Coding A Generalized Rubber Band Pop-Up Mechanism In TurtleStitch

A Generalized Rubber Band Pop-Up Mechanism Coded In TurtleStitch

Here is a video of the Rubber Band Pop-Up Mechanism in action.

In my last blog posting, https://papercraftetc.blogspot.com/2022/10/a-rubber-band-pop-up-haunted-house-for.html, I created a pop-up haunted house for Halloween.  I belong to a group of educators who saw my pop-up and challenged me to recreate this pop-up mechanism in TurtleStitch.  I knew it was an easy endeavor with just some basic math calculations using the Pythagorean theorem.  In coding the mechanism, I decided to create a generalized form with variable dimensions so that I could use the code to design future rubber band pop-ups. 

The rubber band pop-up mechanism is a cube with a diagonal in the middle. The diagonal is separated by a rubber band. When the base is pressed inward at the corners that are opposite to the internal diagonal,   the mechanism becomes flat because a rubber band expands to fill the void in the diagonal.  When the corner pressure is released, the expansion tension on the rubber band is released and the rubber band contracts to its natural state  This phenomenon allows the form to deploy and become three dimensional.

The strip is divided into four sections.  The first section represents the diagonal part #1, the second and third sections are the sides of the pop-up and the fourth section is diagonal part #2. The diagonal needs to divided into two parts for the rubber band to be expanded.The first part is generalized at 0.5 inches long. The second part is the remainder value of the diagonal. 

Using the Pythagorean theorem, a^2 + b^2 = c^2 , the diagonal of the square is calculated. The variable "Length" in my code is the side of the cube.

To Create a Rubber Band Pop-up Mechanism In TurtleStitch:

1). Here is my generalized code for the rubber band pop-up in TurtleStitch, https://www.turtlestitch.org/run#cloud:Username=Elaine&ProjectName=Rubber%20Band%20Pop%2dUp%20Mechanism   Change the variable side for the side length of the pop-up and variable height for the height of the pop-up, if desired. Run the code in TurtleStitch.

2). A rectanglar strip is created. In the TurtleStitch drop down File menu,  Export as DXF for a paper cutting machine. Export this rectanglar strip.

3). Using your paper cutting machine, cut out two copies of these rectangle strips from 65 lb. card stock.  The dotted lines are fold lines. Please follow the directions on when to fold the lines because the paper tends to warp and create uneven sides if the sides are folded too early. The lines with the circles on either end are slits where the rubber band is inserted. The rubber band that I used is a common Rainbow Loom rubber band.

If a Silhouette cutting machine is being used,  I have observed that the dimensions are not preserved. It must be resized in the Silhouette software before cutting. I have included a one inch square for reference. Once in the Silhouette software, release the compound path and observe the size of the one inch square. Divide 1.00 inch by this observed value and then multiply by 100 to get the percentage that the figures needs to be changed.   In the Silhouette's Transform Panel, resize the entire image using the scale window.

The image selected will be transformed 97.2% when the Apply button is pressed. Look at the square's size. It should now measure one inch.  The square is no longer needed and can be deleted.

Make the Pop-Up Rubber Band Base

Fold the rectangular strip in half lengthwise.  Glue this lengthwise side together (I use Aleene's Tacky Glue)  Repeat for the second rectangular strip.

 Let the glue dry completely before proceeding because you want the sides to be rigid. 

 Crease the vertical lines of one of the strips so that a triangle is formed. (not shown as the triangle pulls apart when tension is released)  The two sides with the slits come together to form the diagonal.  Repeat for the second strip (it will be opposite of the first strip) so that a square is formed with a diagonal in the middle of the square. Make sure the slits run in the same direction. 

Glue the diagonal part #1 (small side) together with the corresponding diagonal part #1. together. Make sure that the slits are going in the same direction.

Slide the one inch rubber band into the slit of diagonal #1 and align the rubber band with the round hole in the base of the slit. Fold the base so that a square is made with a diagonal in the middle.  The gap in the diagonal will be closed by the rubber band.

Apply a Glue Dots to the diagonal part #2 as shown above.  Make sure the slit is not covered by the Glue Dot. Bring the two diagonal #2's together. Glue can be used but it needs to be dried completely before inserting the rubber band into the second slit.  I like Glue Dots because I do not feel like waiting for the glue to dry.  Insert the rubber band into the second slit.

The Rubber Band Pop-Up Mechanism is now ready to be used.