Somerset & Dorset Joint 2-8-0 Locomotives in Great_Britain


Class Details by Steve Llanso of Sweat House Media

Class 7F/ G9AS (Locobase 3658)

Data from "New Consolidation Mineral Engine, Somerset & Dorset Joint Ry", Locomotive Magazine, Volume XX [20], No 260 (15 April 1914), p. ; and "Mineral Engines for the Somerset & Dorset Joint Ry", Locomotive Magazine, Volume XX [20], No 261 (15 May 1914), p.

Powerful Consolidation designed by Henry Fowler and first put into service just before World War I. Although smaller in boiler size and lighter on the drivers than most British 2-8-0s, this engine generated a higher tractive effort. It had a relatively large firebox area and good-sized superheater.

The [] link from the West Somerset Railway's link gives a detailed history of this class. "The locomotives were the first on the S&D to have outside cylinders and Walschaerts valve gear," says the history. "The cylinders were inclined at 1 in 12, to clear the platform edges. ...The locomotives were amongst the most powerful in the country at the time."

A later (1925) batch -- 86-90 -- had larger boilers fitted with 146 1 3/4" small tubes and 21 5 1/8" flues and and show a Belpaire firebox with 190.7 sq ft of direct heating surface. The grate area did not change.

Principal Dimensions by Steve Llanso of Sweat House Media

Class7F/ G9AS
Locobase ID3658
RailroadSomerset & Dorset Joint
CountryGreat Britain
Whyte2-8-0
Number in Class6
Road Numbers80-85 /13800-13805
GaugeStd
Number Built6
BuilderDerby
Year1914
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)17.50 / 5.33
Engine Wheelbase (ft / m)25.75 / 7.85
Ratio of driving wheelbase to overall engine wheelbase 0.68
Overall Wheelbase (engine & tender) (ft / m)50.08 / 15.26
Axle Loading (Maximum Weight per Axle) (lbs / kg)35,280 / 16,003
Weight on Drivers (lbs / kg)125,440 / 56,899
Engine Weight (lbs / kg)145,040 / 65,789
Tender Loaded Weight (lbs / kg)102,816 / 46,637
Total Engine and Tender Weight (lbs / kg)247,856 / 112,426
Tender Water Capacity (gals / ML)4200 / 15.91
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 7.70 / 7
Minimum weight of rail (calculated) (lb/yd / kg/m)52 / 26
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)55.50 / 1410
Boiler Pressure (psi / kPa)190 / 13.10
High Pressure Cylinders (dia x stroke) (in / mm)21" x 28" / 533x711
Tractive Effort (lbs / kg)35,932 / 16298.50
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.49
Heating Ability
Tubes (number - dia) (in / mm)148 - 1.75" / 44
Flues (number - dia) (in / mm)21 - 5.125" / 130
Flue/Tube length (ft / m)
Firebox Area (sq ft / m2)151 / 14.03
Grate Area (sq ft / m2)28.40 / 2.64
Evaporative Heating Surface (sq ft / m2)1321 / 122.73
Superheating Surface (sq ft / m2)360 / 33.44
Combined Heating Surface (sq ft / m2)1681 / 156.17
Evaporative Heating Surface/Cylinder Volume117.69
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation5396
Same as above plus superheater percentage6529
Same as above but substitute firebox area for grate area34,715
Power L18324
Power MT585.18

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