Instructions

  • 1

    Here are some of the materials you can use

    • brass fasteners
    • corrugated cardboard (corrugated cardboard has grooves in the middle, like a cardboard shipping box)
    • hole punch (optional)
    • objects to pick up with your device (for example, tennis balls, cotton balls, paper cups)
    • 2–6 paint stirrers (found at paint supply or hardware stores)
    • 2 paper cups
    • rubber bands
    • ruler
    • sandpaper (optional)
    • scissors
    • string
    • tape (duct or masking)
    • wooden skewers or dowels
  • 2

    Prepare ahead of time

    • Have paper and a pencil ready to write down ideas and sketches as you design.
    • Think about things people use to grab objects. (Cooking tongs, chopsticks, tweezers, pliers)
    • Think about how these devices grab things.
  • 3

    Think about the challenge

    • What is the difference between grabbing and scooping?
    • What kind of motion do you use to grab or squeeze something? 
    • How long will you make the arms on your grabber?
    • How does the design of your hand help you grip things? 
    • TIP: Grabbing and scooping are different motions. When you grab something, you get only one or two things at a time and handle them with more control. When you scoop something, you get a lot of something all at once and lift the items up as a group.
    • TIP: When you grip something with your hand, your thumb and fingers act like two sides to hold the object in place. The muscles in your fingers can apply a pinching pressure.
  • 4

    Think about and write down your ideas

    • What are some situations where having a longer reach might be handy?
    • What parts of the body (other than your hand) can make a squeezing action? (Arms, chin, elbows, feet, jaws, legs, lips, toes) 
    • What are some things all grabbing devices have in common? 
    • TIP: To grab something a device needs two parts—or arms—that can go on each side of the item being grabbed. The grabber also needs to have a way to press the two arms together to make a pinching motion. 
    • TIP: Some grabbing devices, like pliers and scissors, act as levers. A lever is a rigid bar that pivots, or turns, around a fulcrum. In these devices, the fulcrum is the point around which the two arms swivel. 
  • 5

    Look at the materials

    • What materials do you have to make long, sturdy arms?
    • How will you make the arms press together? 
    • What materials will you use to make the jaws grip items tightly?
  • 6

    Design and build the arms

    • Decide what materials you will use to build the arms. 
    • Think about how to make the arms long enough to extend at least 2 feet (0.6 m).
    • Choose your materials and build the arms.
    • TIP: You can connect paint stirrers with brass fasteners. Make a hole in the stirrer by turning and twisting a blade of a scissors in one spot until it goes through to the other side. Then connect the stirrers. This step can be tricky, so you might want to get an adult to help you make holes.
    • TIP: If the arms are too long, they might bend and not open and close easily. Short arms don’t bend as easily as long ones.  
  • 7

    Design and build the arms (continued)

    • Measure the reach of your grabber. Does it extend at least 2 feet (0.6 m)?
    • Attach additional length to each arm if needed. 
  • 8

    Connect the arms

    • Decide how you will connect the two arms. 
    • Think about how you will make the arms press together. 
    • Choose the materials and connect the arms. 
  • 9

    Test the grabber arms

    • Open and close the arms to be sure they move smoothly.
    • Redesign your arms if they don’t open and close easily.
    • TIP: If the arms have a weak grip, try increasing their force, or pressure, by adjusting the fulcrum’s position and the arm length.
    • TIP: If the arms bend or twist, reinforce them with something stiff, like a paint stirrer or layers of cardboard. 
    • TIP: Engineers always review and modify their early ideas. It’s part of the design-build-test process. Testing reveals things about a design and the materials. Engineers use that information to improve a design before going any further. 
  • 10

    Build and attach the jaws

    • Decide how your jaws will grip an object and hold on to it. 
    • Think about how your jaws will be attached to the end of the arms.
    • Choose the materials and build the jaws.
    • TIP: If your jaws don’t hold an object, try changing the shape of the jaws so they have a firm grip when they grab hold of an object.
    • TIP: If the gripping surface of the jaws can’t hold on to things, try adding cardboard to make it wider, sandpaper to increase the friction, or toothpicks to bite into an object. 
  • 11

    Grab an object

    • Place an object about 2 feet (0.6 m) away from you.
    • Grab it with your grabber.
    • TIP: If your jaws don’t open, check that nothing is blocking the their movement. Or check that the two parts can slide easily past each other. You can use sandpaper to smooth out a rough patch on an arm’s surface.
    • TIP: You've just built a prototype, which is an early version of a product. Prototypes help engineers understand a product’s strengths and weaknesses and how the product might be improved. 
  • 12

    Did you know?

    • Unusual Arms
      Michael is a boy who was born with 6 inches (15 cm) of his left arm missing. Michael was fit with an artificial hand that allowed him to do a lot of things a natural hand could do—but not everything such as squeezing or pressing very hard.

      Michael’s father wanted him to be able to do more with his artificial hand, so he contacted engineers at the Open Prosthetics Project. Together, they built Michael two more hands—unlike any you’ve seen before. One hand is a dinosaur puppet that lets Michael grip things by controlling its jaws. The other hand is a fishing rod that lets Michael catch fish as well as reel in stray toys! 
  • 13

    Try this next!

    • Build a supersize grabber. Build a grabber that can pick up two objects at once.
    • Add a second motion to your grabber. Build a device that is able to do two motions such as make the stick that holds the jaws also bend like an elbow or extend another two feet.