2-4-6-2

A '''2-4-6-2''' [[steam locomotive]], in the [[Whyte notation]] for describing [[locomotive]] [[wheel arrangement]]s, has a two-wheel [[leading truck]], one set of four [[driving wheel]]s, one set of six [[driving wheel]]s, and a two-wheel [[trailing truck]].

Other equivalent classifications are:<br> [[UIC classification]] (also known as German classification): '''1BC1''' <br> [[French classification]]: potentially '''1231''', although the only example was described as '''151'''<br>

[[File:PLM151ARGCF1932.JPEG|thumb|The 151 A of the [[Chemins de fer de Paris à Lyon et à la Méditerranée|PLM]]]] This most unusual wheel arrangement was only ever used on the {{illm|PLM 151.A class|fr|151 PLM 1 à 10}}, a French [[duplex locomotive]] type built in 1932 for the [[Chemins de fer de Paris à Lyon et à la Méditerranée|PLM]].<ref name="pics" /> Although a rigid locomotive, not articulated, it had some similarities to a [[Mallet locomotive|Mallet]] as it was a [[compound locomotive|compound]] with the two groups of drivers driven by the high pressure cylinders for the rear 6-coupled group and the low pressure for the front 4-coupled group. As the two groups of drivers were also linked with inside [[coupling rod]]s through inside cranks on the second and third drivers, [[André Chapelon]] considered that this made the locomotive a [[2-10-2]] rather than a duplex,<ref name="Douglas Self, PLM" /> which was also consistent with the PLM numbering as 151. Linking the drivers did not transfer appreciable power between them, but it did keep them synchronised in phase, so that the pistons moved as a balanced locomotive.<ref name="Douglas Self, PLM" /> Power from each pair of cylinders was shared in the ratio 2:3 to distribute power equally across each wheelset.<ref name="Douglas Self, PLM" />

The [[compound locomotive]]s were built to haul heavy freight trains on the 0.8% [[grade (slope)|grade]] of the [[Paris–Marseille railway]] between [[Venarey-les-Laumes|Les Laumes]] and [[Dijon]]. Their performance was so good that the company wanted to order more engines, but the nationalization of the French railways in 1938 stopped all projects. These duplex engines were fitted with Lenz-Dabeg rotary cam valve gear and soon thereafter with [[double chimney]]s. The driving wheels had a diameter of {{convert|1.50|m|ftin|abbr=on}}. The highest permissible speed was {{convert|53|mph|abbr=on}}. In a test on 19 December 1933, the engine developed slightly more than {{convert|3000|hp|abbr=on}} at the [[drawbar (haulage)|drawbar]] over a distance of {{convert|37|mi}} and a speed of at least {{convert|46|mph|abbr=on}}, without being overworked. In ordinary service these engines could haul {{convert|1375|ST|LT t}}, sustaining {{convert|31|mph|abbr=on}} at the summit of the 0.8% Blaisy grade. After [[railway electrification system|electrification]] of the line, the 151A's were sent for service in northeastern France. They were withdrawn from service in 1956 and scrapped.

==References== <references> <ref name="pics" >{{Cite web |title=PLM 151-A "fake duplex" locomotives - Pics and Diagrams |date=2 January 2023 |url=https://www.reddit.com/r/trains/comments/101jd7i/plm_151a_fake_duplex_locomotives_pics_and_diagrams/#lightbox }}</ref>

<ref name="Douglas Self, PLM" >{{cite web |title=Duplex Drive Locomotives: The PLM Railway 151A Locomotive: 1932 |website=Unusual Locomotives |author=Douglas Self |url=http://www.douglas-self.com/MUSEUM/LOCOLOCO/duplex/duplex.htm#plm }}</ref> </references>

[[Category:Whyte notation|46,2-4-6-2]] [[Category:Railway locomotives introduced in 1932]]