advanced design applications power and energy © 2014 international technology and engineering...
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Advanced Design ApplicationsAdvanced Design Applications
Power and EnergyPower and Energy
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Teacher Resource
Learning Cycle 3
Machine Components Machine Components Mechanical Advantage Mechanical Advantage
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
What is Mechanical What is Mechanical Advantage? Advantage?
What do you think it means?
Let’s define each word separately:
Mechanical
Having to do with machinery
Advantage
A benefit, gain, or profit
So what about mechanical advantage?
A benefit or gain when using machinery
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
What are the various What are the various components that we learned components that we learned about? about?
Threads
Gears
Bearings
Springs
Pulleys
Clutches
Brakes
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Which machine components Which machine components will allow us to have will allow us to have mechanical advantage? mechanical advantage?
Gears and Pulleys
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Gears Gears
What items can we change with gears?
Number of teeth, speed, and torque
Which of those items (when changed) can represent a mechanical advantage?
TORQUE
So if we have a gearset (two mating gears), how would we change the torque?
Change the teeth!
This is how we can calculate mechanical advantage!
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Gears – Mechanical Gears – Mechanical Advantage Advantage
This is how we determine mechanical advantage of gears:
M.A. of Gears
= Number of Teeth on driven gear
Number of Teeth on driving gear
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Gears – Mechanical Gears – Mechanical Advantage Advantage
Example 1:
You have a gear that has 15 teeth mating with a gear that has 47 teeth. The 15 tooth gear is the driving gear.
MA = 47/15 = 3.13
This means that we have gained 3.13 times more torque than what we started with.
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Gears – Mechanical Gears – Mechanical Advantage Advantage
Example 2:
You have a gear that has 17 teeth mating with a gear that has 51 teeth. The 51 tooth gear is the driver.
MA = 17/51 = 0.33
What happened here?
We went from a higher tooth gear to a lower tooth gear
This decreased our mechanical advantage!
NOTE: In order to increase mechanical advantage with gears, you must increase the number of teeth!
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Gears – Mechanical Gears – Mechanical Advantage Practice Advantage Practice
Practice 1 –
You have a driving gear of 11 teeth with a driven gear of 73.
Practice 2 –
You have a driven gear of 19 teeth with a driving gear of 7.
Practice 3 –
You have a driving gear of 55 with a driven gear of 13.
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Gears – Mechanical Gears – Mechanical Advantage Practice Advantage Practice
Practice 1 –
You have a driving gear of 11 teeth with a driven gear of 73. MA = 6.6
Practice 2 –
You have a driven gear of 19 teeth with a driving gear of 7. MA = 2.7
Practice 3 –
You have a driving gear of 55 with a driven gear of 13. MA = 0.24
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Gears Continued Gears Continued
What happens when you have a double or triple reduction?
We have 2 gearsets for
a double reduction
We have 3 gearsets for
a triple reduction
What do you do?
Find the mechanical advantage of each
Then multiply them together!
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Gears – Multiple Gears – Multiple Reductions Reductions
Practice –
Reduction 1 has a driving gear with 13 teeth and a driven with 41.
Reduction 2 has a driving gear with 17 teeth and a driven with 57.
What is the overall mechanical advantage?
Reduction 1 MA = 41/13 = 3.15
Reduction 2 MA = 57/17 = 3.35
Overall MA = 3.15 x 3.35 = 10.55
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Pulleys Pulleys
What are pulleys used for?
To change the direction of a force
To gain an advantage - (A mechanical advantage)
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Pulleys Mechanical Pulleys Mechanical Advantage Advantage
This is how we determine the mechanical advantage of pulleys:
Count the number of strings that are between moving pulleys!
It is important to count only the number of strings between moving pulleys.
If they do not move relative to one another, there is no mechanical advantage…
This is also called a block and tackle system…
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Pulleys Mechanical Pulleys Mechanical Advantage Example Advantage Example
The MA in this picture is 2!
It is taking half as
much force to lift the
weight as it should.
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Pulleys Mechanical Pulleys Mechanical Advantage Practice Advantage Practice
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Pulleys Mechanical Pulleys Mechanical Advantage Example Advantage Example
Gun Tackle: 2
Luff Tackle: 3
Double Tackle: 4
Gyn Tackle: 5
Threefold purchase: 6
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Multiple Component Multiple Component Systems Systems
What about systems that use gears and pulleys?
There is a greater mechanical advantage!
How is it calculated?
Calculate the gear mechanical advantage
Calculate the pulley mechanical advantage
Multiply them together
The product is the total mechanical advantage of the multiple component system
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
What can affect your What can affect your Mechanical Advantage? Mechanical Advantage?
There are other things that can affect mechanical advantage…
Friction (BAD!)
Levers (GOOD or BAD)
Complexity of device (BAD)
Misalignment (BAD)
Balance (GOOD or BAD)
Materials (GOOD or BAD)
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications
Your Mechanical Your Mechanical Advantage Advantage
In the solar car project, you will try move a car with a given motor.
You will be using gears to increase your mechanical advantage.
You must be sure that your car is properly balanced, utilizes your material effectively, and decreases friction.
What type of mechanical advantage will you have?
© 2014 International Technology and Engineering Educators Association STEMCenter for Teaching and Learning™ Advanced Design Applications