2-6-0 Steam Locomotives in Argentina

Class Clase 7 (Locobase 21235)

Data from FC Roca 6-1957 Locomotive Diagrams supplied in August 2021 by Allen Stanley from his extensive Rail Data Exchange collection. See also D[ouglas] S[tuart] Purdom , pp. 40-41. See also Data from R. Gould, "Some Particulars of the Results of the Compound Locomotive on the Buenos Aires Great Southern Railway", Proceedings of the Institute of Mechanical Engineers (September 1901), pp. 817-823 and plates. Works numbers were 2628-2647 in 1885

Purdom wrote that Beyer, Peacock delivered 28 Clase 7s, but the definitive BP production list shows 20. When delivered, the engines burned wood fuel, so BP installed extended smokeboxes to help complete combustion and capture cinders. Although the ratios between evaporative surface area, firebox area, and grate area seem reasonable, the EHS/cylinder volume ratio is quite low. This helps, perhaps, to explain Purdom's comment:

"Until the advent in 1903 of the first 2-8-0 compounds, class 7 engines had a considerable share in the rapidly growing goods traffic and must have been very hard pressed at times."

Only five remained in service as of 1924 and all of these were gone by 1928.

Class Clase 7A (Locobase 21236)

Data from FC Roca 6-1957 Locomotive Diagrams supplied in August 2021 by Allen Stanley from his extensive Rail Data Exchange collection. See also D[ouglas] S[tuart] Purdom , pp. 40-41. See also Data from R. Gould, "Some Particulars of the Results of the Compound Locomotive on the Buenos Aires Great Southern Railway", Proceedings of the Institute of Mechanical Engineers (September 1901), pp. 817-823 and plates.

Locobase 21235 describes the original 1885 simple-expansion Moguls delivered by Beyer, Peacock.

See Locobase 21233 for a summary of CME R Gould's very positive assessment of the Wordsell-von Borries cross-compound system. In this class, he applied the same system to the 2-6-0 arrangement. His tables comparing simple to compound versions of the Clase 7s don't show quite the advantage in several areas as they did for the American-type Eight-wheeler Clase 6s.

It's important to note the difference in train loads. Clase 6 engines typically hauled less than 170 tons per train on 25 axles while the Clase 7s pulled between 624 tons (simple Clase 7) and 585 tons (compound Class 7a) Coal consumption by the compound 7As measured slightly less per axle and about 15% less per train mile. (Makes sense if we think of the same locomotive traveling one mile per train regardless of the number of goods wagons.) But compound 7A engines used more lubricants per train axle and per train mile than the simple-expansion engine 7s.

Apparently, the

Sometime later, most of the class rec

Class Clase 7B (Locobase 21237)

Data from FC Roca 6-1957 Locomotive Diagrams supplied in August 2021 by Allen Stanley from his extensive Rail Data Exchange collection. See also D[ouglas] S[tuart] Purdom , pp. 40-41. See also R. Gould, "Some Particulars of the Results of the Compound Locomotive on the Buenos Aires Great Southern Railway", Proceedings of the Institute of Mechanical Engineers (September 1901), pp. 817-823 and plates. Works numbers were 4044-4053 and 4234-4245, 4254-4259 in 1900-1901.

Locobase 21236 describes the first Moguls cross-compounds on the BAGS. See Locobase 21233 for CME R Gould's very positive assessment of the Wordsell-von Borries cross-compound system.

Looking up the 7B in the General Roca diagram book showed the cylinders as two 19" and one 26", but that resulted in a very unlikely 1:1 compounding ratio. Even though the diagram book shows a tractive effort approximately equal to Locobase's calculations, changing the cylinder setup to the 1:1 balance of HP and LP cylinders results in a very typical 2.09 compounding ratio.

Their role as goods engines hauling traffic on the mainline soon gave way to compound 2-8-0s. They wound up on branch lines and by the 1930s went into storage to avoid spending on heavy boiler repairs. Some emerged from idleness to supplement passenger engines in the late 1940s. Purdom notes that two of the revived 7Bs provided service on the 372 km (251 mile) from Bahia Blanca to Toay.

The last of the class finally fell to the ferro-knacker in 1967.

Class Clase 7D (Locobase 20046)

Data from "New Engines, Buenos Ayres Great Southern Ry," Locomotive Magazine, Volume 18 (15 July 1912), pp. 143-144; "Six-Coupled Locomotives for the Buenos Aires Great Southern Railway Co., Ltd", Locomotive News and Railway Contractor, Volume XI [11], No. 5 (10 March 1922), pp. 156-157; and FC Roca 6 1957 Locomotive Diagrams supplied in August 2021 by Allen Stanley from his extensive Rail Data Exchange collection. See also D[ouglas] S[tuart] Purdom , pp. 40-41Works numbers were 5521-5522, 5580-5589, 5652-5661 in 1912..

The LNRC report includes a photograph that showed an classic British engine having an upright profile with deep Belpaire firebox, slender, bullet-shaped dome. The superheater dictated the use of piston valves. Like most other Sud Moguls, these had relatively tall drivers.

Purdom, a former locomotive superintendent for the railway, found the 7Ds "easy to maintain, and economical on oil fuel. He described them as "one of the most useful and versatile classes the railway ever possessed, being equally successful on light passenger branch trains, goods trains on secondary lines and livestock trains throughout the system."