This is one of those situations where the use of old technology (i.e. a
book) would not only be quicker but provide greater understanding of the
subject.
The ruling gradient is simply the steepest gradient on a line where the
gradient varies. Thus if a line starts level, climbs at 1 in 150, followed
by 1 in 70, 1 in 65, 1 in 30, 1 in 100, 1 in 450 and finishes on the level
at a higher elevation then the stretch at 1 in 30 will be the ruling
gradient and will determine the weight of train for a given locomotive or
the power requirements for a given weight of train.
Rail weight quoted in 'lbs' is a shorthand and refers to its weight per
yard, i.e. 75lb rail is 75lb per yard of rail. A rail can be as short or as
long as is needed for the job subject to the material of which it is made.
Originally made of cast and later wrought iron rails were as short as 3
feet. Later steel was introduced and lengths extended to 45ft and then 60ft.
They are now laid in lengths of a quarter mile or more. The reason for them
being relatively short previously is due to transport and handling
limitations.
Roger Viggers
----- Original Message -----
From: "John Duncan" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, July 28, 2001 5:32 PM
Subject: Ruling gradients-75lb. rails
> I am researching the 19-mile Peebles Railway, 1855-1876, whose engineer
was
> Thomas Bouch. It was reported that the ruling gradient was about 1 in
90.
> But, when quoting prices to work the line in 1855, the North British
offered '
> to work 5-coach trains on a 1 in 53 ruling gradient or 7-coach trains on a
1
> in 60 ruling gradient.' (Thomas, Forgotten Railways: SCOTLAND). The
Bouch's
> actual elevations had been available from November 1852. I should be
> grateful if someone could explain what a ruling gradient is and how it is
> calculated.
>
> In C.J.A. Robertson's 1974 article on the St Andrews Railway in the
Journal
> of Transport History, he mentioned 'relaying the track with 75 lb. rails
to
> take heavier locomotives.' How long is a 75 Ib. rail, or indeed, any
other
> rail quoted in lbs.?
>
> Many thanks in advance,
>
> John Duncan
>
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