Ferrocarril General Roca Class 8C 2-6-2T
No.3477 was subject to a much heavier modification programme than the other 8Cs worked on. It was a prototype and demonstrator of what was possible. The fact it remained a one off does not indicate it was a failure, far from it, but instead that Argentine Railways decided electric and diesel traction was the way they wished to proceed.
The design had a number of fundamental errors which Porta was, in part, able to correct. In doing so the machine was transformed. Further details can be found in Porta's 1969 I.Loco.E. paper given in Manchester, UK. This is now available from Camden Miniature Steam Services.
This locomotive was fitted with a Kylpor exhaust ejector. This may seem strange given the fitting of a Lempor type to the lightly modified 8Cs and 8Es. At this time Porta was evaluating the Kylpor and Lempor alongside each other. With the Kylpor already fully developed his next work (at Rio Turbio) used the Kylpor but it was always his intention to perfect the Lempor in due course.
To allow the locomotive chassis to absorb the extra power produced by No.3477 the frames were strengthened. The following diagram and text which follows is taken from Porta's 1992 "A Proposal for the Tornado Project" with minor alterations to the English:
"The original 1915 frame proved to be extremely weak. The reinforcement was inspired by CHAPELON'S 'H-frame'. On the bottom inner side, plate reinforcements (1) were riveted. On the outer side, inverted U pieces were riveted over the opening for the axleboxes (dashed lines 2). The fabricated tubes (3) had their flanges (4) riveted to the mainframe plates (5). The horizontal plate (6) ran from the cylinders to the firebox. But perhaps most important of all was the stiff, very robust hornstay (7) of American inspiration, fitted to the wedge shaped horns (8). Bolts (9) were of high strength steel designed to store a large amount of elastic energy. (10) is the hole for the T-spring hanger. The boiler was well tied to the frame by American type expansion plates. A fabricated box was placed between the cylinders (1953).
The scheme was a glamorous success, but given the knowledge now available it would have been simpler, lighter, cheaper and better."
The diagram below shows the impressive acceleration characteristics of the No.3477:
