Scale model

A scale model is a physical model that is geometrically similar to an object (known as the prototype). Scale models are generally smaller than large prototypes such as vehicles, buildings, or people; but may be larger than small prototypes such as anatomical structures or subatomic particles. Models built to the same scale as the prototype are called mockups. Scale models are used as tools in engineering design and testing, promotion and sales, filmmaking special effects, military strategy, and hobbies such as rail transport modeling, wargaming and racing; and as toys. Model building is also pursued as a hobby for the sake of artisanship. Scale models are constructed of plastic, wood, or metal. They are usually painted with enamel, lacquer, or acrylics. Model prototypes include all types of vehicles (railroad trains, cars, trucks, military vehicles, aircraft, and spacecraft), buildings, people, and science fiction themes (spaceships and robots).

Methods

The models are built to scale, defined as the ratio of any linear dimension of the model to the equivalent dimension on the full-size subject (called the "prototype"), expressed either as a ratio with a colon (ex. 1:8 scale), or as a fraction with a slash (1/8 scale). This designates that 1 length unit on the model represents 8 such units on the prototype. In English-speaking countries, the scale is sometimes expressed as the number of feet on the prototype corresponding to one inch on the model, e.g. 1:48 scale = "1 inch to 4 feet", 1:96 = "1 inch to 8 feet", etc. Models are obtained by three different means: kit assembly, scratch building, and collecting pre-assembled models. Scratch building is the only option available to structural engineers, and among hobbyists requires the highest level of skill, craftsmanship, and time; scratch builders tend to be the most concerned with accuracy and detail. Kit assembly is done either "out of the box", or with modifications (known as "kitbashing"). Many kit manufacturers, for various reasons leave something to be desired in terms of accuracy, but using the kit parts as a baseline and adding after-market conversion kits, alternative decal sets, and some scratch building can correct this without the master craftsmanship or time expenditure required by scratch building.

Purposes

Scale models are generally of two types: static and animated. They are used for several purposes in many fields, including:

Hobby Most hobbyist models are built for static display, but some have operational features, such as railroad trains that roll, and airplanes and rockets that fly. Flying airplane models may be simple unpowered gliders, or have sophisticated features such as radio control powered by miniature methanol/nitromethane engines.

Slot car racing

Cars in 1:24, 1:32, or HO scale are fitted with externally powered electric motors which run on plastic road track fitted with metal rails in slots. The track may or may not be augmented with miniature buildings, trees, and people.

Wood car racing

Children can build and race their own gravity-powered, uncontrolled cars carved out of a wood such as pine, with plastic wheels on metal axles, which run on inclined tracks. The most famous wood racing event is the Boy Scouts of America's annual Pinewood Derby which debuted in 1953. Entry is open to Cub Scouts. Entrants are supplied with a kit containing a wooden block out of which to carve the body, four plastic wheels, and four axle nails; or they may purchase their own commercially available kit. Regulations generally limit the car's weight to 5 ounces (141.7 g), width to 2.75 inches (7.0 cm), and length to 7 inches (17.8 cm). The rules permit the cars to be augmented with tungsten carbide weights up to the limit, and graphite axle lubricant.

Wargaming

Miniature wargames are played using miniature soldiers, artillery, vehicles, and scenery built by the players.

Television and film production

Before the advent of computer-generated imagery (CGI), visual effects of vehicles such as marine ships and cyber vehicles were created by filming "miniature" models. These were considerably larger scale than hobby versions to allow inclusion of a high degree of surface detail, and electrical features such as interior lighting and animation. For Star Trek: The Original Series, a 33-inch (0.84 m) pre-production model of the Starship Enterprise was created in December 1964, mostly of pine, with Plexiglass and brass details, for $600. This was followed by a 135.5-inch (3.44 m) production model constructed from plaster, sheet metal, and wood, at ten times the cost of the first. As the Enterprise was originally reckoned to be 947 feet (289 m) long, this put the models at 1:344 and 1:83.9 scale respectively. The Polar Lights company sells a large plastic Enterprise model kit essentially the same size as the first TV model, in 1:350 scale (32 inches long). It can be purchased with an optional electronic lighting and animation (rotating engine domes) kit.

Engineering

Structural Although structural engineering has been a field of study for thousands of years and many of the great problems have been solved using analytical and numerical techniques, many problems are still too complicated to understand in an analytical manner or the current numerical techniques lack real world confirmation. When this is the case, for example a complicated reinforced concrete beam-column-slab interaction problem, scale models can be constructed observing the requirements of similitude to study the problem. Many structural labs exist to test these structural scale models such as the Newmark Civil Engineering Laboratory at the University of Illinois, UC. For structural engineering scale models, it is important for several specific quantities to be scaled according to the theory of similitude. These quantities can be broadly grouped into three categories: loading, geometry, and material properties. A good reference for considering scales for a structural scale model under static loading conditions in the elastic regime is presented in Table 2.2 of the book Structural Modeling and Experimental Techniques. Structural engineering scale models can use different approaches to satisfy the similitude requirements of scale model fabrication and testing. A practical introduction to scale model design and testing is discussed in the paper "Pseudodynamic Testing of Scaled Models".

Aerodynamic

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