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Minor Versionm

by Procheta Mallik


Using rubber bands and ice-cream sticks, both of whose properties are vital for this toy to function, we create a "wow"-inducing flick-knife!

Video Overview

    • Please handle the paper cutter and scissors with extreme care

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  1. Take the first ice cream stick and at about 2cm from each end, make a mark using a coloured pen/marker. Note the 4 points at which these lines meet the edge of the ice-cream stick
    • Take the first ice cream stick and at about 2cm from each end, make a mark using a coloured pen/marker. Note the 4 points at which these lines meet the edge of the ice-cream stick

    • Make `V'- shaped notches at these 4 locations using the cutter.

    • Making the notches isn't trivial; rather than scooping or sawing with the cutter, you just need to press down at the given location with a slight slant of the cutter. Do this with the opposite slant as well, and you should get a `V'-shaped notch

    • Also note that ice-cream sticks break and splinter easily, so you have to be firm and gentle while using the cutter rather than rough and clumsy.

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    • Take another ice cream stick and using a marker, mark the half-way line of the ice cream stick.

    • Cut the ice cream stick in half using a scissor/cutter. We need only one of the halves; the other half can be kept aside

    • On the half stick, like on the full stick previously, make 2 notches about 2cm from the curved end of the stick. Do not make any notches near the flat/cut side of the stick

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    • Now take the third ice-cream stick and again cut it in 2 parts, such that the lengths are about one-third and two-third of the ice-cream stick.

    • The small piece is not needed and may be left aside

    • Once again, using a cutter cut 2 `V'-shaped notches on the sides about 2cm from the curved end of the stick.

    • At the flat end of the stick, cut it as shown, like an arrowhead.

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    • Stack the 2nd ice-cream stick (half-length) on the 1st ice-cream stick (full-length), align the notches and hold them together by winding a small rubber band, 2-3 times, around them at the notches.

    • From one of the discarded ice-cream stick pieces, extract a small strip of ice cream stick of length ~2.5cms and thickness ~2mm and slide it in between the 1st and 2nd ice-cream stick behind the rubber band, as shown.

    • You should be able to press this up and down, like the opening and closing of a crocodile jaw!

    • Similarly, stack the 3rd ice-cream stick (two-third-length) on the other end of the 1st ice-cream stick, aligning the notches, with the arrowhead pointing outwards and wind them together 2-3 times using a rubber band at the notches.

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    • Swing the 3rd ice-cream stick and lock it between the 1st and 2nd ice-cream stick piece.

    • Now when you press the ends of the 1st and 2nd ice-cream stick pieces, the blade (i.e. the 3rd ice-cream stick piece) will flick open in a fraction of a second. Wield your knife with care!

    Would be nice to see a better 3rd picture here; one where you can actually notice the knife sticking out prominently.

    Procheta Mallik - Reply

    • Make sure the depth of notches are good enough to tie the rubber bands around the ice cream sticks.

    • Make sure the notch alignments are correct and you actually place the rubber bands in them

    • Ensure the length of the sticks are appropriate and don't come in each other's way while flicking the knife! Or too short whereby the 3rd stick can't slip under the 2nd!

    • The rubber band tightness also needs to be optimal; sometimes one or both of them may be too tight or too loose

    • The small stick piece needs to create a nice open-and-close jaw; it needs to be thick enough to ensure that happens without slipping around

    • The notches should not be too close to the ends of the sticks.

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    • Which part of the chaku acts as a fulcrum? What about the effort and load?

    • What class of lever would you classify the chaku: first, second or third?

    • Will the chaku work if the fulcrum, i.e. the small strip placed in between the ice-cream sticks, is removed?

    • What is the degree of rotation of the blade w.r.t. the smaller ice-cream stick?

    These type of observation questions can be named as pondering questions

    Suhail Ahanger - Reply

    • Make a chaku with 2 blades or more!

    • Use CD pieces, instead of ice-cream sticks, to make the chaku

    • Make the chaku such that the blade opens up till a particular angle rather than fully straight

    • Make a longer chaku by joining ice-cream sticks or by using 15-30cm rulers instead of the ice-cream sticks!

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Finish Line

Suhail Ahanger

Member since: 05/02/2017

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55 Guides authored


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