Re: BM 1 in 33

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

In article <74fgh9$61t$1@mirv.unsw.edu.au> G.Lambert@unsw.edu.au (Geoff Lambert) writes:
>From: G.Lambert@unsw.edu.au (Geoff Lambert)
>Subject: Re: BM 1 in 33
>Date: Mon, 07 Dec 1998 04:22:11 GMT

>mauried@commslab.gov.au (Maurie Daly) wrote:

>>Its probably worth mentioning that the above is a compensated grade , ie the 
>>grade is modified to include the curve rolling resistance.
>>Some railways (like SRA) quote grades in their compensated form whilst others 
>>dont.
>>VIC & SA gradient diagrams are uncompensated.

>How do you draw a compensated grade on paper- show the slope as it is
>and label it with the uncompensated grade, or fiddle with the
>horizontal scale?

>Geoff Lambert


You cant really , it all gets down to what purpose grade books are for .
Compensated grades are drawn exactly as they would be in uncompensated form ,
but the real grade itself is fiddled , and the drawn grade is labelled as 
compensated. (ie the real grade is less than the grade book says.)
This allows loco engineers to easily determine maximum loads for a given route 
without having to accurately study the curve radii.
Obviously , compensated grades only make sense on lines with sharp radii 
curves which are long .
NSW grade books show the grade with an asterisk next to it  to indicate 
whether it is compensated or not.
Some obvious examples where this is important are 

Unanderra to Moss Vale.	1:30
Bethungra Spiral.	                1:66
Frampton Deviation.	1:66
Cougal Spiral.		1:66

Some other less notable examples are 
Oberon Line.	 1:25
Dorrigo Line.            1:30
Gilmore to Batlow.   1:25

These 3 lines are interesting in that when they were open they would have all 
been worked by locomotives without dynamic brakes, whereas these days , lines 
like the Unanderra line can only be worked in the falling grade direction with 
dynamic braked locos.
Strange how the rules can change. 

I actually made a slight blunder in my previous post in that the Blue Mtns 
arnt shown as being compensated, which is surprising , given the magnitude of 
the grade,although a close examination of the grade book shows that the rising 
grade isnt continuously 1:33 , but varies up and down quite a bit , with bits 
of 1:50 and 1:40 interposed.
Difficult to show this sort of grade in a grade book in compensated form.

cheers
MD