Diesel Engine Locomotives

Replies

• 

  manusaluja

  A Diesel locomotive is a type of railroad locomotive in which the prime mover is a Diesel engine. Several types of Diesel locomotive have been developed, the principal distinction being in the means by which the prime mover's mechanical power is conveyed to the driving wheels.
  
  Bieng an computer engineer, dont know enough technically about this, but still without looking upon history and migration from steam engines to diesel one, I would like to focus only on diesel engines.
  
  Actually, it is more properly called a diesel-electric locomotive. The concept is relatively simple: An oil-burning engine turns an alternator or generator which in turn produces electricity that powers traction motors that connect to the axles of the locomotive. This process is much more efficient than the external-combustion steam locomotive.
  
  I was surprised to know that, diesel engine power is not directly supplied to the engine axle. instead its first converted to electricity and then supplied to traction motor attached with the axle.😛
  
  In a Diesel-electric locomotive the Diesel engine drives an electrical generator whose 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 components used to control or modify the electrical supply to the traction motions, including switchgear, rectifiers, and other Motor controller devices such as Inverters, load resistors or other components. In the simplest case the generator may be directly connected to the motors with only very simple switchgear.
  

  
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  This 270,000-pound (122,470-kg) locomotive is designed to tow passenger-train cars at speeds of up to 110 miles per hour (177 kph). The diesel engine makes 3,200 horsepower, and the generator can turn this into almost 4,700 amps of electrical current. The four drive motors use this electricity to generate over 64,000 pounds of thrust. There is a completely separate V-12 engine and generator to provide electrical power for the rest of the train. This generator is called the head-end power unit. The one on this train can make over 560 kilowatts (kW) of electrical power.
  
  These engines doesn't require mechanical transmissions just like car.
  change gears once you reach 20,40, 60 kmph and fire on the accelerator😀
  
  Your car needs a transmission because of the physics of the gasoline engine. First, any engine has a redline -- a maximum rpm (revolutions per minute) value above which the engine cannot go without exploding. Secondly, engines have a narrow rpm range where horsepower and torque are at their maximum. For example, an engine might produce its maximum horsepower between 5,200 and 5,500 rpm. The transmission allows the gear ratio between the engine and the drive wheels to change as the car speeds up and slows down. You shift gears so that the engine can stay below the redline and near the rpm band of its best performance (maximum power).
  
  The five- or six-speed transmission on most cars allows them to go 110 mph (177 kph) or faster with an engine-speed range of 500 to 6,000 rpm. The engine on our diesel locomotive has a much smaller speed range. Its idle speed is around 269 rpm, and its maximum speed is only 904 rpm. With a speed range like this, a locomotive would need 20 or 30 gears to make it up to 110 mph (177 kph). 😔
  
  A gearbox like this would be huge (it would have to handle 3,200 horsepower), complicated and inefficient. It would also have to provide power to four sets of wheels, which would add to the complexity. :dance:
  
  Steel Wheels
  Ever wonder why trains have steel wheels, rather than tires like a car? It's to reduce rolling friction. When your car is driving on the freeway, something like 25 percent of the engine's power is being used to push the tires down the road. Tires bend and deform a lot as they roll, which uses a lot of energy.
  
  The amount of energy used by the tires is proportional to the weight that is on them. Since a car is relatively light, this amount of energy is acceptable
  
  Since a train weighs thousands of times more than a car, the rolling resistance is a huge factor in determining how much force it takes to pull the train. The steel wheels on the train ride on a tiny contact patch -- the contact area between each wheel and the track is about the size of a dime.
  

  
  

  
  By using steel wheels on a steel track, the amount of deformation is minimized, which reduces the rolling resistance. In fact, a train is about the most efficient way to move heavy goods.
  
  P.S --> most of the material is copied from various sites, I am not a scientist to write on My Own.
  
  Peace 😁
  ​
• 

  manusaluja

  Traction
  Traction when going around turns is not an issue because train wheels have flanges that keep them on the track. But traction when braking and accelerating is an issue.
  
  This locomotive can generate 64,000 pounds of thrust. But in order for it to use this thrust effectively, the eight wheels on the locomotive have to be able to apply this thrust to the track without slipping. The locomotive uses a neat trick to increase the traction.
  
