A PROBLEM faced by narrow-gauge (1000mm to 1067mm) railways in developing countries is the high cost of new locomotives. New, modern and efficient locomotives are available from manufacturers, but the problem such railways face is funding them.
Brazil's mining giant CVRD, the world's largest iron-ore producer, may have found a cost-effective solution to this problem. The method used by CVRD results in a practically-new metre-gauge 2.23MW or 2.68MW locomotive for about $US 1 million, which is much lower than the cost of a new locomotive of similar power.
Brazilian railways have been buying used locomotives in the United States both to replace older power and as a means of increasing capacity. Three metre-gauge railways--Vitoria a Minas Railway (EFVM), Central Atlantic Railway (FCA), and Latin American Logistics (ALL)--have bought used standard-gauge locomotives as a lower cost option than buying new power. Their approaches to converting them to the smaller gauge are completely different, however.
Until recently there were a lot of GE-built C30-7s and C36-7s for sale in the United States as the US Class 1 railways bought new locomotives, but they found few buyers for their used power. Even with the recent increase in prices of used motive power, it is still good business to buy and upgrade locomotives
All broad-gauge (1600mm) railways in Brazil bought some of these as a means of getting new power on the cheap--new in the sense that they were newer than almost anything they had at privatisation in 1996-98. In some cases clearances had to be increased to handle the traffic, as on the Rio de Janeiro-Belo Horizonte line, but on other lines this was not possible so locomotives had to be transferred from other lines. On most lines the newer power was readily accepted after modifying the bogies.
However, about 83% of Brazil's railway network is metre-gauge and given the size and weight of the standard-gauge US locomotives these fines could not be readily adapted, the weight and size of the locomotives proving too much for the infrastructure.
CVRD owns two major metre-gauge railways, iron-ore hauling EFVM, whose main line carries over 120 million tonnes yearly, and grain and limestone hauler FCA, which has considerably less traffic. In simple terms, this means that while EFVM can afford new locomotives, FCA cannot. In recent years, CVRD has had a huge increase in traffic due to the growth of Brazil's exports of iron-ore and soya, as well as the efforts of a more proactive management.
To handle this additional traffic, CVRD bought a significant fleet of used locomotives from the United States (see table).
All the B36-7 locomotives have had their underframes extended 1200mm at each end and were fitted with smaller wheels and smaller fuel tanks. Their total weight was increased to 160 tonnes, and their two two-axle bogies replaced with four two-axle equivalents. All C36-7s have had their chassis extended 0.90m at each end and were also given smaller wheels and smaller fuel tanks. Their total weight was decreased to 160 tonnes to meet axleload limits, and their two three-axle bogies also replaced with four two-axle bogies. This meant that after rebuilding, all these locomotives have an axleload of 20 tonnes, and all ride on four two-axle bogies. They were given a fight overhaul before entering service with CVRD.
The smaller wheels lower the height of the locomotives, which are rather big for the loading gauge on metre-gauge lines. By reducing fuel capacity, engineers were able to place the extra bogies beneath the underframe without having to lengthen it excessively. The GM-built locomotives were given similar treatment.
Two locomotives have been further upgraded and computerised, but they are still having teething problems that the railway is trying to solve. Further conversions into BB36-7MP are dependent on finding a solution to these problems.
Another problem CVRD had was with the traction motors. The original motors would not fit the confines of the narrow-gauge bogies, so the railway replaced those on the SDs with GM-designed D31 0.33MW motors built in Brazil by Manser and MGE. On the GE locomotives, CVRD replaced the motors with GE's 761ANR5 0.37MW motors made in Brazil by Gevisa, Manser, and MGE.
This approach avoids the need to absorb the energy generated by the diesel generators by taking a spare locomotive and sending the traction supply directly to its traction motors (known as a 'slug' in the United States and Brazil). GE GTA24 traction alternators had to be installed in all locomotives that were also fitted with electronic braking and Locotrol, the latter to allow distributed power operation
