Mr. Brunel also looked forward to the advantages which a wider gauge would give for the construction of the locomotive engines. Difficulties had been already experienced from the limited width between the wheels, which cramped the machinery, rendering it difficult of access for repairs; it also limited the size of the boiler and fire-box, on which the power depended. For this reason Mr. Brunel considered that a wider gauge would present great advantages, as it would allow the locomotives to be constructed of greater power, and with their machinery arranged in a more advantageous manner. He also thought that the greater width of base for the carriages would give increased steadiness and smoothness of motion, with greater safety, particularly at high speeds, and that there would be the advantage of being able to use larger wheels for the carriages. Moreover, he had in view the possibility which the broad gauge would give of adopting wheels of a still larger diameter without raising the centre of gravity, the body of the carriage being placed between them, as in the original type of common road vehicles.
The broad gauge was also considered by Mr. Brunel in prominent connection with the peculiarly favourable circumstances of the Great Western line, in regard to its gradients and curves. He thought that ‘it would not have been embracing all the benefits derivable from the gradients of the Great Western Railway, unless a more extended gauge was adopted.’ In the first place, it was evident that a diminution of the frictional resistance would present the greatest advantage where the gradients were flat. In regard to curves, the wider gauge was at that time considered by him to be more advantageously applied where the curves were of large radius than where they were sharp.[48] On the Great Western Railway both gradients and curves were remarkably good; with the exception of two inclines of 1 in 100, on which auxiliary power was proposed to be used, there was no gradient between London and Bristol steeper than 1 in 660, the greater part of the line being nearly level, and except between Bath and Bristol there was no curve sharper than about one mile radius.
For these reasons Mr. Brunel thought that unusually high speed might easily be attained for passengers, and great tractive power for goods. He said:—
I shall not attempt to argue with those who consider any increase of speed unnecessary. The public will always prefer that conveyance which is the most perfect, and speed, within reasonable limits, is a material ingredient in perfection in travelling. (Report in Appendix I. p. 532.)
In deciding that the distance between the rails should be seven feet, Mr. Brunel seems to have been guided by the principle that the wheels should be put sufficiently far apart to admit of an ordinary carriage body being placed between them.[49]
Mr. Brunel did not anticipate that the difference between the gauge he proposed and that of other railways would lead to any important inconvenience. The views he held on this subject were expressed fully by him in a report of December 13, 1838. He says, speaking of the difficulty of communication between the Great Western and other railways:—
This is undoubtedly an inconvenience; it amounts to a prohibition to almost any railway running northwards from London, as they must all more or less depend for their supply upon other lines or districts where railways already exist, and with which they must hope to be connected. In such cases there is no alternative.
The Great Western Railway, however, broke ground in an entirely new district, in which railways were unknown. At present it commands this district, and has already sent forth branches which embrace nearly all that can belong to it; and it will be the fault of the company if it does not effectually and permanently secure to itself the whole trade of this portion of England, with that of South Wales and the south of Ireland; not by a forced monopoly, which could never long resist the wants of the public, but by such attention to these wants as shall render any competition unnecessary and hopeless. Such is the position of the Great Western Railway. It could have no connection with any other of the main lines, and the principal branches likely to be made were well considered, and almost formed part of the original plan; nor can these be dependent upon any other existing lines for the traffic which they will bring to the main trunk.
Mr. Brunel was not singular in holding the opinion that it would be desirable to allot a given district to one railway, which might conveniently serve it by means of a trunk line and branches of a special gauge. In the Eastern Counties line, designed in 1836, by Mr. Braithwaite, and opened in 1839, a gauge of 5 feet was adopted; and Mr. Robert Stephenson, as engineer of another line, the Northern and Eastern Railway, branching out from the Eastern Counties to the northward, adopted the same gauge. It was not till the Northern and Eastern line was extended, some years afterwards, that the rails of the whole system were altered to the narrow gauge.
Mr. Brunel’s recommendation was adopted by the Directors of the Great Western Railway; and, in their report of August 25, 1836, after observing that the generally level character of the line would greatly facilitate the attainment of a higher speed of travelling, they pointed out the advantages of the broad gauge, and stated that engines had been ordered specially adapted to the nature of the line, which would be capable of attaining with facility a rate of from thirty-five to forty miles per hour.