How does a human hand work? How do tendons and joints work together to manipulate fingers? What are the design strengths of a human hand? What are the weaknesses?
Building cardboard grabbers challenges students to think critically about mechanical design. Using simple materials, students will design and build their own visions of what a hand should be, and test the functionality of their machines by lifting an assortment of objects. This project is designed to give students ownership of their learning by offering minimal instruction. Students should learn through the iterative process of design, test, and redesign. This is a crucial element of this project, and should not be viewed as merely supplemental! We encourage you to customize this project to the needs of your class, but maintain the ideal of students’ learning through exploring.
This project was introduced to the Creativity Lab by artist Jeremiah Jenkins. Our Middle School Making Teacher piloted a “Grabber Challenge”, in which the 7th graders competed in making a grabber that could pick up the most objects.
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Step 1: Preparing the Activity: Materials, Time, Tips
This activity can be completed within one class (or, depending on the desired level of complexity, can be extended), is low cost and is overall a low floor, high ceiling activity that allows a certain amount of iteration and design. We use cardboard for this project because it is cheap and plentiful. However, students who show the initiative and enthusiasm to use other materials, and have the means to do so, should be encouraged to go forward with their plans (see Cardboard Grabbers with Older Students).
- Cardboard (recycled)
- String / Yarn
- Masking Tape
- Popsicle Sticks
- Hot Glue Guns
- Cardboard Cutters
- Exacto Knives
- Bandage scissors are great for cutting cardboard, and are safer than utility knives. You can order them from Amazon.
- Students may want/need extra materials for their designs. We accommodate them as much possible, so as not to stifle their creativity. Rubber bands and pipe cleaners are common items that students ask for.
- If space allows it, keep an ongoing supply of recycled cardboard in your class, with different sizes readily available for the students
- Students should work together to overcome setbacks by sharing design ideas. They should only turn to the teacher for help after they have sought each other for advice.
- Exercise caution when handling hot glue guns, scissors, cardboard cutters and exacto knives. Always provide mats for cutting on tables.
Step 2: Before We Make: Parts, Purposes, Complexities of a Hand
With 7-8 Grade, you can challenge students to spend 5–10 minutes examining their hands, and imagining their inner workings. What is going on beneath the skin that lets their fingers move? Let them work in groups, or start a single class discussion. At this point, there are no wrong ideas. After they have had time to ideate, have them journal their thoughts, using a combination of sketches and descriptions.
We use the Thinking Routine entitled "Parts, Purposes, Complexities", created by AgencybyDesign in Oakland:
"Thinking routines are short, engaging, two-or-three-step patterns of intellectual behavior that are highly transferable across contexts. They are designed to be easy to use, easy to remember, easy to transfer, and to be vividly effective when used on a wide variety of topics."
Parts, Purposes and Complexities encourages students to slow down and make detailed and deep observations about an object or system. It helps make students' thinking visible through lists, maps and statements (or questions!).
We introduced this thinking routine through an activity sheet in preparation for the Cardboard Grabber activity.
With older students (9-12 Grade), try to broaden the definition of “hand” to include any sort of prehensile machine: talons, prosthetic hooks, pincers, etc. Show students a variety of these alternatives to human hands, either with physical objects, or projections on the screen. How is each of these hands effective or ineffective? Working in groups or as a class, have students identify the strengths and weaknesses of each design.
Step 3: Step-by-step Guide
If students had unlimited time and resources, we would let them go about their designing and planning without any intrusion.Because we are constrained by pragmatic issues, like class-time, we offer students this basic design as a jumping off point, which they may or may not use as they go forward:
- Cut a finger shape out of cardboard.
- Hot glue one-inch pieces of straw along the finger, leaving small gaps between each piece. The pieces of straw act as bones, and the gaps between the straws are joints.
- Run a piece of string or yarn through the pieces of straw.
- Tie it off or hot glue it at the tip. This will act as a tendon.
- Crease the finger at the joints, then pull the tendon to create a gripping motion.
- Combine several fingers to create a complete hand!
Construction may require several class periods dedicated to independent work time.
Challenge students to design their own mechanical hand, capable of lifting objects of varying weights, shapes, and sizes, and tell them the materials they will have to work with. Give them the remainder of class to create a design and work plan. Do not show them the objects they will be challenged to grab.
Have students refine their designs as necessary, then test them again. As students discover their design flaws, have them return to their journals/blogs to plan how they can improve upon them.
Step 4: Taking the Activity Further!
To further develop this project into a student-driven learning opportunity, have students break into groups and plan a several-month-long unit based around hands. Perhaps students want to build a Claw Machine arcade game, incorporating mechanics, circuitry, and programming. Students should plan budgets and work schedules, and strive for a professional level project. This is a good opportunity to introduce students to more advanced tools, like 3D printers and laser cutters, which they can use for rapid 3D prototyping. The photos above are a 3D printed hand created by Jorge Zuniga, Ivan Owen and Peter Binkley (via Enablingthefuture.org) and a laser-cut hand by Omega via Ponoko.
This activity also served as a starting point for a unit on Anatomy and Linkages in our Fitness class. 9th and 10th grade-students created moving anatomical models to replicate body motions. By doing so they learned about muscle groups, differences between tendons, ligaments, and names of bones.