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Diesel locomotive Three styles of diesel locomotive body: cab unit, hood unit and box cab. These locomot- ives are operated by Pacific National in Australia. A Diesel locomotive is a type of railroad lo- comotive in which the prime mover is a Dies- el engine. Several types of Diesel locomotive have been developed, the principal distinc- tion being in the means by which the prime mover’s mechanical power is conveyed to the driving wheels (drivers). Overview Early internal combustion engine-powered lo- comotives used gasoline as their fuel. Soon after Dr. Rudolf Diesel patented his first com- pression ignition engine in 1892[1], its applic- ation for railway propulsion was considered. Progress was slow, however, due to the poor power-to-weight ratio of the early engines, as well as the difficulty inherent in mechanically applying power to multiple driving wheels on swivelling trucks (bogies). Steady improvements in the Diesel en- gine’s design (many developed by Sulzer Ltd. of Switzerland, with whom Dr. Diesel was as- sociated for a time) gradually reduced its physical size and improved its power-to- weight ratio to a point where one could be mounted in a locomotive. Once the concept of Diesel-electric drive was accepted the pace of development quickened. By the mid 20th century the Diesel locomotive had become the dominant type of locomotive in much of the world, offering greater flexibility and per- formance than the steam locomotive, as well as substantially lower operating and mainten- ance costs. Currently, almost all Diesel loco- motives are Diesel-electric. History Adaptation of the Diesel engine for rail use Following the expiration of Dr. Diesel’s pat- ent in 1912, his engine design was success- fully applied to marine propulsion and sta- tionary applications. However, the massive- ness and poor power-to-weight ratio of these early engines made them unsuitable for propelling land-based vehicles. Therefore, the engine’s potential as a railroad prime mover was not initially recognized.[2] This changed as development reduced the size and weight of the engine. The world’s first Diesel-powered locomot- ive was operated in the summer of 1912 on the Winterthur-Romanshorn Railroad in Switzerland, but was not a commercial suc- cess.[3] Adolphus Busch purchased the Amer- ican manufacturing rights for the Diesel en- gine in 1898 but never applied this new form of power to transportation. Only limited suc- cess was achieved in the early twentieth cen- tury with direct-driven gasoline and Diesel powered railcars.[4] General Electric (GE) entered the railcar market in the early twentieth century, as Thomas Edison possessed an outstanding patent on the electric locomotive, his design actually being a type of electrically propelled railcar.[5] GE built its first electric locomotive prototype in 1895. However, high electrifica- tion costs caused GE to turn its attention to Diesel power to provide electricity for elec- tric railcars. Problems related to co-coordin- ating the Diesel engine and electric motor were immediately encountered, primarily due to limitations of the Ward Leonard electric el- evator drive system that had been chosen. The first significant breakthrough oc- curred in 1914, when Hermann Lemp, a GE electrical engineer, developed and patented a reliable direct current electrical control From Wikipedia, the free encyclopedia Diesel locomotive 1 system (subsequent improvements were also patented by Lemp).[6] Lemp’s design used a single lever to control both engine and gener- ator in a coordinated fashion, and was the prototype for all Diesel-electric locomotive control systems. In 1917, GE produced an experimental Diesel-electric locomotive using Lemp’s con- trol design, the first known to be built in the United States. Following this development, the Kaufman Act of 1923 banned steam loco- motives from New York City due to severe pollution problems. The response to this law was to electrify high traffic rail lines. However, electrification was uneconomical to apply to lower traffic areas. In response to the Kaufman Act, New York City railroads approached Ingersoll-Rand to build a prototype Diesel switching locomotive (shunter), the AGEIR boxcabs. The resulting unit was fitted with a electrical generator and traction motors supplied by GE, as well as a form of Lemp’s control system, and was delivered in July 1925. These locomotives demonstrated that the Diesel-electric power unit could provide many of the benefits of an electric locomotive without the railroad hav- ing to bear the sizeable expense of electrific- ation.[7] In the mid 1920s, Baldwin Locomotive Works produced a prototype Diesel-electric locomotive for "special uses" (such as for runs where providing water for steam loco- motives was scarce) using electrical equip- ment from Westinghouse Electric Com- pany.[8] Industry sources were beginning to suggest “the outstanding advantages of this new form of motive power.”[9] In 1929 the Canadian National Railway became the first North American railway to use diesels in mainline service with 2 units, 9000 and 9001, from Westinghouse. The first regular service of Diesel-electric locomotives was in switching applications. General Electric produced several small switching locomotives in the 1930s (the fam- ous "44-tonner" switcher was introduced in 1940) Westinghouse Electric and Baldwin collaborated to build switching locomotives starting in 1929. However, the Great Depres- sion curtailed demand for Westinghouse’s electrical equipment, and they stopped build- ing locomotives internally, opting to supply electrical parts instead.