REMEMBER: Machines don’t change the work but make the work easier! Basic Mechanics and Machine Design Part I: Mechanics
Common Sense Who has it? Farmer Junk 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?
Work What 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 therefore you 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. = L2 L1
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
Motors
Transmission / Gear Train
Steering Differential Steering Pivot Steering
Differential Steering Minimize Friction Strong Design Flexible (but durable Enough) 3 Points For Stability
Increased Accuracy with Ratios 1 to 3 Gear Ratio Inaccuracy, sensor is loose
Touch sensors
Light Sensors
Differential EXTRA CREDIT HAPPY FARMING