Be the first to write a review. Share This eBook:. Add to Wishlist. Instant Download. Description Table of Contents eBook Details Click on the cover image above to read some pages of this book! More eBooks in Dating See All. Textbook Romance. Is It a Choice? Answers to Three Hundred of the Most Fre. The main advantage of the turbocharger is that it gives more power with no increase in fuel costs because it uses exhaust gas as drive power.
It does need additional maintenance, however, so there are some type of lower power locomotives which are built without it. Locomotives always carry sand to assist adhesion in bad rail conditions. Sand is not often provided on multiple unit trains because the adhesion requirements are lower and there are normally more driven axles. Figure 3: A diesel-mechanical locomotive is the simplest type of diesel locomotive. It has a direct mechanical link between the diesel engine and the wheels instead of electric transmission.
The diesel engine is usually in the hp range and the transmission is similar to that of an automobile with a four speed gearbox. Other parts are similar to the diesel-electric locomotive but there are some variations and often the wheels are coupled. In a diesel-mechanical transmission, the main drive shaft is coupled to the engine by a fluid coupling. This is a hydraulic clutch, consisting of a case filled with oil, a rotating disc with curved blades driven by the engine and another connected to the road wheels. As the engine turns the fan, the oil is driven by one disc towards the other.
This turns under the force of the oil and thus turns the drive shaft. Of course, the start up is gradual until the fan speed is almost matched by the blades. The whole system acts like an automatic clutch to allow a graduated start for the locomotive. This does the same job as that on an automobile. It varies the gear ratio between the engine and the road wheels so that the appropriate level of power can be applied to the wheels.
Gear change is manual. There is no need for a separate clutch because the functions of a clutch are already provided in the fluid coupling. The diesel-mechanical locomotive uses a final drive similar to that of a steam engine. The wheels are coupled to each other to provide more adhesion. The output from the 4-speed gearbox is coupled to a final drive and reversing gearbox which is provided with a transverse drive shaft and balance weights.
This is connected to the driving wheels by connecting rods. Hydraulic transmission works on the same principal as the fluid coupling but it allows a wider range of "slip" between the engine and wheels.
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It is known as a "torque converter". When the train speed has increased sufficiently to match the engine speed, the fluid is drained out of the torque converter so that the engine is virtually coupled directly to the locomotive wheels. It is virtually direct because the coupling is usually a fluid coupling, to give some "slip".
Higher speed locomotives use two or three torque converters in a sequence similar to gear changing in a mechanical transmission and some have used a combination of torque converters and gears. Some designs of diesel-hydraulic locomotives had two diesel engines and two transmission systems, one for each bogie.
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The design was poplar in Germany the V series of locomotives, for example in the s and was imported into parts of the UK in the s. However, it did not work well in heavy or express locomotive designs and has largely been replaced by diesel-electric transmission. Wheels slip is the bane of the driver trying to get a train away smoothly. The tenuous contact between steel wheel and steel rail is one of the weakest parts of the railway system.
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Traditionally, the only cure has been a combination of the skill of the driver and the selective use of sand to improve the adhesion. Today, modern electronic control has produced a very effective answer to this age old problem. The system is called creep control. Extensive research into wheel slip showed that, even after a wheelset starts to slip, there is still a considerable amount of useable adhesion available for traction.
The adhesion is available up to a peak, when it will rapidly fall away to an uncontrolled spin. Monitoring the early stages of slip can be used to adjust the power being applied to the wheels so that the adhesion is kept within the limits of the "creep" towards the peak level before the uncontrolled spin sets in. The slip is measured by detecting the locomotive speed by Doppler radar instead of the usual method using the rotating wheels and comparing it to the motor current to see if the wheel rotation matches the ground speed.
If there is a disparity between the two, the motor current is adjusted to keep the slip within the "creep" range and keep the tractive effort at the maximum level possible under the creep conditions. The diesel engines used in DMUs work on exactly the same principles as those used in locomotives, except that the transmission is normally mechanical with some form of gear change system. DMU engines are smaller and several are used on a train, depending on the configuration.
The diesel engine is often mounted under the car floor and on its side because of the restricted space available. Vibration being transmitted into the passenger saloon has always been a problem but some of the newer designs are very good in this respect. There are some diesel-electric DMUs around and these normally have a separate engine compartment containing the engine and the generator or alternator.
