05 tractive effort mar 12
TRANSCRIPT
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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
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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
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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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!E#T3OG#8
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