[10] Diesel-electric railroad locomotion entered the mainstream when the Burlington Railroad and Union Pacific used Diesel "streamliners" to haul passengers.[4]. Follow- ing the successful 1939 tour of EMD’s FT demonstrator freight locomotive set, the transition from steam to Diesel power began, the pace substantially quickening in the years following the close of World War II. Diesel’s advantages over steam Diesel engines slowly eclipsed those powered by steam as the manufacturing and opera- tional efficiencies of the former made them cheaper to own and operate. While initial costs of diesel engines were high, steam loco- motives were custom made for specific rail- way routes and lines, and as such economies of scale were difficult to achieve.[11] Though more complex to produce with exacting man- ufacturing tolerances (1/10,000th of an inch (0.0025 mm) vs. 1/100th of an inch (0.25 mm) for steam), diesel locomotive parts were more conducive to mass production. As such, while the steam engine manufacturer Bald- win offered almost five hundred steam mod- els in its heyday, EMD offered fewer than ten diesel varieties. [12] Diesel locomotives offer significant operat- ing advantages over steam locomotives. They can safely be operated by one person, making them ideal for switching/shunting duties in yards (although for safety reasons many main-line diesel locomotives continue to have 2-man crews), and the operating environment is much more attractive, being much quieter, fully weatherproof and without the dirt and heat that is an inevitable part of operating a steam locomotive. Diesel engines can be star- ted and stopped almost instantly, meaning that a diesel locomotive has the potential to incur no costs when not being used. Steam locomotives require intensive maintenance, lubrication and cleaning before, during and after use. Preparing a steam locomotive for use can take many hours, especially if the lo- comotive is being fired from cold. However it is still the practice of large North American railroads to use straight water as a coolant in diesel engines instead of coolants that incorporate anti-freezing properties. This res- ults in diesel locomotives being left idling when parked in cold climates instead of be- ing completely shut down. Still, a diesel en- gine can be left idling unattended for hours or even days, especially since practically every diesel engine used in locomotives has From Wikipedia, the free encyclopedia Diesel locomotive 2 systems that automatically shut the engine down if a problem such a loss of oil pressure or coolant loss occur. A steam locomotive, by comparison, may be kept in readiness between uses with a small fire to maintain a slight heat in the boiler, but requires regular and frequent attention to maintain the fire and the level of water in the boiler. Moreover, maintenance and operational costs of steam locomotives were much higher than diesel counterparts even though it would take diesel locomotives almost 50 years to reach the same horsepower output that steam locomotives could achieve at their technological height.[13] Annual maintenance costs for steam locomotives accounted for 25% of the initial purchase price. Spare parts were machined from wooden masters for spe- cific locomotives. The sheer amount of unique steam locomotives meant that there was no feasible way for spare part inventor- ies to be maintained. [14] Steam engines also required large quantities of coal and water, which were expensive variable operating costs. [15] Further, the thermal efficiency of steam was considerably less than that of Diesel engines. Diesel’s theoretical studies demonstrated potential thermal efficiencies for a compression ignition engine of 73% (compared with 6-10% for steam), and an 1897 one-cylinder prototype operated at a re- markable 26% efficiency. [16] By the middle of the twentieth century, Diesel locomotives had effectively replaced steam engines. [15] Transmission types Unlike steam engines, internal combustion engines require a transmission to power the wheels. The engine must be allowed to con- tinue to run when the locomotive is stopped. Diesel-mechanical A diesel-mechanical locomotive uses a mech- anical transmission in a fashion similar to that employed in highway vehicles. The mechanical transmissions used for railroad propulsion are generally more com- plex and much more robust than road ver- sions. There is usually a fluid coupling inter- posed between the engine and gearbox, and the gearbox is often of the epicyclic (planetary) type to permit shifting while un- der load. Various systems have been devised to minimise the break in transmission during A British Rail Class 03 Diesel-mechanical shunter (switcher) with a jackshaft under the cab. gear changing, e.g. the S.S.S. (synchro-self- shifting) gearbox used by Hudswell Clarke. Diesel-mechanical propulsion is limited by the difficulty of building a reasonably sized transmission capable of coping with the power and torque required to move a heavy train. A number of attempts to use Diesel- mechanical propulsion in high power applica- tions have been made (e.g. the 1,500 kW (2000 horsepower) British Rail 10100 loco- motive), although none have proved success- ful in the long run. This type of transmission is generally limited to low-powered shunting (switching) locomotives, lightweight multiple units and self-propelled railcars. In later years, mechanical transmissions have been used again. These modern mech- anical transmissions are originally made for trucks and based on the fact that multiple truck engines are a common solution for Diesel railcars after year 2000, due to high development costs for engines because of en- vironmental requirements. For