GCSE Engineering Theory work (14 x 1 hour Lessons) • There are 36 GCSE Engineering lessons this term that you would received in school under normal circumstances.

• You have been set a 22 hour NEA project (similar to what you will be examined on next year that forms 40% of your final grade). This is compulsory and must be handed in on your return to school. Please see other PowerPoint for this information.

• In this PowerPoint you will find 14 x 1 hour lessons (including questions that must be completed). The exam you will sit next June will count for for 60% of your final grade.

• Each set of questions shows you where a lesson starts and finishes.

• You are all different abilities so how long you take depends on your working speed. For some, this will take longer than 14 hours- work at your own pace.

• Work your way through these chronologically. Write the answers on a separate PowerPoint or Word document as you prefer. These will be submitted on your return to school.

• Watch the videos an read the information before answering questions. Most answers come straight from these 2 sources, but you may need to do additional research using google.

Best of Luck and enjoy your summer as best you can. Tricky times, but lock down won’t last forever.

Mr Corkin and Mr Kennedy

Cams and Followers

A CAM changes the inputmotion, which is usuallyrotary motion (a rotatingmotion), to a reciprocatingmotion of the follower.

They are found in manymachines and toys

KEY PHRASES

ONE CYCLE One rotation/revolution of the cam.

DWELLWhen the cam rotates but the followerdoes not rise or fall.

THE RISEThat part of the cam that causes thefollower to rise

• In diagram 1 the cam is in a vertical position and it slow rotates in an anticlockwise direction. As it rotates the follow drops down.

• In diagram 4 the follower is in its lowest position. • The cam continues to rotate and the follower begins to

rise in diagrams 5 and 6 until it returns to its original position

There are different types offollower but they all slide or rollon the edge of the cam. Varioustypes are shown below.

The cam seen below is a 'pear shaped cam'. As the handle is turned the cam profile rotates.

The model moves forwards and backwards as a result.

The movement is gentle although the faster the handle is turned the faster the movement of the model becomes.

Cams Questions 1 : Lesson 1 (1 hour)

1. Explain what is a Cam?

2. Explain what is a follower?

3. What is does ‘one cycle’ mean?

4. What does ‘the rise’ mean?

5. What does ‘the dwell’ mean?

6. Explain how the cam and follower mechanism works?

7. Name( and get photos) of products that use cams and followers?

8. Explain how this mechanism can be used in an engineering context?

Cams Questions 2 : Lesson 2 (1 hour)

Look at the Automata . Explain what would happen to the figure if you put each different cam in :

Example: Egg shaped CAM:

1) Egg shaped CAM Answer. In this automata when you turn the crank with a egg shaped CAM inside nothing happens to the figure for half the revolution. This is known as the dwell . Therefore the crank rotates (rotary motion) and the figures leg doesn’t move for this period. Then the crank rotates the pointed part (rotary motion) and this causes the leg to go up and down (reciprocating motion). This is known as the rise. The figure move forwards and backward lifting one leg. The automata turns rotary motion into reciprocating motion.

4 Types of motion

• https://www.youtube.com/watch?v=OfOQKv1mjks

Cool motions that combine many mechanisms!!• https://www.youtube.com/watch?v=ruiQR3CZE7k

Motions Questions 1 : Lesson 3 (1 hour)

1. Explain what a mechanism is and does?

2. What is meant by mechanical advantage?

3. Explain what motion is ?

4. Explain what oscillating motion is and used for?

5. Explain what a rotary motion is and used for?

6. Explain what a linear motion is and used for?

7. Explain what a reciprocating motion is and used for?

Hint: Use photos and real world examples for each.

At least separate PowerPoint slides would be best

www.Technology Student.com

• http://www.technologystudent.com/cams/link1.htm web site

• https://www.youtube.com/watch?v=xh1jTtAxs_Q Linkages video

Linkages Questions 1 : Lesson 4 (1 hour)

1. Explain what linkages are

2. Explain what a parallel linkages is and does?

3. Explain what a reverse motion linkage is and does?

4. Explain what a bell crank motion is and does?

Hint: Use photos and real world examples for each.

At least 3 separate PowerPoint slides would be best

Mechanical Understanding Questions 1 : Lesson 5 (1 hour)

1. What are mechanisms design to do?

2. What are the four main types of motion?

3. Describe the different ‘orders of lever’ and provide exampled of these

4. What are linkages and what do they do?

5. Describe push/ pull levers

6. How do you change the magnitude of these levers?

7. Describe bell crank levers

8. How do you change the magnitude of these levers?

9. What are gears and what do they do?

10. What is a gear train?

11. What is meant by the term ‘gear ratio’?

12. Copy down both formulae to calculate gear ratios and output speed

13. Copy the example worked out to aid your revision notes

Mechanical Understanding Questions 1 : Lesson 6 (1 hour)1. What are rotary systems?

