Bird illustration of a G1

766 Class (G1)

A new type of front-coupled trailing bogie tank engine, specially fitted for working suburban traffic through the “Underground” to Moorgate Street, etc., was brought out at the close of 1889. Altogether, 25 engines were built of this class, together with four others of slightly different dimensions, and they were all provided with appliances for condensing steam in the tunnels, and were also built with shorter chimneys than usual, only 12-ft. 7-in. above the rail level, to meet the exigencies of the “Underground” loading gauge. The external appearance of the engines is shown in the accompanying illustration of No. 931, Fig. 81.

The leading dimensions of the 25 engines first built were as follows: cylinders 18-in. in diameter with a stroke of 26-in., angle of inclination towards the driving axle 1 in 8 3/4, driving wheels (four-coupled in front) 5-ft. 7 1/2-in. in diameter, and bogie wheels 3-ft. in diameter ; wheel-base : coupled axles, centre to centre, 7-ft. 3 -in., driving axle to leading bogie wheel axle, centre to centre, 10-ft. 3-in. ; bogie wheel-base 5-ft., with the bogie pin 3-in. in advance of the centre, thus giving a wheel-base from the leading wheel centre to the centre of bogie pin of 19-ft. 9-in. ; total wheel-base 22-ft. 6-in. Total length of frame plates 29-ft. 3-in., the overhang being 5-ft. 3-in. at the leading end and 4-ft. 3-in. at the trailing end, measured from the bogie pin ; height of top of outer frame plates 4-ft. 2-in. The boiler barrel was 10-ft. 1-in. in length, with a diameter outside the smallest ring of 4-ft. o^-in., and it was pitched with its centre line 7-ft. 3-in. above the rail level ; length of firebox casing 5-ft. 6-in. Heating surface and grate area were practically identical with those of the latest standard goods engines already described. Capacity of side tanks 1,000 gallons. Empty, engines of this class weighed 45 tons 4 cwt., while in full working order the total was 53 tons 9 cwt., distributed as follows: leading wheels 17 tons 7 cwt. 2 qrs., driving wheels 17 tons 16 cwt., and bogie wheels 18 tons 5 cwt. 2 qrs. These engines were built at Doncaster and numbered in the order given below :—

Date. Doncaster No. Engine No. Date Doncaster No. Engine No.
1889 499 766 1891 531 829
1890 500 767 1891 535 830
1890 504 768 1892 582 931
1890 506 769 1892 583 932
1890 507 770 1892 589 933
1890 512 821 1892 594 934
1890 513 822 1892 598 935
1890 518 823 1893 601 936
1890 519 824 1893 607 937
1890 520 825 1893 610 938
1890 525 826 1893 614 939
1891 526 827 1893 617 940
1891 528 828      


A modified pattern of the latest standard type of bogie tank engine, fitted for working through the “Underground,” was brought out in 1895. Four engines were built to this new design in the following order : —

Date. Doncaster No. Engine No. Date Doncaster No. Engine No.
1895 688 941 1895 690 943
1895 689 942 1895 691 944

In external appearance, as can be seen from the accompanying illustration. Fig. 86, these engines were very similar to their predecessors, the chief difference being that the side tanks were shorter. The supply of water was, in fact divided over the two side tanks and a well tank placed at the rear of the foot-plate, below the coal bunker. In general dimensions these latter engines were almost identical width their forerunners, as will be gathered from the accompanying list. Diameter of driving wheels 5-ft. 7 1/2 in., and of bogie wheels 3-ft. Wheel-base: coupled wheels 7-ft. 3-in., from centre of driving axle to centre of leading bogie axle lo-ft. g-in., centre to centre of bogie wheels 5 ft., total wheel-base 23-ft. Cylinders 8 in. by 26 in., inclined downwards, as usual, in the ratio of 1 in 8 3/4. Boiler barrel lo-ft. i-in. long, with a diameter outside the smallest ring of 4-ft. o 1/2 in. ; height of centre above rails 7-ft. 3-in. ; and of chimney top above rails 12-ft. 7 in. Firebox casing 5 ft. 6 in. long outside, with a depth below the centre line of the boiler of 5-ft. 2-in. and 4-ft. 8-in., at front and back ends respectively. The weight was approximately the same as in the earlier engines, but rather; differently distributed.

Some or all of the description has been edited from G.F.Bird's Locomotives of the Great Northern Railway

Preserved Locomotives

There are no preserved locomotives of this type.



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