How to build a strong paper crane?

I have to do a project for physics where we build a paper construction crane. It’s a contest to see whose crane can support the most weight, and all we are allowed to use are 20 sheets of A4 paper and 1 roll of scotch tape.
What are some tips to make my crane strong? Any idea for the structure?
Thank you!
(there will be a 1kg weight balancing the crane out on the opposite side of where the weights will be hung, and the boom structure must extend at least 10cm out.

One Response to “How to build a strong paper crane?”

  1. What If  on October 20th, 2010

    How you build this is up to you.

    Here are some suggestion and data

    paper strength example

    http://www.progressiveagencies.net/index.php?option=com_content&view=category&id=56%3Agold-brand-a4-paper&Itemid=38&layout=blog

    A4 60 GSM

    Basis weight 60 + 4% (max) gsm
    Thickness 0.065 – 0.088 mm
    Tensile Strength MD 3.50 – 4.50 kg/15mm
    Tensile Strength CD 2.00 – 3.00 kg/15mm
    Tear Resistance MD 40 – 50 gf
    Tear Resistance CD 40 – 55 gf

    A4 80 GSM

    Basis weight 80 + 4% (max) gsm
    Thickness 0.100 – 0.115 mm
    Tensile Strength MD 4.50 – 5.00 kg/15mm (pull on strip of 15mm width ,length not important)
    Tensile Strength CD 2.50 – 3.50 kg/15mm
    Tear Resistance MD 50 – 60 gf
    Tear Resistance CD 45 – 55 gf

    I’ll explain
    both papers are A4
    A4 80 GSM ~1/3 thicker ,well have better compression and Tensile
    THE paper Weight matters.

    Compression members get complicated
    read
    recommend length / radius of Compression members < 10 ,that might give you 1/2 the Tensile Strength depending if with the grain or cross grain of the paper. if it not creased or buckles.

    Always test material.! How strong is the column.How much more force can I put on if I increase radius of
    column.
    Then give a safety factor greater than 2 (twice as strong as needed)
    tower design
    http://www.sefindia.org/forum/files/4percent20towerpercent20design_198.pdf

    1ltr water =1kg
    If you had a strip of 8mm wide 60 gpm paper taped to a ltr of water .It should hold. at 2~3 ltr break
    If you had a strip of 3mm wide 60 gpm paper taped to a ltr of water .It should just break.

    Test this with your paper.

    To balance the 1kg counter wieght with load .
    Say you want to carry 10kg then the 1kg counter wieght would have to be 10 times father away from center than the load of 10kg .

    min is 10cm ,counter wieght at 100cm
    tower well have with stand 2 times the 11 kg or 22 kg
    paper wieght of 20 sheets is ~1.247 sqm *60 gpm =~75 grams, about 100gram for 80 gpm

    It is a start good luck.

    Reply


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