2. What is a pulley and what are they used for?

3. What is a one pulley system used for?

4. What are 2+ pulley systems used for?

5. What does a belt drive do- give an example of where one was used.

6. What is the formula to calculate the velocity ration?

7. What is the formula to calculate the output speed?

8. What two parts make a cam mechanism?

9. What are the 4 different types of cams?

10. How can the magnitude of output motion be changed?

Gear trains

• Gears can be found in many machines in a workshop or factory and athome they are often an important part of mechanical devices. In a carthe gears help the driver to increase and decrease speed as he/shechanges the gears with the gear stick.

Simple Gear Train

1. Large Gear driving a small gear results in increased speed but decreased torque

2. A smaller gear driving a larger gear results in decreased speed and increased torque

Torque is a twisting or turning force that tends to cause rotation around an axis, which might be a centre of mass or a fixed point

Torque is the turning force about a point. This is also known as a moment or couple The SI unit for torque Is Newton metre (Nm).

1.0m0.5m

A B

If a force of 1 Newton is applied at point A, the torque applied to the beam about the pivot point is 0,5 Nm.

This is a good example of a ‘gear train’. A gear train is usually made up of two or more gears. The driver in this example is gear ‘A’. If a motor turns gear ‘A’ in an anticlockwise direction;Which direction does gear ‘B’ turn ?

Which direction does gear ‘C’’ turn ?

Does gear ‘C’ revolve faster or slower than gear ’A ? - explain your answer.’

Gear Ratio: Learn!

The Gear or Velocity ratio of a simple gear train is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driver gear

Gear Ratio = Number teeth driven gear

Number of teeth driver gear

Video Explaining Gears

• https://www.youtube.com/watch?v=OaujUXfDVGE

Gears Questions 1 : Lesson 7 (1 hour)

1. What do gears do?

2. What is a spur gear?

3. Explain what a gear train does?

4. Explain what a simple gear train is?

5. Explain torque?

6. What does a larger gear driving a smaller gear achieve?

7. What does a smaller gear driving a larger gear achieve?

8. What is the driven gear?

9. What is the driver gear?

10. What is the idler gear?

11. What is the calculation for working out gear ratio?

Gears Questions 2 : Lesson 8 (1 hour)

1. Simple gear train

2. Idler gear

3. Compound gear train

4. Bevel gears

5. Mitre gears

6. Rack and pinion

7. Worm and worm wheel gears

8. Helical gears

Chain and Sprocket

Friday, 24 April 2020

Think about the levers….

Easier

Hard

What happens to the number of teeth when the radius doubles?

Gears • Larger gears will:• Have a larger moment

• Turn slowerLOW GEAR: • Low speed• High

turning effect

HIGH GEAR:• High

speed• Low

turning effect

GearsDriver Driven

LOW GEAR HIGHGEAR

LOW GEAR: • Low speed• High

turning effect

HIGH GEAR:• High

speed• Low

turning effect

GearsQuick Tip

• Gears in line change direction with each gear wheel

• If faced with a question like this, draw in the directional arrows for each cog!

Chain and Sprocket

• Everyone has seen a bicycle or used one and noticed that it is driven by a large driver gear wheel with pedals attached.

• Smaller gears at the back are driven round, in turn driving round the back wheel.

• As the back wheel turns the bicycle moves forwards.

• Gears driven by chains are used in machinery, motorcycles, in car engines and have many more applications.

Chain and Sprocket• A chain is made up of a series of links with

the links held together with steel pins.

• This arrangement makes a chain a strong, long lasting way of transmitting rotary motion from one gear wheel to another.

• Chain drive has one main advantage over a traditional gear train.

• Only two gear wheels and a chain are needed to transmit rotary motion over a distance.

• With a traditional gear train, many gears must be arranged meshing with each other in order to transmit motion.

Chain and Sprocket

• When working out gear / velocity ratio chain driven gears it must be remembered that the chain is ignored.

• This means the you simply find out the teeth per gear wheel use the same method of calculating as you would with a normal, meshing gear

Gear Ratio: Learn!

The Gear or Velocity ratio of a simple gear train is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driver gear

Gear Ratio = Number teeth driven gear

Number of teeth driver gear

Chain and Sprocket Questions 1 : Lesson 9 (1 hour)

1. Explain what a chain and sprocket gear is?

2. What products use this type of gear used?

3. What advantages does this have over spur gears?

4. What is the calculation for working out gear ratio for a chain and sprocket?

5. How important is the length of chain when working out gear ratio?

Gear Systems

Where do we find a gear systems?

Gear systems are found in machines everywhere

What are gear systems used for?• Gear systems are one of the best methods for

transmitting rotary motion from one shaft to another.

• A gear system allows the torque, rotational speed and direction of the output shaft to be varied.

Are there other methods?

