Railway Engineering Chapter 5
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Questions and Answers

What factor increases the likelihood of derailing on a curve?

  • Increased track maintenance
  • Material quality of rails
  • Angular wear on the outer rail (correct)
  • Higher permissible speeds

    • What occurs when vehicles enter a curve at speeds higher than the maximum permissible speed?

  • Increased wheel grip
  • Distortion of the track (correct)
  • Improved traction
  • Enhanced stability

    • Which of the following is NOT an adverse condition that can develop on a curved track?

  • Gauge widening
  • Track distortion
  • Excessive rail repairs (correct)
  • Fracture and failure of rails

    • What is the effect of high superelevation on a wagon stopping on a sharp curve?

    <p>Outer wheels become off-loaded</p> Signup and view all the answers

    What provides a guiding force for the outer leading wheel during movement on a curve?

    <p>Greater force needed to turn the vehicle</p> Signup and view all the answers

    Which type of rail is likely to suffer from excessive angular wear?

    <p>Outer rail</p> Signup and view all the answers

    What is the critical limit referred to in the context of the Y/Q ratio for wheels on a curve?

    <p>Force required to mount the rail</p> Signup and view all the answers

    What primarily causes the centrifugal force acting on a vehicle on a circular curve?

    <p>Constant radial acceleration</p> Signup and view all the answers

    What shape is typically used for transition curves?

    <p>Cubic parabola</p> Signup and view all the answers

    Which formula correctly represents one of the maximum desirable lengths of a transition curve?

    <p>0.008 C_d * V_m</p> Signup and view all the answers

    What is the purpose of measuring versine in railway tracks?

    <p>To evaluate the curvature degree and radius</p> Signup and view all the answers

    When measuring versine on straight track, which chord length is standard?

    <p>7.2 meters</p> Signup and view all the answers

    How frequently should versine measurements be taken on turn-out and turn-in curves?

    <p>Every 1.5 meters</p> Signup and view all the answers

    What formula represents the centrifugal force acting on a vehicle on a curve?

    <p>F = WV2 / GR</p> Signup and view all the answers

    What is the purpose of raising the outer rail on curves?

    <p>To counteract centrifugal force.</p> Signup and view all the answers

    How is equilibrium super elevation represented in the formula?

    <p>e = GV2 / gR</p> Signup and view all the answers

    What does the term 'Cant' refer to in railway curves?

    <p>The elevation of the outer rail compared to the inner rail.</p> Signup and view all the answers

    What is the relationship between degree of curve and radius of curve expressed as?

    <p>D = 1750 / R</p> Signup and view all the answers

    What is the maximum value of superelevation typically prescribed?

    <p>1/10 of gauge</p> Signup and view all the answers

    What is one reason for providing superelevation on railway curves?

    <p>To reduce lateral forces.</p> Signup and view all the answers

    In the metric system, how is equilibrium super elevation represented?

    <p>e = GV2 / 127R</p> Signup and view all the answers

    What is the gauge used to measure the width of rail head expressed in?

    <p>Millimeters</p> Signup and view all the answers

    What happens when the cant for a curve is inadequate?

    <p>There could be excessive wear on the rails.</p> Signup and view all the answers

    What is the primary purpose of providing cant deficiency in railway tracks?

    <p>To ensure passenger comfort and prevent derailments</p> Signup and view all the answers

    What is the maximum cant deficiency allowed for normal speeds up to 100 KMPH on Indian railway B.G.?

    <p>75 mm</p> Signup and view all the answers

    What happens if there is excessive super-elevation on a track?

    <p>Inner rail may fail under excessive strain</p> Signup and view all the answers

    Which factor is most affected by higher cant deficiency in railway designs?

    <p>Passenger comfort and safety</p> Signup and view all the answers

    What could be a consequence of insufficient super elevation on a curve?

    <p>Increased wear on the outer rail</p> Signup and view all the answers

    What happens to fast-moving trains if the cant provided is lower than necessary?

    <p>They experience greater lateral oscillations</p> Signup and view all the answers

    Why is a compromise necessary in the cant design for railways?

