05 Tractive Effort Mar 12

8/21/2019 05 Tractive Effort Mar 12

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5: 1 of 30COPYRIGHT © AREMA 2012

Module 5:Tractive Effort


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Module Objectives

• Learn About Tractive Effort (the

Amount of Force at the Wheels

Available for Moving a Train

• !nderstand the Effects of

"ombining #tee$ %rades and

&ori'ontal "urvature


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Energ !tili'ationThe t)o $rimar as$ects of trans$ortationenerg efficienc:

– *esistance + &o) much )or, is re-uired tomove something

– Energ Efficienc + &o) )ell energ isconverted into useful )or,


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Train *esistance

*esistance is t$icall measured

in .$ounds $er ton/ (in !0#0

Friction

• For our $ur$oses1 *esistance is the combination of forces

that )or, against a train2s movement0• Earl measurement of railcar resistance sim$l involved $iling

on )eight1 w , and determining ho) much )as needed to

ma,e the car move0

• 3f the )eight1 w1 is great enough to overcome the staticfriction1 the car )ill start to move0


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Trains 4#0 Truc,s• Trains re-uire less energto move than truc,sbecause of smaller resistiveforces:

• Lo)er friction factor (067

– #maller contact area

– #teel )heels on steel rails

– *ubber tires on $avement

• Less )ind resistance $er

$ound of load

• #i'e of contact area8


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&orse$o)er Tractive Effort

• Tractive Effort

– The $oint of contactbet)een the )heel andthe rail is )here thetor-ue of the motor is

converted to a forcethat is called tractiveeffort0

Power to a!"#"ar"e$

%&oo#"'( fa'$)*otor +#ower$)

#o&o*ot",e &o'tro#$) a"r

-ra.e &o*/re$$or) et&

o$$ "' (e'erator %or

A#ter'ator re&t"f"er

Co',ert"'( &ra'.$aft

Power to e#e&tr"&"t

Tra&t"o' *otor #o$$e$

Gear fr"&t"o'

Power to *o,e) #"ft)

a&&e#erate we"(t of

#o&o*ot",e "t$e#f

%,ar"e$ w"t $/ee) (rae)

Cr,atre) #o&o tra"'

7e"(t rat"o

%308 lb-f V

HP TE ⋅

=


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Traction Forces

7

TE

W TE max ! µ =

µ = Adhesion

W = Weight on Drivers



Adhesion

Adhesion – 9ercentage of a locomotive2s

)eight on its driving )heels1converted into tractive effort0• " locomotives can achieve a

ma;imum $ea, of


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Factors Affecting Adhesion

Wheel?*ail "ontact Factors• Wheel@*ail materials

• &ert'ian (*olling Wheel#tresses

• *ail Metal "ree$(Longitudinal Movement

Trac, factors

• *ail surface condition

• *ail $rofile irregularities

• "urvature of trac,

4ehicle factors

• Mechanical – Loco )eight and a;le

)eight distribution

– Weight transfer

– #$eed

– Wheel si'e variation

• Electrical – Tor-ue control method

– Traction motor

characteristics – 9o)er circuit

configuration

– #li$@slide control



Train *esistance

• T)o Elements:

– *olling *esistance (On Level Tangent Trac,

• Friction related

• ournal1 )heel1 trac, -ualit1 trac, modulus

• Aerodnamics of e-ui$ment

– %rade B "urve *esistance

• Trac, 9rofile B Alignment related• "hange in $otential energ head


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*olling *esistance*olling *esistance• *olling *esistance

– The resistance for train movement on straight and level trac,can be determined b W0 0 avis formula:

*CAD4D"4

Where*C Train rolling resistance

AC *olling resistance com$onent inde$endent of train s$eed

C Train resistance de$endant on s$eed

"C rag coefficient based on the sha$e of the front of the train and

other features affecting air turbulance4C Train s$eed

– The Train resistance on level tangent trac, is the sum oflocomotive and train resistances0


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Freight Train #$eed 4 *esistance

At lo) s$eeds1 journal resistance dominates1 as s$eed increases airresistance is increasingl most im$ortant

