Title: Basic Mechanics and Machine Design
1Basic Mechanics and Machine Design
Part I Mechanics
REMEMBER Machines dont change the work but
make the work easier!
2Common Sense
Who has it?
Junk Bond Investor
Farmer
Darwin Award Winner
What about book learning?
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.
3Work
What does work feel like?
Is lifting a book work?
Is holding the book at some level work?
What am I working against?
Work Energy Exerting a force through a
distance
4NEWTONS 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
53 Simple Machines
Examples?
1)
Inclined Plane (wedge, ramp)
2)
Lever
3)
Wheel
All other mechanical configurations are a
combination of these.
6Inclined Plane
This is a Bank Barn
Why build a bank barn?
Makes work easier.
How does this inclined plane work?
A ramp spreads out the time over which a force
acts therefore you need less power.
7Trade off Distance for Time
Work Energy Force X Distance
Realize same amount of work but less power!
Power Work / Time (rate of doing work)
The examples below all require same total energy.
1) Stairs vs. climbing a ladder
2) Loading Ramp vs. lifting a barrel straight
3) Hiking up a hill vs. scaling a cliff
8Lever
Why use a lever?
-makes work easier, more force
What is equilibrium?
All forces acting on an object equal zero. -like
a see-saw
9Mechanical Advantage
F1 x L1 F2 x L2
L2 L1
M.A.
Fulcrum Pivot Point
What is the Mechanical Advantage of the
Wheelbarrow?
Approx. 3 to 1
10Backhoe
Pivot is front wheel
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
11Wheel
VS
Why use a wheel?
-easier than fighting friction by sliding -easier
than lifting/carrying an object (Your back is
less sore)
12Width, Pressure, Friction, Traction
13Pulleys and Gears
Ratios
Large Circumference
M.A.
Small Circumference
14Gears
If one gear has 24 teeth and the other 8 teeth,
what is the mechanical advantage?
M.A. 24 teeth to 8 teeth to 3 to 1 Ratio
(This could be in inches instead of teeth.)
15Combinations of Machines I
16Combinations of Machines II
17Machine Design
Part II Lego Design
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.
18Strength, Durability
Strong Design
Strong Design
19Motors
20Transmission / Gear Train
21Steering
Differential Steering
Pivot Steering
22Differential Steering
3 Points For Stability
Strong Design
Flexible (but durable Enough)
Minimize Friction
23Increased Accuracy with Ratios
1 to 3 Gear Ratio
Inaccuracy, sensor is loose
24Touch sensors
25Light Sensors
26Differential
EXTRA CREDIT
HAPPY FARMING