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Thread: Nose leg matter

  1. #1
    Junior Member I'm new!
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    Nose leg matter

    Let introduce my self and forget my english mistakes
    I am a retired mechanical engineer and honored to be now a part of your group.
    I own two CD Shadows, one is ready to fly after some restauration, the other one need more work and I will see that in the future.
    About the nose leg, I have designed a new elastomer suspension inspire by a spring one in the Bruce Conway files.
    The advantages of mine is the shock aborber behaviour and the easy setting of the load forces.
    I double the aluminium tubes and add to the strap a second one made of a small chain and a spring, that way i can easily adjust the leg rotating friction
    Up to now I am grounded by French Administration problems, I have asked BMAA to help me and hope they will do.
    I have a good friend in the Shadow community: John Edwards from Popham.IMG_20170919_153935.jpg1478508203047 (1).jpg1478506773386.jpg

  2. #2
    Senior Member 500 Club
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    Bonjour Philippe,

    Welcome

    A nice solution to replacing the bungee cord but it does nothing to address the real problem and as another retired engineer maybe I can help a little!

    If you study the geometry of the front suspension you will discover the reason why the 'spring' needs to be so tight. If we keep it simple and consider two loads on the wheel from the ground , the first in a vertical direction you will see most of the load is transmitted directly to the alloy support tube because of the small offset of the wheel to the tube. This usually bends the bolt but also results in a small trail (or the wheel to pivot line offset) which gives the caster effect. If we then consider a frontal load this pushes the wheel backwards which increases the trail and effects the caster but also produces a bigger offset so the leverage increases with only the spring to resist. It is a very large rising rate but in the wrong direction so if too much movement in the arm is allowed the spring is overcome and the suspension is only arrested by the safety wire.
    The solution I use involves a lot of machining and bits so not that practical but if you want I could send you the drawings.

    Why two Shadows ?

  3. #3
    Junior Member I'm new!
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    Hello Mick,

    Thanks for your answer, I am always happy to discuss mechanical issues. My design don't need a safety wire, the huge progressive increase of elastomer springs forces from my point of view are enough to stop the backward movement, but I don't have your Shadow experience and I will be please to receive your drawings.
    My e-mail adress is philas2@free.fr.

    Two Shadows, in fact three, one with a lot of work, the second ready to fly after some work already done, the third wrecked for pieces. all came from a Belgium club

    My to day concern is getting the French permit to fly and it seems depend of the BMAA answer to my requests.

  4. #4
    Senior Member 500 Club
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    Will sort out the drawings and send them or possibly drop them off when next in France .
    Keep us up to date with your progress

  5. #5
    Junior Member I'm new!
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    Nice Mick, I eagerly wait for them!

    This week will be probably important for my permit to fly, I wait for two answers, one from DGAC and another one from BMAA, hoping that they will be positive, wait and see!

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