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Mechanical Engineering of Railways > Introduction > Flashcards

Introduction Flashcards

1
Q

At a very high level how can the UK rail industry can be divided into?

A
  1. Mainline network
  2. Underground railways
  3. Light rail and tramways
  4. Minor & heritage railways
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2
Q

How is the work of the rail industry legislatively shaped?

A

The work of the rail industry is shaped by UK and European legislation.

  1. UK legislation:
    Railways Act, Health & Safety at Work Act, Railways Interoperability Regulations, + many more
  2. EU legislation
    Regulations concerning a European rail network for competitive freight, on the allocation of railway infrastructure capacity, the levying of charges for the use of railway infrastructure, and many more
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3
Q

What are the responsible governing bodies for the rail industry?

A 
Government
•  Department for Transport
•  Transport for London
•  Additional bodies in Scotland and Wales
•  Office of Rail and Road
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4
Q

What are the responsible safety bodies for the rail industry?

A
  1. Rail Accident Investigation Branch – responsible for
    investigating rail accidents.
  2. Rail Safety and Standards Board – conducts research and
    gives advice on safety & cross-industry issues
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5
Q

In what categories of companies does the UK industry divide itself into?

A
  1. Network Rail – the rail infrastructure owner and operator
  2. Train operating companies – operate passenger trains
  3. Freight operating companies – who operate freight trains
  4. Rolling stock companies – who own and lease trains to train operating companies
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6
Q

What are some areas that a consultant mechanical engineer might look at in projects within the rail industry?

A

EXAMPLES

  1. Fatigue of rail: predicting the life of rails
  2. Calculating energy use dependence on driving styles, speed, timetable
  3. Influence of welds in vehicle strength in a crash
  4. Noise and vibration: how the surface roughness of rails and wheels is converted into noise, and how loud this sounds to people
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7
Q

How many stations does the main UK rail network have?

A

2,500

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8
Q

How many miles are there in the UK?

A

20,000 miles of track

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9
Q

How many bridges and tunnels does the rail network have?

A

40,000 bridges and tunnels

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10
Q

Who owns and manages the rail track?

A

The track is owned and managed by Network Rail

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11
Q

How is the collaboration between track and vehicle companies facilitated?

A

Several “System Interface Committees” exist to help track and vehicle companies work together

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12
Q

What is the typical design life of passenger vehicles?

A

Design life of 30-35 years

[(Much greater lifetime and distances covered than equivalent road vehicles (either cars or buses)]

[Rough idea – Sheffield to London return (320 miles), twice a day, 330 days/year=211k-miles, 35 years=7.4 million miles]

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13
Q

What does the suspension of most UK passenger vehicles consist of?

A

Suspension consists of 4 axles per vehicle, mounted in pairs on bogies

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14
Q

How long are the typical single vehicles (coaches)?

A

Typically around 20-25m long

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15
Q

How much do single vehicles usually weigh?

A

Around 40 tonnes

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16
Q

Draw a diagram showing a bogie with its main parts

A

Page 7

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17
Q

Why use bogies? Draw a diagram to explain concept

A
  1. Geometry – to allow a long vehicle to move around a curve
  2. Without bogies – moving the wheels closer together fixes the problem, but makes the vehicle unstable.
  3. Without bogies – wheels very badly aligned, will fail to corner well and are likely to derail.
  4. Bogies – allow good support of the vehicle, and the ability of the wheels to align with curvature of the track.

Page 8

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18
Q

What is a wheel set?

A

Within a bogie there’s two ‘wheel sets’

2 wheels + axle = wheelset

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19
Q

Draw a wheel set

A

Page 8

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20
Q

Why are the wheels coned in opposite directions?

A

The wheels are ‘coned’ in opposite directions.

Linking them by an axle creates a self-aligning system which should run without flange contact.

The rails have a curved surface to create a ‘point’ contact.

Going around a corner the ‘outside’ wheel needs to roll further than the ‘inside’ wheel

The coning allows this to happen in a controlled way

21
Q

What happens during steering?

