How A Steam Engine Works

The steam engine is a now outdated, but still a marvelous piece of engineering. Today, we will explore its inner workings. As the name would suggest, a steam locomotive leverages the strength of steam. Most locomotives built in the 20th century, including this model, burn oil to generate the heat, which is located in the tender along with the water. Both of these make it to the locomotive via pipes. The oil is ignited in the firebox, the heat from which passes through the dozens of pipes found in the boiler. The water that surrounds these pipes is boiled to steam and is collected at the top of the boiler in a dome. From here, it is circulated into what is called a superheater, which takes the steam for a round trip into the hot air in smaller pipes called flues to further heat the steam, increasing its strength. The superheated steam then makes its way to the pistons. Both sides of the locomotive contain a system of two pistons, a valve which controls the flow of steam, and the main piston which generates the motion of the vehicle. In this starting configuration, the valve lets steam enter the left side of the piston, pushing it to the right. Thanks to the linkage system that we will look at later, the valve follows the piston's motion with a small delay, now letting the used steam escape on the left, while letting new steam enter This sequence then repeats in the opposite direction, completing one cycle. Let's now look at the linkage system. It may seem complicated at first, but it is really just a main rod that drives one wheel, which drives the rest of the wheels with connecting rods. The rest of the configuration is what's responsible for the correct movement of the timing valve. The valve's offset can be controlled with the Johnson bar, so that the locomotive can change direction based on which side the valve lets steam out. But it can also be set to any position in between. This allows the engineer to use less steam, as keeping a vehicle in motion requires less power than getting one started from standstill, and so the use of additional steam would have a negligible effect. One problem with the linkage system that the eagle-eyed of you may have spotted is that the locomotive could get stuck in place when the wheel connections are at a non-optimal angle. Neither pulling or pushing on the bar will do much in such a scenario. This is doctored by having the wheels on the other side of the locomotive be rotated by 90 degrees. In this case, this side will get moving without any fuss and so there cannot be a situation where no wheel can be driven. For this reason, the iconic sound of the exhaust is doubled, which is heard as it escapes through the chimney. The steam exiting here creates a draft in the boiler to improve heating. Steam is also ejected through the drain cocks to get rid of any condensed steam, as that can cause damage. This is done mainly when starting the engine, or if the engineer just wants to show off. Steam locomotives feature a large number of pipes, all of which serve a number of different purposes. For one, a steam locomotive has more uses for steam than just propulsion, such as a whistle. Or a bell. Additionally, a locomotive comes with an air pump that pressurizes air, which among other things is used for the brake system. The piston powered by the pressurized air pushes and pulls on the linkage system that connects to all the brakes. The second dome that can be found on most engines contains sand. It is dispensed onto the rails in case the locomotive is having trouble with traction. This is most common when hauling heavy freight up considerable gradients. Further pipes found on locomotives usually have the job of dispensing condensed steam or operating gauges and control surfaces. For example, the temperature and pressure inside the boiler is monitored at all times. Modern locomotives also feature a dynamo-powered light on the front. A less known piece of information is the white notation, which is used to describe the wheel arrangement of a locomotive. It became a popular system in the United States and based on it, our model here in this video is a consolidation. A large number of wheel arrangements were built over the decades. The main differences between them being tractive effort and stability. While today's steam locomotives only serve the purpose of nostalgia, they continue to amaze current generations and will forever hold a special place in many people's hearts.