The built Mechanical Hand kit

Smartivity bonus

Mechanical Hand bonus activities

4 missions and 3 tinker tests. Can you win all 7 stars?

Four new things to try with your Mechanical Hand. None of them are in the manual. Pick one, or try them all this week.

0 of 7 done

Tap Done! on a mission to win its star.

Your missions

  1. Mission 1 of 4

    Dance-hand shapes

    • Just your kit

    Classical dancers in India, like Bharatanatyam dancers, make one-hand shapes called mudras. Try three with the Mechanical Hand: Pataka (all four fingers straight and together, thumb bent in), Ardhachandra (all four fingers straight and together, thumb stretched out) and Shikhara (a fist with the thumb pointing up). Which can the hand make, and which are hard?

  2. Mission 2 of 4

    Rock, paper, scissors robot

    • 2 players

    Play rock, paper, scissors against a family member while wearing the Mechanical Hand. Best of 5.

  3. Mission 3 of 4

    Tool race

    • 2 katoris + chimta
    • Timer

    Time how long it takes to move 10 Blocks from one katori (small bowl) to another three ways: with the Mechanical Hand, with kitchen tongs (chimta) and with your bare hand. Which tool was fastest, and why?

  4. Mission 4 of 4

    Measure two hands

    • Paper + pencil
    • Ruler

    Trace your real hand and the Mechanical Hand on paper. Measure each finger in centimetres and make a bar chart. Which finger is longest on each hand?

Tinker it

Change one thing. Guess. Test 3 times. Write it down.

  1. Tinker test 1 of 3

    Grippy fingertips

    • Rubber bands
    • Plastic glass + 1-rupee coins

    What you'll change: Wrap a household rubber band around each fingertip to make the tips grippier.

    1. Predict: with rubber-band tips, will the hand hold more 1-rupee coins in a glass than with bare tips? Write down your guess.
    2. Bare tips test: hold a small, light plastic glass in a Power Grip (all four fingers and the thumb). Keep the same squeeze the whole time. A helper drops in 1-rupee coins one at a time until the glass slips. Write down how many coins it held. Do this 3 times.
    3. Make the change: gently loop one rubber band twice around each Finger-Tip Cushion and the Thumb-Tip Cushion, over the tip plates. Keep it snug, not tight.
    4. Grippy tips test: use the same glass and the same squeeze, and do the coin test 3 more times. Write down each number.
    5. Record: compare the average for bare tips and rubber tips. Was your guess right?

    What's going on: Friction is the force that stops one surface sliding over another. Rubber usually grips smooth plastic better than the bare cushions do, so the same squeeze holds more weight before the cup slips.

    Safety and undo: Loop the bands gently so the cushions don't bend, and slide them off when you're done to put the hand back as it was. Keep coins away from little ones under 3.

  2. Tinker test 2 of 3

    How Far Can It Hang?

    • 30 cm ruler
    • Cloth clips

    What you'll change: Clip cloth clips onto a ruler held by the hand, then slide them farther from the grip.

    1. Hold a 30 cm plastic ruler flat, with the thumb on top and the fingertips underneath, in a Pinch Grip at its middle (the 15 cm mark), low over a table. Keep the same squeeze the whole time.
    2. A helper clips 1 cloth clip onto one long edge of the ruler, 2 cm from your grip. They slide it out 1 cm at a time until the ruler tips. Write down the cm mark where it tipped. Do this 3 times.
    3. Predict: with 2 cloth clips at the same mark (one on each long edge), will the ruler tip closer to your grip, farther away or at the same spot?
    4. Do the same test with 2 cloth clips, 3 times. Write down each mark.
    5. Record: compare the averages. Did 2 cloth clips tip at about half the distance? (If 1 cloth clip reaches the end without tipping, use 2 for the first test and 4 for the second.)

    What's going on: A weight twists the ruler harder the farther it hangs from your grip. This twist is called torque, and it equals weight times distance. Twice the weight needs only about half the distance to twist just as hard.

    Safety and undo: Clip the cloth clips only onto the ruler, never onto the Finger Straps, Strips or any other kit part. Hold the ruler low over the table so a tip-over is a short drop. Nothing on the kit is changed. Unclip the cloth clips when you're done.

  3. Tinker test 3 of 3

    Longer Card Fingers

    • Biscuit-box card
    • Masking tape

    What you'll change: Tape a strip of card from a cereal or biscuit box to the tip of the Wooden Index Finger so it sticks out 5 cm past the end.

    1. Predict: with a longer finger, will the tip rise higher or lower as you close the hand? Will it press harder or more gently? Write down your guesses.
    2. Bare finger test: wear the hand and rest its back flat on a table, palm up, with the Wooden Fingers straight. A helper holds a ruler upright beside the tip of the Wooden Index Finger. Slowly close just that finger and the helper reads the highest point the tip reaches. Write it down. Do this 3 times.
    3. Make the change: a grown-up cuts a 2.5 x 7.5 cm strip of card from a cereal or biscuit box and rounds its corners. Use masking tape to stick 2.5 cm of it flat on the back of the Finger-Tip Cushion, so 5 cm sticks out straight past the tip. Keep the tape off the Strips and Finger Straps.
    4. Card finger test: do the same test 3 times, this time reading the highest point the end of the card reaches. If you want, also rest the card end and then the bare tip on a helper's open palm, close gently, and feel which one presses harder.
    5. Record: compare the average heights for the bare finger and the card finger. Were your guesses right?

    What's going on: The tip section of the finger is a lever that turns at its joint. Make it longer and the same turn swings the far end through a bigger arc, but the same pull on the Strip pushes more gently out there. You gain reach and lose squeeze.

    Safety and undo: A grown-up cuts the card and rounds the corners. Use only masking tape, never glue, and don't force the finger past where it stops. To put the hand back as it was, peel the tape off slowly.

Missing or broken piece? We send it free: Request a part

More about the Mechanical Hand