|MadSci Network: Science History|
Steam engines provided a simple power source for trains. In the early days, wood for heating the boiler was available beside the tracks. Water was often available nearby, since tracks frequently paralleled rivers. However, steam was not an efficient source of power.
A railroad steam engine was fair in efficiency, when working hard. However, one of the largest problems with steam power was the amount of energy input needed just to keep the boiler hot, with steam at operating pressure. A boiler needs time and energy to be able to produce steam under pressure. It also takes time to shut down. If a locomotive was kept busy 24 hours a day, the inefficiency of steam power could be tolerated.
Railroads are one of the most efficient means of transportation since rails provide exceptionally low rolling friction. When a more efficient power plant became available, the railroad industry adapted to it. This also happened with road vehicles. The first cars were powered by steam engines. In 1770, the Cugnot steam traction engine was used in Europe. Better steam cars, such as the Bordino, came into use during the 1800's. When railroads were introduced, the heavy and cumbersome steam engines became the power plants of choice for locomotives. Steam engines evolved into very large and very powerful propulsion units for railroad service.
The gasoline engine replaced steam for the early automobiles, because it was smaller, lighter, simpler, and safer. You may be surprised to discover that diesel engines are not particularly efficient at full power. Diesel engines evolved into the preferred power plants for commercial uses, such as large trucks because of their durability and overall fuel efficiency. The great advantage of diesel engines is that they have very low fuel consumption at reduced power outputs. Diesel engines use very little fuel when idling. This is where they have a great advantage over steam, even gasoline engines.
Corbin, the answer to your question should be clear to you now. People changed to diesel engines because they were more efficient. To continue on your project, your library should have books on railroads and steam engines, and you might search the internet (start with the sites listed below). You will soon discover much more than your project requires, and you will be impressed by the photographs of the magnificent steam engines from the past. Despite the awesome size and power of steam locomotives, diesel engines replaced them because diesels do the same job with much lower cost.
Try the links in the MadSci Library for more information on Science History.