Heavy Lifting


  • 1

    Here are some of the materials you can use

    • cardboard box (shoebox size or bigger)
    • paper clips
    • paper cup
    • 3 pencils (1 sharpened for poking holes in cardboard)
    • scissors
    • string (fishing line or kite string) 
    • 3 strips of corrugated cardboard (2 x 11 in. [5 x 28 cm]) (corrugated cardboard has grooves in the middle, like a cardboard shipping box)
    • tape
    • weights (marbles, pennies, or washers)
    • wooden spool
  • 2

    Prepare ahead of time

    • Have paper and a pencil ready to write down ideas and sketches as you design.
    • There are a lot of steps to building a crane, so you might want to have an adult help you with some of the steps.
    • Think about cranes. What is a crane? Where have you seen them? How do they lift heavy loads?
    • TIP: Cranes are huge machines used for moving heavy loads. They have a long arm that holds a strong wire or rope called a cable with a hook on the end. 
  • 3

    Think about the challenge

    • Why do people use cranes? (To move heavy materials or objects, to lift objects to high places)
    • How might astronauts use a crane on the moon? (To dig for minerals, to lift ice)
    • A crane has to overcome the force of gravity. How will you design your crane to deal with the pull of gravity? 
    • TIP: Huge cranes are used to dig, move, and relocate large objects. Whether a crane is on Earth, the space station, or the moon, it has to be strong to lift heavy loads without breaking.
    • TIP: Gravity is a force that acts like a magnet in that it attracts one object to another. Gravity will pull an object to the ground, such as the cable and arm on a crane.
  • 4

    Think about and write down your ideas

    • How long will you make the crane’s arm?
    • How will you keep the crane’s arm from breaking as it lifts a heavy load? 
    • How will you stop a heavy load from pulling the arm to the left or right?
    • How will you attach the arm to the crane?
    • How will you turn the arm of the crane?
    • TIP: The crane has to overcome gravity. The arm and any extra supports, such as string or additional pieces of cardboard, will help spread out the force equally. If all forces balance one another, the arm won’t move. 
    • TIP: A crane can work with or without a crank handle. But having a crank handle is useful because it makes it easier to wind the cable. 
  • 5

    Look at the materials

    • What materials do you have to build the body? The arm?
    • What strong materials will you use as the cable that lifts the load up and down?
    • What materials do you have to build the reel to wind the cable around?
    • TIP: Inventors’ and engineers’ first ideas rarely solve a problem. They brainstorm ideas, try different ideas, learn from mistakes, and try again––this is part of the design process.
  • 6

    Design and build the arm

    • Use the box as the crane’s body.
    • Decide what materials you will use to make the arm.
    • Decide how long you will make the arm. How many parts will the arm have?
    • Choose your materials and build the arm.
  • 7

    Attach the arm 

    • Decide at what angle you want the arm to hang away from the body of the crane. 
    • Think about how you can make the arm sit at an angle on the body. 
    • Attach the arm to the body. 
    • TIP: The end of the arm needs to be far enough away from the body so the cable can move up and down smoothly without hitting the edge of the body.
    • TIP: If the crane’s arm is not strong enough it can break off as it lifts a heavy load. Secure the arm firmly on the body with extra tape. Or cut slits in the box, slip the arm into the slits, and secure firmly with tape. 
    • TIP: If your crane arm is too thin, it might bend from the heavy load. You can try adding extra pieces of cardboard above, below, and next to the arm for extra support. 
  • 8

    Design and build the take-up reel

    • Decide how to make a take-up reel that lets you shorten and lengthen the cable.
    • Think about what the cable will wrap around as you wind it up and down.
    • Think about how you will wind the cable.
  • 9

    Attach the take-up reel

    • Decide how you will attach the take-up reel to the crane. 
    • Modify your crane body to accommodate the take-up reel.
    • Attach the take-up reel to the body.
    • TIP: If it is hard to keep the reel in place on the crane, try cutting and bending flaps out of the top of the box; then poke a pencil through the flaps. Or use pieces of cardboard to build a holder and attach it to the top of the box.
    • TIP: Attach the take-up reel in a location on the body that will allow the cable to pull in a tight, straight line as it lifts the load.
  • 10

    Prepare the cable

    • Think about how you will secure the cable to the take-up reel.
    • Secure the cable and wind the cable around the reel.
    • TIP: Secure the end of the cable to the take-up reel so you can wind it easily and so it won’t come off the reel when it unwinds. 
  • 11

    Prepare the cable (continued)

    • Decide how the arm will hold the cable as you wind and unwind.
    • Modify the arm and run the cable up the length of the arm.
    • TIP: If the cable keeps sliding from one side to another, try adding tape to each side of the pencil and leave a clean section in the middle so the cable can run through without sliding from side to side.
  • 12

    Prepare the cable (continued)

    • Decide how the crane will hook the load so it can lift it up.
    • Add the hook device that will catch the load.
    • Test the cable. 
    • TIP: You can test a design at different steps along the building process. As you test, you’ll find ways to make your design better. Improving a design based on testing is part of the engineering design process.
  • 13

    Design and build the bucket 

    • Decide what materials you will use for a bucket to hold the load.
    • Think about how the bucket will slip onto the cable hook.
    • Choose the materials and build the handle on the bucket.
  • 14

    Attach the bucket to the crane

    • Attach the bucket to the crane hook.
    • TIP: If the bucket slips from side to side on the hook, try wrapping thin tape on each side of where the hook sits on the handle. This keeps the bucket, and the load weight, in the middle. 
    • 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. 
  • 15

    Test your crane

    • Add weight to your bucket.
    • Wind up the crane.
    • Redesign if needed. Then retest.
    • TIP: If the load rips the arm off the box, try reinforcing where it is attached by adding cardboard supports.
    • TIP: If the arm crumples, try starting over with a sturdy piece, or several pieces, of cardboard. 
    • TIP: If the arm sways under the heavy load, make sure the cable is in the center of the arm. Or try supporting the arm with strings or strips of cardboard. If you put the cardboard strip with the length running side to side, most of the cardboard will resist the load’s downward pull. This is the strongest way to position the strip. 
  • 16

    Did you know?

    • More Precious Than Gold?
      The surface of the moon is drier than the driest desert on Earth. But under the surface, it might be a different story. NASA is sending several spacecraft to look for ice on the moon. Ice can be made into water, and water can be made into oxygen for breathing and fuel for the return home to Earth. If they do find ice on the moon, one way NASA will remove it is by using cranes.


  • 17

    Try this next!

    • Crank it up with a handle. Modify your take-up reel by adding a hand crank. A crane can work with or without a crank. Having a hand crank might be useful and make it easier to turn the rod. 
    • Expand the cable. Try picking up a load from the floor as your crane sits on a tabletop.