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YR 11 TECH > Mechanical Control Systems > Flashcards

Mechanical Control Systems Flashcards

1
Q

What are the four types of motion?

A

Reciprocating ↔️ (jack hammer, yo-yo)
Linear ➡️ (toaster, firework)
Oscillating ↪️ (swing, pondulem, windscreen wipers)
Rotary ➰🔄 (wheel)

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2
Q

What is mechanical control made of? (eg. Key)

A

Input (turn key)
Process (motion transmitted by levers)
Output (snib withdrawn)

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3
Q

What is the input? (Mechanical control)

A

a force/Change of condition that will influence the output

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4
Q

What is the process? (Mechanical control)

A

Transfers or converts information provided by the input

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5
Q

What is the output? (Mechanical control)

A

Performs the desired task of the mechanism

A predictable end result produced by the input.

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6
Q

A mechanism…

4 points

A

Has an input, process and output
can change the direction of the force
Can change the size of the force
Can change the place where the force acts

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7
Q

Safety rules when using mechanical systems?

6

A
  • keep fingers clear of all moving parts
  • never attempt to remove an obstruction from a mechanical system in motion
  • keep moving parts clean to avoid obstruction or sticking
  • never try to slow moving parts with your hands
  • ensure machine guards are in place before using machinery
  • dress appropriately, wearing eye protection and avoid clothing that could get stuck.
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8
Q

What are levers used for?

A

To lift heavy weights with the least amount of effort possible

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9
Q

What is a class one lever?

A

Load⬇️- falcrum - effort⬇️

Trolly, to carry large package cases, the falcrum is the wheel

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10
Q

What is a class two lever?

A

Falcrum - Load ⬇️- effort⬆️

Wheel barrow, to lift tools and garden waste, load is in the centre of the barrow

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11
Q

What is a class 3 lever?

A

Load⬇️ - effort⬆️ - fulcrum

Fishing rod, fisherman catches fish which becomes the load at the end of the lever.

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12
Q

What does a cam do?

A

Changes the input motion, which is usually a rotary motion, to a reciprocating motion of the follower

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13
Q

What are the parts of a CAM?

A

The follower and the CAM profile.

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14
Q

Define one cycle

cams

A

One full rotation of cam

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15
Q

Define dwell

Cams

A

The part of the cycle where the cam stays at the same height

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16
Q

Define rise

Cams

A

The part of the cam that causes the follower to rise

17
Q

Define fall

Cams

A

The part of the cam that causes the follower to fall

18
Q

What are the 3 types of follower

Cams

A

•Flat follower

  • used in cars to open/close valves
  • used when a small force is required
  • used when you don’t need a detailed profile

•Knife follower

  • used when you have a detailed cam profile
  • the point will become rounder with wear and tear
  • bigger push will be achieved

•Roller follower

  • reduced wear and tear
  • used in aircraft engines
19
Q

What are the four different types of cam profiles?

A

•Pear

  • usually used on the shafts of cars
  • follower remains motionless for half the cycle of the cam and during the second half it rises and falls
  • RECIPROCATING motion

•Eccentric

  • circular cams produce smooth motion
  • used in steam engines

•Snail
-gradual rise and sudden drop

•Heart
-allow the follower to rise and fall with ‘uniform’ vilocity

20
Q

Describe belts

A
  • they are quiet in operation
  • require no lubrication and are relatively cheap to produce
  • disadvantages are that they can slip and can only be used if slip will not harm the operation system
21
Q

What are the 3 types of belts?

A

•Round belts

  • used for light machines that require small force or only turn 90°
  • used for CD players, light duty milling machines, vacuum cleaners, drills and power tools

•Toothed belts

  • belts with teeth cut into the inside of them
  • used in situations where slippage needs to be avoided for safety reasons
  • used for applications of constant speeds and timing
  • quietest option
  • used for car timing belts and car fan belts.

•V-belts
-larger are of belt is in contact with the pully
This gives greater force before the belt starts to slip because of the increased friction (eg. Pillar drills)
-the shaft speed can be controlled
-used for pillar drills

22
Q

Name the 5 types of gears

A 
Spur gears
Bevel gears
Worm and wheel
Rack and pinion
Sprocket and chains
23
Q

Explain spur gears

A
  • used to transmit rotary motion in the driver wheel to rotary motion in the driver pinion
  • mounted on parallel shafts
  • wind up alarm clock
  • washing machines
  • salad spinner
24
Q

Explain bevel gears

A
  • useful when the direction of a shaft’s rotation needs to be changed
  • transmits motions at 90°
  • teeth are cut on a cone instead of a dusk or wheel
  • hand drills
  • Hand whisks
  • shaft driven major cycles
25
Q

Explain worm and wheel gears

A
  • used to give large speed reduction
  • Worm drives the wheel
  • worm is like a threaded screw that will move the gear by one tooth for every revolution it makes
  • musical nstruments
  • small electrical devices + toys
  • band hose clamps
26
Q

Explain the rack and pinion gears

A

Change the rotary meeting turn of the pinion to the linear of the rack

27
Q

Explain sprockets and chains gears

A
  • Used to transmit rotary motion from one gear to another
  • only needs two gear wheels and a chain to transmit rotary motion
  • made up of a series of links joined with steel pins
  • the sprockets are profiled wheels with teeth that mesh with their chain
28
Q

What is a gear?

A

Wheels with teeth on the outer edge

Designed to mesh with other gears

29
Q

What is a gear train?

A

Two or more gears arranged to transmit rotary motion within a system.
A key feature is that the two adjacent gears (beside each other) will turn the opposite directions

30
Q

Equation for gear ratio

A

Number of teeth in the driven gear / number of teeth in the driver gear

31
Q

What is an idler gear?

A

A small gear which is positioned between the driver and the driven gear.
It does not effect gear ratios or speed of the other gears.
Used to make the dr gear and driven gears spin in the same direction

32
Q

What is a driver and driven gear?

A

Gears need a power source, which is often an electric motor.
The gear that is attached to the motor is a driver gear.
The gear meshing with this is known as the driven gear.

33
Q

In What type of gear does a shaft turn 90° to the driver?

A

Bevel gears

34
Q

Wheee are bevel gears used?

A

Hand drills

YR 11 TECH (2 decks)

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