Mevhanical Devices Flashcards
Mechanical devices
Machines or tools that have at least one moving part that performs some functions
Motion
That act of something being moved
Motionless
Something at rest
Mechanism
A series of parts that work together to control forces and motion in a desired way
Rotary motion
Motion that follows the path of a circle
Linear motion
Motion in a straight line
Speed (equation)
Distance/ Time
Oscillating motion
Motion that moves back and forth in a circular motion
Reciprocating motion
Motion that moves back and forth in a straight line
What does a Cam mechanism include?
-A cam attached to a shaft and a crank
-A follower that touches the cam and follows its shape
Cycle
One complete rotation of the cam
Dwell
When the cam rotates but the follower doesn’t move
Fall
The movement of the follower
Circular cam (3)
- Use an off-centre pivot to cause the follower to move up and down
- Produce a smooth up and down movement
- Used in steam engines
Pear cam (2)
- Remains stationary for half a rotation then rises and falls
- Used in carousel houses
Heart cam
- Allow follower too rise and fall at a regular speed
- 0 dwell time
- Used in some stop watches
Snail cam
- Causes follower to remain stationary for half a turn before gently rising and then suddenly falling
- Only works in one direction
- Often used at production lines
Types of follower (3)
- Flat
- Knife
- Roller
Drive gear
The gear that is moving
Driven gear
The gear that only moves due to the drive gear
Idler gear
A gear in between the drive and driven gear that ensures they go in the same direction
Drive belts
Used to transfer drive from one pulley to another
Lever
- A simple mechanism that controls and changes motion
Effort
The input forces
Load
The output forces
Mechanical advantage (equation)
Load/ Effort
Class 1 levers
- Act in a scissor or seesaw motion
- Load and effort at opposite sides with fulcrum inbetween
Class 2 levers
- Act in a wheelbarrow motion
- Effort at opposite end to fulcrum with load inbetween
Class 3 levers
- A pincer-like action like tweezers and tongs
- The load is at opposite end to the fulcrum with the effort inbetween
Equilibrium
When the effort and the load are equal
Arm length
The distance between the fulcrum and the force
