Big Bertha

Big Bertha is a Banker on the railway, she often helps around on the London Railway

Technical Details:
Big Bertha's cylinder arrangement was unusual. There were four cylinders but only two sets of piston valves because there was insufficient space under the smokebox to fit piston valves for the inside cylinders. Instead, the large outside piston valves (as well as supplying the outside cylinders) supplied the inside cylinders through cross-over steam ports. The steam-flow characteristics would have been poor (because of the length of the ports) but this would not have mattered unduly in an engine that ran only at slow speed. It has been suggested that this design has been influenced by the four-cylinder cross-ported arrangement of the Italian 0-10-0 FS Class 470 heavy freight locomotive (in which this was motivated by its being part of an asymmetrical compound design), of which a complete set of drawings were stored at Derby.

With a weight of 105 long tons (107 t) and 10 driving wheels with a diameter of 4 ft 7 1⁄2 in (1.410 m), she had a tractive effort of 43,300 lbf (193 kN). She was the only locomotive not given a power classification by either the LMS or BR, since she was designed specifically for the job of providing extra power and was not suitable for normal train working.

VA:
Gingercat65