Re: Fate of 85/86 class

["Ray McDermott" <raymcd@ozemail.com.au>]

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Ray McDermott   raymcd@ozemail.com.au
Dion Williams <onamission@start.com.au> wrote in message
389D1316.3F46@start.com.au">news:389D1316.3F46@start.com.au...
> Maurie Daly wrote:
>
> > Please dont confuse as a lot of people do horsepower with pulling power.
> > Horsepower is simply a measure of the power output of the main prime
> > mover with a small reduction due to the non perfect efficiency of
> > the rectifiers and traction motors .
> > The pulling power is determined solely by the gearing ratios of the
traction
> > motors and by their design , ie the amount of iron in the motor, the
guages of
> > copper in the armature and the field coil current.
> > Pulling power is measured usually in either Kn (kilo newtons or Lbs).
>
> Fair enough my mistake. Thanks for explaining that.
>
> Dion

I think MD's statements require a little qualification.  Consider these
(simplified) basics:

POWER: The capacity for exerting mechanical force or doing WORK (dictionary)

WORK = FORCE X DISTANCE (F x D)

POWER = Rate of doing Work  = (FxD)/T

D/T = Velocity (Speed)

Therefore; Power = Force x Speed

Applying to locomotives; Tractive Force, Power and Speed are interrelated in
accordance with the above.   HP = TF x SPEED/550.
 Calculating drawbar HP for the examples given in MD's earler posting (taken
as read and using Imperial Units):

For 81 class  HP = 75730 x 17.3 = 2384 HP
For 86 class  HP = 49887 x 41.0 = 3760 HP

Therefore, the 86 is more *powerful*.  There are of course, many other
factors which have been discussed by others in this very interesting thread.
I believe the original thinking (1950s) about electrification w.r.t. freight
was to pull moderate mass trains at much greater speed than steam and
therefore improve track capacity and the locos were designed accordingly
(high TE at speed).  Ignoring power supply capacity and regulation, there is
no theoretical reason why a straight electric cannot be designed with same
characteristics as a diesel (you might have to increase the mass to maintain
adhesion at low speed/high TE, but this counters the high power/weight ratio
advantage of electrics).  It comes down to horses for courses.

Ray