna type spring gear, including Eurotubs, rely on tire scrub to dissipate spring energy but that type of gear has serious shortcomings; alight one wheel first and get pole vaulted sideways or become a jack rabbit on an iced over runway.

          Long stroke landing gear with vertical wheel travel and hydraulic damping is hard to beat. And that doesn’t require the sort of monkey motion incorporated in “"G-force"” landing gear.

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          • #6
            Dough, Chuck thanks for your help

            Don't want to mimic matt pearson you tube nearly vertical landings
            I am flying a monoseat and building a light 2 seats which I'd love to give low speed/seep descent landing capabilities but i Am not planning to perform vertical landings at all
            I understand now that the g-force is not the solution ...
            I am going to investigate more classic solutions and this one is giving me hope

            Click image for larger version  Name:	 Views:	1 Size:	196.7 KB ID:	1125464


            Last edited by jm-urbani; 10-04-2017, 01:29 AM.

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            • #7
              I had the wide rough terrain g force on mine with the mechanism to hold it up. I never once let it down, 5000' paved runway. I often thought I would use it in an emergency but probably should have gotten familiar with how it landed extended. Dan

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