Ten engines of unusual design were built by Messrs. Longridge & Co., and delivered to the railway company during the years 1851 and 1852, though it appears that they were actually ordered prior to Mr. Sturrock’s assumption of office on the line.
They were of practically the same type as the well-known “Folkestone” of the South-Eastern Railway, and were built in accordance with one of Mr. T. R. Crampton’s patents, a principal feature of the design consisting in the boiler resting upon three points: the centre of a cross-spring, which bears upon the axleboxes of the driving wheels at the back of the firebox, and one on each side in the front, on compensating springs, each of which springs bears upon the two axleboxes of the small supporting wheels.
In the case of the G.N.R. engines, the large reversed springs at each side, which, in the original specification spanned the interval between the two sets of leading wheels, were not employed, each of the four leading axleboxes having its own spring, with equalizing levers between the two on each side, this method of suspension being, for all practical purposes, the same as that above quoted.
An important feature of the design consisted in the use of inside cylinders, which necessitated the employment of a “dummy” crank axle in front of the firebox, with outside cranks coupling it to the driving wheels at the extreme rear of the engine.
These engines bore the G.N.R. Nos. 91 to 99 and 200, and one of them had the honour, at seven o’clock on the morning of October 14th, 1852, to draw the first train out of King’s Cross terminus on its way to York.
The illustration of No. 91 as here given. Fig, 13, shows the general external appearance of these engines as originally built. They were speedily found, however, to be wholly unsuitable for the service they were intended to work, one very vital reason undoubtedly being the small proportion of weight available for purposes of adhesion, consequent on the position of the driving wheels. Mr. Sturrock, therefore, undertook the task of altering the arrangement of wheels to a more usual design, and in course of time they were all modified to the condition shown in our second illustration of No. 91, Fig. 14, in which the driving wheels are shown in the normal position, with the crank axle in front of the firebox casing, one pair of the carrying wheels being removed from the front of the engine to a more suitable place immediately behind the firebox. In this form the engines had outside bearings to all the wheels, and the driving axle had inside bearings as well.
One of the engines, No. 200, passed through an intermediate stage, which is shown in the accompanying illustration. Fig. 15, being for a short period a four-coupled engine, having in its outside appearance a strong resemblance to the handsome coupled engines afterwards put upon the line by Mr. Patrick Stirling; but this form only existed for a comparatively short period, and the engine was subsequently reconstructed in the single driving form to which the others had been transformed.
In their new condition these ten engines became known as the “converted Cramptons,” and did excellent service for many years.
The dimensions of the converted engines were:— cylinders 15-in. by 21-in.; driving wheels 6-ft. 6-in.; carrying wheels 3-ft. 6-in. in diameter ; wheel-base: leading to driving wheels, 9-ft. 6-in., driving to trailing wheels 7-ft., total 16-ft. 6-in.; boiler barrel 10-ft. in length by 4-ft. diameter, containing 168 tubes 2-in. in diameter, inside firebox 4-ft. 2-in. by 3-ft. 5-in. ; heating surface : firebox 97 sq. ft., tubes 875 sq. ft., total 972 sq. ft. ; weight in working order 28 tons 7 cwt.