EMD MP15DC
The EMD MP15DC is a switcher-type diesel locomotive model produced by General Motors' Electro-Motive Division between March 1974 and January 1983. 351 examples were built. An MP15AC variant, with an AC drive, was also offered. Between August 1975 and August 1984, 246 MP15ACs were built, including 25 for export to Mexico, and four built in Canada. The MP15DC replaced the SW1500 in EMD's catalog, and is superficially very similar to the predecessor model, using the same engine in a similar design of hood and bodywork. The primary difference is the MP15's standard Blomberg B trucks.
Development
Switchers up to the SW1500 had been restricted to AAR type A switcher or Flexicoil lightweight trucks, both with a wheelbase. In 1973 60 special order Mexico-only SW1504s were built on a slightly longer frame, allowing EMD's standard Blomberg B trucks, with a wheelbase, to be used. In EMD's eyes this made the new locomotive a road switcher rather than a pure switcher, since it was capable of road speeds up to or so. The new model MP15DC designation thus meant Multi-Purpose locomotive, 1500 hp, DC generator. Originally the locomotive was simply designated the MP15; the arrival of the alternator/rectifier MP15AC in 1975 changed the name.With the success of the MP15, there was a demand for a model with an advanced AC drive system. The MP15AC replaced the MP15DC's DC generator with an alternator producing AC power which is converted to DC for the traction motors with a silicon rectifier. The MP15AC is longer than an MP15DC, the extra space being needed for the rectifier equipment. The alternator-rectifier combination is more reliable than a generator, and this equipment became the standard for new diesel-electric locomotive designs.
The MP15AC is easily distinguished from the DC models. Instead of the front-mounted radiator intake and belt-driven fan used on all previous EMD switchers, these have intakes on the lower forward nose sides and electric fans. Side intakes allowed the unit to take in cooler air, and the electric fans improved a serious reliability issue found in its earlier DC sisters.
Engine
The MP15 used a 12-cylinder version of the 645E series engine developing 1500 hp at 900 r.p.m. Introduced in the SW1500, this was a 2-stroke, 45-degree V type, with a 9-inch bore by 10-inch stroke, giving 645 cubic inches displacement per cylinder. The 645 series, introduced in 1966, was EMD's standard engine through the 1980s.Original owners
MP15DC
Early railroad buyers were the Pittsburgh & Lake Erie, with 25, and the Missouri Pacific, who would buy 62 between 1974 and 1982. The Chicago & Northwestern, Southern Pacific, Louisville & Nashville, and Reading made smaller orders. Later, from 1977 to 1982, Southern bought the largest fleet, 88 units under six names. Over 50 more were sold to 37 other customers.| Owner | Quantity |
| American Cyanamid Company | 2 |
| Aluminum Corporation of America | 1 |
| Alton and Southern Railroad | 1 |
| Altos Hornos de Mexico | 5 |
| Arizona Public Service | 1 |
| Bauxite and Northern Railway | 2 |
| Belt Railway of Chicago | 4 |
| Birmingham Southern Railroad | 2 |
| BC Hydro | 3 |
| Cambria and Indiana Railroad | 2 |
| Chicago and North Western Railway | 15 |
| Cities Service Company | 1 |
| W.R. Grace and Company | 4 |
| Graysonia, Nashville and Ashdown Railroad | 1 |
| Genesee and Wyoming Railroad | 2 |
| Gulf Oil | 1 |
| Georgetown Railroad | 2 |
| Houston Belt and Terminal Railroad | 5 |
| Industrial Minera de Mexico | 2 |
| Kansas City Southern | 4 |
| Kelly's Creek and Northwestern Railroad | 2 |
| Lake Erie, Franklin and Clarion Railroad | 4 |
| Louisville and Nashville Railroad | 10 |
| Manufacturers Railway | 3 |
| Metropolitan Sanitary District of Greater Chicago | 1 |
| Missouri Pacific Railroad | 62 |
| North Louisiana and Gulf Railroad | 4 |
| Philadelphia Bethlehem and New England Railroad | 2 |
| Pittsburgh and Lake Erie Railroad | 25 |
| Point Comfort and Northern Railroad | 4 |
| Quebec Iron and Titanium | 2 |
| Reading Railroad | 10 |
| Rockdale, Sandow and Southern Railroad | 3 |
| Sandersville Railroad | 1 |
| St. Louis - San Francisco Railway | 5 |
| St. Mary's Railroad | 2 |
| Southern Railway | 88 |
| Southern Pacific Railroad | 12 |
| Southern Railway of British Columbia | 3 |
| Estech Inc. | 1 |
| Tennessee Eastman | 1 |
| Terminal Railway Alabama State Docks | 7 |
| Texas City Terminal Railroad | 3 |
| Texas and Northern Railway | 2 |
| Union Railroad | 24 |
| US Steel | 15 |
| Total | 351 |