REMEMBER: Machines don’t change the work but make the work easier!

Basic Mechanics and Machine Design

Part I: Mechanics

Common SenseWho has it?

FarmerJunk Bond Investor

Darwin Award Winner

What does it take to have common sense?

1) To observe the world around you.

2) Take note of how things behave.

3) Apply all your learned knowledge to a new situation.

WHAT DO YOU KNOW ABOUT MECHANICS?

More than you think.

What about book learning?

WorkWhat does work feel like?

Work = Energy = Exerting a force through a distance

Is lifting a book work?

Is holding the book at some level work?

What am I working against?

NEWTONS LAWS

1) Inertia: Things in motion tend stay in motion, Things at rest tend to stay at rest.

2) F =ma: Force = Mass x Acceleration

3) For every action there is an equal and opposite reaction

HE’S GETTING BORING!!!Math Optional

3 Simple Machines

1)

2)

3) Wheel

Inclined Plane (wedge, ramp)

Lever

All other mechanical configurations are a combination of these.

Examples?

Inclined Plane

Why build a bank barn?

How does this inclined plane work?

A ramp spreads out the time over which a force acts thereforeyou need less power.

Makes work easier.

This is a Bank Barn

Trade off Distance for Time

Power = Work / Time (rate of doing work)

Work = Energy = Force X Distance

3) Hiking up a hill vs. scaling a cliff

2) Loading Ramp vs. lifting a barrel straight

1) Stairs vs. climbing a ladder

Realize same amount of work but less power!

The examples below all require same total energy.

Lever

Why use a lever?

What is equilibrium?

All forces acting on an object equal zero. -like a see-saw

-makes work easier, more force

Mechanical Advantage

F1 x L1 = F2 x L2

Fulcrum = Pivot Point

What is the Mechanical Advantage of the Wheelbarrow?

Approx. 3 to 1

M.A. = L2L1

Backhoe

Which position has more mechanical advantage for digging?

Which position is easier to dig with? (stick out your hand and try it)

Longer Distance, more M.A. for ground to lift Backhoe

Pivot is front wheel

Wheel

Why use a wheel?

VS

-easier than fighting friction by sliding-easier than lifting/carrying an object (Your back is less sore)

Width, Pressure, Friction, Traction

Pulleys and Gears

Ratios

M.A. = Large Circumference

Small Circumference

Gears

M.A. = 24 teeth to 8 teeth to = 3 to 1 Ratio

If one gear has 24 teeth and the other 8 teeth, what is the mechanical advantage?

(This could be in inches instead of teeth.)

Combinations of Machines I

Combinations of Machines II

Machine Design

Part II: Lego Design

AND REMEMBER: K.I.S.S.

NOW USE THAT COMMON SENSE:1) To observe the world around you.

2) Take note of how things behave.

3) Apply all your learned knowledge to a new situation.

Strength, Durability

Strong Design

Strong Design

Motors

Transmission / Gear Train

Steering

Differential SteeringPivot Steering

Differential Steering

Minimize Friction

Strong Design

Flexible(but durableEnough)

3 Points For Stability

Increased Accuracy with Ratios1 to 3 Gear Ratio

Inaccuracy, sensor is loose

Touch sensors

Light Sensors

Differential

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HAPPY FARMING