1. Mechanisms and Movement

2. What is a Mechanism?
A mechanism takes an input motion or force and creates a desired output motion or force
Simple machines or a combination

3. What are Simple Machines?
Simple machines are very basic devices that are used to make things work
Often, these simple machines are put together to make more complicated machines

4. The Six Machines Lever Inclined Plane Wheel and Axle Wedge Pulley
Screw

5. Lever A lever is an arm that is on a pivot
This pivot is called a “fulcrum”
The force that is being used to move the lever is called the “effort”
What the lever is moving is called a “load”
The distances between the effort and load to the fulcrum determine how easy or hard it will be to move the load.

6. Classes of Levers
A First Class lever has the fulcrum in the middle, and the effort and load on either end
A Second Class lever has the load in the middle, and the effort and fulcrum on either side
A Third Class lever has the effort in the middle and the load and fulcrum on either side

7. Mechanical Advantage Ratio between load and effort moments
MA>1 = gain in output force
Gain in output force = loss in output motion

8. Velocity Ratio VR = ratio of distance moved by effort and load
MA is gained through loss of VR
VR is gained through loss of MA
VR>1 means that the effort is moving a greater distance than the load

9. Inclined Plane The inclined plane is a ramp
It is used to make it easier to push something up and down a distance.
How hard is it to move a heavy brick up a 10 foot high wall?
How hard is it to move a heavy brick up a gradual slope, or inclined plane?

10. Wheel and Axle
Wheels are circular, and axles go through their middle to allow them to spin
These simple machines allow for uniform rotation
Off-center wheels are called cams and affect motion depending on their shape

11. Wedge A wedge is a special type of inclined plane
A wedge acts to push apart material
A fork and knife are both wedges
Wedges are used to join things together
Nails

12. Pulley A pulley is used to lift heavy things.
A rope or cable is set around a wheel and axle. By pulling on the rope around the wheel, whatever the other end of the rope is attached to will move. This is a simple pulley.
Many pulleys in sequence are called compound pulleys.

13. Screw
A screw is a special inclined plane that is wrapped around a central shaft
Screws are useful to make really strong connections between materials
Screws are also used to slow down a descent without taking up the space of a straight ramp (spiral staircase)

14. Kinematics Kinematics is the study of movement in a mechanical system
Does not regard forces or masses, just movements

15. Kinematics
The individual elements that are used in a mechanism are called members or links. One end is fixed to a point.
All links are held together by elements called joints.
A combination is called a “kinematic chain.”
If the system is incapable of movement, it is no longer a mechanism, but rather, a structure

16. Motion There are a number of different types of motion.
These types of motion can be converted into one another
Mechanisms transfer this motion

17. Linear Motion Straight-line motion that occurs in one direction
CD drive on a computer
A drawer

18. Reciprocal Motion Back and forth linear motion
Piston in a combustion engine
Needle in a sewing machine

20. Rotary Motion Movement around a center point or axle
Very common and very efficient

21. Oscillating Motion Back and forth movement in an arc A clock pendulum
Windshield wipers

22. Linkages Linkages transmit motion or force to a desired location
Change direction
Change length
Split motion or force over multiple paths

23. Bell Crank Changes direction of force 90 degrees Brakes on a bike
Used to ring church bells
Pulling down on a rope would swing bell

25. Reversing Linkage
Changes direction by 180 degrees

26. Parallel Linkages
Allows parts to move in a parallel relationship

27. Crank and Slider

28. Treadle Linkage Changes oscillating motion to rotary motion
Came from foot-operated pedals for sewing machines and other tools

29. Toggle Linkage “Snaps” in place
Locking pliers
Vice grips
Locking legs of a foldable table
Additional force is needed to unlock the toggle linkage