Tower Crane

(2020-2021) 5th

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Purpose

The purpose of this experiment is find out which direction can the crane lift a heavier load?

Hypothesis

I think the crane can lift heavier loads if the string hands closer to the tower then the crane can’t lift that much weight if the load is positioned at the end of the jib.

Materials

• Small container 12. scissors
• String 13. glue
• Thick cardboard 14. pencil
• Duct tape 15. paint brushes
• Toothpicks 16. Bottle cap
• Wooden skewer 17. Marbles
• Modeling clay 18. Paint
• Two tall paper cups 19. ruler
• Clothespin 20. sand
• Large plastic bottle full of water
• Large flower pot

Design/plan

b

Procedure

• Use your ruler to draw a 14 in line on a cardboard, near the top. Make pencils 2 in and 6 in from left end of the line.
• Add four vertical lines a 1 ½ in line at the left end, two 3 in line and a 1 ¼ in line. Join up the end of the four vertical, cut out and make another one.
• On one of the shapes, add a dot along in the middle of the rectangular section. Draw dots along the edges, and stack the two pieces of cardboard together. Carefully push toothpicks through both pieces of cardboard,using the dots as guide.

4 . Remove the toothpick in the middle of the rectangular section. Dab glue on the tips of the toothpicks and let the glue dry. Turn the jib over and do the other side.

5. Draw a rectangle on a cardboard 3 in by 4 in to make the base of your jib. Turn a jib upside down and glue it.

6. To make a crane your crane’s handle, draw two circles using the bottle cap and cut out.

7. Use a wooden skewer to poke a hole in the middle of each circle . Then make extra hole halfway between the middle and the edge in one of the circle.

8. Measure and cut the skewer into a 3 ½ in length and a 1 ½ in length. The longer piece goes into the center. The shorter goes into the hole at the side. Glue them on both sides.

9. Push the long piece of the skewer through the hole in the middle of the jib’s rectangular section and out the other side. Glue the second circle to the end of the skewer.

10. Turn the jib upside down and glue the bottom of the paper cup to the base.

11. Paint the jib, paper cup and toothpicks.

12. Cut 3ft of string and tie one end to the middle of the crank, carefully poke the long end through the small container. Tie a knot.

13. Make two thick of modeling clay and sandwich them together over the toothpicks at the rear of the jibs.

14. Stand the bottle in the flowerpot and packsand around it.

15. Place the second paper cup over the bottle and secure in place with duct tape.

16. Place the marbles inside the lip of the base of the upturned cup.

17. Mount the crane’s jib on the tower by placing the painted cup on top of the marbles.

18. Attach the container with a load inside it to the clothespin and raise or lower it by turning the handle. See how heavy a load your crane can lift depend on how far out of the crane arm it is.

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Record on the data sheet .

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Conclusion

My hypothesis was accepted. Large loads are lifted close to the tower ; see data table position C can lift 1.6lbs and small loads are lifted farther out ; position A can lift up to 0.8lbs. The tower crane can lift huge loads without falling because they can control how far along the jib the load is positioned. Any load pulls down on the jib, creating a turning force of torque (The torque equals the load’s weight multiplied by its distance from the tower). They don’t need to be perfectly balanced because the crane is also anchored to the ground.

Real World Connections

In the real tower crane, a steel cable hangs from a mobile trolly that can move back and forth along the jib. By varying the position of the trolly, the operator can change the torque created by the load. In your crane, threading the string over different toothpicks does the same thing. A tower crane can lift up to about 22 tons as much as 20 cars.

Improve/Test

See how tower crane work without toppling over.

Try treading the string so it hangs closer to the crane tower. Can the crane lift more now ? If you make the wheel of the crane handle bigger, so that your handle moves in a bigger circle. Why not try the scaling up the design so that you can lift a heavier load, or see what happens if you increases or decrease the weight of the counterweight. Perhaps you could use skewers instead of toothpicks, and use a double thickness of cardboard for extra strength.