Editing LMS Princess Royal Class (section)

== Construction ==
A prototype batch of three locomotives was to be constructed in 1933. Two were constructed as drawn but the third set of frames was retained as the basis for an experimental [[steam turbine locomotive|turbine locomotive]].<ref name="Nock, Turbomotive construction" >{{harvnb|Nock|page = 114}}</ref><ref name="Raising Steam, Turbomotive" /><!-- Prototypes and the early boiler --><ref name="Rowledge, First two" >{{Cite book
  |title=The LMS Pacifics
  |last=Rowledge  |first=J.W.P. 
  |year=1987
  |publisher=[[David & Charles]]
  |isbn=0-7153-8776-6
  |chapter=3: The Princess Royal Class – The First Two
  |pages=24–35
}}</ref>

=== Turbomotive ===
{{main|LMS Turbomotive}}
The third prototype was constructed with the aid of the Swedish [[Fredrik Ljungström|Ljungstrom]] turbine company and known as the [[LMS Turbomotive|Turbomotive]], although not named. It was numbered 6202, in sequence with the Princess Royals. Although 'generally similar' to the rest of the Princess Royals,<ref name="Nock, Turbomotive construction" /> and 'not all that much different',<ref>{{harvnb|Fryer|1990|page= 165 }}</ref> it used a larger 40 element [[superheater]] to give a higher steam temperature, more suitable for turbine use.<ref name="Raising Steam, Turbomotive" >{{Cite book
  |title=Raising Steam on the LMS
  |last=Cook  |first=A.F.
  |year=1999
  |publisher=[[RCTS]]
  |isbn=0-901115-85-1
  |pages=126–127
}}</ref><ref>{{Cite book
  |title=The LMS Pacifics
  |last=Rowledge  |first=J.W.P. 
  |year=1987
  |publisher=[[David & Charles]]
  |isbn=0-7153-8776-6
  |chapter=4: The 'Turbomotive'
  |page=47
}}</ref>{{#tag:ref|This trifurcated superheater design was later used on the [[LMS Coronation Class|Duchess class]].<ref name="Raising Steam, Turbomotive" />|group=note}} This boiler was also domeless as would later be used for the second batch of the Princess Royals. The continuous exhaust of the turbine, rather than the sharper intermittent blast of the piston engine, also required changes to the [[boiler draught|draughting]] and the use of a [[double chimney]].<ref name="Nock, Turbomotive" >{{Cite book
  |title=The British Steam Railway Locomotive
  |volume=II: from 1925 to 1965
  |chapter=9: Unconventional Locomotives 1929–1935
  |publisher=[[Ian Allan Publishing|Ian Allan]]
  |year=1966
  |isbn=0-7110-0125-1
  |ref={{harvid|Nock}}
  |pages=112–117
}}</ref><ref name="Experiments With Steam, Turbomotive" >{{Cite book
  |title=Experiments With Steam 
  |chapter=18: Stanier's 'Turbomotive'
  |publisher=Patrick Stephens Limited
  |year=1990
  |isbn=1-85260-269-4
  |ref={{harvid|Fryer|1990}}
  |pages=163–171
}}</ref> It entered service in June 1935 on the London–Liverpool service.<ref>{{harvnb|Fryer|1990| page=167 }}</ref>

This ''Turbomotive'' was rebuilt in 1952 with conventional '[[LMS Coronation Class|Coronation]]' cylinders and named ''Princess Anne'', but was soon destroyed in the [[Harrow and Wealdstone rail crash]].<ref name="Experiments With Steam, Turbomotive" />

=== Later production ===
A second batch of eleven locomotives was constructed later.<ref name="Rowledge, 1935 batch" >{{Cite book
  |title=The LMS Pacifics
  |last=Rowledge  |first=J.W.P. 
  |year=1987
  |publisher=[[David & Charles]]
  |isbn=0-7153-8776-6
  |chapter=5: The Princess Royal Class – Modifications, and the 1935 Batch
  |pages=44–51
}}</ref> The first two locomotives of the class to be produced had a firebox combustion volume too small for the grate area, and the subsequent locomotives had enlarged fireboxes.<ref name=Tuplin107/>