The Geeps
It is undeniable that the creation of the GP (General Purpose) 7 changed railroading drastically. The GP7 units were designed by Dick Dilworth of EMD. His goal was to make a road switcher which would work well "out where the real work was being done." The design was based on observations from Alco and Baldwin Locomotives, as well as considerations of the needs of a freight train crew. Originally the GP7 was made with limited visibility. This was partly because the union atmosphere at the time, wanted to keep the fireman on the locomotive, to simply watch the left side. In reality, Firemen were kept on the crew until the mid 80's or early 90's in some cases - strictly due to union pressure. Another consideration in building the GP7 with long high hoods, and a centrally located drivers cab was the consideration of the old Steam Era Engineers and Firemen. They often liked the idea of a buffer between them and the front of the train - in case of collision. Although these hoods were not structural, and would not stop a collision as well as a heavy boiler would, the impression of the high hood did play a key role in how popular the GP7 became. The other critical aspect which made the GP's popular was the control stand. Dilworth brought in locomotive engineers from various railroads, and sat them down as a mock up engine cab. The Engineers told Dilworth what they wanted. And Dilworth followed through, to create a control stand, which stands in the middle of the cab, close to the right hand window. From which the Engineer could easily operate the controls while looking either forward or backwards. This design became the AAR Standard Control Stand. EMD Could not produce GP7's fast enough to keep up with demand, and opened up an Engine Plant in Cleveland, Ohio to try to meet demands. In total, 2,729 GP7's were produced. The GP9 replaced the GP7 in 1954 and ended up becoming even more popular with 3,444 units being sold. The GP18 made its debut in 1959 and augmented the GP9 until 1963 when both the GP9 and GP18 ceased production. The GP18 was less popular, with only 350 units being built. All in all, these GPs or Geeps were the turning point of freight operations in North America.
ITC #1605 GP7 - Photo by Sean Lamb
The Geeps were all very similar looking. The unique differences are subtle, but easily identifiable. GP7's generally have 3 vents below the drivers cab, such as the photo above. GP7's also have a pair of grills in the access doors towards the rear of the long hood on each side. The GP7 also had a skirt covering part of the gas tank, however in late model GP7's and early model GP9's the skirt was retained, however with access holes added. Eventually the skirt was often removed completely later for access.
GTW #4621 GP9 with a short hood
DGVR #40 GP9 with dynamic breaking (as evident by the rounded vent at the top)
The GP9 is identifiable by often just one vent, or small half sized vents below the drivers cab. The GP9 also only has one set of grills on the access hatch doors at the rear of the long hood. And 3 sets of double grills on the central access hatch doors of the long hood as well.
An EMD GP18. Photo by Doug Kroll
The GP18 looks very similar to the GP9. The only exception is the Fuel Fill cap, which is positioned a little higher on the GP18. Instead of coming out of the Skirt on the GP9, it comes out of the side of the frame / lower walkway portion on the GP18. The GP18 also had a Roots Pump Supercharger.
The authors favorite Diesel-Electric Locomotive, has to be the GP9 short-hood. It was the most common locomotive I saw growing up near the CN Lines in and around Toronto, and the fact that the GP9's are still kicking and in revenue service on several railroads, just proves their worth in my eyes. These locomotives are beasts which deserve some respect.