Cant Deficiency, Curving Speeds Cant Deficiency, Curving Speeds and - - PowerPoint PPT Presentation

Cant Deficiency/Tilt Marquis / Page 1 US DOT Volpe Center Federal Railroad Administration

Cant Deficiency, Curving Speeds Cant Deficiency, Curving Speeds and Tilt and Tilt

Brian Marquis Brian Marquis – – Mechanical Engineer Mechanical Engineer Volpe National Transportation Systems Center Volpe National Transportation Systems Center Cambridge, Massachusetts Cambridge, Massachusetts

Cant Deficiency/Tilt Marquis / Page 2 US DOT Volpe Center Federal Railroad Administration

Topics Topics

Cant Deficiency Cant Deficiency

• Definition of Cant Deficiency

Definition of Cant Deficiency

• Benefits of Operating at Cant Deficiency

Benefits of Operating at Cant Deficiency

• Effect of Cant Deficiency on Rail Vehicle Performance

Effect of Cant Deficiency on Rail Vehicle Performance

• Use of Tilt at High Cant Deficiency

Use of Tilt at High Cant Deficiency

Cant Deficiency/Tilt Marquis / Page 3 US DOT Volpe Center Federal Railroad Administration

Steady State Forces on Trains in Curves Steady State Forces on Trains in Curves

Cant Deficiency/Tilt Marquis / Page 4 US DOT Volpe Center Federal Railroad Administration

• Trains operating in curves experience net lateral force (centrif

Trains operating in curves experience net lateral force (centrif ugal ugal force) to the outside of the curve that is a function of the vel force) to the outside of the curve that is a function of the velocity.

• city.
• With superelevation (cant), the centrifugal force acting on the

With superelevation (cant), the centrifugal force acting on the passengers is reduced, or eliminated, by a component of the passengers is reduced, or eliminated, by a component of the gravitational force (weight). gravitational force (weight).

• Balance speed for any given curve is the speed at which the late

Balance speed for any given curve is the speed at which the lateral ral component of centrifugal force will be exactly compensated (or component of centrifugal force will be exactly compensated (or balanced). balanced).

• Cant deficiency involves traveling through a curve faster than t

Cant deficiency involves traveling through a curve faster than t he he balance speed and produces a net lateral force to the outside of balance speed and produces a net lateral force to the outside of the the curve. curve.

• Cant deficiency is measured in inches and is the amount of

Cant deficiency is measured in inches and is the amount of superelevation that would need to be added to achieve balance superelevation that would need to be added to achieve balance speed. speed.

Definition of Cant Deficiency Definition of Cant Deficiency

Cant Deficiency/Tilt Marquis / Page 5 US DOT Volpe Center Federal Railroad Administration

Increasing Speed Increasing Speed

Superelevation Superelevation Superelevation

Stopped

Superelevation Center of Gravity Resultant

Increase superelevation to create balance condition Superelevation counteracts centripetal acceleration Decrease superelevation to create balance condition Remove superelevation to create balance condition Lateral acceleration=0

Underbalance Underbalance (Cant Deficiency) (Cant Deficiency) Balance Balance Overbalance Overbalance (Cant Excess) (Cant Excess) Overbalance Overbalance (Cant Excess) (Cant Excess)

Lateral acceleration<0 Lateral acceleration<0 Lateral acceleration>0

Definition of Cant Deficiency Definition of Cant Deficiency

Center of Gravity Resultant Center of Gravity Resultant Center of Gravity Resultant

Cant Deficiency/Tilt Marquis / Page 6 US DOT Volpe Center Federal Railroad Administration

Benefits of Operating at CD Benefits of Operating at CD

• Higher curving speeds

Higher curving speeds V Vmax

max

– – Depends on curve Depends on curve characteristics characteristics – – curvature curvature and superelevation (cant) and superelevation (cant)

• Reduce trip time without

Reduce trip time without reconfiguring existing route reconfiguring existing route layout layout

– – S trongly dependent on S trongly dependent on route makeup route makeup – – Can improve speed on Can improve speed on tangents as well tangents as well

• Can reduce need for braking

Can reduce need for braking

• r accelerating when
• r accelerating when

entering or exiting curves entering or exiting curves

D . E E V

u a

007   max

49 CFR 213.57 and 213.329 49 CFR 213.57 and 213.329 Curves; Elevation and Speed Limitations Curves; Elevation and Speed Limitations

Eu = Cant Deficiency (inches)

Cant Deficiency/Tilt Marquis / Page 7 US DOT Volpe Center Federal Railroad Administration

Vehicle Speed (3" Superelevation)

