A4 Single and A5 Single

Mr. Ivatt’s new single wheeler, No. 266, had already been running sufficiently long to prove its success in first-class express work, and another engine of a similar type was put in hand. It differed from its forerunner, however, in details of the motion, having cylinders 19-in. in diameter with balanced valves on top, the movement of the link motion being transmitted by means of a rocking shaft. The valves are balanced by strips on the Richardson system, and the exhaust takes place straight through the top. The leading dimensions were as follows:-

Cylinders 19-in, in diameter, with a stroke of 26-in.

Diameter of bogie wheels with 3-in. tyres 3-ft. 8-in., of driving wheels 7-ft. 8-in., and of trailing wheels 4-ft. 2-in. Wheelbase: bogie 6-ft. 3-in., from the trailing bogie wheel to driving wheel centres 7-ft. 9-in., and from driving to trailing wheel centres 9-ft. Length of frames 27-ft. 8-in., with an overhang at leading and trailing ends of 2-ft. 8-in. and 3-ft. respectively.

Boiler barrel: length 11-ft. 4-in., diameter outside smallest ring 4-ft. 3 7/8-in., thickness of plates 9/16-in., height of centre above rails 8-ft. 3-in., length of smokebox 3-ft. 3 7/8-in., length of outside firebox 7-ft., width 4-ft. ½-in. Heating surface: firebox 125.8 sq. ft., tubes 1143.8 sq. ft. total 1269.6 sq. ft., grate area 23.2 sq. ft., working pressure 175 lbs. per sq. in. Weight of engine in full working order 48 tons 11 cwt., of which 17 tons 15 cwt, was available for adhesion.

Weight of tender with 3,670 gallons of water and 5 tons of coal 40 tons 18 cwt.

The accompanying illustration, fig. 105, also shows this engine to have had a deeper frame at the forward end, but with these exceptions it was practically A reproduction of No. 266. So far, 11 engines have been built to the design here shown, in the following order:-

Will be noted with regret that these engines have displaced some historic veterans which now drop into the fatal “A” list.

Pre Groves, all twelve were withdrawn in December 1917, and had been broken up by 3rd July 1918. This was to be the last Single locomotive class ever to be built in Great Britain.