example, the Danish IC3 and IC4 railcars use mechanical transmissions for 294 kW (400 horsepower) and 560 kW (750 horsepower) engines respectively. Diesel-electric For locomotives powered by both external electricity and diesel fuel, see electro-diesel below. For locomotives powered by a combination of diesel or fuel-cells and batteries or ultracapacitors, see hybrid locomotive. In a Diesel-electric locomotive the Diesel engine drives an electrical generator whose From Wikipedia, the free encyclopedia Diesel locomotive 3 General Motors FT demonstrator set #103, the locomotive that sold American railroads on the freight-hauling Diesel-electric locomotive. Soviet 2TE10U locomotive output provides power to the traction motors. There is no mechanical connection between the engine and the wheels. The important components of Diesel-electric propulsion are the diesel engine (also known as the prime mover), the main generator, traction motors and a control system consisting of the engine governor, and electrical or electronic com- ponents used to control or modify the elec- trical supply to the traction motions, includ- ing switchgear, rectifiers, and other Motor controller devices such as Inverters, load res- istors or other components. In the simplest case the generator may be directly connected to the motors with only very simple switchgear. Originally, the traction motors and gener- ator were DC machines. Following the devel- opment of high capacity silicon rectifiers in the 1960s, the DC generator was replaced by an alternator using a diode bridge to rectify its output to DC. This advance greatly im- proved locomotive reliability and decreased generator maintenance costs by elimination of the commutator and brushes in the gener- ator. This disposed of a particularly destructive type of event referred to as flashover, which would could result in imme- diate generator failure and, in some cases, start an engine room fire. More recently, the development of high power Variable Frequency/Variable Voltage (VVVF) drives, or "traction inverters," has al- lowed the use of polyphase AC traction mo- tors, thus also eliminating the motor commut- ator and brushes. The result is a more effi- cient and reliable drive that requires relat- ively little maintenance and is better able to cope with overload conditions that often des- troyed the older types of motors. Engineer’s controls in a Diesel-electric loco- motive cab. The lever near bottom-center is the throttle and the lever visible at bottom left is the automatic brake valve control. Diesel-electric control A Diesel-electric locomotive’s power output, at any given throttle setting should (in the- ory) be the same without regard to road speed, as long as the unit is actually in mo- tion. Therefore, the unit’s ability to develop tractive effort (also referred to as drawbar pull or tractive force, which is what actually propels the train) will tend to inversely vary with speed. Due to the characteristics of the electrical transmission, the control system must be de- signed to, at all times, apply the maximum load to the prime mover that it can safely withstand, if maximum performance and effi- ciency are to be realized. Underloading, while not actually harmful, will cause a loss of efficiency, as the prime mover’s output will not be fully utilized. On the other hand, over- loading will cause efficiency loss due to the prime mover being forced to run too slowly for the rate at which fuel is being consumed, an effect referred to as "lugging." Lugging may cause abnormally high cylinder pres- sures during combustion, the emission of From Wikipedia, the free encyclopedia Diesel locomotive 4 S3 Diesel Electric Locomotive made by Montreal Locomotive Works in 1957 for the CPR adhering to designs by ALCO excessive smoke in the exhaust and, if al- lowed to continue, could result in severe mechanical damage. Maintaining acceptable operating para- meters was one of the principal design con- siderations that had to be solved in early Diesel-electric locomotive development, and ultimately led to the complex control systems in place on modern units. Throttle operation An EMD 12-567B 12 cylinder Diesel engine, stored pending rebuild, and missing some components. The prime mover’s power output is primarily determined by its rotational speed (RPM) and fuel rate, which are regulated by a governor or similar mechanism. The gov- ernor is designed to react to both the throttle setting, as determined by the engineer (driver), and the speed at which the prime mover is running. Locomotive power output, and thus speed, is typically controlled by the engineer (driver) using a stepped or "notched" throttle that produces binary-like electrical signals corresponding to throttle position. This basic design lends itself well to multiple unit (MU) operation by producing discrete conditions that assure that all units in a consist respond in the same way to throttle position. Binary encoding also helps to minimize the number of trainlines (electrical connections) that are required to pass signals from unit to unit. For example, only four trainlines are required to encode all throttle positions. North American locomotives, such as those built by EMD or General Electric, have nine throttle positions, one idle and eight power (as well as an emergency stop position that shuts down the prime mover). Many UK- built locomotives have a ten-position throttle. The power positions are often referred to by locomotive crews as "run 3" or "notch 7," de- pending upon the throttle setting. In older locomotives, the throttle mechan- ism was ratcheted so that it was not possible to advance more than one power position at a