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.

4-8-0+0-8-4 (Double Mastodon)
Bengal Nagpur Railway class N No. 815
Equivalent classifications
UIC class2D+D2
French class240+042
Turkish class46+46
Swiss class4/6+4/6, 8/12 from 1920s
Russian class2-4-0+0-4-2
First known tank engine version
First use1929
LocomotiveBNR class N
RailwayBengal Nagpur Railway
DesignerBeyer, Peacock and Company
BuilderBeyer, Peacock and Company


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


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


  1. 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
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