Part 58 (2/2)
Every argument here adduced, and every calculation made, would tend to the adoption of about 7 feet on the Great Western Railway.
The gradients of the lines laid down by the Irish Commission are considerably steeper than those of the London and Birmingham Railway, and four and five times the inclination of those on the Great Western Railway; the curves are by no means of very large radius, and indeed the Commissioners, after fixing the gauge of 6 feet 2 inches, express their opinion, that upon examination into the question of curves, with a view to economy, they do not find that the effect is so injurious as might have been antic.i.p.ated, and imply therefore that curves, generally considered of small radius on our English lines, are not incompatible with the 6 feet 2 inch gauge; and, lastly, the traffic, instead of being unusually large, so as to justify any expense beyond that absolutely required, is such as to render a.s.sistance from Government necessary to ensure a return for the capital embarked. As compared with this, what are the circ.u.mstances in our case?
The object to be attained is the placing an ordinary coach body, which is upwards of 6 feet 6 inches in width, between the wheels. This necessarily involves a gauge of rail of about 6 feet 10 inches to 6 feet 11 inches, but 7 feet allows of its being done easily; it allows, moreover, of a different arrangement of the body: it admits all sorts of carriages, stage-coaches, and carts to be carried between the wheels.
And what are the limits in the case of the Great Western Railway, as compared to those on Irish railways? Gradients of one-fifth the inclination, very favourable curves, and probably the largest traffic in England.
I think it unnecessary to say another word to show that the Irish Commissioners would have arrived at 7 feet on the Great Western Railway by exactly the same train of argument that led them to adopt 6 feet 2 inches in the case then before them.
All these arguments were advanced by me in my first Report to you, and the subject was well considered. The circ.u.mstance of the Great Western Railway, and other princ.i.p.al railways likely to extend beyond it, having no connection with other lines then made, leaving us free from any prescribed dimension, the 7-feet gauge was ultimately determined upon.
Many objections were certainly urged against it: the deviation from the established 4 feet 8 inches was then considered as the abandonment of the principle: this, however, was a mere a.s.sertion, unsupported even by plausible argument, and was gradually disused; but objections were still urged, that the original cost of construction of all the works connected with the formation of the line must be greatly increased; that the carriages must be so much stronger; that they would be proportionally heavier; that they would not run round the curves, and would be more liable to run off the rails; and particularly, that the increased length of the axles would render them liable to be broken: and these objections were not advanced as difficulties which, as existing in all railways, might be somewhat increased by the increase of gauge, but as peculiar to this, and fatal to the system.
With regard to the first objection, namely, the increased cost in the original construction of the line, if there be any, it is a question of calculation which is easily estimated, and was so estimated before the increased gauge was determined upon. Here, however, preconceived opinions have been allowed weight in lieu of arguments and calculations; cause and effect are mixed up, and without much consideration it was a.s.sumed at once that an increased gauge necessarily involved increased width of way, and dimensions of bridges, tunnels, &c.
Yet such is not the case within the limits we are now treating of: a 7-feet rail requires no wider bridge or tunnel than a 5-feet; the breadth is governed by a maximum width allowed for a loaded waggon, or the largest load to be carried on the railway, and the clear s.p.a.ce to be allowed on either side beyond this.
On the Manchester and Liverpool Railway this total breadth is only 9 feet 10 inches, and the bridge and viaducts need only have been twice this, or 19 feet 8 inches; 9 feet 10 inches was found, however, rather too small, and in the London and Birmingham, with the same width of way, this was increased to 11 feet by widening the interval between the two rails.
In the s.p.a.ce of 11 feet, allowed for each rail, a 7-feet gauge might be placed just as well as a 5-feet, leaving the bridges, tunnels, and viaducts exactly the same; but 11 feet was thought by some still too narrow: and when it is remembered that this barely allows a width of 10 feet for loads, whether of cotton, wool, agricultural produce, or other light goods, and which are liable also to be displaced in travelling, 13 feet (which has been fixed upon in the Great Western Railway, and which limits the maximum breadth, under any circ.u.mstances, to about 12 feet) will not be found excessive.
It is this which makes the minimum width, actually required under bridges and tunnels, 26 feet instead of 22 feet, and not the increased gauge.
The earthwork is slightly affected by the gauge, but only to the extent of 2 feet on the embankment, and not quite so much in the cuttings; but what, in practice, has been the result? The bridges over the railway on the London and Birmingham are 30 feet, and the width of viaducts 28 feet; on the Great Western Railway they are both 30 feet; no great expense is therefore incurred on these items, and certainly a very small one compared to the increased s.p.a.ce gained, which, as I have stated, is from 10 to 12 feet. In the tunnels exists the greatest difference; on the London and Birmingham Railway, which I refer to as being the best and most a.n.a.logous case to that of the Great Western Railway, the tunnels are 24 feet wide. On the Great Western Railway the constant width of 30 feet is maintained, more with a view of diminis.h.i.+ng the objections to tunnels, and maintaining the same minimum s.p.a.ce which hereafter may form a limit to the size and form of everything carried on the railway, than from such a width being absolutely necessary.
Without pretending to find fault with the dimensions fixed, and which have, no doubt, been well considered, upon the works on other lines, I may state that the principle which has governed has been to fix the minimum width, and to make all the works the same, considering it unnecessary to have a greater width between the parapet walls of a viaduct, which admits of being altered, than between the sides of a tunnel which cannot be altered.
The embankments on the London and Birmingham Railway are 26 feet, on the Great Western 30 feet, making an excess of about six and a half per cent. on the actual quant.i.ty of earthwork.
The difference in the quant.i.ty of land required is under half an acre to a mile. On the whole, the increased dimensions from 10 to 12 feet will not cause any average increased expense in the construction of the works, and purchase of land, of above seven per cent.--eight per cent.
having originally been a.s.sumed in my Report in 1835 as the excess to be provided for.
With respect to the weight of the carriages, although we have wheels of 4 feet diameter, instead of 3 feet, which, of course, involves an increased weight quite independent of the increase of width, and although the s.p.a.ce allowed for each pa.s.senger is a trifle more, and the height of the body greater, yet the gross weight per pa.s.senger is somewhat less.
Tons cwt. qrs. lbs.
A Birmingham first-cla.s.s coach weighs 3 17 2 0 Which with 18 pa.s.sengers at 15 to the ton 1 4 0 0 ---------------- 5 1 2 0 Or 631 lbs. per pa.s.senger ================
A Great Western first-cla.s.s weighs 4 14 0 0 And with 24 pa.s.sengers 1 12 0 0 ---------------- 6 6 0 0 Or 588 lbs. per pa.s.senger ================
And our 6-wheeled first-cla.s.s 6 11 0 0 With 32 pa.s.sengers 2 2 2 0 ---------------- 8 13 2 0 Or 600 lbs. per pa.s.senger ================
Being an average of 594 lbs. on the two carriages.
This saving of weight does not arise from the increased width, and is notwithstanding the increased strength of the framing and the increased diameter and weight of the wheels; I have not weighed our second-cla.s.s open carriages, but I should think the same proportion would exist.
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