Diesel+Locomotives

By the middle of 20th century, diesel engines had effectively replaced steam engines. Advantages over steam engines- Disadvantages of diesel vs. steam-
 * safely operated by one person (still run with 2-men crew sometimes) Since not as many people were needed that was less money that had to come from somewhere whether it was ticket prices or from the government.
 * working environment is safer and more attractive: quieter, fully weather proof, no dirt and heat
 * started and stopped instantly
 * no cost when not in use
 * less maintenance
 * more weight
 * less fuel effective
 * needs high tech electronics with the use of ac generators and motor

__**How does a diesel train work?**__ Diesel power is a revolutionary invention by Mr. Rudolph Diesel in the late 1800's. Mr. Diesel is a French engineer and who used tremendous physics to develop his engine. A diesel engine basically works on the principles of Thermodynamics and Newton's basic laws of motion.

Shown to the right is a very basic diagram of how a diesel engine produces power. The laws of motion and conservation are fairly obvious - the crankshaft and the valves move linearly or in circular motion to cause other parts to move also. The physics for this can be calculated, but friction, which is all too evident in an engine, makes this difficult. The thermodynamics aspects, however, require much more discussion. It would be best to first explain what happens. A diesel engine is different from a gasoline engine because it does not require a spark to ignite the fuel. 1. When the piston is in the bottom of the stroke, a cam presses down on the intake valve causing it to open, letting raw air enter the cylinder. 2. The piston moves back up to the top of the stroke, and by this time the intake valve has closed. This air is now being compressed inside the cylinder by the piston, which raises the pressure and temperature by decreasing the volume, a relationship shown in the ideal gas law: PV=nRT, where P is pressure, V is volume and T is Temperature. The air gets very hot. 3. At this time the fuel injector injects the heavy fuel in a mist form, into the heated air, which causes it to automatically ignite. This is caused autoignition. This ignition creates pressure, which presses the piston down, in turn turning the crankshaft, making the engine work. 4. A second cam then presses the exhaust valve down, letting the burned gas out of the cylinder, and the cycle continues.

__**Engineering Changes Everything**__ Diesel trains, of all of the types discussed, have proven to be the most beneficial to society. Unlike a lot of other major projects, the development of trains was not exactly funded by the government. Now, the laying of the track and the expanding of the railways was almost 100% government funded, but not much physics is involved in literally nailing track to the ground. But the train itself was not government funded. As it turns out, Mr. Diesel was an engineer who was trying to design a Carnot engine - which is one that is 100% efficient. He did this as his own work, not for a company or project but just as an engineer. He did not know at the time, that his engine would change transportation forever. The diesel engine didn't catch on immediately, but when it did catch on, it took over the locomotive world. Steam engines were dirty, required more people to run them, had limits on their strength, and had a lot more problems with upkeep. Diesel engines, while more expensive to buy, could be started and stopped when needed, did not need someone to shovel coal into a furnace, were more compact, more reliable, and much quieter while still polluting less. Diesel also began to be used in passenger vehicles and later to transform the trucking industry. By around 1920 steam engines were nearly obsolete and diesel had taken over.