Encyclopedia of Trains and Locomotives: Diesel Locomotives

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On other than electrified lines and the few rare roads still operating steam, the diesel (or more correctly, diesel-electric) locomotive is the worldwide freight hauler. An oil- burning internal-combustion engine (called the prime mover) actually turns a generator (or alternator), which produces electricity that operates the motors mounted on the trucks and powers the axles.



There have been various attempts at direct mechanical connections from the engine to the trucks, and even diesel hydraulic drives, but at this time the diesel-electric is the standard, and references to a diesel locomotive refer to this arrangement.

Efficiency, flexibility, maintenance, and changing fuel costs ultimately doomed steam power in the industrialized world, and the high costs of capitalization for generating and distribution facilities made a significant increase in electrification unlikely outside of relatively short and heavily traveled corridors, or for special industrial and regulatory conditions.

But these simple facts were not so obvious in the 1920s, when early experiments in internal combustion railroad equipment met with mixed results.

The diesel engine was invented by Rudolf Diesel (1858 - 1913), a German mechanical engineer who was born in Paris and educated in England. His 1893 book, The Theory and Construction of a Rational Heat Motor, describes his ideas on internal combustion power. Diesel survived the explosion of his first engine, which nevertheless proved the practicality of the principle. Many more failures preceded the first successful model, built in 1897.

Shortly thereafter, Adolphus Busch, the noted St. Louis brewer, purchased the manufacturing rights for the United States. Unfortunately, wealth eluded the inventor, as patent lawsuits and unscrupulous associates siphoned profits, and Rudolf Diesel died when he mysteriously fell overboard on a crossing of the English Channel.

The engine Diesel invented operates on oil, which is cheaper than gasoline, and has no spark plugs or carburetor. It depends on heat generated by compression of the intake air in the cylinder (to 500—600 psi), which raises its temperature to 1,000 degrees F (540° C). When oil is injected into the hot air, it ignites and the expanding gas forces the piston down (the power stroke), thereby turning the crankshaft and flywheel. As the momentum of the fly wheel carries the piston back up, the burned gases are expelled, readying the cylinder for a new intake stroke.

Each piston movement, either up or down, is called a stroke, and each stroke has a job to do. The minimum number of strokes necessary to produce one power stroke is called a cycle—diesel engines are either two strokes per cycle or four strokes per cycle. The four-stroke engine takes in air on the first downstroke’ compressing it as it returns to the top. The ignition hap pens at that time, driving the piston down on the power stroke. As it returns to the top, it forces out the exhaust and is ready for the next cycle. The two-cycle engine requires only a compression stroke and a power stroke; the intake happens at the end of the power stroke and helps to force out the exhaust before the compression stroke begins.

Some diesels have two opposed pistons in each cylinder, which move toward each other on the compression stroke. When the fuel is injected and ignites, the pistons are forced apart and turn a common shaft to which they are


Above: The early experiments of Rudolf Diesel, inventor of the internal combustion engine named for him, were the beginning of the end of steam locomotives in most of the world. Below: After a number of experimental diesels and a successful tour by a General Electric/Ingersoll-Rand demonstrator, American Locomotive Works was added to the consortium that produced the first standardized line of diesel-electric locomotives. Five 60-ton (54 t) units were built for stock in 1924, and the first was sold to the Central Railroad of New Jersey (becoming CNJ 1000) the following year.

On a diesel locomotive, the energy of the turning crankshaft is connected to an alternator (for alternating current—AC) or to a generator (for direct current—DC). The two-stroke engines deliver a power stroke for each revolution of the crank shaft, but the four-strokes deliver power on alternate strokes and are therefore less efficient. The European invention of turbo- supercharging saved the four-stroke diesel from obsolescence.

While fuel costs for diesels were low, the engines were very large and heavy, required skilled crews for operation and repair, and were suitable for stationary industrial engines and ships. A diesel engine with sufficient horsepower to pull a train, yet small enough to fit in the confined space of a locomotive, was beyond reach until Charles Kettering directed a project in the research facilities of General Motors (GM) that was experimenting with two-cycle diesels, and by 1930 had achieved the same horsepower in an engine 25 percent smaller and with a 20 percent weight reduction. In 1935, the 900-hp twelve-cylinder, two-cycle engine, designated 201-A, was produced with the help of new lightweight alloys. The diesel locomotive engine had left the experimental stage and become an industry reality.

Not to be outdone, the American Loco motive Works (Alco), already well established as a builder of superb steam locomotives, also introduced a 900-hp engine but with only six cylinders and using a four-cycle unit with turbo-charging. From that point, turbocharged four-cycle engines competed fully with two-cycle engines, mainly in the arena of maintenance costs since both designs performed very well.

