This contraption is a Pulley Door System made of materials you can find in your home. The types of simple machines in this system are a pulley (in the main contraption) and a wheel and axle (in the thing that actually controls the door).

Supplies

24 cm by 14 cm cardboard
(x2) 11 cm by 11 cm cardboard
9 cm by 7 cm cardboard
Scissors
Blade
Straw
String
Hex nuts
Pencil
Hot Glue Gun
Tape
Paper Clip (bent into a straight piece of metal)
Tweezers to help make holes

Step 1: Pulley Door System: Base Pieces #1

Get a piece of cardboard that is 24 cm by 14 cm. You can color it if you want. If not, just leave it like its normal color. Set it aside. As you can see above (I left everything its original brown color)

Step 2: Base Pieces #2 and #3

Next, get two 11 by 11 cm pieces of cardboard and one 9 by 7 cm piece of cardboard.

Step 3: Door Frame

Get both of the 11 by 11 pieces and sketch out the shape of the door. Then, cut the door shape out. After doing this, hot glue (or glue) both pieces together so they look like a thicker door.

Step 4: Side Sticks

Now get 4 small, thicker, pieces of cardboard. It doesn’t matter how thick or long they are. Use the picture above as a reference. I made each of mine 2 cm by 7 ½ cm. Stack them in pairs (see above) to make 2 thick pieces of cardboard. Now stack these together. Repeat this step.

Step 5: Cut Out the Door

Get the 11 by 11 (which I will now call the door frame), and make 2 small pencil marks above each side of the door. Then, carve both holes.

Step 6: Start Building

Get the door frame and hot glue it on your initial piece from the first step. You want to glue it about half an inch away from the border of the cardboard.

Hot glue both of the small (thick) cardboard pieces on either side of the door frame.

Step 7: Straw in the Door

Get two straws and cut them right below the bendable joint on the straw. Now push each piece of straw (face first), into each hole in the door frame. If the hole isn’t big enough, don’t be scared to make it a little bigger.

The second picture is the front view and the third is the backview

Step 8: Drawbridge Door Part One

Now get the 9 by 7 cm piece. Drill 2 SMALL holes on each side of the top of the piece. (Make sure that the 9 cm is the height and not the length)

Step 9: Drawbridge Door Part Two

Get 2 long pieces of string. On each end, put a dot of hot glue. Use the hot glue to make the end of the string spikey and hard. After it dries, put each piece of string through each hole of the 9 by 7 piece of cardboard.

After doing this, get the opposite end of each string (the side not in the cardboard), and knot them each once.

Get 2 small Hex Nuts and put them on the ends of each string. Knot the string around the nut a few times until it is secure. Now pull the string until each nut is right next to the holes.

Step 10: Attach the Door

Put each string fully through each straw on the doorframe until you can pull up the door.

Hot glue the straws against the doorframe so they aren’t sticking out. We are now calling the 9 by 7 piece the door. Using tape, get the end of the door right against the frame. If you do it successfully, you should be able to pull up the door and it should stay in place.

Step 11: Building the "Wheel" Part One

Get two round pieces of cardboard (see above), and make a small hole in the middle of each of them. Hot glue them together to make a thicker piece of cardboard. Repeat this step

Hot glue them to the right side of the pulley. Both of the pieces should be a good distance apart.

Step 12: Building the "Wheel" Part Two

Get a long, skinny piece of metal (a straightened paper clip is what I used) and bend it (in the shape above). Stick it through each of the pieces that we just hot glued.

Put a little bit of hot glue on both sides of the metal to stop it from falling out. Make sure not to hot glue the metal in place. It should still turn freely.

Step 13: Finish Assembly

Get both strings (from the straws) and knot them around the metal. Using the handle part (of the metal), spin it until the string is fully around the metal (See Above). (If you need to, add some support behind the doorframe).

Step 14: All Done!

To use the pulley, turn the metal piece on the "wheel" until the string starts being pulled. Make sure the string isn't caught on the straws or that will prevent you from pulling up the door. Now keep rotating it and the door will come up. Do this in the other direction to pull it back down. I hope you have fun making this!!!