time. The engineer could not, for example, pull the throttle from notch 2 to notch 4 without stopping at notch 3. This feature was intended to prevent rough train handling due to abrupt power increases caused by rapid throttle motion ("throttle stripping," an oper- ating rules violation on many railroads). Modern locomotives no longer have this re- striction, as their control systems are able to smoothly modulate power and avoid sudden changes in train loading regardless of how the engineer (driver) operates the controls. When the throttle is in the idle position, the prime mover will be receiving minimal fuel, causing it to idle at low RPM. Also, the traction motors will not be connected to the main generator and the generator’s field windings will not be excited (energized)—the generator will not produce electricity with no excitation. Therefore, the locomotive will be in "neutral." Conceptually, this is the same as placing an automobile’s transmission into neutral while the engine is running. To set the locomotive in motion, the re- verser control handle is placed into the cor- rect position (forward or reverse), the brake is released and the throttle is moved to the run 1 position (the first power notch). An ex- perienced engineer (driver) can accomplish these steps in a coordinated fashion that will From Wikipedia, the free encyclopedia Diesel locomotive 5 result in a nearly imperceptible start. The po- sitioning of the reverser and movement of the throttle together is conceptually like shifting an automobile’s automatic transmission into gear while the engine is idling Placing the throttle into the first power position will cause the traction motors to be connected to the main generator and the lat- ter’s field coils to be excited. It will not, however, increase prime mover RPM. With excitation applied, the main generator will deliver electricity to the traction motors, res- ulting in motion. If the locomotive is running "light" (that is, not coupled to a train) and is not on an ascending grade it will easily accel- erate. On the other hand, if a long train is be- ing started, the locomotive may stall as soon as some of the slack has been taken up, as the drag imposed by the train will exceed the tractive force being developed. An experi- enced engineer (driver) will be able to recog- nize an incipient stall and will gradually ad- vance the throttle as required to maintain the pace of acceleration. As the throttle is moved to higher power notches, the fuel rate to the prime mover will increase, resulting in a corresponding in- crease in RPM and horsepower output. At the same time, main generator field excitation will be proportionally increased to absorb the higher power. This will translate into in- creased electrical output to the traction mo- tors, with a corresponding increase in tract- ive force. Eventually, depending on the re- quirements of the train’s schedule, the engin- eer (driver) will have moved the throttle to the position of maximum power and will maintain it there until the train has acceler- ated to the desired speed. As will be seen in the following discussion, the propulsion system is designed to produce maximum traction motor torque at start-up, which explains why modern locomotives are capable of starting trains weighing in excess of 15,000 tons, even on ascending grades. Current technology allows a locomotive to develop as much as 30 percent of its loaded driver weight in tractive force, amounting to some 120,000 pounds of drawbar pull for a large, six-axle freight (goods) unit. In fact, a consist of such units can produce more than enough drawbar pull at start-up to damage or derail cars (if on a curve), or break couplers (the latter being referred to in North Americ- an railroad slang as "jerking a lung"). There- fore, it is incumbent upon the engineer (driver) to carefully monitor the amount of power being applied at start-up to avoid dam- age. In particular, "jerking a lung" could be a calamitous matter if it were to occur on an ascending grade. Propulsion system operation As previously explained, the locomotive’s control system is designed so that the main generator output for any given engine speed will be constant and ideally will be exactly matched to the maximum horsepower pro- duced by the prime mover at that RPM. Due to the innate characteristics of traction mo- tors, as well as the way in which the motors are connected to the main generator, the generator will produce high current and low voltage at low locomotive speeds, gradually changing to low current and high voltage as the locomotive accelerates. Therefore the net power produced by the locomotive will re- main substantially constant for any given throttle setting (see power curve graph). Typical main generator constant power curve at "notch 8". In older designs, the prime mover’s gov- ernor and a companion device, the load regu- lator, play a central role in the control sys- tem. The governor has two external inputs: requested engine speed, determined by the engineer’s throttle setting, and actual engine speed (feedback). The governor has two ex- ternal control outputs: fuel injector setting, which determines the engine fuel rate, and load regulator position, which affects main generator excitation. The governor also in- corporates a separate overspeed protective mechanism that will immediately cut off the fuel supply to the injectors and sound an alarm in the cab in the event the prime mover exceeds a defined RPM. It should be noted that not all of these inputs and outputs are necessarily electrical. From Wikipedia, the free encyclopedia Diesel locomotive 6 The load regulator is essentially a large potentiometer that