1. Mechanisms Mechanisms Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Mechanisms

2. What is a Mechanism? In a machine - one part causing another to move
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
What is a Mechanism?
In a machine - one part causing another to move
Used to transfer or change speed, torque, force, type of motion and / or direction of motion.

3. Mechanisms - Change Direction
Meshed gears in a gear train always turn in opposite directions

4. Mechanisms - Change Movement
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Mechanisms - Change Movement
Rotary
Oscillating
Linear
Reciprocating

5. Mechanisms - Change Speed
Gear ratios compare the output (or driven gear) to the input (or drive gear)
Output : Input
Gear Ratios can be determined using number (n) of teeth on the gear or diameter (d) of the gear
If the output gear is larger than the input gear the speed will decrease
If the output gear is smaller than the input gear the speed will increase

6. Mechanisms – Change Force or Torque
A force is a push or pull in a straight line.
Torque is a push or pull in a circular direction or twisting motion

7. Simple Gear Train A. B. Input and Output Shafts parallel (A & B)
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Simple Gear Train
Input and Output Shafts parallel (A & B)
A – Ratio 1:1 [Output to Input]
Speed is constant
Torque is constant
B – Ratio 3:5 [Output to Input]
36 teeth : 60 teeth
Speed is increased
Torque is decreased
Flow of power - reversible
Motion - rotational to rotational
Direction – opposite
Driven / Output A.
Drive / Input
Driven / output
Drive gear is on the input shaft, driven gear is on the output shaft. B.
Drive / Input

8. Where Do You Find a Simple Gear Train?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Do You Find a Simple Gear Train?
Found in:
Watch
Sewing Machine
Motor
Watch gears
Two meshed gears will rotate in opposite directions

9. Simple Gear Train with Idler
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Simple Gear Train with Idler
Input and Output Shafts parallel
Ratio 1:1 [Output to Input]
Speed is constant
Torque is constant
Flow of power - reversible
Motion - rotational to rotational to rotational
Direction – same
Driven / Output
Drive / Input
Idler

10. Where Do You Find a Simple Gear Train with Idler?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Do You Find a Simple Gear Train with Idler?
Two meshed gears will rotate in opposite directions.
An Idler Gear allows the drive and driven gears to rotate in the same direction.
7. Found in - Paper Transport Rollers / Car Transmission

11. Bevel Gear Input and Output Shafts 90 degrees
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Bevel Gear
Input and Output Shafts degrees
Ratio 1:1 [Output to Input]
Speed is constant
Torque is constant
Flow of power - reversible
Motion - rotational to rotational
Direction – same

12. Where Can You Find a Bevel Gear?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Can You Find a Bevel Gear?
The bevel gear is used to change rotational motion at a 90˚ angle.
Found in:
Hand drill
Car Differential

13. Differential Gear Gears used – Bevel
Mechanisms
Gateway To Technology
Unit 2 – Lesson 2.2 – Mechanical Systems
Differential Gear
Gears used – Bevel
Used in – rear end of rear wheel drive vehicles
Purpose – Wheels spin at different speeds when turning

14. Worm and Wheel Input and Output Shafts 90 Degrees
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Worm and Wheel
Wheel
Input and Output Shafts Degrees
Ratio 1:24 [Output to Input]
Speed is decreased
Torque is increased
Flow of power – not reversible
Motion - rotational to rotational
Direction – same & reversible
Ratio - The input axle turns 32 times every time the output axle turns once.
Worm

15. Where Do You Find a Worm and Wheel?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Do You Find a Worm and Wheel?
Found in:
Tuning mechanism on string instruments
Electric motors
Winch
A worm is used to reduce speed and increase torque.

16. Leadscrew Speed is decreased Force is increased
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Leadscrew
Speed is decreased
Force is increased
Revolutions 4.75 (per design)
Flow of power – not reversible
Motion - rotational to linear
Direction – reversible

17. Where Do You Find a Lead Screw?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Do You Find a Lead Screw?
Changes rotary movement into linear movement
Significantly increases force
A person can put a little force into turning the handle to lift a heavy car
Jack
Vice
Increases force, not torque, because the output is in a linear direction.