    <p>To ensure safety for both fast and slow-moving trains</p> Signup and view all the answers

    What does a high cant deficiency require from the track infrastructure?

    <p>Stronger track and fastening</p> Signup and view all the answers

    What is the cant deficiency for high-speed operations on Indian railway B.G.?

    <p>100 mm</p> Signup and view all the answers

    Which of the following is NOT a consequence of improper cant and super elevation?

    <p>Improved ride comfort for passengers</p> Signup and view all the answers

    What is the main purpose of providing transition curves in railway design?

    <p>To gradually increase curvature and superelevation.</p> Signup and view all the answers

    According to the specified permissible limits, which radius supports a maximum equilibrium cant of 160 mm?

    <p>1746 meters</p> Signup and view all the answers

    What common issue occurs when a vehicle stops on a sharp curve with high cant?

    <p>The outer wheels can become off-loaded.</p> Signup and view all the answers

    What maintenance precaution is NOT mentioned for curves in the content?

    <p>Increase the degree of curve.</p> Signup and view all the answers

    What design principle is emphasized for transition curves?

    <p>The curvature change should be uniform.</p> Signup and view all the answers

    What is the proposed cant for a curve with a radius of 1164 meters?

    <p>150 mm</p> Signup and view all the answers

    During the transition into a circular curve, which force increases affecting the track alignment?

    <p>Centrifugal force</p> Signup and view all the answers

    Which degree of curve has the lowest maximum permissible cant according to the data?

    <p>6 degrees</p> Signup and view all the answers

    What should the cant gradient on transition be to accommodate irregularities?

    <p>As flat as possible</p> Signup and view all the answers

    Which option is necessary for minimizing wear on the gauge face of the rail during maintenance?

    <p>Lubrication</p> Signup and view all the answers

    What is the length of the transition curve dependent upon?

    <p>The degree of curve, max permissible speed, and amount of superelevation</p> Signup and view all the answers

    Which formula provides the maximum desirable length of a transition curve based on cant deficiency?

    <p>0.008 Cd * Vm</p> Signup and view all the answers

    What is the objective of measuring versine on a curved track?

    <p>To determine the radius and degree of curvature</p> Signup and view all the answers

    Under what condition should the maximum lengths of transition curves be reduced to 2/3 or 1/2 of their standard values?

    <p>In cases where space is insufficient</p> Signup and view all the answers

    What technique is used to ensure accurate versine measurement on curves?

    <p>Stretching a wire at running side of the rail</p> Signup and view all the answers

    What is a consequence of excessive angular wear on curved tracks?

    <p>Reduces the contact area between the wheel and rail</p> Signup and view all the answers

    How does track distortion generally occur in curvy sections?

    <p>When vehicles are operated at excessive speeds</p> Signup and view all the answers

    Which factor does NOT contribute to the likelihood of a vehicle derailing on a curve?

    <p>Higher superelevation of the outer rail</p> Signup and view all the answers

    What is likely to happen to the guiding force acting on the outer leading wheel during curve negotiation?

    <p>It increases due to the higher force needed to follow the track</p> Signup and view all the answers

    What results from a wagon stopping on a sharp curve with high superelevation?

    <p>The outer wheels will become off-loaded</p> Signup and view all the answers

    What typically happens when gauge widening occurs on a curved track?

    <p>It increases lateral movement of the rolling stock</p> Signup and view all the answers

    What role does centrifugal force play when a vehicle moves on a circular curve?

    <p>It acts away from the center and may lead to derailment</p> Signup and view all the answers

    Which of the following describes a situation that can lead to wheel mounting during curve navigation?

    <p>Sudden braking on a curve</p> Signup and view all the answers

    What is the maximum permissible cant for a curve with a radius of 291 meters?

    <p>85 mm</p> Signup and view all the answers

    Which radius corresponds to a maximum equilibrium speed of 250 mm?

    <p>1395 meters</p> Signup and view all the answers

    What is the recommended practice for the cant gradient on transition curves?

    <p>Must be as flat as possible</p> Signup and view all the answers

    Which factor primarily affects lateral flange force when a vehicle enters a curve?

