| Bavarian B IX (old) | 
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| Type and origin | 
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 | Builder | Strousberg | 
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 | Build date | 1870 | 
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 | Total produced | 4 | 
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| Specifications | 
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 Configuration:
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 |  • Whyte | 0-4-2 | 
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 |  • UIC | B1 n2 | 
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 | Gauge | 1,435 mm (4 ft 8+1⁄2 in) | 
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 | Driver dia. | 1,412 mm (4 ft 7+5⁄8 in) | 
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 | Adhesive weight | 25.2 t (24.8 long tons; 27.8 short tons) | 
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 | Service weight | 31.7 t (31.2 long tons; 34.9 short tons) | 
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 | Tender type | 2 T 8 | 
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 | Fuel capacity | 3.5 t (7,720 lb) | 
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 | Water cap. | 8.0 m3 (1,800 imp gal; 2,100 US gal) | 
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 | Boiler pressure | 8.5 kgf/cm2 (834 kPa; 121 lbf/in2) | 
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 | Heating surface: |  | 
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 |  • Firebox | 1.30 m2 (14.0 sq ft) | 
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 |  • Evaporative | 89.00 m2 (958.0 sq ft) | 
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 | Cylinders | 2 | 
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 | Cylinder size | 418 mm (16+7⁄16 in) | 
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 | Piston stroke | 602 mm (23+11⁄16 in) | 
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 | Valve gear | Allan | 
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| Performance figures | 
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 | Maximum speed | 60 km/h (37 mph) | 
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| Career | 
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 | Numbers | - K.Bay.Sts.E: 503 WÖRTH to 506 MARS LA TOUR
 - EL: 347 THUR to 350 MOSSIG
 
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The first four steam locomotives designated as Class B IX by the Royal Bavarian State Railways were procured from the locomotive works of Strousberg. They were transferred in 1872 to the Imperial Railways in Alsace-Lorraine. For the remainder, see Bavarian B IX.
They were equipped with tenders of Class 3 T 10.