18. Rack and Pinion Force increased Input Movement rotary Output Movement
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Rack and Pinion
Force increased
Input Movement
rotary
Output Movement
linear
With a Larger Pinion Gear -
the rack will move a longer distance
Flow of power - reversible
Motion - rotational to linear
Direction – same & Reversible
Pinion
Rack

19. Where Do You Find a Rack and Pinion?
Mechanisms
Where Do You Find a Rack and Pinion?
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Used in steering systems of cars to convert rotary motion of steering wheel to the side to side motion in the wheels.
Used to convert between rotary and linear motion.
Provides gear reduction to make it easier to turn the wheels.
Rack
Pinion

20. Universal Joint Angular Range > 90˚ and < 270˚ Ratio 1:1
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Universal Joint
Angular Range
> 90˚ and < 270˚
Ratio 1:1
Speed is constant
Torque is constant
Flow of power - reversible
Motion - rotational to rotational
Direction – same
Angular Range – Discuss the purpose of a universal joint as being flexible, for example, when your vehicle hits a pot hole the drive shaft doesn’t break.
Flow of Power – If you turn the output shaft, will the input shaft turn?
Direction of Travel – Can the handle be turned both clockwise and counterclockwise?

21. Where Can You Find a Universal Joint?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Can You Find a Universal Joint?
Drive shaft of vehicles
Power take-off
Universal joints are used to transmit rotary movement at an angle that is not 90°.

22. Chain Drive A - Shafts are parallel
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Chain Drive
A - Shafts are parallel
Ratio 30:18 or 5:3 [Output to Input]
Speed is increased
Torque is decreased
B – Shafts are parallel
Ratio 18:30 or 3:5 [Output to Input]
Speed is decreased
Torque is increased
Flow of power - reversible
Motion - rotational to rotational
Direction – same
Driven / Output A
Drive / Input
Drive / Input
Driven / Output B

23. Where Do You Find a Chain and Sprocket?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Do You Find a Chain and Sprocket?
Found in:
Bicycle
Motorcycle
Advantage of Chain and Sprocket over spur gears:
Transfer torque and speed over long distances

24. Belt Drive Input and Output Shafts parallel
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Belt Drive
Drive
Input and Output Shafts parallel
Ratio 1:1 [Output to Input]
Speed is constant
Torque is constant
Flow of power - reversible
Motion - rotational to rotational to rotational
Direction – open belt same
- crossed belt opposite
Driven

25. Where Do You Find a Pulley and Belt?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Do You Find a Pulley and Belt?
Found in:
Lawn mower
Car engine
BELTS
Belts instead of chains:
Quieter /Less expensive
Less durable / slip

26. Crank and Slider Speed / Force – N/A Input Movement rotary
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Crank and Slider
Speed / Force – N/A
Input Movement
rotary
Output Movement
reciprocating
Slider moves-
diameter of the crank
Flow of power – not reversible
Direction – same & reversible
Crank
Slider

27. Where Do You Find a Crank and Slider?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Do You Find a Crank and Slider?
Found in:
Steam train
Internal combustion engine
As the slider moves to the right, the connecting rod pushes the wheel round for the first 180 degrees of wheel rotation. When the slider begins to move back into the tube, the connecting rod pulls the wheel round to complete the rotation.

28. Cam and Follower Speed & Force N/A Input Movement rotary
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Cam and Follower
Speed & Force N/A
Input Movement rotary
Output Movement reciprocating
Follower moves up and down 1 time for every revolution of the crank
Flow of Power not reversible
Direction of Travel not reversible
FOLLOWER
CAM

29. Where Do You Find a Cam and Follower?
Mechanisms
Gateway To Technology®
Unit 2 – Lesson 2.2 – Mechanical Systems
Where Do You Find a Cam and Follower?
Found in:
Cam shaft
As a cam rotates, the flat follower is raised and lowered, converting rotary motion to reciprocating (back and forth) motion.
The cam pictured here would be reversible, as it is symmetrical.