  

  
  
  

  In front of each wheel is a nozzle that uses compressed air to spray sand, which is stored in two tanks on the locomotive. The sand dramatically increases the traction of the drive wheels. The train has an electronic traction-control system that automatically starts the sand sprayers when the wheels slip or when the engineer makes an emergency stop. The system can also reduce the power of any traction motor whose wheels are slipping.
  
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• 

  manusaluja

  The Layout: Main Engine and Generator
  Nearly every inch of the 54-ft (16.2-m) locomotive is tightly packed with equipment.
  The giant two-stroke, turbocharged V-12 and electrical generator provide the huge amount of power needed to pull heavy loads at high speeds. The engine alone weighs over 30,000 pounds (13,608 kg), and the generator weighs 17,700 pounds (8,029 kg)
  
  Trucks
  The trucks are the complete assembly of two axles with wheels, traction motors, gearing, suspension and brakes.
  
  Head-end Power Unit
  The head-end power unit consists of another big diesel engine, this time a four-stroke, twin-turbocharged Caterpillar V-12. The engine itself is more powerful than the engine in almost any semi-truck. It drives a generator that provides 480-volt, 3-phase AC power for the rest of the train. This engine and generator provide over 560 kW of electrical power to the rest of the train, to be used by the electric air conditioners, lights and kitchen facilities. By using a completely separate engine and generator for these systems, the train can keep the passengers comfortable even if the main engine fails. It also decreases the load on the main engine.
  
  
  Fuel Tank
  This huge tank in the underbelly of the locomotive holds 2,200 gallons (8,328 L) of diesel fuel. The fuel tank is compartmentalized, so if any compartment is damaged or starts to leak, pumps can remove the fuel from that compartment.
  
  Batteries
  The locomotive operates on a nominal 64-volt electrical system. The locomotive has eight 8-volt batteries, each weighing over 300 pounds (136 kg). These batteries provide the power needed to start the engine (it has a huge starter motor), as well as to run the electronics in the locomotive. Once the main engine is running, an alternator supplies power to the electronics and the batteries.
  
  The Engine and Generator
  The main engine in this locomotive is a General Motors EMD 710 series engine. The "710" means that each cylinder in this turbocharged, two-stroke, diesel V-12 has a displacement of 710 cubic inches (11.6 L). That's more than double the size of most of the biggest gasoline V-8 car engines -- and we're only talking about one of the 12 cylinders in this 3,200-hp engine.
  
  
• 

  manusaluja

  So why two-stroke? Even though this engine is huge, if it operated on the four-stroke diesel cycle, like most smaller diesel engines do, it would only make about half the power. This is because with the two-stroke cycle, there are twice as many combustion events (which produce the power) per revolution. It turns out that the diesel two-stoke engine is really much more elegant and efficient than the two-stroke gasoline engine.
  
  
  
  You might be thinking, if this engine is about 24 times the size of a big V-8 car engine, and uses a two-stroke instead of a four-stroke cycle, why does it only make about 10 times the power? The reason is that this engine is designed to produce 3,200 hp continuously, and it lasts for decades. If you continuously ran the engine in your car at full power, you'd be lucky if it lasted a week.
  
  Here are some of the specifications of this engine:
  
  * Number of cylinders: 12
  * Compression ratio: 16:1
  * Displacement per cylinder: 11.6 L (710 in3)
  * Cylinder bore: 230 mm (9.2 inches)
  * Cylinder stroke: 279 mm (11.1 inches)
  * Full speed: 904 rpm
  * Normal idle speed: 269 rpm
  
  This giant engine is hooked up to an equally impressive generator. It is about 6 feet (1.8 m) in diameter and weights about 17,700 pounds (8,029 kg). At peak power, this generator makes enough electricity to power a neighborhood of about 1,000 houses!
  
  So where does all this power go? It goes into four, massive electric motors located in the trucks.
• 

  manusaluja

  The Trucks: Propulsion & Suspension
  The trucks are the heaviest things on the train -- each one weighs 37,000 pounds (16,783 kg). The trucks do several jobs. They support the weight of the locomotive. They provide the propulsion, the suspensions and the braking. As you can imagine, they are tremendous structures.
  