    <p>Speed of the vehicle</p> Signup and view all the answers

    When a vehicle stands on a high cant, what issue can happen upon starting movement?

    <p>Off-loading of outer wheels</p> Signup and view all the answers

    What is the maximum equilibrium cant for a curve with a radius of 1746 meters?

    <p>160 mm</p> Signup and view all the answers

    What is the consequence of having a cant gradient that is too steep during maintenance?

    <p>Improper alignment of the track</p> Signup and view all the answers

    To achieve gradual superelevation, which aspect must increase uniformly in a transition curve?

    <p>Curvature</p> Signup and view all the answers

    What is an important consideration during the design of transition curves?

    <p>Smooth entry to the curve</p> Signup and view all the answers

    What is one of the consequences of excessive super-elevation on railway tracks?

    <p>The inner rail experiencing gauge widening.</p> Signup and view all the answers

    What is the relationship between cant deficiency and passenger comfort?

    <p>Higher cant deficiency may cause discomfort.</p> Signup and view all the answers

    Which of the following factors is affected by higher cant deficiency in track design?

    <p>The requirement for stronger tracks and fastening.</p> Signup and view all the answers

    Given the limits for cant deficiency, what is the maximum allowable value for high-speed operations on Indian railway B.G.?

    <p>100 mm</p> Signup and view all the answers

    What compromise must be made to accommodate both fast and slow-moving trains on curves?

    <p>Establishing a suitable level of cant deficiency.</p> Signup and view all the answers

    When cant deficiency is high, what is likely to be required from railway infrastructure?

    <p>Heightened resilience in track design.</p> Signup and view all the answers

    What risk is associated with inadequate super elevation on railway curves?

    <p>Derailment of slow-moving freight trains.</p> Signup and view all the answers

    Which of the following is NOT a consideration when designing cant for railway curves?

    <p>Maximizing the speed of freight transport.</p> Signup and view all the answers

    What is the impact of lower cant on the outer rail during fast train operations?

    <p>The outer rail experiences more strain.</p> Signup and view all the answers

    What does a compromise in cant design allow for slow-moving trains?

    <p>Safe traversal without risk of derailments.</p> Signup and view all the answers

    What does the term 'equilibrium super elevation' refer to?

    <p>The height difference between the outer and inner rail on a curve.</p> Signup and view all the answers

    What is the relationship between the degree of the curve and the radius expressed by the equation?

    <p>D = 1750/R</p> Signup and view all the answers

    Which factor influences the design of superelevation on railway curves?

    <p>Weight of the vehicle and curve radius.</p> Signup and view all the answers

    What is the significance of raising the outer rail in railway curves?

    <p>To achieve better load distribution and reduce wear.</p> Signup and view all the answers

    What is the maximum recommended cant for curves generally stipulated by railways?

    <p>1/10 of gauge.</p> Signup and view all the answers

    How is equilibrium super elevation calculated in the metric system?

    <p>e = GV2 / 127R</p> Signup and view all the answers

    What happens if there is excessive cant on a railway track?

    <p>Potential derailment risk increases.</p> Signup and view all the answers

    Which measurement is used to identify the allowable cant deficiency for high-speed rail operations?

    <p>Maximum permissible speed in kilometers per hour.</p> Signup and view all the answers

    What is the consequence of providing inadequate cant on curves?

    <p>Increased likelihood of lateral forces causing derailment.</p> Signup and view all the answers

    What is the specified gauge when referring to the width of the rail head?

    <p>200 mm</p> Signup and view all the answers

    Study Notes

    Chapter 5: Derailment on Curves

    • Rolling stock has a higher chance of derailing on curved tracks due to the flange constantly pressing against the outer rail, in addition to normal tread contact.
    • Analysis of derailments on the Central Railway shows a higher number on curved alignments compared to straight tracks.
    • Proper maintenance of curved tracks is essential.

