Paris-Orleans 2-4-2 Locomotives in France

Class 101 (Locobase 7595)

Data from from Ernest Polonceau, "Locomotives of the Paris-Orleans Railway", Railway Engineer, Volume 11, No 10 (October 1890), pp. 253-254, 328-332; William Frank Pettigrew, A Manual of Locomotive Engineering (London: Charles Griffin & Co, 1899), p. 351 and Charles Rous-Marten, "Modern French Locomotive Practice" (Cassier's Magazine 1901-1902, pp 411).

Both Pettigrew and Rous-Marten single out this trio as characteristic of the express passenger engine of the 2-4-2 layout. It was a bit bigger than the other PO engines of this arrangement, but it had the Polonceau type firebox (having a crown sheet of flanged plates riveted together), a Ten-Brinck water arch, and the typical two-dome steam system.

---

Class 366 (Locobase 7942)

Data from [] . These relatively large tanks with exceptionally tall drivers for tank engines were derived from the 2-4-2s shown in Locobase 7941. The tank engines served secondary lines on the Paris-Orleans. The driver diameter is surprising because such locomotives typically ran in local service that required frequent starts and stops. Consequently, they would use smaller drivers to gain more power and reduce slipping.

---

Class 448 (Locobase 7941)

Data from "XII: Locomotives des Trains a Tres Grande Vitesse," Compte Rendu General, Congres Internationale de Chemins des Fer, Sixieme Session, Troisieme Volume (Brussels, Belgium: P Weissenbruch, 1901), pp. XII-51 to XII- . See also [] and from Maurice Demoulin, Traite Pratique de la Machine Locomotive (Paris: Libraire Polytechnique, Baudry et Cie, 1898), p.91.

This locomotive appeared in large numbers as a tender engine. It had a Ten-Brinck firebox that used a water chamber in place of the brick arch and a single dome placed even further to the rear than earlier Forquenot 2-4-2. Its lead truck enjoyed lateral play and was centered using inclined planes.

Production extended over a decade and amounted to several dozen. Seventeen others with much taller drivers went into service as tank engines; see Locobase 7942.

In 1899, Ernest Polonceau modified eight of these engines with two domes, one placed well forward on the boiler and the other over the firebox. He also used the Durant-Lencauchez steam distribution system to feed their cylinders. See his "Corliss Valve Gear for Locomotive Engines", Engineering (26 February 1897) , pp. 291-294. This system used four cylindrical Corliss valves in each cylinder, two for admission, one at each end, and two exhaust valves under the cylinders.

Polonceau cited the rapid opening of the valves, the lesser drop in temperature and pressure in the small valve volume, even the higher back pressure when reversing the motion.

---

Class 51 (Locobase 6938)

Data from Titre Exposition universelle internationale de 1878 a Paris. Rapports du jury internationale..Volume Groupe VI - Classe 64. Rapport sur le materiel des chemins de fer. p. 50 (cnum.cnam.fr/CGI/fpage.cgi?8XAE277-11.1/54/100/312/0/0 (accessed 1 September 2005). See also [], accessed 6 November 2006, which details the long history of this arrangement on the PO.

This balanced wheel arrangement was especially popular in France where several railways adopted it. On the PO, Victor Forquenot's design responded to the demands of the line's profile which featured adverse grades of 1 to 1.6% and curve radii measuring 300-500 metres. In the face of a relatively tight alignment, says the jury report, the extreme wheelbase was reduced as much as possible. To counteract the instability such close-coupling might induce, the locomotive-tender coupling was tightened with springs. Trimming weight growth meant resorting to a steel firebox in place of the more usual copper.

In part because the French engineers tweaked the design to address shortcomings, some of these 2-4-2s ran on through World War Two.

---

Class Express (Locobase 7408)

Data from Titre Exposition universelle internationale de 1889 a Paris. Rapports du jury internationale. Auteur - Volume France. Ministere du Commerce, de l'industrie. Picard, Alfred, ed. Volume Groupe VI - -Outillage et precedes des industries mecaniques. Electricite (5e partie) Classes 60 a 63. Rapport sur le materiel des chemins de fer; tables beginning on p. 183 ([] (accessed 1 September 2005)).

Twelve years after displaying a 2-4-2 at the 1878 Exposition (Locobase 6938), the Orleans came back with a larger and more powerful version. Designed to pull 224 tons, the design boasted one of the largest fireboxes used in such service, but slightly smaller boiler than the earlier engine.. It was heavier than the 1873 design shown in the earlier expo, and sported higher boiler pressure. The result was a relatively powerful express engine with tall drivers.