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Mechanical Chair questions

  1. Mar 17, 2013 #1
    Hello I am building a chair that will mechanically open itself remotely from a folded form. I decided to make this chair mobile I already have the electronics planned but i need help on the chairs easy mobility.

    My first question what materials are sturdy enough to hold a person that is lighter than a Pine Wood chair. A list of materials lighter than Pine would be nice to suggest that is sturdy. I have checked Google already but yet to find the solution. Also the density of the overall material suggested if possible.

    I want something within 10 lbs of carry weight. If not possible give me possible suggestions that could be light weight and sturdy or a combination of different materials.

    Thank you , Also this is my first time on this forum site :=D
  2. jcsd
  3. Mar 17, 2013 #2


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    Hi goggles and welcome to PF.

    You believe you need a wood that is lighter than pine.
    Pine wood density is about 0.5, bamboo about 0.3 and balsa about 0.2.
    My guess is bamboo would be a better chair material than balsa, simply because balsa is so soft.
    Good luck with your design. Please keep us posted.
  4. Mar 18, 2013 #3
    Thank you for your suggestion, and an introduction etudiant

    I will experiment with bamboo, and hope to have my mechanical chair easy to move. :+D
  5. Mar 19, 2013 #4


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    Is using wood a mandantory requirement? Is it possible some other material might fall within your carry weight of 10 lbs. and weigh less than pine wood? Have you looked at aluminum?
  6. Mar 19, 2013 #5
    Try using a laminated spruce/ balsa wood lay-up. (or spruce-cedar) Spruce is very strong for its weight, which is why it's used for guitar tops and home-built aircraft construction. (It has the highest strength to weight ratio of all woods, except perhaps pitch pine, which is nearly impossible to get now.)
    You'd glue thin spruce veneer/ strips on to a core of balsa-spruce-balsa, and if you want, the balsa wood can be honey-combed to reduce weight.
    Or you can go for the slightly heavier and much stronger cedar...
    The spruce strips/ veneer can be quite thin, say 3/32", or glue up 2 1/16th inch strips on each side.
    Use a vacuum bag to form the laminations, if you can arrange that. By going this route, you can also fabricate curved pieces.

    A a rule of thumb, the more layers your laminations have, the stronger it gets. a piece made from 6 layers will be about 6 times as strong as a 1-piece layer. (rule of thumb number there...) because the glue makes it a lot harder for the layers to slip past each other when in compression.
    I have a 5/8" square piece out in my shop made from 5 1/8" pine layers, and I can't bend it, let alone break it...

    For an ordinary-sized chair, I'm fairly confident that one can bring the weight down below 6 lbs, not counting the mechanical elements. [ nb: I have built a lot of chairs ].
  7. Mar 19, 2013 #6
    I have thought about the aluminum idea, however I live in a dry hot area and would not like the metal to heat up when i am sitting in the sun , plus i worry about the material warping.Technically i would like something wood mandatory to insulate the heat I should have inserted this information in the beggining post to be specific. I apologize for such and thank you for your advice.
  8. Mar 19, 2013 #7
    A very interesting idea indeed, I will experiment with the Spruce laminations for I can understand the strength in the supports and the amount of light weight in it all.
    Thank you for the suggestive material.
    I will experiment soon :+D
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