HWYRAILENG
The Typical components are Rails, Sleepers (or ties), Fasteners, Ballast (or slab track), Subgrade
True
Can be considered as steel girders for the purpose of carrying loads
Rails
Made up of high carbon steel to withstand wear and tear
Rails
Flat footed rails are mostly used in railway track
Rails
There are 3 types of rails used in the construction of railway tracks
True
The rail sections, having their head and foot of same dimensions, are known as double headed or Dumb-bell rails. These rails have less strength and stiffness as compared to flat footed rails.
Double Headed Rails
The rail section, having the head a little thicker and stronger (Bull size) than the lower part is known as Bull headed rails. These rails have less strength and stiffness as compared to flat footed rails. Bull headed rails are generally used for constructing points and crossings.
Bull Headed Rails
The rail sections, having a flat foot, are known as flat-footed rails. These rails have more strength and stiffness as compared to Double Headed Rails & Bullheaded Rails.
Flat Footed Rails
The separation or cutting of rail due to friction and abnormal heavy load.
wear
The metal from the top of rail flows and forms projections which are known as burns.
Wear of rails on top or head of rail
This wear of rails takes place at the ends of rails and is found to be very much greater than the wear at the top of rails. At the expansion gap, the wheels of the vehicle have to take a jump and during this jump, they impart a blow is the ends of the rails.
Wear at the End of Rails
This is the most destructive type of wear and occurs on the rails laid on curves.
Wear at the side of head of Rails
The cost of such rail is more but considerable reduction of wear of such rails justifies the extra cost.
Special Alloy Steel
The backward thrust of the driving wheels of a locomotive has the tendency to push the rail backwards, while the thrust of the other wheels of the locomotive pushes the rail in the direction in which the locomotive is moving. This results in the longitudinal movement of the rail in the direction of traffic, thereby causing creep.
Drag Theory
• Creep is due to impact of wheels at the rail end ahead at joints Reaction R is normal to the surface of contact
• Horizontal component H causes creep
• Vertical component V tends to bend the rail vertically – results battering of rail end
PERCUSSION THEORY
If the expansion gap has increased beyond a certain limit, it should be reduced by packing the sleepers at the joints and tightening fish bolts. This will result in the reduction of wear of end of rails.
Reduction of Expansion Gap
Mostly on curves, where there is heavy wear at the top of head of inner rail and heavy wear of the side of head of outer rail then the top wear rail is exchanged with the side wear rail and thereby life of rail is increased.
Exchange of Inner and Outer Rails on Curves
The wear of rails can also be reduced by applying lubricating oil on curves on the side of head of rails. The lubrication of rails can be carried out manually or by mechanical equipment attached to locomotive for rail.
Use of Lubricating Oil
• The flanges of wheel is never made flat, but they are in the shape of cone with a slope of 1 in 20
• The coning of wheels is mainly done to maintain the vehicle in the central position with respect to the track
CONING OF WHEELS
- Flanges of wheels have equal circumference
- Equal diameters on both rail
- Equal pressure on both rail
At level surface
- Outer rails has to cover great distance than inner rail
- Vehicle has tendency to move sideways towards outer rail
- Circumference of flange of outer wheel will be greater than that of inner wheel
- Helps the outer wheel to cover longer distance than inner rail
At curves
• Creep is defined as the longitudinal movement of the rail with respect to the sleepers.
• Rails have a tendency to gradually move in the direction of dominant traffic.
• Creep is common to all railway tracks, but its magnitude varies considerably from place to place; the rail may move by several centimetres in a month at few places, while at other locations the movement may be almost negligible.
CREEP OF RAILS
Creep is developed due to wave motion of wheels on rails
• Due to movement of wheel loads on rails, the rail deflects as a continuous beam and crests are formed near supports
• When wheels of train strike against these crests, creep is developed
• The wheels push the wave with a tendency to force the rail in the direction of traffic
WAVE ACTION OR WAVE THEORY
• Rails provide hard, smooth and unchanging surface for passage of heavy moving loads with minimum friction between steel rail and steel wheel
• Rails bear the stresses developed due to heavy vertical loads, lateral and braking forces and thermal stresses
• The rail material used is such that it gives minimum wear to avoid replacement charges and failure due to wear
• Rails transmit the loads to sleepers and consequently reduce pressure on ballast and formation below
FUNCTIONS OF RAILS
• They keep better alignment and give a more solid and smoother track.
• The rails can be easily removed and replaced quickly. Hence renewal of the track is easy.
• The heavy chair with a large bearing on sleepers gives longer life to the wooden sleepers and greater stability to the track.
• These rails facilitate easy manufacturing of points and crossings.
Advantages of Bull Headed Rails
• They require costly fastenings.
• They have less strength and stiffness.
• They require heavy maintenance costs.
Disadvantages of Bull Headed Rails
• These rails have more strength and stiffness.
• Fitting of rails with sleepers is simpler so they can be easily laid and re-laid.
• No chairs and keys are required as in case B.H. rails.
• Maintenance of points and crossings made with these rails is easy.
They give better stability and longer life to the track and reduces maintenance cost.
• These rails are less costly than other types of rails.
• These rails require less number of fastenings.
Advantages of Flat Footed Rails
• The fitting gets loosened more frequently.
• The straightening of bent rails, replacing of rails, and de-hogging of battered rails are difficult.
• These rails sink into the wooden sleepers under heavy trainloads. Hence they require a bearing plate to overcome this problem.
• Manufacturing of points and crossing with these rails is difficult.
Disadvantages of Flat Footed Rails
The separation or cutting of rail due to friction and abnormal heavy load is called wear.
• Wear of rails on top or head of rail
• Wear of rails at ends of rail
• Wear of rail on the sides of head of rail
WEAR ON RAILS
• To reduce wear & tear of the wheel flanges and rails, which is due to rubbing action of flanges with inside face of the rail head
• To provide a possibility of lateral movement of the axle with its wheels
• To prevent the wheels from slipping to some extent
ADVANTAGES OF CONING THE WHEELS
• Smooth riding is produced by coning of wheels. But the pressure of the horizontal component near the inner edge of the rail has a tendency to wear the rail quickly
• The horizontal component tends to turn the rail outwardly and hence the gauge is widened sometimes
• If no base plate are provided, the sleepers under the outer edge of the rail are damaged
Disadvantages of coning
To minimize the disadvantages of coning, rails are tilted inwards. Inclined base plates are used with slope of base plate being 1 in 20.
TILTING OF RAIL
- Angular and heavy ballast which develops good interlock
- Increased stiffness of track
- Lesser sleeper spacing
- Bigger section of rail
Wave action can be reduced by