History of rail transport
James Watt, a Scottish inventor and mechanical engineer, greatly improved the steam engine of Thomas Newcomen, hitherto used to pump water out of mines. Watt developed a reciprocating engine in 1769, capable of powering a wheel. Although the Watt engine powered cotton mills and a variety of machinery, it was a large stationary engine. It could not be otherwise: the state of boiler technology necessitated the use of low pressure steam acting upon a vacuum in the cylinder; this required a separate condenser and an air pump. Nevertheless, as the construction of boilers improved, Watt investigated the use of high-pressure steam acting directly upon a piston. This raised the possibility of a smaller engine, that might be used to power a vehicle and he patented a design for a steam locomotive in 1784. His employee William Murdoch produced a working model of a self-propelled steam carriage in that year.
The first full-scale working railway steam locomotive was built in the United Kingdom in 1804 by Richard Trevithick, a British engineer born in Cornwall. This used high-pressure steam to drive the engine by one power stroke. The transmission system employed a large flywheel to even out the action of the piston rod. On 21 February 1804, the world's first steam-powered railway journey took place when Trevithick's unnamed steam locomotive hauled a train along the tramway of the Penydarren ironworks, near Merthyr Tydfil in South Wales. Trevithick later demonstrated a locomotive operating upon a piece of circular rail track in Bloomsbury, London, the "Catch Me Who Can", but never got beyond the experimental stage with railway locomotives, not least because his engines were too heavy for the cast-iron plateway track then in use.
The first commercially successful steam locomotive was Matthew Murray's rack locomotive "Salamanca" built for the Middleton Railway in Leeds in 1812. This twin-cylinder locomotive was not heavy enough to break the edge-rails track and solved the problem of adhesion by a cog-wheel using teeth cast on the side of one of the rails. Thus it was also the first rack railway.
Lego Trains
Lego trains were first introduced in 1966 with Lego set number 080. The train sets used blue rails, and the first train sets were simply push-along. Set number 115 introduced 4.5 volt battery-operated trains (initially the battery box was handheld, but train sets soon contained a railcar that carried the battery box), and train sets numbered 720 (1969) and up operated on 12-volt electrified rails, introduced in 1969. In 1972, 4.5-volt trains gained a monolithic railcar that carried the batteries and contained both a bottom-mounted stop button to be actuated by signals, as well as a side-mounted lever for manual go/stop/back control and tripping by a track-side pivot. All three kinds (push trains, 4.5-volt battery-operated trains and 12-volt electric trains) existed next to each other and even allowed for upgrade. The motors were the same size, the push trains used a motor-shaped dummy block of bricks, and all used the same wheel style. These wheels had the same press-fit metal axles as used in the two larger sizes of rubber-tire Lego wheels, which also meant that both 4.5-volt and 12-volt motors were not restricted to use in trains. A push train could be updated to a battery-operated train, and a battery-operated train could be updated to an electric train. Since 1969 the motor housings for 4.5-volt and 12-volt are equal and can be equipped with either a 4.5-volt or 12-volt Bühler motor unit. These motor units were sold separately as a replacement part until around 1990. In or before 1976, the 4.5-volt motor gained a hole for driving the then white cross-axles of the size that would later be known as Technic. Railcars began as spartan constructions of train-specific wheels and couplers attached to car bases made from universal plates and bricks, but these were quickly replaced by black single-piece bases in two lengths that included captive wheels and couplings.