Paris-Orleans 4-6-2 Locomotives in France

Class 3 -701/231 F (Locobase 1053)

Data from "231 n° 3 701 à 3 721 du PO" on the WikiPO website at [], last accessed 3 November 2024; and Gustav Reder (Michael Reynolds, trans), The World of Steam Locomotives (New York: Putnam, 1974). See also "Rebuilt 4-6-2 Compound Locomotives Show Economies", Railway Mechanical Engineer, Volume 105, No 11 (November 1931), pp 527-533; and "New French Superheaters", Railway Gazette, Volume 62, No 8 22 (February 1935), pp 332-333.

SNCF figure for tractive effort was 28,440 lb.

Rebuilds of the Series 3.501-3.520 by noted locomotive designer Andre Chapelon. (See Series 3.501-3.590 in Locobases for further information on these de Glehn-Solacroup Pacifics). At least 90 were built for the Paris and Orleans, the Nord, and the Est.

Chapelon threw most of what he'd learned so far into the redesign of these engines. His trial horse (the ex-3556, later renumbered 3701) boiler limited the small tube count to 90 tubes with an external diameter of 50 mm, This made room for a Robinson superheater of considerable size (40 flues with elements presenting 72.5 sq m (780 sq ft). Firebox and tubes combined to yield an evaporative heating surface area totalling 185.71 sq m (2,020 sq ft).

The other 42 rebuilds used the Houlet superheater shown in the Locobase specifications. The Railway Gazette report featured a full explanation and photographs describing an annular design in which each flue held a large-diameter element tube that contained an intertwined pair of smaller tubes. Steam flowed from the header at the smokebox tubesheeet to within 450 mm of the firebox tubesheet before heading toward the front. In a bundle of 28 flues, the effective superheater area nearly doubled compared to the Schmidt Type A design.

Chapelon added 26.5 sq ft (2.465 sq m) of Nicholson thermic syphons to the firebox, a modest increase in firebox heating surface area. The upgrade raised the superheat from 300 deg C to 400 deg C, doubled the size of all steam passages, used a poppet-type valve gear, add an ACFI feedwater heater, and fitted the Kylchap type of double blast-pipe nozzle. According to Reder, the improvement was immediately apparent in increases in indicated horsepower to 2,500-2,600 hp while maintaining a low coal consumption rate.

Chapelon's tweaks resulted in a powerful and free-running engine. John Blyth, in one of his columns published on [], recited a test run that indicates how perfectly suited was Chapelon's design for the peculiarities of French operational requirements. French regulations limited maximum speed to 75 mph and in the P-O's case, the profile of the Poiters-Angouleme rose and fell. So the engine had to be able to maintain as high a speed as possible with heavy trains.

It succeeded brilliantly in tests by achieving a 71-mph (114 kph) average over the distance (71 miles/114 km) while never exceeding 75 mph (121 kph). Blyth adds, "The speed graph, many times published, shows a straight line all the way, despite the undulating nature of the route." Even more tellingly, "The one-hour schedule was adopted for all trains on this section, and time was never lost."

The design saw steam out on the fast boat trains between Paris and the Channel.

Class 3 501 (Locobase 2579)

Data from Henri Desarces, Grande encyclopedie practique de Mechanique et d'Electricity, Volume 4 (Éditions Quillet, 1913 ), Fig. 942; and "231 n° 3 501 à 3 520 du PO" on the WikiPO website at [], last accessed 3 November 2024..

Part of the de Glehn-Solacroup design series for the PO, Series 3500 locomotives rolled on tall 77" drivers for the flatland expresses between Paris and Bordeaux. Like the others (Locobase 2580), these had Belpaire fireboxes of a trapezoid profile. But unlike the others, these began their service without superheaters.

See Locobase 1053 for the 1930 Chapelon makeover.

Class 3 521 (Locobase 2580)

It appears that this is the batch referred to by Edouard Sauvage in the May 1916 RME. Data from his table constitute the specs in this entry, supplemented by cnum_8XAE739, Exposition universelle, Groupe VII. Classes 39 et 40: Industrie des Transports-Chemins de fer et Tramways. Exposition internationale des industries et du travail de Turin 1911 (Paris: Comite Francais des Expositions a l'Etranger, 1911), p. 18; and "N° 3 501 à 3 590 de 1909-1914 du PO" on the WikiPO website at N° 3 501 à 3 590 de 1909-1914 du PO, last accessed 3 November 2024.

The WikiPO site shows Société anonyme Baume et Marpent in Brussels, Belgium as the builder of the 3 521-3 550 in 1910. Compagnie Fives-Lille produced works numbers 3919-3938 as PO 4 321-5 340 in 1913. SACM added works numbers 6501-6520 in 192 as 3 551-3 570, and Cail delivered works numbers 3599-3618 in 1914 as 3 571-3 590. (Cail's 20 each weighed less than a 1/2 ton more than the others.)

By far the more numerous of the 3.500 class de Glehn-Solacroup compound Pacifics for the PO, these left the builder ( with superheaters installed. Otherwise, they too had Belpaire fireboxes and trapezoidal sloping grates.

It was 3566 of this group that was made over by Andre Chapelon in 1930. See Locobase 1053.

Class 3 591/231D (Locobase 14995)

Data from M Lunier, "Locomotive 'Pacific' A Surchauffe de al Compagnie D'Orleans", Revue Generale des Chemins de Fer et des Tramways, Juilliet 1923, pp. 15-24; and English-language version in Railway Mechanical Engineer, Volume 97, No 10 (October 1923), pp.679-380.. See also Roy V Wright (Ed.) 1922 Locomotive Cyclopedia of American Practice, Sixth Edition (New York: Simmons-Boardman Publishing Company, 1922), p. 1021

This simple-expansion Pacific design immediately succeeded the long line of compound 4-6-2s on the P-O. Its piston valves measured 13.75" (350 mm) in diameter. Lunier's commentary in the RA stressed the American connection, which is borne out by the many American details such as 545 flexible stays, straight top boiler, and the component suppliers. On the other hand, the variable exhaust was of the Nord type and the cylinder dimensions were squarer than most American Pacifics.

