Invention and Engineering
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. A similar wheel arrangement exists for the Union Pacific Big Boy, but is referred to as 4-8-8-4 since only the front engine unit swivels.
Driving wheel.
EMC AB6.
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