The diesel engine was first patented by Dr Rudolf Diesel in Germany in and he actually got a successful engine working by By , when he died, his engine was in use on locomotives and he had set up a facility with Sulzer in Switzerland to manufacture them. His death was mysterious in that he simply disappeared from a ship taking him to London. The diesel engine is a compression-ignition engine, as opposed to the petrol or gasoline engine, which is a spark-ignition engine. The spark ignition engine uses an electrical spark from a "spark plug" to ignite the fuel in the engine's cylinders, whereas the fuel in the diesel engine's cylinders is ignited by the heat caused by air being suddenly compressed in the cylinder.
This would be expressed as a compression ratio of 25 to 1. The advantage of the diesel engine over the petrol engine is that it has a higher thermal capacity it gets more work out of the fuel , the fuel is cheaper because it is less refined than petrol and it can do heavy work under extended periods of overload.
It can however, in a high speed form, be sensitive to maintenance and noisy, which is why it is still not popular for passenger automobiles. There are two types of diesel engine, the two-stroke engine and the four-stroke engine. As the names suggest, they differ in the number of movements of the piston required to complete each cycle of operation. The simplest is the two-stroke engine. It has no valves.
The exhaust from the combustion and the air for the new stroke is drawn in through openings in the cylinder wall as the piston reaches the bottom of the downstroke. Compression and combustion occurs on the upstroke. As one might guess, there are twice as many revolutions for the two-stroke engine as for equivalent power in a four-stroke engine. Valves are required for air intake and exhaust, usually two for each.
In this respect it is more similar to the modern petrol engine than the 2-stroke design. In the UK, both types of diesel engine were used but the 4-stroke became the standard. The UK Class 55 "Deltic" not now in regular main line service unusually had a two-stroke engine. The reason for using one type or the other is really a question of preference.
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However, it can be said that the 2-stroke design is simpler than the 4-stroke but the 4-stroke engine is more fuel efficient. Basically, the more power you need, the bigger the engine has to be. Early diesel engines were less than horse power hp but today the US is building hp locomotives. The maximum rotational speed of the engine when producing full power will be about rpm revolutions per minute and the engine will idle at about rpm.
These relatively low speeds mean that the engine design is heavy, as opposed to a high speed, lightweight engine. However, the UK HST High Speed Train, developed in the s engine has a speed of 1, rpm and this is regarded as high speed in the railway diesel engine category. The slow, heavy engine used in railway locomotives will give low maintenance requirements and an extended life.
There is a limit to the size of the engine which can be accommodated within the railway loading gauge, so the power of a single locomotive is limited. Where additional power is required, it has become usual to add locomotives. In the US, where freight trains run into tens of thousands of tons weight, four locomotives at the head of a train are common and several additional ones in the middle or at the end are not unusual.
Diesel engines can be designed with the cylinders "in-line", "double banked" or in a "V". The double banked engine has two rows of cylinders in line. Most diesel locomotives now have V form engines. This means that the cylinders are split into two sets, with half forming one side of the V. A V8 engine has 4 cylinders set at an angle forming one side of the V with the other set of four forming the other side.
The crankshaft, providing the drive, is at the base of the V. The V12 was a popular design used in the UK. In the US, V16 is usual for freight locomotives and there are some designs with V20 engines. Engines used for DMU diesel multiple unit trains in the UK are often mounted under the floor of the passenger cars.
This restricts the design to in-line engines, which have to be mounted on their side to fit in the restricted space.
Before going too much further, we need to understand the definitions of tractive effort, drawbar pull and power. The definition of tractive effort TE is simply the force exerted at the wheel rim of the locomotive and is usually expressed in pounds lbs or kilo Newtons kN. By the time the tractive effort is transmitted to the coupling between the locomotive and the train, the drawbar pull, as it is called will have reduced because of the friction of the mechanical parts of the drive and some wind resistance. Power is expressed as horsepower hp or kilo Watts kW and is actually a rate of doing work.
A unit of horsepower is defined as the work involved by a horse lifting 33, lbs one foot in one minute. In the metric system it is calculated as the power Watts needed when one Newton of force is moved one metre in one second. One horsepower equals Watts. The relationship between power and drawbar pull is that a low speed and a high drawbar pull can produce the same power as high speed and low drawbar pull.
If you need to increase higher tractive effort and high speed, you need to increase the power. To get the variations needed by a locomotive to operate on the railway, you need to have a suitable means of transmission between the diesel engine and the wheels.
One thing worth remembering is that the power produced by the diesel engine is not all available for traction. Subsequent implementations are scheduled for more than 10 additional sites nationwide.
The working relationship has been a positive one, and we continue to be excited about the project. We are extremely proud of this project and look forward to continuing our partnership with Dot Foods as we complete the rollout of JDA Warehouse Management 9. Through Dot Transportation Inc. Dot Foods operates ten U.