GM, through its Electro-Motive Division (EMD), built a new plant at La Grange, Illinois, exclusively to manufacture diesel-electric locomotives. Early business at La Grange consisted primarily of switch engines powered by eight- and twelve-cylinder diesels still manufactured by the Winton Engine plant, the company having been purchased by GM. A passenger locomotive, designated “TA” and built for the Rock Island in 1937, was the first locomotive with the car body built by GM, and it was followed by the stylish E Unit, both still Winton-powered.

By 1938, La Grange was ready for production of GM’s own two-cycle engine, following years of exhaustive testing. GM was well aware that road failures of their new diesel, particularly in highly publicized premium service, would destroy the image and acceptability of the product. Corporate concern was strong enough that sleeping beds were installed in the engine rooms of the early units, so that EMD technicians could ride around the clock to ensure proper maintenance and handle emergency repairs.

Above: Southern Railway No. 6100, the original EMD FT demonstrator set, swings across the Cumberland River near Burnside, Kentucky, in 1961. After a barnstorming tour on twenty railroads in thirty-five states, the units were purchased by Southern and operated for twenty years until retirement to the National Museum of Transportation in St. Louis.

Once General Motors sent their FT freight demonstrators on a wildly successful barnstorming tour of American rail roads, steam power was doomed, despite the best efforts of the steam locomotive manufacturers to delay the inevitable. The fuel economy, lack of water stops, and the operational simplicity of a diesel locomotive—a single module that could be assembled into a block of horsepower matched to the weight of any tram and controlled by one crew—were very appealing. When the components that make up an assembled locomotive are very much interchangeable between different models built by a manufacturer, then parts inventory and training for maintenance are also simplified.

Diesels performed at their best at low speeds, such as during switching, where steam was least efficient, so it was not surprising that low-horsepower switchers were the first market penetration. In round- the-clock yard service, a diesel switcher might operate almost continuously for several days before stopping for fuel and water. The lack of smoke made diesels the choice in urban areas with anti-smoke legislation. Further, large coaling, water, turning, and ash removal facilities could be eliminated, along with round-the-clock hostlers for tending fires and water levels.

In passenger service, streamlined diesels implied speed, modernity, comfort, and progress. Long-distance passenger trains began to be quickly dieselized in the late 1930s, but the early locomotives did not accelerate well above speeds of 15 or 20 mph (20 or 32 kph), the speed where steam engines were getting into stride. Once a train was started, a steam locomotive of 3,000 hp could easily outperform a diesel locomotive set of twice the horse power, so the railroads were reluctant to replace steam on freights.

World War II came at a very opportune time for the diesel builders. Steam development was frozen while diesel engines, critical technology for ships, tanks, trucks, and a myriad of other wartime machinery, were given priority for development and improvement. Once the diesel builders were able to extract higher horsepower and smaller size from their units, they attained a techno logical lead against which developers of advanced steam concepts such as turbines could not compete. Steam power was relegated to high-efficiency stationary plants, while diesels became mobile.


Above: The power plant of the Zephyr included this eight-cylinder diesel engine, which drove the cylindrical generator (on the far right), there by providing electrical power to axle-mounted motors. This is the same combination that powers today’s massive diesel-electric locomotives.

Below: Gulf Mobile & Ohio No. 733 was one of the first American Locomotive Works FA-1 diesels, built in 1945. The GM&O FAs differed from later production in having a smaller, lower grille around the headlight and a curved trim piece on the vent grille behind the door, which was typical of the PA-1 and PA-2 passenger versions of the locomotive.

North American passenger trains were quickly converted after the war, and dieselization was virtually complete by the mid-1950s. Coal haulers such as the Chesapeake & Ohio and the Norfolk & Western held on longer than most. Fast freight lines of the flatlands, like the Nickel Plate with its modern fleet of Lima’s “Superpower” steam locomotives, were the last holdouts. The cost of keeping facilities for both steam and diesel power, and the large forces of semiskilled personnel necessary for steam maintenance overcame the higher initial cost of the diesels and the theoretical advantages of steam, and the conversion was all but complete in the United States by 1960. The ultimate cost saving is open to argument. The postwar years saw major efforts at reductions of expenses and increases of efficiency, but, it is fair to say, the claim that diesel power saved the railroads from bankruptcy is probably exaggerated. The diesel locomotive has performed well, however, and has been equal to the task assigned to it.

Electrification, although common in Europe, has not been attempted on a large scale in North America since the Pennsylvania Railroad’s New York to Washington and Philadelphia to Harrisburg projects of the 1930s. Light rail commuter operations and a few captive coal mine—to—power plant lines have been built or converted, but the overwhelming capital costs required have prevented any significant new installations. Continuing experiments with coal- fired steam such as the ACE 3000 project of the 1980s and other experiments with coal- burning diesel locomotives have not yet come into production, so it appears that the diesel-electric locomotive will continue to churn out the miles around the world for years to come.

Above: Green and gold Central Vermont 4442, an Alco locomotive of the RS series, contrasts with the snow of New England as it leads a freight train.

See also: Alco; Baldwin; General Electric Company; Ingalls Shipbuilding Company.

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