EMD SD7
The EMD SD7 is a series of diesel-electric locomotives, 6-axis of the U.S. locomotive manufacturer General Motors Electro-Motive Division (EMD ).
A total of 118 vehicles of this series originated in the EMD workshops in La Grange Illinois.
Development
With the introduction of the GP7 in 1949 a machine was available that met the requirements of the railway companies in terms of line service and Rangiertauglichkeit. However, these machines were with an axle load of 28 tonnes too heavy for some routes. So the idea of creating by extending the GP7 and use a machine with three-axle bogies lower axle load was. These considerations led in 1952 to the delivery of SD7 series.
The machines were, however, due to the higher number of traction motors in purchase and maintain expensive than the GP7. Therefore, the sales figures of the early models of the SD series lagged behind those of the GP series.
Construction
The SD7 technically based on the successful series GP7. Due to the longer bogies of the locomotive frame had to be stretched. The EMD SD7 had a stable framework, which was lined with doors. This results in a very low-maintenance design was created because all aggregates were easily accessible from the outside. The series had a cab, with whom she could be in contrast to the machines of the E- and F- series driven in both directions. Behind the engine room was with the traction generator which supplied the DC power to the traction motors and the diesel engine EMD 567B. The type designation EMD 567 means that the engine had a swept volume of 567 cubic inches. The vehicles of the early SD series had 16- cylinder engines.
The fuel tank was positioned between the bogies and took about 4,500 liters of diesel oil. Along the engine cover a walkway for the shunter was arranged on both sides. So this could get from the cab directly to the two ends of the vehicle.
Equipment
Many models have been delivered to the customer with a dynamic brake. Here, the kinetic energy is converted by the traction motors in electric energy and this then produces heat through resistive elements. This causes the brake wear could be reduced because the dynamic brake operates largely wear-free. To deliver the heat to the environment, the so -equipped locomotives had an additional roof vent. In the photo of the SP 1518 on the right of the air intake to cool the resistors above the lettering ' Southern ' can be seen.