Re: Fate of 85/86 class

[mauried@commslab.gov.au (Maurie Daly)]

In article <389D12EE.E3CFAFC2@lisp.com.au> John MacCallum <johnmac@lisp.com.au> writes:
>From: John MacCallum <johnmac@lisp.com.au>
>Subject: Re: Fate of 85/86 class
>Date: Sun, 06 Feb 2000 17:21:34 +1100

>> > Err,little confusion here , the 85 / 86s are nowhere near as powerful as an NR
>> or indeed an 81.
>> 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).
>> 
>> here are a couple of examples.(these are continous ratings)
>> 81 class 75730 lbs at 19 km/h.
>> 85 class 49910 lbs at 45 km/h.
>> 86 class 49887 lbs at 45 km/h.
>> 
>> Railpages loco info has tractive effort figures for most Aus locos and its a

>Err a little more confusion here!
>Tractive effort and Horsepower are different but they are related.
>An 86 class indeed more powerful than an 81 class as indeed an 85 class
>is more powerful than an 86 class.
>To compare an 81 with a 86 directly is like comparing apples with
>oranges. Tractive effort is a function of traction motor current,
>wheel diameter, gearing and adhesion. An 86 can pull a given load
>faster than an 81 can because it has more power available. An
>81 can pull more load up the ruling grade than an 86 because it has
>lower gearing and more adhesive ability.

>85 class and 86 class engines do indeed have a fairly complicated 
>wheel slip control circuit but it is only single channel in its
>operation. So where a GM fitted with super series control each axle
>independent of the rest an 85/86 class can only control one axle at a
>time.

>Operationally high horsepower, high adhesive diesel locomotives are
>more flexible than Electric Locos and that's why a lot of USA railroads
>opted out of electric traction. 

>i.e. You can't double stack under overhead wiring and you can't haul
>as heavy loads with 1500 V DC up hills as diesels.

>Pope

>Alias   John MacCallum


Yes , its all a question of what is meant by powerful.
Horsepower is directly equal to the product of RPM X Rotational torque 
for a given constant efficiency.
A 81 class can deliver 3000 HP to the rail , 2 81s can deliver 6000 Hp , 4 
12000 Hp etc.
In the case of electrics though,its the law of diminishing returns as the 
overhead voltage falls as we add more electric locos,so that whilst a single 
86 can deliver 4000 hp to the rail , no chance that 4 86s together can deliver
16000 HP , the overhead simply cant deliver the current.
Things would be differant though if we were talking about 25 KV AC.

As to the costs of running electrics vs diesels there is something wrong here
although I dont know what.
When the 85/86 s were bought , and indeed the same argument would go for the 
original 46s,the price of diesel would have been the cheapest it has ever been
as Govt railways didnt then pay any fuel excise.
Fuel excise for railways is a relatively recent thing,being originally levied 
as a road usage tax by the Keating Govt.
If diesel is cheaper today than electricity ,then maybe we should be using 
diesels to haul cityrails trains,and Qrail should dismantle the electrification
on the main north.


MD