B - Rails, Stress Analysis, Sleepers/Fastenings and Switches and Crossings Flashcards
Name three types of fastening system
Spike - driven into wooden sleeper (traditional)
Bolt - early method for concrete sleepers
Clip - steel bar spring against the foot of the rail (usual today)
What do fastening systerms do?
Ensure the rail is maintained upright and that the gauge is within limits
What is the function of the sleeper?
Typical material?
Support to rail and maintain gauge
Wood, concrete or steel
What are pads effectiev at doing?
Damping out high frequency vibrations of small amplitude which might give rise to corrugations
What do pads do?
Typical material
Protect sleeper from high contact forces
Absorb energy
Electrical insulation
Rubber, EVA, polypropylene
What is a crossing?
Where a track crosses another without the opportunity to join it
How are crossings installed?
Pre-fabricated off-site and once in position welded or jointed to the adjacent track
Why are there gaps at certain locations of track?
As the rail has to be able to pass adjacent to one rail but through the line of another
What is the solution to the higher impact forces at gaps?
Expensive hardened steel
Design detailed shape to minimise force
Allow flange running
Use check rails
Use swing nose crossings
How are switch and crossings maintained?
Specially designed tamping machines
With variable arm widths to the sides
Why are crossings a problem? (Although also vital)
Very difficult to maintain track qwuality at the same level as on plain line because of the difficulty in ensuring the raios are lifted to their correct alignment