A
  1. Going around a corner the ‘outside’ wheel needs to roll further than the ‘inside’ wheel
  2. The coning allows this to happen in a controlled way
  3. The wheelset shifts laterally, changing the radius of the wheel at the point of contact
  4. The larger (outside) and smaller (inside) radius enable the wheel-rail contact to stay close to pure rolling at both sides, and go around a corner
  5. Excess sliding in the contact leads to rail & wheel wear and consumes energy
22
Q

Why do trains tilt?

A

Tilting trains are all about passenger comfort during cornering

The angle of the body doesn’t change the equations of circular motion

23
Q

What is a cant?

A

‘Cant’ refers to the difference in height between low and high rails

24
Q

Why is there sometimes a height difference between the two rails?

A

The height difference means a component of train weight is directed towards the centre of the curve

Cant allows trains to corner faster

The cant needed depends on speed – it must be set to accommodate the speeds of trains which will use the line

25
Q

What defines the required cant?

A

The cant needed depends on speed – it must be set to accommodate the speeds of trains which will use the line

26
Q

What is the limit for cant

A

It’s not possible to increase cant above 150-180mm without problems for stationary trains

27
Q

What is the limiting factor on cornering at speed?

A

The limiting factor on cornering at speed is usually passenger comfort not vehicle stability; standing passengers are vulnerable to being thrown sideways

28
Q

Is the rail support solid?

A

Not usually solid.

29
Q

What is a sleeper?

A

The component upon which rails are fixed. It can be made either out of wood or concrete.

30
Q

Why do sleepers lie in ballast (crushed stone)?

A
  1. Distribution of load

2. Drainage

31
Q

What controls the stiffness of the track?

A

The ballast controls the stiffness of the track – how much it moves under load

32
Q

Why is it important for the track to be able to move slightly under load?

A

That movement controls rail bending, the growth of large cracks and dynamics of the vehicles

33
Q

What is a slab track?

A

Where the support of the rails is solid (concrete and no ballast)

34
Q

Is the concrete slab upon which the rails are fixed rigid?

A

No, they are stiff, not rigid.

35
Q

Where is the load from the concrete slabs transferred to?

A

Transfers the load to the underlying ground and maintains track alignment

36
Q

What are the disadvantages of concrete slabs?

A
  1. Expensive to build
  2. High environmental impact from CO2 generated by concrete
  3. Difficult to repair
  4. Used mainly for very high speed lines.
37
Q

What are the two main shapes of rail which are in use?

A

1, ‘Flat bottom’ rail, used in almost all modern installations
2. Bullhead rail, used in old lines, sidings etc.

38
Q

Why are railpads important?

A

very significant in noise and vibration control

39
Q

Draw a typical fastening system

A

Page 12

40
Q

How are train wheels produced?

A

They are forged.

41
Q

What happens to the wheels are they are used constantly?

A
  1. Wheels loose their surface profile as they wear down

2. Wheel lathes are used to maintain the wheels while still fitted to the vehicles

42
Q

How rail and wheel fit together controls…

A

Dynamic behaviour of the vehicle!

  1. noise
  2. vibration
  3. steering
43
Q

What percentage of the UK network is equipped with power supplied for electric trains?

A

Around 40%

44
Q

What is the voltage of the overhead supply?

A

25kV ac overhead supply

45
Q

What is a catenary?

A

A catenary is the curve that an idealized hanging chain or cable assumes under its own weight when supported only at its ends.

46
Q

How is the electricity transmitted from the overhead to the train?

A

Collected by a pantograph on the roof

47
Q

How is the electricity collected from the ground when there is no overhead?

A

750V dc third rail supply, provided by a third rail running alongside the running lines, collected by shoes fitted to the locomotive or train bogies

48
Q

What is the current state of the electric network?

A

Large expansion of 25kv system now beginning

Mechanical Engineering of Railways (5 decks)

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