R e $ " $ t a ' & e % # + $ ; 2

t o ' 0

or'a#= Re$"$ta'&e %A

=?#a'(e= Re$"$ta'&e %-@

A"r Re$"$ta'&e %C@2

CV2

BV

A


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avis E-uation Modifications• The avis E-uation has been substantiall u$dated to reflect

modern develo$ments1 but its basic form is the same0

• *o C 605 D 67G?W D 0


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*esistance 4ersus #$eed

0

10)000

20)000

30)000

40)000

50)000

60)000

0 10 20 30 40 50 60 90 80

R e $ " $ t a ' & e % # + $ ; 0


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%rade *esistance

1 Grae B A//ro!"*ate# 20 #+f to'


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"urve *esistance

10 B 0;8 #+f to'


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"om$ensated %rade

G& B G D& 0;04


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T$ical Freight "onsist

T$ical modern freight consist

6000 horsepower,212 tons

100 cars x 143 tons each = 14,300 tons

T$ical modern locomotive


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#$eed?Tractive Effort "urve

0

20)000

40)000

60)000

80)000

100)000

120)000

140)000

160)000

180)000

0 10 20 30 40 50 60 90 80

T r a & t " , e E f f o r t

% # + $ ; 0


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0

20)000

40)000

60)000

80)000

100)000

120)000

140)000

160)000

180)000

0 10 20 30 40 50 60 90 80

T r a

& t " , e E f f o r t % # +

$ ; 0


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0

20)000

40)000

60)000

80)000

100)000

120)000

140)000

160)000

180)000

0 10 20 30 40 50 60 90 80


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Ca/a+"#"t of F*#t"/#e '"t &o'tro# *a.e$ t"$ /o$$"+#e

0

50)000

100)000

150)000

200)000

250)000

300)000

350)000

0 10 20 30 40 50 60 90 80


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Freight Time?#$eed %ra$h

This curve de$icts a single locomotive0

&o) )ill the curve change if a second locomotive is added8

0

10

20

30

40

50

60

90

0 500 1000 1500 2000 2500 3000

< / e e 6 % * / 3 0

T"*e %$e&o'$

About 900 seconds = 15 minutes

How long will it take for thistrain to reach 40 mph?


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Time?#$eed %ra$h

0

10

20

30

40

50

60

90

0 500 1000 1500 2000 2500 3000

T"*e %$e&o'$

Now how long will it take to reach 40 mph?

About 300 seconds≈ 5 minutes <

/ e e 6 % M

P H 0


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Freight istance?#$eed %ra$h

0

10

20

30

40

50

60

90

0

5 0 ) 0

0 0

1 0 0 ) 0 0

0

1 5 0 ) 0 0

0

2 0 0 ) 0 0

0

2 5 0 ) 0 0

0

3 0 0 ) 0 0

0

3 5 0 ) 0 0

0

4 0 0 ) 0 0

0

D"$ta'&e %feet

How many miles until this

train reaches 40 mph?

4elocit 9rofile h (ft C 0< 4H

About 75,000 feet 14 miles

< / e e 6 % M P H 0


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H !nit istance?#$eed %ra$h

0

10

20

30

40

50

60

90

0

5 0 ) 0

0 0

1 0 0 ) 0

0 0

1 5 0 ) 0

0 0

2 0 0 ) 0

0 0

2 5 0 ) 0

0 0

3 0 0 ) 0

0 0

3 5 0 ) 0

0 0

4 0 0 ) 0

0 0

D"$ta'&e %feet

With 2 locomotives, only about25,000 feet ≈ 5 miles

< / e e 6 % M P H 0


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&orse$o)er:Trailing Tonnage• Long@distance train )ith

fe) sto$s along the )a0 – Lo) horse$o)er:trailing ton

ratio0 6H1 h$: 6>1 h$:ton

– T$ical of intermodal trainsand ma be even higher for$assenger trains


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#to$$ing the Train

• #afet is the most im$ortant considerationK

• Adhesion Limits ra,ing Abilit0

• #to$$ing Train 4s0 Motor 4ehicle0

J12

#t i i t 4 # d


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#to$$ing istance 4 #$eed

0

10

20

30

40

50

60

90

0 1)000 2)000 3)000 4)000 5)000 6)000 9)000 8)000

D"$ta'&e %feet

Stopping a train can oftentake a mile or more


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5: 30 of 30

!E#T3OG#8

Authors:ose$h E0 *ile1 90E0

Federal *ailroad Administration

(HH >I

$aul0liNuma0aecom0com

*evisions:

*obert imicata1 90E0

imicata *ail "onsulting(7> @>65

rd,imicataN,railinc0com

ohn %0 %reen1 9h001 90E0

"&HM &ill1 inc0(H6

05 Tractive Effort Mar 12

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