controls the main gener- ator power output by varying its field excita- tion and hence the degree of loading applied to the engine. The load regulator’s job is rel- atively complex, because although the prime mover’s power output is somewhat propor- tional to RPM, the main generator’s output is not (which characteristic was not correctly handled by the Ward Leonard elevator drive system that was initially tried in early locomotives). As the load on the engine changes, its ro- tational speed will also tend to change. This is detected by the governor via a change in the engine speed feedback signal. The net ef- fect is to adjust both the fuel rate and the load regulator position. Therefore, engine RPM and torque will remain relatively con- stant for any given throttle setting, regard- less of actual road speed. In newer designs controlled by a “traction computer,” each engine speed step is allotted an appropriate power output, or “kW refer- ence”, in software. The computer compares this value with actual main generator power output, or “kW feedback”, calculated from traction motor current and main generator voltage feedback values. The computer ad- justs the feedback value to match the refer- ence value by controlling the excitation of the main generator, as described above. The gov- ernor still has control of engine speed, but the load regulator no longer plays a central role in this type of control system. However, the load regulator is retained as a “back-up” in case of engine overload. Modern locomot- ives fitted with electronic fuel injection (EFI) may have no governor, however a “virtual” load regulator is retained. Traction motor performance is controlled either by varying the DC voltage output of the main generator, for DC motors, or by varying the frequency and voltage output of the VVVF for AC motors. With DC motors, various connection combinations are utilized to adapt the drive to varying operating conditions. At standstill, main generator output is ini- tially low voltage/high current, often in ex- cess of 1000 amperes per motor at full power. When the locomotive is at or near standstill, current flow will be limited only by the DC resistance of the motor windings and interconnecting circuitry, as well as the capa- city of the main generator itself. Torque in a series-wound motor is approximately propor- tional to the square of the current. Hence, the traction motors will produce their highest torque, causing the locomotive to develop maximum tractive effort, enabling it to over- come the inertia of the train. This effect is analogous to what happens in an automobile automatic transmission at start-up, where it is in first gear and thus producing maximum torque multiplication. As the locomotive accelerates, the now-ro- tating motor armatures will start to generate a counter-electromotive force (back EMF, meaning the motors are also trying to act as generators), which will oppose the output of the main generator and cause traction motor current to decrease. main generator voltage will correspondingly increase in an attempt to maintain motor power, but will eventually reach a plateau. At this point, the locomotive will essentially cease to accelerate, unless on a downgrade. Since this plateau will usually be reached at a speed substantially less than the maximum that may be desired, something must be done to change the drive character- istics to allow continued acceleration. This change is referred to as "transition," a pro- cess that is analogous to shifting gears in an automobile. Transition methods include: • Series / Parallel or "motor transition." • Initially, pairs of motors are connected in series across the main generator. At higher speed, motors are re-connected in parallel across the main generator. • Field shunting," "field diverting" or "weak fielding." • Resistance is connected in parallel with the motor field. This has the effect of increasing the armature current, producing a corresponding increase in motor torque and speed. Note: Both methods may also be combined, to increase the operating speed range. • Generator transition • Reconnecting the two separate internal main generator stator windings from parallel to series to increase the output voltage. In older locomotives, it was necessary for the engineer to manually execute transition by use of a separate control. As an aid to per- forming transition at the right time, the load meter (an indicator that informs the engineer on how much current is being drawn by the traction motors) was calibrated to indicate at From Wikipedia, the free encyclopedia Diesel locomotive 7 which points forward or backward transition should take place. Automatic transition was subsequently developed to produce better op- erating efficiency, and to protect the main generator and traction motors from overload- ing due to improper transition. Dynamic braking A common option on Diesel-electric locomot- ives is dynamic (rheostatic) braking. Dynamic braking takes advantage of the fact that the traction motor armatures are al- ways rotating when the locomotive is in mo- tion and that a motor can be made to act as a generator by separately exciting the field winding. When dynamic braking is utilized, the traction control circuits are configured as follows: • The field winding of each traction motor is connected across the main generator. • The armature of each traction motor is connected across a forced-air cooled resistance grid (the dynamic braking grid) in the roof of the locomotive’s hood. • The prime mover RPM is increased and the main generator field is excited, causing a corresponding excitation of the traction motor fields. The aggregate effect of the above is to