The first of the Company’s engines to be put to work were fifty built by the firm of Sharp Brothers & Co., of Manchester, who were formerly known under the style of Sharp, Roberts & Co., subsequently becoming Sharp, Stewart & Co., Ltd., of Atlas Works, Glasgow, and now one of the three component firms comprised in the North British Locomotive Co., Ltd. These engines, which were numbered in the company’s books from 1 to 50, were delivered to the G.N.R. during the years 1847, 1848 and 1849, and, as can be gathered from the accompanying illustration, Fig. 1, were of the builders’ well-known design of the period.
They had cylinders 15-in. in diameter, with a 20-in. stroke, and a pair of single driving wheels 5-ft. 6-in. in diameter, with leading and trailing wheels each 3-ft. 6-in. in diameter, the wheel-base being 12-ft. 8-in., of which 5-ft. 9-in. separated the leading and driving wheel centres, and 6-ft. 11-in. separated the driving and trailing wheel centres.
The boiler barrel was 10-ft. in length, with a diameter of 3-ft. 6 3/4-in., and contained 147 tubes 10-ft. 5-in. long and 1 3/4-in. in diameter. The inside firebox measured 3-ft. in length by 3-ft. 6 1/2-in. in breadth, and the heating surface was distributed as follows : firebox 57.9 sq. ft. ; tubes 690.3 sq. ft. ; total, 748.2 sq. ft. The weight of these “Little Sharps” was 18 tons 8 1/2 cwt.
At a subsequent date, equalising levers connected the springs of the leading and driving wheels. These levers were not, however, introduced until some time after 1850, in which year the device was patented by Messrs. Hawthorn. A number of the “Little Sharps” were converted into tank locomotives in the year 1852.
Conversion to Tank Locomotives
In 1863 the Great Northern Railway were suddenly called upon to provide locomotive power for the working of their trains through the portion of the Metropolitan Railway over which they possessed running powers, and this necessity being unexpectedly brought forward, found the company in some difficulty, as at the time they had no tank engines which were specially fitted for the purpose. There were, however, a certain number of the “Little Sharps” which had already been converted into passenger tank locomotives by Mr. Sturrock, in 1852-3, which were utilized as makeshifts pending the provision of engines suitable for “underground” traffic.
The main features in the conversion thus effected consisted in the lengthening of the frames to the rear of the driving wheels, and placing the trailing wheels further back to the extent of 3-ft. 1-in., thus increasing the normal wheel-base of 12-ft. 8-in. to 15-ft. 9-in. This extra length of framing allowed of the addition of a water tank and coal bunker, and, as is above stated, a number of the “Little Sharps” were converted in this manner, so as to present the external appearance indicated in the accompanying illustration. Fig. 26, showing No. 9, which was one of those so treated. The following are the numbers of the engines thus converted, with the dates of conversion :—
|Engine No.||Date||Engine No.||Date|
|19||Jan 1852||2||May 1852|
|40||March 1852||6||May 1852|
|46||March 1852||9||May 1852|
|45||April 1852||18||May 1852|
|10||April 1852||39||June 1852|
Two Others, Nos. 23 and 12, were also converted, the former into a front-coupled tender engine, and the latter into a front-coupled tank. In the earlier conversions a certain degree of end play was allowed to the trailing axles to permit of the easier negotiation of sharp curves such as are necessitated in underground work ; but subsequent rebuilds were provided with radial axleboxes to the rear wheels, which gave so much satisfaction as to result in the construction of a new type of locomotive embodying that as a principal feature.