#5 History of Model Railway Trains.

Overhead line

Where the model is of an electric locomotive, it may be supplied by overhead lines, like the full-size locomotive. Before Digital Command Control became available, this was one way of controlling two trains separately on the same track. The electric-outline model would be supplied by the overhead wire and the other model could be supplied by one of the running rails. The other running rail would act as a common return.

Battery

Early electric trains ran on trackside batteries because few homes in the late 19th century and early 20th century had electricity. Today, inexpensive train sets running on batteries are again common but regarded as toys and seldom used by hobbyists. Batteries located in the model often power garden railway and larger scale systems because of the difficulty in obtaining reliable power supply through the outdoor rails. The high power consumption and current draw of large scale garden models is more easily and safely met with internal rechargeable batteries. Most large scale battery powered models use radio control.

Live steam

Engines powered by live steam are often built in large outdoor gauges of 5 inches (130 mm) and 7 1⁄2 inches (190 mm), are also available in Gauge 1, G scale, 16 mm scale and can be found in O and OO/HO. Hornby Railways produce live steam locomotives in OO, based on designs first arrived at by an amateur modeller. Other modellers have built live steam models in HO/OO, OO9 and N, and there is one in Z in Australia.

Internal combustion

Occasionally gasoline-electric models, patterned after real diesel-electric locomotives, come up among hobbyists and companies like Pilgrim Locomotive Works have sold such locomotives. Large-scale petrol-mechanical and petrol-hydraulic models are available but unusual and pricier than the electrically powered versions.

Scratch building

Modern manufacturing techniques mean mass-produced models achieve a high degree of precision and realism. In the past this was not the case and scratch building was very common. Simple models are made using cardboard engineering techniques. More sophisticated models can be made using a combination of etched sheets of brass and low temperature castings. Parts that need machining, such as wheels and couplings are purchased.

Etched kits are still popular, still accompanied by low temperature castings. These kits produce models that are not covered by the major manufacturers or in scales that are not in mass production. Laser machining techniques have extended this ability to thicker materials for scale steam and other locomotive types. Scratch builders may also make silicone rubber moulds of the parts they create, and cast them in various plastic resins (see Resin casting), or plasters. This may be done to save duplication of effort, or to sell to others. Resin "craftsman kits" are also available for a wide range of prototypes.

Control

The first clockwork (spring-drive) and live steam locomotives ran until out of power, with no way for the operator to stop and restart the locomotive or vary its speed. The advent of electric trains, which appeared commercially in the 1890s, allowed control of the speed by varying the current or voltage. As trains began to be powered by transformers and rectifiers more sophisticated throttles appeared, and soon trains powered by AC contained mechanisms to change direction or go into neutral gear when the operator cycled the power. Trains powered by DC can change direction by reversing polarity.

Electricity permits control by dividing the layout into isolated blocks, where trains can be slowed or stopped by lowering or cutting power to a block. Dividing a layout into blocks permits operators to run more than one train with less risk of a fast train catching and hitting a slow train. Blocks can also trigger signals or other accessories, adding realism or whimsy. Three-rail systems often insulate one of the common rails on a section of track, and use a passing train to complete the circuit and activate an accessory.

Many layout builders are choosing digital operation of their layouts rather than the more traditional DC design. The industry standard command system is Digital Command Control (DCC). The advantages to DCC are that track voltage is constant (usually in the range of 20 volts AC) and the command throttle sends a signal to small circuit cards, or decoders, hidden inside the piece of equipment which control several functions of an individual locomotive, including speed, direction of travel, lights, smoke and various sound effects. This allows more realistic operation in that the modeller can operate independently several locomotives on the same stretch of track.