  
  Propulsion
  The traction motors provide propulsion power to the wheels. There is one on each axle. Each motor drives a small gear, which meshes with a larger gear on the axle shaft. This provides the gear reduction that allows the motor to drive the train at speeds of up to 110 mph.
  
  
  Each motor weighs 6,000 pounds (2,722 kg) and can draw up to 1,170 amps of electrical current.
  
  Suspension
  The trucks also provide the suspension for the locomotive. The weight of the locomotive rests on a big, round bearing, which allows the trucks to pivot so the train can make a turn. Below the pivot is a huge leaf spring that rests on a platform. The platform is suspended by four, giant metal links, which connect to the truck assembly. These links allow the locomotive to swing from side to side.
  
  
  The weight of the locomotive rests on the leaf springs, which compress when it passes over a bump. This isolates the body of the locomotive from the bump. The links allow the trucks to move from side to side with fluctuations in the track. The track is not perfectly straight, and at high speeds, the small variations in the track would make for a rough ride if the trucks could not swing laterally. The system also keeps the amount of weight on each rail relatively equal, reducing wear on the tracks and wheels.
  
  The Trucks: Braking
  Braking is provided by a mechanism that is similar to a car drum brake. An air-powered piston pushes a pad against the outer surface of the train wheel.
  
  
  In conjunction with the mechanical brakes, the locomotive has dynamic braking. In this mode, each of the four traction motors acts like a generator, using the wheels of the train to apply torque to the motors and generate electrical current. The torque that the wheels apply to turn the motors slows the train down (instead of the motors turning the wheels, the wheels turn the motors). The current generated (up to 760 amps) is routed into a giant resistive mesh that turns that current into heat. A cooling fan sucks air through the mesh and blows it out the top of the locomotive -- effectively the world's most powerful hair dryer.
  
  On the rear truck there is also a hand brake -- yes, even trains need hand brakes. Since the brakes are air powered, they can only function while the compressor is running. If the train has been shut down for a while, there will be no air pressure to keep the brakes engaged. Without a hand brake and the failsafe of an air pressure reservoir, even a slight slope would be enough to get the train rolling because of its immense weight and the very low rolling friction between the wheels and the track.
  
  The hand brake is a crank that pulls a chain. It takes many turns of the crank to tighten the chain. The chain pulls the piston out to apply the brakes.
• 

  ShrinkDWorld

  thanks man realy important information
  My many ideas are cleard now about rail-engine.
  Can you post information about bracks??
• 

  sauravgoswami

  Nice information Dude,can you tell me,how locomotives are placed if two or more than tow locomotives are required to pull the wagons???
• 

  manusaluja

  gg_gaurav

  thanks man realy important information
  My many ideas are cleard now about rail-engine.
  Can you post information about bracks??

  BRACKS?? dont know dude, what are they..😕
• 

  Kaustubh Katdare

  Please mention the source if you are not the author of the articles. It's always a good idea to write your own content.
• 

  manusaluja

  sauravgoswami

  Nice information Dude,can you tell me,how locomotives are placed if two or more than tow locomotives are required to pull the wagons???

  In himachal pradesh, meter gauge trains are still in operation, i have travelled many times on that route (pathankot to jogindernagar). two engines pull the wagons, and most of the the time its like, two locomotives @ front pulls the train. Most of the time second engine remains Idle and used only when train climbs the steep slope.
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  sauravgoswami

  thats true many a times they are connected at the rear end,what they take into consideration???
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  manusaluja

  might be they are pulling a dead engine connected @ End....😁
  
  Sorry friend dont know abt that...😉
• 

  gohm

  The rear engine is used as a pushing unit.
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  raj87verma88

  Nice information and a good research done.
  But as Biggie mentioned do tell us the source of your knowledge.
• 

  manusaluja

  gohm

  The rear engine is used as a pushing unit.

  Hi Buddy.
  
  Requires your help to understand between pushing and pulling...
  
  Does that make difference.
  
  2 pulling || 1 pulling + 1 pushing
• 

  manusaluja

  raj87verma88

  Nice information and a good research done.
  But as Biggie mentioned do tell us the source of your knowledge.