Gear Types ~ Spur

• Parallel Shafts• Suitable for a wide

range of gear ratios and loads

• Simplest tooth form of all the gear types

• Good efficiency

Noisy, especially at high speeds

Gear Types ~ Helical

• Parallel Shafts• Suitable for higher

speeds and loads than spur gear

• Quieter than spur gear• Load spread over longer

teeth

• Not as efficient as a spur gear• Thrust forces along the shafts

Gear Types ~ Bevel

• Non Parallel Shafts• Can have helical gear form

Suitable for non parallel shaft applications

• Noisy, especially at high speeds

• Not suitable for very high gear ratios

Gear Types ~ Worm

• Non Parallel Shafts• The worm shaft is always

the driver

• Suitable for non parallel shaft applications

• High gear ratios can be achieved

• Quiet

• Low efficiency• Sliding action of teeth

Gear Types ~ Rack and Pinion

For converting between rotatory and linear motion

Pinion Gear

Rack

Gear Types ~ Epicyclic

Parallel Shafts

• Suitable for high torque applications

• Compact design• Gear ratio can be varied

without the need to engage gears

• Complexity

Can you recognise these gears?

Can you recognise these gears?

A

B

Analysis of a gear systemA gear system (sometimes called a gear train) is an arrangement of gears used to transmit rotational power from the driving shaft to the driven shaft. In doing so the speed, torque and direction of the driven shaft can be varied to that of the driving shaft.

Input/Driving shaftSpeed Ni r.p.m.Torque Ti NmDirection

Output/Driven shaftSpeed No r.p.m.Torque To NmDirection

Friday, 24 April 2020

Think about the levers….

EasierHard

A spanner is a lever that can be used to unscrew a nut.

force

pivot

distance from force

to pivot

It is important to be able to identify where the pivot is, where the force is being applied as a distance from the pivot, and the size of that force

The spanner exerts a moment or turning effect on the nut.

Levers

Rack and Pinion Videos

• https://www.youtube.com/watch?v=nSdjaM1dkKk

• https://www.youtube.com/watch?v=iHqOyAOeDis

• https://www.youtube.com/watch?v=Z1Y14AejfQU

A ‘rack and pinion’ gears system looks quite unusual. However, it is still composed of two gears. The ‘pinion’ is the normal round gear and the ‘rack’ is straight or flat. The ‘rack’ has teeth cut in it and they mesh with the teeth of the pinion gear.

If gear ‘A’ rotates how would you describe the movement of the rack ?

The pinion rotates and moves the rack in a straight line -another way of describing this is to say ‘rotary motion’ changes to ‘linear motion’

If gear ‘A’ rotates how would you describe the movement of the rack ?

The pinion rotates and moves the rack in a straight line -another way of describing this is to say ‘rotary motion’ changes to ‘linear motion’

• However, if a train has to go up a steep bank or hill it is likely to slip backwards.

• A ‘rack and pinion’ system is added to some trains to overcome this problem. A large gear wheel is added to the centre of the train and an extra track is, with teeth, called a ‘rack’ is added to the track.

• As the train approaches a steep hill or slope the gear is lowered to the track and it meshes with the ‘rack’. The train does not slip backwards but it is pulled up the steep slope

• A good example of a ‘rack and pinion’ gear system can be seen on trains that are designed to travel up steep inclines.

• The wheels on a train are steel and they have no way of griping the steel track.

• Usually the weight of the train is enough to allow the train to travel safely and at speed along the track.

Crank and slider This mechanism is composed of 3 important parts:1) The crank which is the rotating disc,2) The slider which slides inside the tube3) The connecting rod which joins the partstogether.

As the slider moves to the right the connecting rod pushes the wheel round for the first 180 degrees of wheel rotation.

When the slider begins to move back into the tube, the connecting rod pulls the wheel round to complete the rotation.

Crank and slider

Rack and Pinion Questions 1 : Lesson 10 (1 hour)

1. Explain how a rack and pinion mechanism works.

2. What types of motion does it use?

3. Write down (and get photos) as many examples of products that use a rack and pinion as you can think of.

4. Evaluate why a rack and pinion is a good mechanical solution for each of your examples.

Gears Questions 1 : Lesson 11 (1 hour)

1. Explain how a Crank & Slider mechanism works.

2. What types of motion does it use?

3. Write down (and get photos) as many examples of products that use a Crank & Slider as you can think of.

4. Evaluate why a Crank & Slider is a good mechanical solution for each of your examples.

Key Terms 1 : Lesson 12-14 (3 hours)

12. Go through this PowerPoint and make a list of Key Terms on a new slide.

13. Write a 1 sentence explanation of each Key term.

14. Revise all Key terms and an explanation for a Key Term test on your return to school.

• Please revise all of the information on this PowerPoint.

• You will receive a test on this information on your return.

• This test form your first assessment grade of year.

Best of Luck !

Mr Corkin & Mr Kennedy

Revision :