Mechanical Devises

Question 1

What is motion

Answer 1

• Motion is the action of something being moved
• Motionless is something at rest
• There are different types of motion which can be added together and even changed from one to another

Question 2

What are all the different types of motion

Answer 2

• Linear motion
  (movement in one direction along a straight line)
• Reciprocating motion
  (A repetitive back-and-forth or up-and-down linear action)
• Oscillating motion
  (A repetitive back-and-forth motion along a curved path)
• Rotary motion
  (Objects moving in a circular motion usually around a fixed axis)

Question 3

What are levers

Answer 3

They have two parts – a bar and a pivot also known as the fulcrum

Question 4

What is mechanical advantage

Answer 4

• Levers help provide mechanical advantage (MA)

Question 5

What is the equation for mechanical advantage (MA)

Answer 5

MA = Load/Effort
It can also be made into a ratio Load : Effort

Question 6

What is a First order lever (Class 1)

Answer 6

• Class 1 levers act in a seesaw or scissor action
• The load and effort are at opposite sides with the fulcrum positioned at any point between

Question 7

What is a Second order lever (Class 2)

Answer 7

• Class 2 levers act in a wheelbarrow action or that similar to a nutcracker
• The effort is at the opposite end to the fulcrum, with the load positioned between

Question 8

What is a Third order lever (Class 3)

Answer 8

• Class 3 levers have a pincer-like action seen with tweezers and tongs
• The load is at the opposite end to the fulcrum, with the effort positioned between

Question 9

What does equilibrium mean

Answer 9

• When the effort and the load are equal, equilibrium can be created in a mechanism

Question 10

What are linkages

Answer 10

Linkages are mechanisms that use rigid parts to:
• Change the magnitude of a force
• Change the direction of a force, or
• Transform it into a different motion

Question 11

What is a reverse motion linkage

Answer 11

• This changes the direction of the input motion
• If the input is pulled, the output will push
• The linkage uses a fixed central pivot

Question 12

What is a Parallel motion linkage

Answer 12

• Also known as push / pull linkage as it keeps the direction of the output the same as the input

Question 13

What is a Bell crank linkage

Answer 13

• Input direction is converted through 90 degrees
• It changes horizontal motion to vertical and vice versa
• Often found in steering and throttle mechanisms on vehicles

Question 14

What is a crank and slider

Answer 14

• Crank and sliders convert rotary motion into reciprocating motion and vice versa
• A linkage commonly found in engines to transfer the energy from pistons
• The slider is guided along a set path

Question 15

What is a treadle linkage

Answer 15

• Treadle linkages convert rotary motion into
oscillating motion and vice versa

Question 16

What are rotary systems

Answer 16

• Rotary systems drive mechanisms in machinery and equipment
• A rotating axle called a camshaft is used to drive, or is driven by, other mechanical components

Question 17

How are cams used in rotary sytems

Answer 17

• Cams are shaped pieces of material that are attached to the camshaft
• Cams change rotary motion into reciprocating motion through a follower

Question 18

How are followers used in rotary systems

Answer 18

• Followers rest on a cam and track its rise and fall
There are:
- flat followers
- knife-edged followers
- roller followers

Question 19

What are gear trains

Answer 19

• Cog wheels are meshed to create gear trains
• A simple gear train has a drive cog or ‘drive gear’ which rotates the ‘driven gear’

Question 20

How can gear ratios be calculated

Answer 20

• Gear ratios can be worked out by comparing the number of teeth on each gear
• If the drive gear has 20 teeth and the driven gear has 10, then the driven gear will rotate twice for each turn of the drive gear

Question 21

What is an idler gear

Answer 21

• An idler gear ensures that the direction of the drive gear and the driven gear are the same
• The idler gear sits between the two gears and directly transfers the drive

Question 22

What are pulleys and belts

Answer 22

• Drive belts are used to transfer drive from one pulley to another
• Belts rely on friction to grip the pully and are often made from rubber but also many other materials
• A pulley is often grooved to help increase the friction on the belt

Question 23

What are ‘block and tackle’ systems

Answer 23

• Block and tackle systems combine pulleys to liftheavy weights
• A rope is looped around pulleys in a block to form a tackle, to reduce the effort needed to lift
• As more pulleys are added, the lighter it becomes, although more rope needs to be pulled through