Midi 4-8-0 Locomotives in France

Class 4301/240 T A (Locobase 20283)

Data from "4-8-0 Two-Cylinder Simple Tank Locomotive, Chemin de Fer du Midi", Locomotive Magazine, Volume 20 (15 August 1914), pp. 216-217. See also Eric Seibel, "VouTes, DFs La Planche + Dessin, + La Grande Route, Et Quelle Route !", drafted June-August 2014 in French and last accessed at [] on 21 September 2017. Six were delivered in 1913, six in 1921, and six in 1922.

Midi's Beziers-Neussargues line covered 277 km (172 miles) of varying gradients over a third of the distance that inclined at 2.7 to 3.3%. Other sections "only" rose at 1.8%.

In designing the locomotives, the railway's staff offered a curious rationale for adopting a tank engine to succeed its four-cylinder Ten-wheel compounds with tenders. They explained that a tender's weight would "form no inconsiderable portion" of the trailing load, the maximum of which was set at 150 tonnes (165 short tons). thus "an engine itself carrying its provision of water and fuel was indicated." Locobase's puzzlement arises from noting that the locomotive would still be moving the steam-generating components and the only saving would be deleting the tare weight of the tender. In exchange, depletion of the supplies reduced the adhesive weight and thus the factor of adhesion.

The 4301's boiler contained 65 internally finned Serve tubes, 14 more plain tubes measuring 50 mm (1.97"), and 24 large flues that featured an unusually tapered diameter that began at 133 mm at the front sheet and slimmed to 119 mm (4.68 mm) at the rear. The firebox used a Moutte rocking grate.

On long downgrades, a steam injection system injected a water mist into the steam chests, cooling them and preventing a damaging heat buildup. (Locobase isn't sure, but this seems to be the equivalent of a drifting valve.)

Springing in the first and second coupled axles was connected through compensation (equalizing) beams as were the 3rd and 4th.

Eric Seibel's commentary accompanying his own attempt at building a model of this class notes that while the engines initially served the main line section described above, they later made inroads on the Tournemire-St Affrique, Tournemire-Le Vigan, Plaisance-Andabre, Espalion, Marvejols, Mende et Rodez routes as well. When the Causses line was electrified in 1932, they were found on the Tarbes, Mont-de-Marsan, Auch, Pau, La-Tour-de-Carol, Foix, Carcassonne lines.

Seibel comments that while the slight gap between the first two and the last two sets of drivers (probably reflecting the compensation-beam arrangement described above) might have seemed awkward, the layout had "a certain charm".

NB: Heating surface areas shown in the specs were calculated by the builder based on the inside (fire side) diameter, as often applied on Continental railways.