4-8-0+0-8-4

4-8-0+0-8-4 (Double Mastodon)

Bengal Nagpur Railway class N No. 815

Equivalent classifications UIC class 2D+D2 French class 240+042 Turkish class 46+46 Swiss class 4/6+4/6, 8/12 from 1920s Russian class 2-4-0+0-4-2

First known tank engine version First use 1929 Country India Locomotive BNR class N Railway Bengal Nagpur Railway Designer Beyer, Peacock and Company Builder Beyer, Peacock and Company

Under the Whyte notation for the classification of steam locomotives by wheel arrangement, the 4-8-0+0-8-4 is a Garratt articulated locomotive. The wheel arrangement is effectively two 4-8-0 locomotives operating back to back, with the boiler and cab suspended between the two engine units. Each engine unit has two pairs of leading wheels in a leading bogie, followed by four coupled pairs of driving wheels and no trailing wheels. Since the 4-8-0 type is known as a Mastodon type, the corresponding Garratt type would be referred to as a Double Mastodon. A similar wheel arrangement exists for Mallet locomotives, but is referred to as 4-8-8-4.

Overview

The 4-8-0+0-8-4 was the fifth rarest Garratt wheel arrangement, with a total of 26 locomotives constructed.

Usage

All the 4-8-0+0-8-4 Garratts were built by Beyer, Peacock and Company for the 5 ft 6 in (1,676 mm) gauge Bengal Nagpur Railway in India. The first sixteen were designated Class N and were delivered in 1929, while ten more arrived in 1931 and were designated class NM. The locomotives had Belpaire fireboxes and piston valves.^[1]

Two of the type survive, both of Class N. No. 811 is staged at Kharagpur Workshop, while no. 815 is on display at the National Rail Museum in New Delhi.^[2]

References

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