Mechanical

Question 1

Types of motion

Answer 1

Reciprocating - back and forth
Oscillating - back and forth on a curve like a pendulum
Rotary - circular
Linear - straight in one direction like train

Question 2

Class 1 lever

Answer 2

Fulcrum in the middle load on one end and effort on the other e.g see saw

Question 3

Class 2 lever

Answer 3

Fulcrum at one end with load in the middle and effort on the end e.g wheelbarrow

Question 4

Class 3 lever

Answer 4

Fulcrum at one end with effort in the middle and load at one end e.g tweezers

Question 5

Mechanical advantage formula for levers

Answer 5

Mechanical advantage = load / effort

Question 6

Velocity ratio formula for a lever

Answer 6

Velocity ratio = distance moved by effort / distance moved by load

Question 7

Bell crank

Answer 7

1 immovable pivot and 2 movable pivots on a quarter circle shaped crank

Creates a perpendicular movement to the input

Question 8

Reverse motion linkage

Answer 8

One immobile pivot in the centre of a bar with two moving pivots at each end

Reverses motion

Question 9

Cam definition

Answer 9

Convert a rotary movement to a reciprocating/oscillating movement

Question 10

Answer 10

Pear shaped cam

Creates a slow rising and falling motion with a stationary period in between

Question 11

Answer 11

Eccentric cam

Off centre circle creates a smooth rising and falling motion

Question 12

Answer 12

Snail cam or drop cam

Creates a slow rising action then a sudden falling action

Question 13

Roller follower

Answer 13

Pros - low friction so can be used for high speeds
Cons - can jam and cant bear heavy loads

Question 14

Knife edge follower

Answer 14

Pros - low friction, precise

Cons - wears quickly

Question 15

Velocity ratio formula for pulleys/belts

Answer 15

Velocity ratio = driven pully diameter / driver pully diameter

Question 16

Output speed formula for belts/pulleys

Answer 16

Output speed = input speed x velocity ratio

Question 17

Velocity ratio formula for gears

Answer 17

Velocity ratio = number of teeth on driven gear / number of teeth on driver gear

Question 18

Compound gear train

Answer 18

When simple gear trains wont give a large enough change in speed and it uses multiple gears on one shaft

Question 19

Velocity ratio formula for a compound gear train

Answer 19

VR = VR of gears A+B x VR of gears C+D

Question 20

Idler gear

Answer 20

Doesn’t change speed of gears only means that the two gears either side spin the same direction therefore idler gears are removed from calculations

Question 21

RPM

Answer 21

Revolutions per minute - the amount of times a gear can fully rotate around its axis in a minute

Question 22

RPM calculation formula

Answer 22

Output speed (output RPM) = input speed (input RPM) / gear ratio

Question 23

Rack and pinion

Answer 23

Uses a gear and a rack to change rotary movement to linear
The number of teeth is given in teeth per meter (TPM)

Question 24

Output movement of a rack and pinion formula

Answer 24

Output movement = number of teeth on pinion / number of teeth on track per metre x 1 metre

Question 25

Bevel gear

Answer 25

Allows rotary motion to be transmitted through 90 degrees and if they are the same size they are called mitre gears