What it shows
A windmill pump turns the spin of its blades into an up and down stroke that lifts water. It shows how farmers use wind to irrigate fields with no electricity.
The science
The blades turn a crank, and the crank turns circular motion into back and forth motion of a rod. The rod pushes and pulls the syringe plunger, which draws water in on one stroke and pushes it out on the other through one-way valves. Each stroke lifts a small volume of water.
Materials
Cost: under Rs 500. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A multi-blade rotor from card or plastic bottle
- A cardboard crank disc and a stiff wire connecting rod
- A large syringe (20 ml) with two small tubes
- Two simple one-way flaps made from balloon pieces
- A bottle as the water tank
- A wooden frame and a table fan
Safety
For this project: An adult must cut wire and plastic. Keep fingers away from the moving crank and blades. Do not use a mains fan near water; place water below and use a battery fan.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Build the wooden frame and fix the rotor on an axle with a crank disc.
Fix the connecting rod from the crank pin to the syringe plunger with a loop of wire.
Fit a one-way flap on the inlet tube and another on the outlet tube.
Place the inlet tube in the lower water tank and the outlet over a higher container.
Turn the rotor by hand to test that the water is drawn and pushed.
Place a fan one metre away and count turns per minute.
Measure the water lifted in two minutes.
Repeat at two fan speeds and compare the water lifted.
What you should see
Each turn of the rotor lifts a small amount of water to the higher container, and faster wind gives more water per minute. A table of turns and volume shows the relation.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What does the crank do?
It changes circular motion to back and forth motion.
2Why are one-way valves needed?
They stop water flowing back.
3What fuel does the pump use?
None, only wind.
4How would a bigger pump be better?
A larger piston lifts more water per stroke.
Take it further
Change the crank radius and see how the stroke length and flow rate change.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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