This is a simple mechanical cardboard hand that you can wear and use to pick up objects. The design allows you to easily swap out the gripping mechanism so you can experiment with different gripper styles without rebuilding the whole arm.
- Cardboard - at least 16” x 16”
- Straws - bendable straws are preferred
- String - small enough to fit through straws
- Tape - clear scotch tape works well, but anything that sticks to cardboard is good
- Box Cutter
- Markers - for marking cut lines and decorating
- Single Hole Puncher ¼”
Step 1: Mark and Cut Out the Forearm Extension
- Cut out a 16" x 7" cardboard rectangle, make sure the long side aligns with the corrugation
- Score the cardboard along the three long lines
- Cut out two 1.5" slots then use a marker to widen the holes
Step 2: Cut Out Strap and Assemble Forearm Extention
- Cut out a 13" x 1.5" strip of cardboard. Align the corrugation with the short side.
- Fold the forearm extension along the scored lines and feed the strap through the slots
- Tape together the Forearm extension into a triangular tube.
- Tape the strap together into a loop that you hand fits into
Step 3: Cut Out and Assemble the Gripper Platform
- Mark a piece of cardboard with the measurements in the first picture. Match the direction of the corrugation to the picture.
- Cut along the perimeter of the shape. Also cut along the red doted line.
- Fold the small flaps outward and the big flaps inward. (refer to the second picture)
- Tape the smaller flaps together into a small triangular tube and fold the tube onto the bigger flaps.
- Tape the bigger flaps into a triangular tube that incases the smaller triangular tube.
- Now slide the Gripper Platform onto the Forearm Extension to test that everything fits well.
Step 4: Preparing the Gripper Fingers
- Mark straws about every 1.25". This is where they will bend.
- Fold the straws flat and cut out a notch at every mark using the hole punch.
- Use scissors to cut off rounded sharp edges of the holes.
- Thread a string through the straw and tape it to one end. Leave about 1.5' of string on the other side.
- Pull the string and test that the straw bends at every joint.
- Repeat this process until you have the number of fingers you want.
Step 5: Putting It All Together
- Tape the straw fingers to the Gripper Platform one by one. Make sure that the strings all come out on the correct side of the Gripper Platform so that they align with the Forearm Extension.
- Slide the Gripper Platform into the Forearm Extension.
- Tie loops to the end of the strings or tape cardboard loops for your fingers to fit in. This will allow you to control each straw with a different finger. Alternatively, you can tie all of the strings together and add only one loop on the end. This makes all of the straws curl simultaneously with just one pull.
Step 6: Alternative Gripper Designs
Here are some alternative gripper designs I made. Feel free to experiment and see what you can come up with.