2.2 Making water-wheels

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