20 40 60 80 100 120 140 1 2 3 4 5 6 Curvature (deg) Speed (mph) 0" CD 1" CD 2" CD 3" CD 4" CD 5" CD 6" CD 7" CD 8" CD 9" CD

Benefits of Operating at CD Benefits of Operating at CD

D . E E V

u a

007   max

Higher Speed with Increasing CD

Cant Deficiency/Tilt Marquis / Page 8 US DOT Volpe Center Federal Railroad Administration

Time per Mile (3" Superelevation)

0.0 0.5 1.0 1.5 2.0 2.5 1 2 3 4 5 6 Curvature (deg) Time per Mile (min) 0" CD 1" CD 2" CD 3" CD 4" CD 5" CD 6" CD 7" CD 8" CD 9" CD

Benefits of Operating at CD Benefits of Operating at CD

Lower Trip Time with Increasing CD

Cant Deficiency/Tilt Marquis / Page 9 US DOT Volpe Center Federal Railroad Administration

Time Savings per Mile Over Balance Speed (3" Superelevation)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1 2 3 4 5 6 Curvature (deg) Time Savings per Mile (min) 1" CD 2" CD 3" CD 4" CD 5" CD 6" CD 7" CD 8" CD 9" CD

Benefits of Operating at CD Benefits of Operating at CD

Larger Time Savings with Increasing CD Greater Time Savings in Higher Degree Curves

Cant Deficiency/Tilt Marquis / Page 10 US DOT Volpe Center Federal Railroad Administration

Benefits of Operating at CD Benefits of Operating at CD

• Example Trip Time Comparison for 2 routes

Example Trip Time Comparison for 2 routes

– – Route 1: NEC Boston to Washington DC Route 1: NEC Boston to Washington DC – – Route 2: S eattle to Portland Route 2: S eattle to Portland

• This analysis does not include tangent miles

This analysis does not include tangent miles and assumes speed in curve is constant at and assumes speed in curve is constant at either either Vmax Vmax or the maximum operating

• r the maximum operating

speed (the lesser of the two) speed (the lesser of the two)

Cant Deficiency/Tilt Marquis / Page 11 US DOT Volpe Center Federal Railroad Administration

Benefits of Operating at CD Benefits of Operating at CD

Percentage of Track Length Below Curvature

10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 6 7 8 9 10 Curvature (deg) Percent of Track Length (%)

Curves on NEC (129.3 miles) Curves Seattle to Portland (71.0 miles)

* This analysis does not include tangent miles and assumes speed in curve is constant at either Vmax or the maximum operating speed (the lesser of the two)

Cant Deficiency/Tilt Marquis / Page 12 US DOT Volpe Center Federal Railroad Administration

NEC: 129.3 miles, 125mph maximum speed Seattle-Portland: 71.0 miles, 80mph maximum speed

10 20 30 40 50 60 70 80 90 100 3 4 5 6 7 8 9 Cant Deficiency (in) Trip Time (min) NEC Seattle - Portland

Benefits of Operating at CD Benefits of Operating at CD

* This analysis does not include tangent miles and assumes speed in curve is constant at either Vmax or the maximum operating speed (the lesser of the two)

90 73 68 53

Cant Deficiency/Tilt Marquis / Page 13 US DOT Volpe Center Federal Railroad Administration

Benefits of Operating at CD Benefits of Operating at CD

• Estimate of reduction in trip time in previous example

Estimate of reduction in trip time in previous example does not account for all factors that affect actual trip does not account for all factors that affect actual trip

– – Time strongly dependent on route makeup Time strongly dependent on route makeup – – order of curves, etc.

• rder of curves, etc.

– – Although equipment qualified for higher CD, Although equipment qualified for higher CD, Vmax Vmax in a particular in a particular curve may not be achievable due to constraints of neighboring curve may not be achievable due to constraints of neighboring curves, etc. curves, etc. – – May not want to maintain to higher track class corresponding to May not want to maintain to higher track class corresponding to higher speed higher speed – – Higher CD may permit higher speed on tangents as well Higher CD may permit higher speed on tangents as well – – Reduces need for slowing down when entering a curve Reduces need for slowing down when entering a curve – – Reduces need for accelerating when exiting a curve Reduces need for accelerating when exiting a curve – – Etc. Etc.

