4-8-0+0-8-4

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4-8-0+0-8-4 (Double Mastodon)
Diagram of two small leading wheels, eight large driving wheels in two foursomes, each foursome joined by coupling rods, and two small trailing wheels
Beyer Garratt 6594.jpg
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[edit]

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

Usage[edit]

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]

4-8-0+0-8-4 Garratt production list – All manufacturers[1][3]
Gauge Railway Class Works no. Units Year Builder
5 ft 6 in Bengal Nagpur Railway, India N 6583–6598 16 1929 Beyer, Peacock
5 ft 6 in Bengal Nagpur Railway, India NM 6705–6714 10 1931 Beyer, Peacock

References[edit]

  1. ^ a b Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives produced by Beyer, Peacock, retrieved 10 November 2012 
  2. ^ Hamilton, Gavin N., The Garratt Locomotive - Surviving Garratt Locomotives, retrieved 10 November 2012. 
  3. ^ Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives from Other Builders, retrieved 10 November 2012