Mechanical devices Flashcards
1
Q
4 different types of motion
A
- Linear motion: something moves in a straight line in ONE direction. E.G: a train along a track
- Rotary motion: something moves around a point in ONE direction. E.G: a wheel
- Reciprocating motion: something has a repetetic back and forth motion in BOTH directions. E.G: a pump
- Oscillating motion: a curved backwards and forwards motion around a point in BOTH directions. E.G: a pendulum
2
Q
What are the different parts of a lever?
A
- Effort: the force applied by the user (the input)
- Fulcrum - where the lever pivots
- Load: the weight that needs to be moved
3
Q
Different classes of levers
A
- First class: Effort, Fulcrum, Load (EFL) - crowbar
- Second class: Effort, Load, Fulcrum (ELF) - wheelbarrow
- Third class: Fulcrum, Effort, Load (FEL) - tweezers
4
Q
Reverse motion linkages
A
- Output is in the opposite direction of the input
5
Q
Parallel motion linkages
A
- Output is in the same direction as the input
6
Q
Bell crank linkages
A
- Direction of output is 90 degrees rotated from the input
7
Q
Crank and slider linkage
A
- Change rotary motion into reciprocating motion
8
Q
Treadle linkage
A
- Uses a rotary input to turn a crank on a fixed pivot
9
Q
What is a cam and a follower?
A
- Cam: a wheel attached to a crankshaft that rotates
- Follower: a bar that followes a cam around its circumference
10
Q
Different types of cams
A
- Circular: off-centre pivot causes follower to move up and down
- Pear: follower remains stationary for half a turn then slowly rises and falls
- Snail: follower gently rises then suddenly falls
- Heart: rises and falls steadily with a uniform velocity, no stationary period
11
Q
Different types of followers
A
- Flat: cope well under load but not accurate and have lots of friction
- Knife: low friction and very precise but wear very quickly
- Roller: low friction, accurate and can withstand high loads but expensive to produce
12
Q
How to calculate required effort in pulley?
A
- Effort = load / number of pulleys
