6-8-6

Under the Whyte notation for the classification of steam locomotives by wheel arrangement, 6-8-6 represents the arrangement of six unpowered leading wheels, eight powered and coupled driving wheels, and six unpowered trailing wheels.

Front of locomotive to the left

The single S2, No. 6200, in a PRR promotional image.

Other equivalent classifications are:

• UIC classification: 3D3 (also known as German classification and Italian classification)
• French classification: 343
• Turkish classification: 410
• Swiss classification: 4/10.

The only known example of the 6-8-6 wheel arrangement is the experimental Pennsylvania Railroad S2 steam turbine locomotive.

References

• Staufer, Alvin F.; Pennypacker, Bert (1962). Pennsy Power: Steam and Electric Locomotives of the Pennsylvania Railroad, 1900-1957. Research by Martin Flattley. Carollton, Ohio: Alvin F. Staufer. ISBN 978-0-9445-1304-0.