As early as 1804, Richard Trevithick was experimenting with a steam engine which ran on cast iron rails. Early trains were used to haul heavy loads at low speeds as their single boiler design was incapable of producing enough steam for continued high speed running. In 1829 Robert Stephenson designed and built a multi-tubular boiler design steam engine called the `Rocket,' which had a top speed of 29mph. When it opened in 1830 Britain's Liverpool and Manchester railway became the world's first railway expressly designed for steam powered haulage.
Steam locomotives provided nearly all the traction for the world's railways for nearly a century. As technology advanced so steam engines became larger and faster until around the 1930's they began to decline and diesel/electric locomotives began to appear. Diesel engines reach their optimum speed more quickly than their steam powered counterparts and convert 25-45 percent of their fuel to useful energy whereas steam engines typically only convert about 8 percent. Because of their advantage over steam, diesel engines began replacing them from 1935 onwards until today only railways in Africa and Asia continue to still utilise steam power.
The diesel engine is linked to the drive wheels by either hydraulic or electrical means. Turbines linked together by oil driven under high pressure provides up to 2000hp in the hydraulic version. In the diesel/electric variation the turbines drive generators which supply current to the traction motors.
The oil crisis in the early 1970's prompted many Western nations to switch to electricity to power their locomotives. The power car carries on its roof a device known as a Pantagraph which is raised up to come into contact with overhead power cables which typically carry around 25,000 volts AC. This high voltage is transformed down to around 1,500 volts DC which is then used to drive the traction motors. Electric trains accelerate smoothly and quickly up to their operating speeds which are typically 125mph or greater.
