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4120 'Atbara' class introduction

Running numbers: original numbers 3373 - 3412,
        renumbered 4120 - 4148 ( ten engines were rebuilt as 'Cities' in 1902 - 9 ).

Built:      1900           (4120 - 4138) to lot number 125,
             1901           (4139 - 4148) to lot number 126.

    The 'Atbara' class were the express locomotive version of the 'Bulldog' class as 'Atbara' class, number 3385 ( later 4131 ) Powerful these engines were fitted with 6 feet 8½ inch driving wheels. The name of 'Atbara' for the class was due to the Boer war being fought in South Africa when the class was first built, therefore it was thought "proper" to the use the names which were so much in the public eye. The class was fitted with the Standard number 2 parallel boiler, cast iron chimney and used the straight framing similar to the 'Bulldogs'.

Modifications.
    Reboilering to half-cone and full-cone types began 1904, while superheating and top feed was fitted from 1909 and 1911 respectively. The frame area around the trailing axles was strengthened between 1905 and 1907.

    Ten members of the class ( numbers 3400 - 3409 ) were fitted with the Standard number 4 boiler to add to the 'City' class; the first of these rebuilds being number 3405 Mauritius in September 1902.

    As with all other classes, the 'Atbaras' were renumbered in December 1912, into the 4120 - 4148 series.

Identification.
    The first twenty-three engines were introduced with the oval combined name and number plates on the cab sides, while the remainder carried the full segment type of nameplate around the driving wheel splashers. These full segment type were replaced by the standard type of nameplate from 1904.

Withdrawal.
    The first 'Atbara' withdrawn was number 3382 Mafeking which was scrapped in September 1911 after a severe accident at Henley-in-Arden.

    When 4-6-0 express passenger locomotive construction resumed in 1922, the 'Atbaras' at first were relegated to stopping train workings, but eventually the class became surplus to requirements and withdrawals began in April 1927 with number 4125 (ex 3378) Khartoum. The last 'Atbara' to be withdrawn was number 4148 (ex 3412) Singapore in May 1931.


Specifications (long cone boiler with superheater).

Cylinders (2) 18 x 26 inches Driving wheel diameter 6 feet 8 inches
Bogie wheel diameter 3 feet 8 inches Tractive Effort 17,790 pounds
Boiler type Number 2 Boiler maximum dia. 5 feet 0 inches
Boiler minimum dia. 4 feet 5 1/8 inches Fire tubes, no. and dia. 218 x 1 5/8 inches
Flue tubes, no. and dia. 6 x 5 1/8 inches Superheater tubes, no. and dia. 36 x 1 inch
Boiler pressure 200 lbs/square inch. Boiler length 11 feet 0 inches
Area of firegrate 20.35 square feet Heating surfaces, tubes 1,144.95 square feet
Heating surfaces, firebox 121.8 square feet Heating surfaces, superheater 82.2 square feet


    

Details: Atbara class, 4120 to 4148    Bird class introduction     Bulldog class introduction     City class introduction
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