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Technology

Grade 7

Working with wind and water

Module 8

Making a water-wheel

INVESTIGATION

Problem situation

You are required to lift a certain number of drawing pins over a distance of 60 cm. Your power source is 4 ℓ of water that is supplied 1,5 m above the rotor in a 3 mm plastic pipe.

Design limitations

You may use any one of the following:

For the rotor:

  • a cork stopper or
  • two cardboard circles, each with a diameter of 20 cm or
  • an empty cotton reel

For the axle:

  • two toothpicks or
  • a knitting needle or
  • a 15 cm nail or
  • a long rounded pencil or
  • a kebab skewer

For the blades:

  • two egg boxes from which the “cups” have been cut out or
  • thick cardboard or
  • an empty 2 ℓ plastic cool drink bottle from which the blades can be cut or
  • a plastic margarine punnet from which the blades can be cut or
  • plastic teaspoons or
  • plastic ice-cream scoops (the flat kind)

Examples of water-wheels:

For the stand:

  • a ruler with wire that is fastened to the axle at both ends or
  • a piece of wood with string that is fastened to the axle or
  • an empty 2 ℓ plastic bottle with the bottom cut out or
  • a large plastic juice bottle or
  • a 2 ℓ plastic milk bottle

To supply the water source:

  • a jug that is marked in litres
  • a length of plastic tubing (1,5 m long, 3 mm in diameter) fastened to a funnel

To catch up the water: a large, flat plastic bowl

To lift the drawing pins (the hoisting apparatus):

  • string or
  • wool
  • a bowl with a flat bottom for the drawing pins
  • an eyelet

You will also need:

  • a pair of scissors
  • Prestik
  • plasticine
  • adhesive tape
  • a knife
  • glue
  • waterproof paint and varnish
  • a paint brush
  • a stapler
  • a pencil
  • a ruler
  • a stylus
  • a protractor (for positioning the blades)

Assignment 1:

To analyse a situation

[lo 1.5]

Let us analyse the situation and write a design proposal. (A design proposal is a short statement that could describe a probable solution.)

Complete the following:

I am going to design and make a ________that will be capable of lifting a

number of __________over a distance of _________cm vertically

by using some of the suitable material and tools that have been mentioned.

Design

Assignment 2:

To do research on hoisting apparatus and turbines

[lo 1.4]

Do research on hoisting apparatus (pulleys) and turbines (water-wheels) and draw or paste pictures of existing or antique machines. Briefly explain how they worked. (Find out more about the Egyptian shadoof or the water-wheels of Archimedes.)

Name the reference sources you made use of________________

Memorandum

Assignment 1

  • water wheel/crane (hoisting apparatus)
  • drawing pins
  • 60cm

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Source:  OpenStax, Technology grade 7. OpenStax CNX. Sep 10, 2009 Download for free at http://cnx.org/content/col11032/1.1
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