A steam engine is a railroad locomotive powered by steam. Once the dominant type of locomotive, steam engines have been superseded by diesel and electric locomotives, but many still operate as part of novelty or nostalgia train lines. There are also many kinds of steam engine models collected and operated by hobbyists. These range in size from the width of a finger to trains so large they can carry human passengers. “Live steam” enthusiasts create models that actually operate on steam power, just as the original steam locomotives did.
The steam engine was developed during the Industrial Revolution of the 18th century. Steam-powered trains were the primary means of land transportation around the world throughout the 1800s. Even after the advent of the automobile, many steam engines operated well into the 20th century. By this time, rail travel had developed a romantic image as a symbol of a simpler time. This contributed to the popularity of steam engine models and model railroading in general.
Model railroaders, or railway modellers as they are known in many parts of the world, build, collect and operate miniature trains. Often, this involves creating vast sets, or layouts, where their trains can run, including miniature towns, tunnels, and nature environments. These hobbyists are so numerous that they have divided into sub-groups based on the size or scale of their trains. These are standardized and are often based on the span of their tracks, known as the gauge; each gauge or scale is identified by a letter or series of letters. While some of these steam engine models are actually powered by steam, others simulate the effect with electrical power and chemical smoke.
The most popular size among model railroaders worldwide is the HO scale, with trains that are smaller than a human hand. Other common scales for steam engine models are O, S, and Z, but these smaller scales, such as Z, often use simulated steam. At the larger end of the scale are so-called garden railways and backyard railroads. Garden railways are so large that many hobbyists use entire yards or gardens for their layouts, but they are not big enough to carry human riders. Backyard railroads, in contrast, actually can carry people, although they are far smaller than real trains; either type can be powered by miniature steam engines.
The most realistic steam engine models are known as “live steam” engines. Live steam hobbyists are skilled machinists, often building their own complicated and detailed steam-powered trains. Live steam railroading is popular enough to have specialized magazines, websites, and conventions, separate from the wider world of model railroading. One of the most famous live steam engines was operated by filmmaker Walt Disney at his California home in the 1950s. Disney later built a narrow-gauge railway to carry visitors at his Disneyland theme park; as a slightly smaller but otherwise fully functional train, this could be considered a very large steam engine model.