1 - Intro and Background Flashcards
Categories the rail industry can be split into
Mainline network
Underground railways
Light rail and tramways
Minor and heritage railways
UK legislation
Railways Act
Health and Safety at Work Act
Railways Interoperability Regulations
EU legislation (now UK law)
Regulations concerning European rail network for competitive freight, allocation of railway infrastructure capacity, levying of charges for the use of railway infrastructure
Particular focus on ‘inter-operability’
Government bodies related to industry
Department for Transport
Transport for London
Office of Rail and Road
Additional bodies in Scotland and Wales
Safety bodies in the industry
Rail Accident Investigation Branch (investigates rail accidents)
Rail Safety and Standards Board (conducts research and gives advice on safety and cross-industry issues)
Companies in industry
Network Rail (rail infrastructure owner and operator)
Train operating companies (operate passenger trains, to be combined as Great British Railways from 2024?)
Freight operating companies
Rolling stock companies (own and lease trains to train operating companies)
Points about UK rail network
Approx. 2500 stations on main rail network
20,000 miles of track
40,000 bridges and tunnels
Track is managed by Network Rail (government owned)
Trains are run by other companies (several in public ownership or as management agreements with government)
‘System Interface Committees’ exist to help track and vehicle companies work together
Typical design life of passenger vehicles
30-35 years
Typical passenger vehicle suspension
4 axles per vehicle
Mounted in pairs on bogies
Typical length and weight of single vehicles (coaches)
20-25m
40 tonnes
Why are two suspension systems used?
Each can be tuned to a different frequency
Why are bogies used?
To allow a long vehicle to move around a curve
Allow good support of vehicle and ability of wheels to align with track curvature
What would happen if the bogies are too far apart?
Wheels badly aligned
Fail to corner well
Likely to derail
What would happen if the bogies are too close together?
Makes the vehicle very unstable
Wheelset components
2 wheels
Axle
Points about wheel design
Flanges are not what keeps wheels on the track
Wheels are ‘coned’ in opposite directions - linking them by an axle creates self-aligning system which should run without flange contact
Rails have a curved surface to create a ‘point’ contact
Points about steering
Around a corner, outside wheel needs to roll further than inside wheel
Coning allows this to happen in controlled way
Wheelset shifts laterally, changing wheel radius at contact point
Larger (outside) and smaller (inside) radius enable wheel-rail contact to stay close to pure rolling at both sides and go around the corner
Excess sliding in the contact leads to rail and wheel wear and consumes energy
Typical rail gauge
1435mm (4ft 8.5in)
Define cant
Difference in height between low and high rails
Points about cant
Height difference means a component of train weight is directed towards centre of curve
Allows train to corner faster
Cant needed depends on speed - must be set to accommodate speed of trains using the line
Tilting trains are for passenger comfort
Angle of body doesn’t change equations of circular motion
Limiting factor on cornering speed is passenger comfort
Maximum possible cant for stationary trains
150-180mm
Points about below the rail (not solid)
Rails fixed to sleepers
Sleepers lie in ballast (crushed stone) for load distribution and drainage
Ballast controls track stiffness - how much it moves under load
That movement controls rail bending, large crack growth and vehicle dynamics
Points about below the rail (solid)
‘Slab track’
Rails fixed to stiff, but not rigid, concrete slab
Transfers load to underlying ground and maintains track alignment
Expensive to build, high environmental impact from CO2 generated in concrete manufacture
Difficult to repair
Often used for very high speed lines
Main rail shapes
Flat bottom
Bullhead
What is a railpad?
Used in fixing between rail and sleeper to reduce noise and control vibration
How are wheels produced?
Forging
Typical wheel diameter
650-1250mm
Points about power supplies
Around 40% of GB network has power supplies for electric trains
25kV AC overhead supply, provided through overhead cables (catenary), collected by a pantograph on roof
750V DC third rail supply, third rail alongside running lines, collected by shoes fitted to the loco or train bogies
71% electric, 18% diesel, 7% bi-mode trains, 4% loco hauled
Electrification benefits
Cleaner
Potentially ecologically better than diesel
Electrification drawbacks
Moving interface between wires and train is a failure point
Wires wear out, repeated movement leads to fatigue cracks, severe weather (climate change) takes systems beyond design loads