  Google, HowStuffWorks, and other forums, actually i do have liking for diesel engines, coz of their power and noisy operation.
• 

  gohm

  Yes, it does. Pushing is a more efficient means of transfering power than pulling. This becomes critical when inclines are involved causing a reduction having to counteract gravity in addition to lateral movement. the secondary engine also assist with braking. With all that mass in motion it requires a lot of stopping force!
  
  

  manusaluja

  Hi Buddy.
  
  Requires your help to understand between pushing and pulling...
  
  Does that make difference.
  
  2 pulling || 1 pulling + 1 pushing

• 

  sauravgoswami

  Ok got your point,so does it mean were there is inclination we should go for pushing and were we have extra load then we can go for pulling secondly are deiseld engines have more power than electric engines as they are preferred to pull freight wagons!!!
• 

  gohm

  Yes, a push & pull system is ideal whenever you have an above average gradient. Modern diesel engines are actually electric. The diesel engine generates electrical power that drives motors.
• 

  Rohan_sK

  @gohm: Didnt much get why Pushing is a better mode of Power transfer than Pulling, specially on inclinations. Yes I can understand the case on the ground level tractive effort, but can you please explain the case on the inclined path.
• 

  gohm

  Sure, I can even go one step further and give an test/demo for you as an illustration.
  
  Take a medium sized cardboard box. Fill it with books. Take it outside to a sidewalk with a positive slope/incline {uphill =)}. Stand uphill of the box, grab onto the box and try pulling it uphill a few feet. Now relocate the box back to the original starting point(by carrying it). This time stand downhill of the box and push it up the hill. Which one was easier?
  
  If you repeat this test on flat level ground you will notice less of a difference, however it still is easier to push than pull.
  
  This is not just because of physical anatomy. In Europe there are many small gauge old mountain railroads that use pusher engines. If you remove friction, gravity, etc. then the laws of physics dictate that the force is the same. However in real-world practice we cannot do this. We've actually been debating push/pull mechanical locomotion around the office & so far the winning argument is that even in mechanical locomotion, push locomotion is not only the most prevelent, it is also the most efficient except for one lone form of locomotion. Can you guess what form that is?
  
  
  
  motorized flight
  
  though a couple folks are insisting that is also using push motion, not pull (we've tied those crazies up in the coat closet, laugh) =) trouble abounds when engineers pretend they are physics experts!
• 

  Rohan_sK

  @Gohm : Thanks a lot for replying back.
  
  I had already tried a similar test before posting my doubt, but with my drawing board slanting against the wall as the inclined surface and used a small iron block fom the junk as the weight to be lifted.
  I did feel the difference between both the methods of moving the weight.
  
  But the question still remains unanswered, ie WHY this happens, WHY do we FEEL/EXPERIENCE this difference??
  Note that we are talking only of the FEEL OF EASE but do we have a reason to support this feeling of ease in moving the weight on an inclination. Note that the friction and gravity both remain the same along with the total mass of the system, and still this difference in the ease to move the weight.
  
  I mean as Engineers who know their physics well we must answer every thing in terms of WHY and HOW 😀
  
  So please can you explain the WHY part of this, it will be helpful to have unshaky fundamentals ( we dont want to be locked in a closet... 😁 lol..)
• 

  Ashraf HZ

  We should have those people from the Strongest Man competitions to pull planes and trucks on an inclination then. Thats more impressive *grin*
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  Rohan_sK

  Well men with no brains and no desire to learn, well be happy with the choice!!
• 

  ashwinsraj

  Really, thank you very much.
• 

  Rohan_sK

  Whats this guys?? Not a single CEan to answer the WHY that I asked in the above discussion!! Why dont experts just explain it ,if my question seems so stupid to them, it must be a piece of cake for them...
  
  Thats the problem with majority engineers. Guys, people flaunting their expertise in mechanical field surprisingly fail to explain the basic physics behind things happening,
  isnt it strange huh...???
  
  Guys we Engineers must not stop at only seeing things occur, leave it to the mechanic, we should go further to find a logical explaination to WHY it happened, isnt it.
  
  Well still expecting someone to help me get some fundas clear, I am always ready to learn.
• 

  jhbalaji

  Nice Stuff from HowStuffworks Buddy...