Paris-Orleans 2-2-2 Locomotives in France

Class Forquenot (Locobase 20254)

Data from "French Locomotives", Engineering, Volume 3 (15 February 1867), p. 167.

These Victor Fourquenot single-wheelers hauled express passenger trains on the Tours-Bordeaux line, which had relatively gentle grades. In the summer, one of these engines might trail 16-19 fully loaded carriages at 40 mph (64 kph) average speed.

Class Montgolfier (Locobase 609)

See Reder (1974) and SEZANNE. Data corrected and supplemented by Alexandre Louis Deghilage, Origine de la Locomotive (Paris: Imprierie A Broise et Courtier, 1886), p.38.

First of the long-boilered Patentees with Stephenson link motion to run in Europe and exemplary of the "long-boiler" types that ran in Great Britain and Europe. Engines built by Robert Stephenson and Meyer of Mulhouse.

These engines had inside bearings and a softer exhaust beat. Flues were lengthened from approx 9 ft to 13-14 ft to permit more complete combustion.

Clement Edwin Stretton , The Locomotive Engine and Its Development, a Popular Treatise on the Gradual , Lockwood and Son, 1892, pp 72 outlines how the "longboiler" design came to be. He notes that early in 1842, Stephenson confirmed that the rapid rate of wear of smokeboxes and chimneys (stacks) was due to the very high temperatures of the gases at the time they finished their travel through the firetubes.

Stephenson's program of trials to uncover the source of the problem betrays a sound engineering mind:

"First he placed tin in small iron conical cups and suspended them in the " smoke box," and it was found to disappear quickly; next, lead was tried in the same manner, and was found to melt nearly as easily; and, lastly, zinc was tried, which was soon driven off in vapour, clearly indicating a temperature of 773 degs. in the chimney." Stretton adds that such high temperatures revealed how much heat was wasted in non-productive (indeed, de-structive) assaults on the components.

Stephenson's solution demonstrates the designer's business sense. He saw that the proper action was to lengthen locomotive boilers from 9 ft. to 13 or 14 ft, but discovered that he should avoid stating a length in his patent application to avoid a battle with other builders who would merely change the length of tubes and patent that length. Stretton notes: "[Stephenson] therefore adopted the name "long boiler," and placed all the axles under the barrel or circular part of the boiler."

Lengthening the tubes turned the trick, reducing smokebox temperatures by over 300 degrees to 442 deg (at which the tin in the test cups just melted).

All sources say longboilers were relatively efficient (although their tiny grates had a 1:193 relationship with the combined heating surface) and easy to maintain, but their long boilers and short wheelbases made them unsteady. The first longboilers were 2-2-2s, but in 1844 Stephenson adopted a 4-2-0 arrangement and in 1846, some engines appeared with a 4-2-2 layout with the trailing axle behind the firebox.

Class Polonceau (Locobase 11293)

Data from August Perdonnet, Traite Elementaire des Chemins de Fer, Tome Second (Paris: Garnier Freres, , 1860), pp. 563-570.

Among the features of this class of high-wheeled singles was Polonceau's valve gear, which used a double-stacked valve that had two valve-gear rods. The lower valve acted as a normal D-valve (i.e., a slide valve with the usual ports) and the solid upper valve rode piggyback and could be adjusted to provide for early-cutoff at any point in the stroke. Each had its own lever, so the driver might have to manipulate both on starting (for example) even as he advance the regulator.

As far as the rest of the design was concerned, Perdonnet noted that the driver diameter would permit speeds equal to or even a little faster than the Cramptons then in service. On the other hand, this was a smaller locomotive and in service where a Crampton could pull 15 voitures (carriages) at 60 km/h (37 mph), this design manage only 12.

Fuel consumption seems remarkably low, even considering that the rake in question totalled only 70 tons; Perdonnet credits it with 5.3 kg/km (18.8 lb/mile).

Class Type 4/Le Dramah (Locobase 20379)

Data from Schneider Catalogue, last accessed 29 May 2018 at []. Works number was 10.

Schneider's catalogue is mute concerning the reason this was the only locomotive in its class. The profle shows a short-coupled three-axle "Single" that used relatively large 129 cm wheels on the leading axe and much smaller 99 cm trailing wheels. The tall dome sat over the firebox A tall, capped stack rose out of the firebox.

As was usual for the time, the footplate crew operated in completely open discomfort.