Re: 422 Class

[mauried@tpg.com.au (Maurie Daly)]

On Mon, 30 Apr 2001 20:13:24 +1000, "Paul Jones"
<dj_wiseguy2_nospam@yahoo.com> wrote:

>I think 42220 and 42203 are still at delec.
>
>
>--
>Paul Jones
>http://pj_rail.tripod.com
>icq: 4499597
>
>"bruce edwards" <bruceedwards@yahoo.com> wrote in message
>3AED15BD.326617DA@yahoo.com">news:3AED15BD.326617DA@yahoo.com...
>> Many thanks to those that replied re my G class query.
>>
>> Another question, what has been the fate of the 422 class 42203 and
>> 42220.
>>
>> Further to this could someone please explain the significance of the
>> terminology "Tractive effort" and what a loco with 285/239 kN Tractive
>> effort means.
>>
>> Thanks for your patience
>>
>> Regards
>>
>> Bruce
>>
>
Tractive effort is a measure of a locomotives pulling power , ie a
measure of how much pull it can exert on its drawbar.
1 newton of pull will accelerate a 1 kg mass at a rate of 1 M/sec ^2 .

There are usually 2 figures given , one always being higher than the
other.
The higher of the 2 figures is what is called the intermittant or
short term tractive effort , and is applied where the locomotive is
only required to exert this amount of pull for a short time , usually
30 minutes or less.
The lower of the two figures is the maximum pull that the loco can
exert on a continuous basis , ie when in notch 8 for hours on end.
The continuous tractive effort is determined primarily by the design
of the traction motors , the bigger and heavier the motors , the
higher is the continuous tractive effort , which also determines the
intermittant figure .
Tractive effort falls as speed rises, generally peaking somewhere
between 10 and 25 km/h .

Tractive effort is not always related to locomotive horsepower.
A good example of this is to compare a loco like the NR class
(a 4000 HP loco ) with a continous tractive effort of 370 KN against
a SRA 82 class (a 3000 HP loco) with a continuous tractive effort of
413 KN.

Another factor which affects tractive effort is the final gear ratio
of the traction motors , the lower the ratio , the higher is the locos
top speed and the lower is its tractive effort.

Another good comparison is the AN class against the NR class.
Both are 4000 HP locos but the NR class is much higher at 370 KN
against the ANs 320 KN , simply because the AN class is geared for 150
KM/H running as against the NRs 115 KM/H.

Tractive effort essentially determins what load can be pulled up a
hill, but doesnt determine the speed .
HP determines what speed a load can be pulled up a hill, but doesnt
determine the load .

MD