Cant Deficiency/Tilt Marquis / Page 14 US DOT Volpe Center Federal Railroad Administration

Benefits of Operating at CD Benefits of Operating at CD

25 50 75 100 125 150 175 200 225 250 275 300 325

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Curve Number

Speed (mph)

7" CD speed for curve 9" CD speed for curve 7" Line Speed 9" Line Speed New Haven MP 75 Boston MP 225 MP 155 MP 170 10 Short Curves Providence MP 185 Interlockings Xing Bridge Xing 5 10 Class 9 Class 8 Class 7 Class 6 Class 5 Class 4 Class 3 Class 2 Class 1

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• Increase in lateral force exerted on track during curving

Increase in lateral force exerted on track during curving

– – Increased deterioration of track, lower safety margin for curvin Increased deterioration of track, lower safety margin for curving, g, and may result in unsafe wheel force conditions and may result in unsafe wheel force conditions

• Decrease in load on wheels on inside rail

Decrease in load on wheels on inside rail

– – Increased risk of vehicle overturn, especially if high winds pre Increased risk of vehicle overturn, especially if high winds present sent

• Reduction in margin of safety associated with vehicle

Reduction in margin of safety associated with vehicle response to track geometry variations response to track geometry variations

– – S uspension elements operating at performance limits S uspension elements operating at performance limits

• Increase in net steady stated carbody lateral acceleration

Increase in net steady stated carbody lateral acceleration

– – Decreased passenger ride comfort Decreased passenger ride comfort – – Tilt can be used at high cant deficiency to reduce the net later Tilt can be used at high cant deficiency to reduce the net later al al acceleration acting on the passengers acceleration acting on the passengers

Effect of CD on Vehicle Performance Effect of CD on Vehicle Performance

Cant Deficiency/Tilt Marquis / Page 16 US DOT Volpe Center Federal Railroad Administration

Increasing Speed Increasing Speed

Superelevation Superelevation Superelevation

Stopped

Superelevation Center of Gravity Resultant

Increase superelevation to create balance condition Superelevation counteracts centripetal acceleration Decrease superelevation to create balance condition Remove superelevation to create balance condition Lateral acceleration=0

Underbalance Underbalance (Cant Deficiency) (Cant Deficiency) Balance Balance Overbalance Overbalance (Cant Excess) (Cant Excess) Overbalance Overbalance (Cant Excess) (Cant Excess)

Lateral acceleration<0 Lateral acceleration<0 Lateral acceleration>0

Center of Gravity Resultant Center of Gravity Resultant Center of Gravity Resultant

Effect of CD on Vehicle Performance Effect of CD on Vehicle Performance

Cant Deficiency/Tilt Marquis / Page 17 US DOT Volpe Center Federal Railroad Administration

Use of Tilt at High Cant Deficiency Use of Tilt at High Cant Deficiency

Lateral acceleration>0.12 Lateral acceleration<0.12

Operating at High CD Operating at High CD without without Tilt Tilt Operating at High CD Operating at High CD with with Tilt Tilt

Cant Deficiency/Tilt Marquis / Page 18 US DOT Volpe Center Federal Railroad Administration

Cant Deficiency at which Tilt-body Compensation Becomes Necessary 1 2 3 4 5 6 7 8 9 10 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Suspension flexibility (S) Cant Deficiency (inch) Limit of 0.1g Limit of 0.15g Limit of 0.12g

Use of Tilt at High Cant Deficiency Use of Tilt at High Cant Deficiency

Suspension with No Carbody Roll Typical Roll Suspension Soft Roll Suspension

The choice of tilt is dependent on the criterion for lateral acceleration, the roll suspension of the vehicle, and the desired level of CD to make trip time.

Cant Deficiency/Tilt Marquis / Page 19 US DOT Volpe Center Federal Railroad Administration

Use of Tilt at High Cant Deficiency Use of Tilt at High Cant Deficiency

plane) track to relative (measured tion supereleva to due roll ation) (superelev horizontal and plane track between angle       

Rstatic track track Rstatic

where S

Cant Deficiency/Tilt Marquis / Page 20 US DOT Volpe Center Federal Railroad Administration

Use of Tilt at High Cant Deficiency Use of Tilt at High Cant Deficiency

Benefits Benefits – – not a complete list not a complete list

• Addresses ride comfort at higher cant deficiency

Addresses ride comfort at higher cant deficiency – – Reduces steady state lateral acceleration felt by passengers Reduces steady state lateral acceleration felt by passengers

• Allows operation at higher cant deficiency by meeting

Allows operation at higher cant deficiency by meeting regulatory requirements on steady state lateral acceleration regulatory requirements on steady state lateral acceleration

• Has little to no effect on wheel rail forces or derailment safet

Has little to no effect on wheel rail forces or derailment safet y y

Drawbacks Drawbacks – – not a complete list not a complete list

• Compatibility with clearance envelopes for existing lines and

Compatibility with clearance envelopes for existing lines and equipment equipment

• Increased suspension complexity and maintenance

Increased suspension complexity and maintenance

• Motion sickness

Motion sickness