Lunier added some performance details, saying that the locomotive's stability at 125 kph (77.6 mph) was "parfait". A train run between Toury and les Aubrais averaged 100 kph (62.1 mph), an average superior to those of the four-cylinder compounds. Moreover, locomotive resistance decreased from that shown by the compound designs as did fuel and water consumption.

Class 4 501 (Locobase 2536)

Data from Gustav Reder (Michael Reynolds, trans), The World of Steam Locomotives (New York: Putnam, 1974), pl 289; "231 n° 4 501 à 4 570 du PO" on the WikiPO website at [];_4_501_à_4_570_du_PO, last accessed 26 October 2024; and OS Nock, RWC IV, Pl 66 and Albert H Bone, "Some Recent Designs of Locomotives for Service on Continental Railways", Cassier's Magazine, 1910, pp. 561-609. SACM produced the first ten (works numbers were 5698-5700, 5901-5807 in 1907 and the last 20 (works number 5825-5844 in 1908). Sandwiched between those batches were Hanomag contributing ten (road numbered 4511-4520; works numbers 5170-5179 in 1908.

Noteworthy for being the first Pacifics to operate in France (or, for that matter, any European main line); the last 30 of this class -- 4541-4570 -- were built at Alco's Schenectady, NY works; see Locobase 4191.

A collaboration of Alfred De Glehn of the Ste Alsacienne and the PO's chief engineer George Solacroup, these engines introduced the trapezoid shaped firebox. Wide at the rear and narrow at the front, to fit between the drivers, the firebox offered more heating surface and had its weight distributed farther forward. Square shoulders signified the flat-top Belpaire shape.The HP cylinders lay outside, were served by piston valves and drove the second coupled axle. The LP cylinders were inside the frame, operated slide valves, and drove on the first axle.

A faulty design in the exhaust nozzle was a noticeable defect in the first couple to enter service in 1907. All of the class was soon equipped with the Nord adjustable-cone type and saw a 5-10% improvement in economy.

The first batch of a long line of compound Pacifics for the PO, 4501-4570 were built without superheaters, although the provision of piston valves was intended to facilitate fitting them with the equipment later. Even in their saturated state, an engine of this class pulled a 360-ton train between Paris and Les Aubrais at 54.7 mph (88 km/h) and between Les Aubrais at an average speed of 95 km/h (59 mph ).

The last 30--4571-4600--in 1910 (Locobase 2578), were delivered with superheaters. Series 3501-3520, saturated steamers, had 77" drivers for the flatland expresses between Paris and Bordeaux. 3521-3589 had superheaters from the start.

Class 4 541 (Locobase 4191)

Data from "De Glehn Four-Cylinder Compound Pacific Type Locos, Paris-Orleans Ry", The Locomotive Magazine, Vol XIV (15 September 1908), pp. 159-161; and "Four-Cylinder Compound Pacific Locomotive for the Paris-Orleans Railway", Railway Age Gazette, Volume XLV [45], No. 15 (11 September 1907), pp. 897-901; and "231 n° 4 501 à 4 570 du PO", on the WikiPO at [], last accessed 3 November 2024. Works numbers were 42008-42037 in July 1907.

This was the thirty-locomotive subclass of the first de Glehn compounds built by the American Locomotive Company for the Paris & Orleans (see Locobase 2535). RAG profiled the class, which notes that all the data for construction was given to Alco in metric and used directly. The table of data gives an incorrect diameter for the HP cylinders (11.81"), but the accompanying diagrams show the more reasonable 15.35" used in Locobase. The Belpaire boiler seems to have more heating surface than those of the 40 French-built examples, although this represents Alco's measurement of tube area from the water side, rather than the usual "fire side" area inside the tube walls.

RG notes that the spec called for locomotives that could pull a 400-ton train up a 1% grade at 50 kph (31 mph). The division was the line between Limoges and Brive, which had constant adverse gradients. From the Brive direction, the grade rose at an average of 0.75% for 47.5 km (29.5 miles).

RG notes with interest the trapezoidal firebox and the fact that the rear truck wasn't equalized with the last driving axle. The truck had 90 mm (3.54") of play to either side

Class 4 571 (Locobase 2578)

Data from J B Flamme, Les Chemins de Fer A l'Exposition de Bruxelles (Paris: H Dunod et Pinat, 1911), p. 45.

Part of the large complement of compound Pacifics for the PO (see Locobases 2536 & 4191), these were equipped with superheaters from the start. Their high-pressure cylinders measured 30 mm (1.18") wider in diameter. The HP cylinders used piston valves, the LP cylinders were supplied through slide valves. The distinctive Belpaire firebox and trapezoid sloping grate were a feature of all of these Pacifics.

In 1926, the PO-Midi installed KylChap exhaust nozzles and "elephant ear" smoke lifters on each side of the smokebox. Piston valves were fitted to the low-pressure cylinders in some in the class

In 1929, these engines received feedwater heaters of three different types. The lowest-number 20 used ACFI and the last five had Dabegs. 4591-4595 were fitted with non-French Worthingtons.

NB: Tube diameters are measured on the fire side, as per usual French practice. Anglo-American water side measurements would have been approximately 10% , which would reduce the superheater percentage of combined heating surface area to about 20.7%.

They later served as the foundation for Andre Chapelon's massive reworking into outstanding 4-8-0 engines (see Locobase 9572 and 1054)..