Gears
Understanding Gears,
Fun with Gears
Ralph Pugh
24th October 2019
Gears
Topics to investigate and ask questions about :-
What are gears?
Where do we find gears in everyday life?
History of Gears - When were gears first used?
What are the different types of gears?
Fun with gears?
How do gears work?
How and why can we use gears for the Wind Turbine project?
What are gears? (click for answer to fade in)
Can you give me examples of gears, or things that use gears? (click for answer to fade in)
Gears are also used in Wind Turbines
A gear is a wheel with teeth that meshes together with other gears.
A wheel is just a lever, which is one type of simple machine.
Have you learnt about levers and simple machine at school?
Gears are defined by 2 important items, the gear diameter and number of teeth
Wind-up toys, Non-digital clocks, Drills, Bicycles, Car transmissions
Examples of gears
In an egg whisk, gears help to make light work of mixing by increasing speed. Each rotation of the large hand wheel (blue) makes the smaller whisk wheels turn around several times (red), giving a dramatic increase in speed at the blades.
Examples of gears
A hand drill works in a similar way to an egg whisk
The Hand is connected to the large gear, So the drill bit turns approximately 3.5 times faster than the users hand.
The purpose of the gears is to change direction of motion and increase the speed.
Examples of gears
A toy electric motor with a gear box.
The purpose of the gearbox is to change direction of motion and speed change.
The high speed of the motor shaft changed to a slow drive shaft speed.
History of Gears - When were gears first used?
Gears were already in use about 2300 years ago.
We know this from the writings and
drawings from that time.
Aristotle (384-322 B.C.)
Archimedes (287-212 B.C.)
Later Leonardo da Vinci (1452-1519)
gave us many drawings of gears.
Different types of gears
Bevel Gears
Rack and Pinion
Internal Gears
Planetary Gears
Worm Gear
Different types of gears
Bevel Gears
Rack and Pinion
Internal Gears
Worm Gear
Different types of gears - Fun with gears
Bevel Gears
Rack and Pinion
Worm Gear
Although they are not used much in industry, non-circular gears are fun.
Courtesy Clayton
Boyer design.
Different types of gears - Fun with gears
Weird gears!
Courtesy Clayton Boyer design.
How do gears work
We have seen from our examples that Gears come in various sizes and types.
We will talk about the Spur gear, it is the most common type of gear.
What is a gear used for?
Changing speed
Changing direction of motion (circular motion to linear motion, or clockwise/anticlockwise rotation)
Changing torque (the force needed to produce rotation)
Experiments with Gears - using the Makersmiths Gear Wall
Now we are going to do some experiments with gears
On the back of each gear is the number of teeth.
You are now going to connect two gear together, this is called a gear train.
What did you notice about the size of the teeth on the large and small gears? (fade in answer)
What did you notice about the direction of rotation of the 2 gears. (fade in answer)
What can you say about the relationship of number of teeth and number of gear revolutions?
We are going to do more experiments, we aim to show...
The teeth size are the same for both gears,
The direction of rotation of each gear is opposite
Number of teeth Gear #1 Number of rotations of Gear #2
——————————— = ——————————————-
Number of teeth Gear #2 Number of rotations of Gear #1
Gear Wall at Makersmiths
The gears on this gear wall can be turned by hand.
The gears can moved by sliding them, so they can be placed in to any connection pattern you like.
Two Gears
Please connect a 80 tooth gear and a 20 tooth gear.
Turn the 80 tooth gear, 1 turn clockwise,
How many times did the 20 tooth gear turn?
Which direction did the 20 tooth gear turn?
Experiments with Gears - using the Makersmiths Gear Wall
4 times
Anti-Clockwise
Three Gears
Now connect a 80, 50 and 20 tooth gears.
Turn the 80 tooth gear 1 turn clockwise,
How many times did the 50 tooth gear turn?
Turn the 50 tooth gear 1 turn
How many times did the 20 tooth gear turn?
Which direction did the 20 tooth gear turn.
Turn the 80 tooth 1 turn, how many times does the 20 tooth gear turn
So compare with the previous 2 gear test, the small gear also turned 4 times.
Experiments with Gears - using the Makersmiths Gear Wall
1.6 times
2.5 times
Clockwise
4 times
Gear Ratio
Gear Ratio is expressed this way:
(Driving Gear Teeth) : (Driven Gear Teeth)
What does ‘Driving’ and ‘Driven’ mean?
For a car - the driving gear is the one connected to the car engine
For a Wind turbine - the driving gear is the one connected to the wind turbine blades.
For a car - the driven gear is the one connected to the car wheels.
For a Wind turbine - the driven gear is the one connected to the wind turbine generator.
For our experiment- the driving gear is the one you are turning by hand.
Gear Ratio
12 : 36
Say "12 to 36 Gear Ratio"
What did you learn from the experiments?
Number of turns Gear number 1 will make
Number of turns Gear number 2 will make
Number of teeth for Gear number 1
Number of teeth for Gear number 2
How gears work in Wind Turbines
The below link shows an animated view of a Wind turbine
https://www.energy.gov/eere/wind/inside-wind-turbine
(scroll down to the animation of the wind turbine, may need to enable Flash in browser settings)
This website shows the inside of a wind turbine
What does a wind turbine do? It harnesses the power of the wind to generate electricity.
How does it work? The wind turns the blade, the blade shaft is connected to the generator, the generator turns and creates electricity.
The gearbox increases the speed of the generator.
Gears and the Wind Turbine
Let’s think about how to make as much energy as possible from the wind turbine.
For the Kid Wind project, The faster the generator turns, the more energy it will generate. If we generate more energy, we can power the light connected to the wind turbine.
See the results of an experiment on the next slide.
Who can tell me how can we make the generator turn faster?
Increase the wind speed - that is difficult !
Use a high Gear Ratio GearBox
So we want a large gear on the windmill blade side and a small gear on the generator side.
But there is a limitation to the size of a gear that we can put into the Wind Turbine, so we use many gear connected together.
Wind Turbine Generator - experiment
Here, the generator was
turned, and the voltage
produced by the
generator was measured
for different speeds.
Two gears on same axle
We can combine 4 gears together to give a higher gear ratio.
From the left. The first gear has 50 teeth, the small second gear has 10 teeth. The second gear is glued to the 3rd big 50 tooth gear on the same shaft. The 3rd big gear turns the 4th small 10 tooth gear.
One turn of the 1st gear causes the 4th gear to turn 25 times.
Gear Ratio=25:1.
For Gear 1 and Gear 2
= (50/10) x = 5 x
For Gear 3 and Gear 4
= = 10/50 = x 5
Gear 3 and 4 are on the same shaft, So =
So = 25 x
Review
Look back at the handout notes,
Can anyone tell me the name of the type of gear used in the Hand Drill, how about the Gear Wall?
What is a Gear Ratio.
What is a Gear Train.
What are the 3 properties of the way gears work.
Resources
Gear Generator - https://geargenerator.com/#200,200,100,6,0,0,0,1,1,10,2.5,4,20,0,0,0,0,0,0,1,3,926 This website allow you to create and connect gears on your computer and then animate the gear train.
You may wish to try this with your parents at home, and make your own gear train on your computer
Start off with a 10 tooth gear,
In the lower left window, Scroll down, Deselect Grid and Gear Guides.
Set the scale to 50 pixel per unit.
In the top left window, select Gears - ‘Add New’. In the bottom left window, change the number of teeth to 20.
In the top left window, Select Start/Stop - and the gears turn.
For more information on this App, see the YouTube video
https://www.youtube.com/watch?v=dBfvKPmGfwg