Under the Whyte notation for the classification of steam locomotives by wheel arrangement, the 4-6-0+0-6-4 is a Garratt locomotive. The wheel arrangement is effectively two 4-6-0 ten-wheeler locomotives operating back to back, with the boiler and cab suspended between the two swivelling power units. Each power unit has two pairs of leading wheels in a leading bogie, followed by three coupled pairs of driving wheels and no trailing wheels.
A similar wheel arrangement exists for simple articulated locomotives, but is referred to as 4-6-6-4. On a simple articulated locomotive, only the front engine unit swivels while the rear unit is rigid in relation to the main frame.
Overview
This was a rare wheel arrangement for Garratt locomotives, with only seven locomotives built for two South American customers.
The first was for the metre-gauge Mogyana Railway of Brazil, with five examples built by Beyer, Peacock and Company in 1912 and 1914.[1]
The other was two locomotives built for the 3-foot gauge Ferrocarril Pacifico de Colombia by Armstrong Whitworth in 1924.[2]
4-6-0+0-6-4 Garratt production list – All manufacturers[1][2]
