Download - Advanced Design Applications Power and Energy © 2014 International Technology and Engineering Educators Association STEM Center for Teaching and Learning™

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


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


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


Which machine components Which machine components will allow us to have will allow us to have mechanical advantage? mechanical advantage?

Gears and Pulleys


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!


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



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.



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!


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.


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


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!


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


Pulleys Pulleys

What are pulleys used for?

To change the direction of a force

To gain an advantage - (A mechanical advantage)


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…


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.


Pulleys Mechanical Pulleys Mechanical Advantage Practice Advantage Practice


Pulleys Mechanical Pulleys Mechanical Advantage Example Advantage Example

Gun Tackle: 2

Luff Tackle: 3

Double Tackle: 4

Gyn Tackle: 5

Threefold purchase: 6


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


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)


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?


Download - Advanced Design Applications Power and Energy © 2014 International Technology and Engineering Educators Association STEM Center for Teaching and Learning™

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