Roger's response is accurate and to the point. There's just one detail I'd
like to add to it. Nowdadays of course rail weights are referred to in kgs.
But note that the new measurement is also a ratio, that is kgs per m, just
as the old ratio was lbs per yd. So don't convert the old weights by the
usual lb into kgs ratio of around 2.2. The factor of conversion for rail
weights is so near to 2 that it makes no practical difference. So 110lb
rail has become 55kg rail and so on. It's one conversion that's very easy
(for a change!).
Robert Lee
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>Date: Sun, 29 Jul 2001 08:19:45 +0100
>Reply-To: Roger Viggers <[log in to unmask]>
>Sender: "Scholarly discussion of all aspects of railways, past,
present and future." <[log in to unmask]>
>From: Roger Viggers <[log in to unmask]>
>Subject: Re: Ruling gradients-75lb. rails
>Comments: To: [log in to unmask]
>To: [log in to unmask]
>
>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Originally made of cast and later wrought iron rails were as short as 3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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