Roly Poly Rollers

A Roly-Poly roller is a physics toy that contains a weight inside, and when rolled down a slight slope, it moves in unexpected ways, depending on the amount of weight placed inside. These rollers come in a variety of shapes and sizes, and each one moves in a unique and interesting way.

We're sharing this Instructable as an early prototype at the Tinkering Studio, so there's still some room for tinkering and making changes in terms of how to build and play with them. We'd love to hear from you if you create your own Roly-Poly roller and even experiment with different shapes to make it truly one-of-a-kind! Please share your remixes, questions, and work in progress here or on Twitter with #ExploringRolling @TinkeringStudio.

Essential materials

• 2L plastic bottle
• ¼” laser cut plywood
• 1” diameter ball bearings
• Epoxy 3M DP 100 Plus for stronger connections

Tools

• Laser cutter
• Box cutter
• Sharpie 

Find a 2L plastic bottle and mark a line at the bottom. This line will serve as the baseline for your project.

Starting from the baseline, measure 2.5" up the bottle and cut it out to get a 2.5" plastic cylinder (wrapping a strip of tape around the bottle instead of marking it with a pen will also help to cut at the line).

We have three different shapes: Triangular shape, Grain shape, and Pill shape. You can download the laser-cut files here.

https://www.thingiverse.com/thing:5801317/files

We've put both .svg files and .ai files so that you could modify our design. For example, it's up to you whether you want the side openings to be wide open to make it easier to get the ball(s) in, smaller to make it harder for the ball(s) to pop out, or completely closed to prevent the ball(s) from getting in and out.

Important note: The circumference of the bottle we're using is 13.7". We believe that the circumferences of most 2L bottles are the same, so you can use the file as is, but please double-check that your bottle's circumference is the same. If you're designing your own shape with Illustrator, make sure the circumference of the bottle and the perimeter of your shape are the same. In Illustrator, you can find the perimeter of a shape by going to Window > Document Info > (Expand the menu) > Objects.

After laser-cutting the shape, stick it onto the clear plastic cylinder you cut out of the plastic bottle. The cool thing about making these rollers is that your laser-cut shape will fit right into the cylinder with a press fit. Try pressing the shape into the plastic cylinder and see how well it fits perfectly without needing any glue! Finally, try rolling it down a slope with a ball or two and experiment with how it rolls!