cause each traction motor to generate electric power and dissipate it as heat in the dynamic braking grid. Forced air-cooling is provided by a fan that is connected across the grid. Consequently, the fan is powered by the out- put of the traction motors and will tend to run faster and produce more airflow as more energy is applied to the grid. Ultimately, the source of the energy dis- sipated in the dynamic braking grid is the motion of the locomotive as imparted to the traction motor armatures. Therefore, the traction motors impose drag and the locomot- ive acts as a brake. As speed decreases, the braking effect decays and usually becomes ineffective below approximately 16 km/h (10 mph), depending on the gear ratio between the traction motors and axles. Dynamic braking is particularly beneficial when operating in mountainous regions, where there is always the danger of a run- away due to overheated friction brakes dur- ing descent (see also comments in the air brake article regarding loss of braking due to improper train handling). In such cases, dy- namic brakes are usually applied in conjunc- tion with the air brakes, the combined effect being referred to as blended braking. The use of blended braking can also assist in keeping the slack in a long train stretched as it crests a grade, helping to prevent a "run- in," an abrupt bunching of train slack that can cause a derailment. Blended braking is also commonly used with commuter trains to reduce wear and tear on the mechanical brakes that is a natural result of the numer- ous stops such trains typically make during a run. Advantages • Regenerative braking. • No gearshifting • No backlash and breaking of couplings during shifting. • Constant availability of maximum diesel generator power. • Easy addition of multiple power units. • Less maintenance with modern ac generators and motors without commutators. Disadvantages • More weight • Less efficient in fuel use. • Needs high tech electronics with use of ac generators and motors . Electro-diesel These are special locomotives that can either operate as an electric locomotive or as a Diesel locomotive. The Long Island Rail Road and Metro-North Railroad operate dual-mode diesel-electric/third-rail locomotives between non-electrified territory and New York City because of a local law banning diesel- powered locomotives in Manhattan tunnels. For the same reason, Amtrak operates a fleet of dual-mode locomotives in the New York area. British Rail operated dual diesel-elec- tric/electric locomotives designed to run primarily as electric locomotives. This al- lowed railway yards to remain un-electrified, as the third-rail power system is extremely hazardous in a yard area. Diesel-hydraulic Diesel-hydraulic locomotives use hydraulic transmission to convey the power from the diesel engine to the wheels. On this type of locomotive, the power is transmitted to the wheels by means of a device called a torque converter. A torque converter consists of three main parts, two of which rotate,and From Wikipedia, the free encyclopedia Diesel locomotive 8 DB class V 200. one that has a lock preventing backwards ro- tation and adding output torque by redirect- ing the oilflow at low output rpm. For de- tailed operation see the torque converter art- icle. All three main parts are sealed in an oil- filled housing. To match engine speed to load speed over the entire speed range of a loco- motive some additional method is required to give sufficient range. One method is to follow the torque converter with a mechanical gear- box which switches ratios automatically, sim- ilar to an automatic transmission on a car. Another method is to provide several torque converters each with a range of variability covering part of the total required; all the torque converters are mechanically connec- ted all the time, and the appropriate one for the speed range required is selected by filling it with oil and draining the others. The filling and draining is carried out with the transmission under load, and results in very smooth range changes with no break in the transmitted power. Diesel-hydraulic multiple units, a less ar- duous duty, often use a simplification of this system, with a torque converter for the lower speed ranges and a fluid coupling for the high speed range. A fluid coupling is similar to a torque converter but it lacks the stator. The output torque is equal to the input torque regardless of the ratio of input to out- put speed; loading the output shaft results not in torque multiplication and constant power throughput but in reduction of the in- put speed with consequent lower power throughput. (In car terms, the fluid coupling provides top gear and the torque converter provides all the lower gears.) The result is that the power available at the rail is reduced when operating in the lower speed part of the fluid coupling range, but the less arduous duty of a passenger multiple unit compared to a locomotive makes this an acceptable trade-off for reduced mechanical complexity. Diesel-hydraulic locomotives are slightly more efficient than diesel-electrics, but initial versions were found in many countries to be mechanically more complicated and more likely to break down. Hydraulic transmission for locomotives was developed in Germany. The bad reputation of diesel-hydraulic prin- ciple was caused by the poor durability and reliability of the Maybach Mekydro hydraulic transmission. The Mekydro consisted of a hy- draulic torque converter followed by a four speed automatic mechanical gearbox. A dif- ferent solution using several torque convert- ers was developed by Voith, and it has proven to be extremely durable and very well suited for the