Why Steam Turbine Locomotives?

Updated: 24 May 2003
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By 1920-ish, steam turbines had swept reciprocating engines from ships and power stations. It was clear that turbines offered improvements in thermal efficiency, simplicity and reliability. Inevitably there were attempts to extend their use to steam locomotives. It proved to be a bad idea.


  • High efficiency at full load
  • Mechanical simplicity and hence potential reliability.
  • Conventional reciprocating steam locomotives give a varying torque through the cycle, resembling a sine characteristic. This makes wheelslip at starting much more likely.
  • Conventional steam locomotives have substantial reciprocating masses such as connecting rods and valve gear. This creates fore-and-aft forces that cannot be completely balanced without unacceptably increasing the up-and-down forces on the track.



  • High efficiency is only obtained at full-load. Naval vessels very often had cruising turbines which could be run at full output while the main turbines were shut down.
  • High efficiency is only obtained when the turbine exhausts into a near-vacuum, generated by a condenser. These are very large pieces of equipment to carry around.
  • Turbines cannot run in reverse. Ships carried separate turbines solely for reversing, and locomotives had to do the same (see the Turbomotive for an example)

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