05 Tractive Effort Mar 12

Module 5:Tractive Effort

Module Objectives • Learn About Tractive Effort (the Amount of Force at the Wheels Available Available for Moving Moving a Train • !nderstand the Effects of "ombining #tee$ %rades and &ori'ontal "urvature

Module Objectives • Learn About Tractive Effort (the Amount of Force at the Wheels Available Available for Moving Moving a Train • !nderstand the Effects of "ombining #tee$ %rades and &ori'ontal "urvature

Energ !tili'ation The t)o $rimar as$ects of trans$ortation energ efficienc:  – *esistance *esistance +  + &o) much )or, is re-uired to move something  – Energ Efficienc + Efficienc + &o) )ell energ is converted into useful )or,

Train *esistance • For our $ur$oses1 *esistance is the combination of forces that )or, against a train2s movement0 • Earl measurement of railcar resistance sim$l involved $iling on )eight1 w , and determining ho) much )as needed to ma,e the car move0 • 3f the )eight1 w1 is great enough to overcome the static friction1 the car )ill start to move0 *esistance is t$icall measured in .$ounds $er ton/ (in !0#0

Friction

Trains 4#0 Truc,s • Trains re-uire less energ to move than truc,s because of smaller resistive forces: • 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

&orse$o)er

Tractive Effort • Tractive Effort

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) (rae) Cr,atre) #o&o tra"' 7e"(t rat"o

 – The $oint of contact bet)een the )heel and the rail is )here the tor-ue of the motor is converted to a force that is called tractive effort0

HP  308 ⋅

TE 

=

V 

% lb-f  

Traction Forces

7 TE

TE max 

=

 µ 

!

W 

= Adhesion W = Weight on Drivers  µ

Adhesion Adhesion  – 9ercentage of a locomotive2s )eight on its driving )heels1 converted into tractive effort0 • " locomotives can achieve a ma;imum $ea, of