S&DJR 7F 2-8-0

S&DJR 7F 2-8-0

LMS 13809, a preserved 7F locomotive, working the Hellifield to Carnforth leg of a Cumbrian Mountain Pullman in 1983

Type and origin Power type Steam Designer Henry Fowler Builder Midland Railway, Derby Works (1914), Robert Stephenson & Co. (1925) Serial number RS: 3892–3896 Build date 1914 (6), 1925 (5) Total produced 11

Specifications Configuration 2-8-0 UIC class 1′D h2 Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Driver dia. 4 ft 7 1⁄2 in (1,410 mm) Minimum curve 6 chains (400 ft; 120 m) normal 4.5 chains (300 ft; 91 m) dead slow Length 58 ft 10 1⁄8 in (17.936 m) Width 8 ft 11 7⁄8 in (2.740 m) Height 13 ft 3 in (4.04 m) Axle load 16 long tons 0 cwt (35,800 lb or 16.3 t) Adhesive weight 56 long tons 0 cwt (125,400 lb or 56.9 t) 56.9 t; 62.7 short tons Loco weight 64 long tons 15 cwt (145,000 lb or 65.8 t) 65.8 t; 72.5 short tons Tender weight 42 long tons 14 cwt (95,600 lb or 43.4 t) 43.4 t; 47.8 short tons Fuel type Coal Firebox:  • Firegrate area 28.4 sq ft (2.64 m2) Boiler G9AS or G9BS Boiler pressure 190 lbf/in2 (1.31 MPa) Heating surface G9AS: 1,681 sq ft (156.2 m2) G9BS: 1,845 sq ft (171.4 m2) (both include superheater) Cylinders Two, outside Cylinder size 21 in × 28 in (533 mm × 711 mm) Valve gear Walschaerts Valve type Outside admission piston valves Loco brake Steam Train brakes Vacuum

Performance figures Tractive effort 35,295 lbf (157.00 kN) Factor of adh. 3.5

Career Operators Somerset & Dorset Joint Railway → London, Midland & Scottish Railway → British Railways Power class SDJR: 5P/5G LMS: 7F Numbers S&DJR: 80–90 LMS: 9670–9680 later 13800–13810 BR: 53800–53810 Withdrawn 1959–1964 Disposition Two preserved, nine scrapped

The Somerset and Dorset Joint Railway (S&DJR) 7F 2-8-0 is a class of steam locomotive designed for hauling heavy coal and goods trains. Eleven were built in two batches in 1914 and 1925, and were used until withdrawal between 1959 and 1964. Two are preserved.

The Midland Railway, joint owners of the S&DJR with the London and South Western Railway (L&SWR), were in charge of locomotive policy on the line. The S&DJR which was heavily graded and required power over and above what was available from the Midland's small engines. M. H. Ryan, S&DJR locomotive superintendent argued for a type specific to the line.

Two plans for 0-8-0s were suggested in 1907 but would have been too heavy. Clearly a special exception to the small engine policy, James Clayton the draughtsman at Derby was given a free hand to design the engine, and produced something unlike any other Derby-designed locomotive of the time.

The design used the G9AS boiler from the Midland Compounds, with a Belpaire firebox and Walschaerts valve gear. A leading pony truck was added, to distribute the weight, making it a 2-8-0. The cylinders were mounted high on the frame, and sloped, to avoid fouling platforms. Because of the gradients that the loco would face, Clayton provided two steam brake cylinders on the engine and a further one on the tender.In service, the cast iron brake blocks originally fitted wore very quickly, and Ferodo blocks were substituted. The Derby standard axle boxes were fitted, so the engines were still subject to the hot boxes that were a fact of life on the Midland. As the locomotives were initially too large for some of the turntables, it was envisaged that they would spend half their time travelling in reverse. Consequently, they were fitted with tablet exchanging apparatus on both sides of the locomotive. In addition, the first six were equipped with cab tenders, but these were later removed circa 1920. The 1914-built locomotives were right-hand drive, while the 1925-built were left-hand drive. In all cases the vacuum brake ejector was located on the driver's side of the smokebox.