    5.1 Adverse Factors on a Curve

    • Curved tracks have a higher chance of developing the following:
      • Excessive angular wear on the outer rail
      • Excessive flattening of the head on the inner rail
      • Fracture and failure of rails
      • Gauge widening
      • Track distortion

    5.1.1 Vehicles Entering a Curve

    • Vehicles entering a curve at speeds exceeding the maximum permissible speed can cause track distortion or wheel mounting on the outer rail.
    • Wheel mounting on the inner rail can also occur during sudden braking, potentially causing vehicle bunching.
    • Gaping holes in ballast, often caused by shifting of sleepers, are another indication of curve problems.

    5.1.2 Outer Rails on Curves

    • Outer rails on curves experience increased angular wear, creating an inclined plane that can cause wheel slippage.

    5.1.3 Wagon Stopping on a Curve

    • Wagons stopping on sharp curves with high superelevation can cause the outer wheels to unload.
    • When the wagon starts moving even at a slow speed, the guiding force on the outer leading wheel increases significantly.
    • The Y/Q ratio for the outer leading wheel increases and mounting on the rail can occur if it exceeds the critical limit.

    5.2 Cant or Superelevation

    • When a vehicle moves on a circular curve, centrifugal force acts away from the center.

    • This force is calculated using the formula: F = WV²/GR

      • F = centrifugal force (tons)
      • W = weight of the vehicle (tons)
      • V = speed (feet/sec)
      • G = acceleration due to gravity (feet/sec²)
      • R = radius of the curve (feet)

    • To counter the centrifugal force, the outer rail on curved tracks is kept slightly elevated above the inner rail.

    • This elevation is called cant or superelevation.

    • A state of equilibrium occurs when both wheels bear equally on the rails.

    • The equilibrium super elevation is given by: - e = GV²/gR (metric) - e = GV²/GR (imperial)

    • where:

      • e = equilibrium superelevation
      • G = gauge + width of rail head (mm)
      • V = velocity
      • R = radius of the curve

    • Cant for curves is normally indicated on the inside of the inner rail.

    5.2.1 Reasons for Providing Superelevation

    • Provides better distribution of load on the rails.
    • Reduces wear and tear on rails and rolling stock.
    • Neutralizes the effect of lateral forces.
    • Provides comfort to passengers.

    5.2.2 Degree of Curve V/S Radius of Curve

    • The degree of a curve (D) is the angle subtended by the curve at its center by a chord of 30.5 meters.
    • The relationship between radius and degree of a curve is given by: D = 1750/R

    5.2.3 Effect of Excessive or Inadequate Cant

    • Maximum superelevation is approximately 1/10 to 1/12 of the gauge.
    • Prescribed values of maximum superelevation for Indian Railways are provided in Table 5.1.

    5.3 Cant Deficiency

    • Cant deficiency is the difference between equilibrium cant required for maximum permissible speed and the actual cant provided.
    • Higher cant deficiency leads to passenger discomfort and requires stronger track and fastenings.
    • Normal speeds in Indian railways (B.G.) - 75 mm, high speeds - 100 mm cant deficiency.

    5.4 Transition Curve

    • Transition curves are provided on either side of circular curves to smoothly transition from straight tracks into circular curves.
    • This ensures a gradual increase in curvature and superelevation.
    • The shape of the transition curve is usually a cubic parabola.

    5.4.1 Length of Transition Curve

    • The length of transition curves depends on the degree of curve, permissible speed, superelevation rate, and the rate of cant runoff.

    • Length is maximum of 3 values:

      • 0.008 Ca * Vm
      • 0.008 Cd * Vm
      • 0.72 Ca.

    • In exceptional cases, length can be up to 2/3 of (1), 2/3 of (2) or 1/2 of (3).

    5.5 Versine

    • Versine is the perpendicular distance from the chord line to the arc between 2 marked stations.

    5.5.1 Objective of Measuring Versine

    • To check the degree and radius of curved tracks.

    5.5.2 How to Measure Versine

    • Versines are measured using 20-meter overlapping chords.

    5.5.3 Determining Degree of Curve using Versine

    • Versine on a 11.8-meter chord directly gives the curve degree.
    • For a 6-meter chord, it's 1/4 of the curve degree.
    • 3-meter chord is 1/16 of the curve degree.

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