What are Gears?
Gears are wheels with teeth that slot together. When one gear is turned the other one turns as well.
If the gears are of different sizes, they can be used to increase the power of a turning force.
A turning force is called TORQUE.
The smaller wheel turns more quickly but with less force, while the bigger one turns more slowly with more force.
In the animation the Red Gear is turning the Green Gear.
We can say that the Green Gear is being driven by the Red Gear.
You will notice that the Green Gear is rotating in an anti-clockwise direction and the Red Gear is rotating in a Clockwise direction.
Two Meshing Gears: One gear is Driving the Driven Gear
Where can gears be found? Where are they used?
Gears are used in many engineered products like egg-whisks and food mixers, tin-openers, mechanical clocks, children’s toys, bicycles and cars and machines for example.
Gears can be found in so many things that you see every day.
Gears can be found in many machines in a workshop or a factory. In your home they are often an important part of mechanical devices.
In your car the gears help the driver to increase and decrease speed as he/she changes the gears with the gear stick. Some cars have automatic gear boxes that change gear automatically when the car engine is going slower or faster.
Spend some time looking around your own home to see if you can find a product that uses gears.
A Bicycle is an example of a mechanical device or a machine which has gears to help the rider to climb steep hills and to maintain a steady speed on flat roads.
Can you find images of gears on the internet?
Type in "what are gears used for?" or "Different Types of Gears"
Write down a few things that you find out.
Your Task is to Produce a really good quality coloured and fully labelled Drawing of two meshing gears. Spend time practicing drawing gears, watch both "Draw Gears Videos" below to help and guide you. Each video shows a different technique. Have a go at the Anagram, labelled drawing and word search games. Write a list of the Keywords you find in the word search game. Your labels should show the Direction of rotation, Driver Gear and Driven Gear. Additional labels to add are those Keywords found in the word search game.
Draw Gears Video 1
Draw Gears Video 2
What are Gears used For?
Gears are used to turn other gears.
Gears are made with different diameters or sizes.
Usually the larger the diameter the more teeth they have.
Gears are usually attached to other parts of a machine, like the wheel of a bicycle for example.
Gears are used to transfer motion and torque between the moving parts in a machine.
Gears are used to change the direction of movement of other gears and parts of a machine.
Gears are used to slow down or increase the speed of machine parts.
“TORQUE” is the name for a "turning" or "twisting" force.
How do Bicycle Gears Work?
Task 2: Try and complete all four parts of this task
1. Write down as many facts as you can about Gears, make a list of what have you found out about gears.
2. Watch the video "How do Bike Gears Work", and then write sentences to try and explain how the gears on a Bicycle work. Try and include the term "gear ratio".
3. Research the internet or magazines for "labelled drawings of Bicycle gears "
4. Produce a fully labelled drawing of Bicycle gears or even a whole bicycle. Add as many labels as you can. Use the games and quiz to help you.
WATCH THIS BBC VIDEO “Operation Awesome”
This video shows children meeting an Olympic hill-climb cycling champion to learn about gears on a bike. They find out why their bikes have eight gears, the difference between high and low gears, and when you should use them. The children experience that the lowest gear (gear one, the smallest gear) makes it easier to cycle but they go slower, whereas the highest gear (gear eight, the biggest gear) makes it harder to cycle but they go faster.
The video helps to explain how gears work. A model is used that has gears linked or meshed together in pairs on a board.
You will learn about the importance of the number of teeth on a gear.
Teeth on Gears, and Gear Ratio:
To understand about gear ratios you have to count the number of teeth on different sized gears, and also count the number of times each linked gear turns.
The children carry out a simple experiment on their bikes, to demonstrate the distance travelled for one turn of the pedal in different gears.
The bike with a high gear (high gear ratio) has a smaller gear wheel and moves further than the bike with a low gear (low gear ratio).
The bike with the low gear is easier to pedal.
The children then use their understanding of gears to decide which gear they will need to use to pull a piano uphill !!
Task 3. Complete this task after you have watched the video "Operation Awesome". Complete as many parts of the task that you can.
1.Use sentences to describe what experiments the children carried out.
2.Write sentences to explain how the experiments helped the children to understand how the gears on a bicycle work.
3.In the video a model was used to help explain gear ratios. What could use to make a model to help explain gear ratios. Examples of things you may find in the house are Bottle tops, Card, wheels, plastic gears, corrugated card board.
Make a model to show two "Gears" rotating using objects and materials you find in the house. This requires your imagination.
Calculating Gear Ratios
There are usually 3 front gears and 8 rear gears on a bicycle.
Each Gear has a different number of teeth.
It is this combination of gear teeth that allows the rider to ride up a steep hill with less effort required, and ride at a fast speed on a flat road with less effort required.
The gear ratio on a Bicycle is all to with understanding how many times the wheels will go around as the pedals are turned.
The front gears drive the rear gears
The fronts gears are known as the Driving Gear, and the rear gears are known as the Driven gear.
The gear Ratio can be calculated by divided the number of teeth on the Front Gear by the number of teeth on the Rear Gear.
Task 4 : Gear Ratios
Below are the Equations that Engineers use to calculate Gear Ratios.
There are also two worked examples of gear ratios, that show help you to understand more about the importance of gear ratios.
Make a neat copy of the equations and worked examples in your note book.
You will be asked to calculate Gear Ratios in Task 5, so you need to understand how to present and write out your answers.
Task 5, Calculate the Gear ratios
Play the Quiz to practise your understanding of gear ratios and then answer each of the following questions
Show ALL OF YOUR WORKING OUT, DO NOT JUST WRITE DOWN AN ANSWER.
Use the example calculations above to help you the write out your answer correctly.