purpose. In Germany and Finland diesel-hydraulic systems have achieved extremely high reliab- ility in operation. Persistent argument contin- ues over the relative reliability of hydraulic systems, with continuing questions over whether data was manipulated politically to favour local suppliers over German ones. In the US and Canada, they are now greatly out- numbered by diesel-electric locomotives, while they remain dominant in some European countries. The diesel-hydraulic locomotive has two distinct advantages over the the diesel-elec- tric. First, it is lighter for the same power output. This is particularly important for us- age on branch lines allowing only smaller axle loads, which had been the case in Ger- many for a long time. Main lines, built for higher axle loads, had already been electri- fied over there which, e.g., was not the case in the US where diesel locomotives were used on main lines as well. Secondly, the factor of adhesion is better meaning higher starting tractive effort relative to the loco- motive weight. This is because in a diesel- electric all driven axles are driven by indi- vidual electric motors and can lose grip indi- vidually whereas in a diesel-hydraulic all axles are interconnected via shafts and uni- versal joints. Thus, all axles must rotate at the same speed which makes individual slip- ping of axles impossible. The most famous diesel-hydraulic locomot- ive is the German V 200, which were built from 1953 in a total number of 136. The only diesel-electric locomotives of the Deutsche From Wikipedia, the free encyclopedia Diesel locomotive 9 Bundesbahn were BR 288 (V 188), of which 12 were built in 1939 by the Deutsche Reichsbahn. In the UK, the Western Region of British Rail bought a number of Diesel-hy- draulic locomotives, ranging from small light duty freight locos to high powered mainline passenger locomotives, but these were with- drawn early due to being non standard, and also in some cases suffering from reliability problems (see below), being replaced by Diesel Electrics. A number were rescued for preservation though, and some are capable of running on the mainline. In Finland, over 200 Finnish-built VR class Dv12 and Dr14 diesel- hydraulics with Voith transmissions have been continuously used since the early 60’s. As of 2009, all units are still in normal duty and in perfect working condition. The high reliability of the German loco- motives was paralleled by higher reliability of non-German locomotives built with German- made parts compared to that of the same designs built using parts made locally to Ger- man patterns under licence. Much of the un- reliability experienced outside Germany was due to poor quality control in the local manu- facture of engines and transmissions. Anoth- er contributing factor was poor maintenance due to staff accustomed to steam locomotives now working on unfamiliar and much more complex designs in unsuitable conditions, and failing to follow the unit-replacement maintenance methods which were part of the German success. It is notable that diesel-hy- draulic multiple units, with the advantages of modern manufacturing techniques and im- proved maintenance procedures, are now ex- tremely successful in widespread use, achiev- ing excellent reliability. In the 1960s the Southern Pacific bought 18 diesel hydraulic locomotives from the Kraus-Maffei company. The Denver & Rio Grande Western also bought 3, all of which it later sold to the SP.[17] Only the outer shell of one of these (converted into a camera car by SP in the 1970s) exists today, the other 20 having been scrapped when SP terminated the experiment in 1970. Diesel-steam Steam diesel hybrid locomotive can use steam generated from a boiler or diesel to power a piston engine. The Cristiani Com- pressed Steam System used a diesel engine to power a compressor to drive and recirculate steam produced by a boiler; ef- fectivly using steam as the power transmis- sion medium, with the diesel engine being the prime mover[18] Additionally diesel fuel can be used as a medium to power a steam boiler, as is done with fuel oil; In 2007 the first biodiesel powered steam locomotive was operated at the Mount Washington Cog Railway.[19] Multiple unit operation Diesel-electric locomotive built by EMD for service in the UK and continental Europe. Most Diesel locomotives are capable of multiple unit operation (MU) as a means of increasing horsepower and tractive effort when hauling heavy trains. All North Americ- an locomotives, including export models, use a standardised AAR electrical control system interconnected by a 27-pin jumper cable between the units. For UK built locomotives, a number of incompatible control systems are used, but the most common is the Blue Star system, which is electro-pneumatic and fitted to most early diesel classes. A small number of types, typically higher-powered locomot- ives intended for passenger only work, do not have multiple control systems. In all cases, the electrical control connections made com- mon to all units in a consist are referred to as trainlines. The result is that all locomotives in a consist behave as one in response to the en- gineer’s (driver’s) control movements. The ability to MU Diesel-electric locomot- ives was first introduced in the EMD FT four- unit demonstrator that toured the USA in 1939. At the time, American railroad work rules required that each operating locomot- ive in a train had to have on board a full crew. EMD circumvented that requirement by joining the individual units of the demon- strator with drawbars instead of conventional From Wikipedia, the free encyclopedia Diesel locomotive 10 knuckle couplers and declaring the consist to be