Chapelon's "enhanced" 3500 & 4500 P.O. Pacifics; 3800 & 4800 series (later S.N.C.F. 4 - 231 G & A). History - Technical data

Briefly, these units are big (3500 series) or small (4500s) wheels Pacifics of the P.O. improved at the lowest possible cost. Various transformations have been applied on small batches of locomotives, such as an enlarged piping for H.P. cylinders feeding on some units, Willoteaux's piston valves on the L.P. or ordinary piston valve with increased stroke, new larger regulators, A.C.F.I. feed water heaters on some units, .. resulting in about 4 or 5 different variant.

Depot of Limoges, 1936; Photo Felix Fénino. 3824 in the depot of Bordeaux St. Jean, 1953. Photo Raymond Floquet.  4578 again in Bordeaux. Photo L.M. Vilain  


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