Pennsylvania Railroad’s 6–8–6 Steam Turbine Locomotive Class S2, #6200.

Overtaken by Time and Diesel locomotives.

Pennsylvania Railroad class S2 6200 in a PRR promotional image By Original uploader was Morven at en.wikipedia — Transferred from en.wikipedia, Public Domain, https://commons.wikimedia.org/w/index.php?curid=6813472 (public domain).

Pennsylvania Railroad’s S2
steam turbine locomotive
built by Baldwin and
Westinghouse Electric,
Attempt to prolong
steam’s dominance,
One was built,
No. 6200 Class S2
delivered September 1944.

Diagram showing how the turbine works on PRR S2. Creative Commons CC0 1.0 Universal Public Domain Dedication. (https://commons.wikimedia.org/wiki/File:PRR_S2_Forward_and_Backward_Turbine.jpg).

6200 was to be 4–8–4,
Wartime restrictions on
light steel alloys
increased weight and
necessitated six-wheel
leading and trailing trucks.

S2 used direct-drive
steam turbines,
Modified marine units,
Turbines only spin
in one direction so
two turbines fitted,
One for forward and
smaller for reverse,
Large boiler with
Belpaire firebox and
long combustion chamber
ensured adequate steaming.