a single locomotive. Electrical intercon- nections were made so one engineer (driver) could operate the entire consist from the head-end unit. Later on, work rules were amended and the semi-permanent joining of units via drawbars was eliminated in favor of couplers, as servicing had proved to be some- what cumbersome due to the total length of the consist (about 200 feet (61 m) or nearly 61 meters). In mountainous regions, it is common to interpose helper locomotives in the middle of the train, both to provide the extra power needed to ascend a grade and to limit the amount of stress applied to the draft gear of the car coupled to the head-end power. The helper units in such configurations are con- trolled from the lead unit’s cab via coded ra- dio signals. Although this is technically not MUing, the behavior is the same as with physically interconnected units. Cab arrangements Cab arrangements vary by builder and oper- ator. Practice in the U.S. has traditionally been for a cab at one end of the locomotive with limited visibility if the loco is not oper- ated cab forward. This is not usually a prob- lem as U.S. locomotives are usually operated in pairs, or threes, and arranged so that a cab is at each end of each set. European practice is usually for a cab at each end of the locomotive as trains are usually light enough to operate with one locomotive. Early U.S. practice was to add power units without cabs (B-units) and the arrangement was often A-B, A-B-A, or A-B-B-A where A was a unit with a cab. Center cabs were sometimes used for switch locomotives. Cow-calf In North American railroading, a cow-calf set is a pair of switcher-type diesel locomotives: one (the cow) equipped with a driving cab, the other (the calf) without a cab, and getting power from the cow through cables. Cow-calf sets are used in heavy switching and hump yard switching. Some are radio controlled without an operating engineer present in the cab. Flameproof diesel locomotive A standard diesel locomotive presents a very low fire risk but the risk can be reduced even further by "flameproofing". This involves fit- ting a water-filled box to the exhaust pipe to quench any red-hot carbon particles which may be emitted. Other precautions may in- clude a fully insulated electrical system (neither side earthed to the frame) and all electric wiring enclosed in conduit. The flameproof diesel locomotive has re- placed the fireless steam locomotive in areas of high fire risk such as oil refineries and am- munition dumps. Preserved examples of flameproof diesel locomotives include: • Francis Baily of Thatcham (ex-RAF Welford) at Southall Railway Centre • Naworth (ex-National Coal Board) at the South Tynedale Railway [20] Latest development of the "Flameproof Diesel Vehicle Applied New Exhaust Gas Dry Type Treatment System " does not need the water supply. [21] In Popular Culture Musician Shotgun Jimmie has a song entitled ’Diesel Locomotive’ on his album ’The 6000 True Stories of Love’. The song deals with the idea of a diesel locomotive travelling around and never stopping for long. One lyric mentions that, "on a good day they can weigh as much as forty-nine tonnes." References [1] Diesel, Rudolf. U.S. Patent No. 608,845, filed July 15, 1895, and issued August 9, 1898 Accessed via Google Patent Search at: US Patent #608,845 on February 8, 2007. [2] Churella, Albert J. (1998). From Steam to Diesel: Managerial Customs and Organizational Capabilities in the Twentieth-Century American Locomotive Industry. Princeton, New Jersey: Princeton University Press. pp. 15. ISBN 0-691-02776-5. [3] Churella, page 12 [4] ^ Stover, John F. (1997). American Railroads. Chicago, Illinois: The University of Chicago Press. pp. 212. ISBN 0-226-77658-I. From Wikipedia, the free encyclopedia Diesel locomotive 11 [5] Edison, Thomas A. U.S. Patent No. 493,425, filed January 19, 1891, and issued March 14, 1891 Accessed via the Edison Papers at: US Patent #493,425 on February 8, 2007. [6] Lemp, Hermann. U.S. Patent No. 1,154,785, filed April 8, 1914, and issued September 28, 1915. Accessed via Google Patent Search at: US Patent #1,154,785 on February 8, 2007. [7] Churella, 25-27 [8] "Railroads To Try Diesel Locomotive", Special to the New York Times: 1, February 18, 1925 [9] Churella, 27 [10]Churella, 28-30 [11]Churella, 10 [12]Churella, 19 [13] "Diesel Locomotives". American- Rails.com. http://www.american- rails.com/diesel-locomotives.html. Retrieved on 2009-04-01. [14]Churella, 12-17 [15]^ Stover, 213 [16]Churella, 14 [17]Marre, Louis A. (1995). Diesel Locomotives: The First Fifty Years. Waukesha, WI, USA: Kalmbach. pp. 384-385. ISBN 0890242585. [18]The Paragon-Cristiani Compressed Steam System dslef.dsl.pipex.com [19]Converting Mount Washington No.9 to Biodiesel Fuel matrynbane.co.uk [20]http://www.strps.org.uk/str/stocklist/ locos/04-Naworth.htm [21]http://sciencelinks.jp/j-east/article/ 200210/000020021002A0274001.php/ See also • Diesel multiple unit • Diesel-electric transmission • Electric locomotive • Hybrid locomotive External links • US Government test of GP38-2 locomotive with biodiesel fuel. • A 1926 article The Diesel Engine in Railway Transportation on Diesel locomotives • [1] -Diesel locomotive Retrieved from "http://en.wikipedia.org/wiki/Diesel_locomotive" Categories: Diesel locomotives This page was last modified on 21 May 2009, at 23:36 (UTC). All text is available under the terms of the GNU Free Documentation License. (See Copyrights for details.) Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a U.S. registered 501(c)(3) tax- deductible nonprofit charity. Privacy policy About Wikipedia Disclaimers From Wikipedia, the free encyclopedia Diesel locomotive 12
