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John Loudon McAdam, 1830, National Gallery, London. John Loudon McAdam (23 September 1756 [1] – 26 November 1836) was a Scottish civil engineer and road-builder. He invented a new process, "macadamisation", for building roads with a smooth hard surface, using controlled materials of mixed particle size and predetermined structure, that would be more durable and less muddy than soil-based tracks.
New macadam road construction at McRoberts, Kentucky: pouring tar. 1926 With the advent of motor vehicles , dust became a serious problem on macadam roads. The area of low air pressure created under fast-moving vehicles sucked dust from the road surface, creating dust clouds and a gradual unraveling of the road material. [ 18 ]
Tarmacadam is a concrete road surfacing material made by combining tar and macadam (crushed stone and sand), patented by Welsh inventor Edgar Purnell Hooley in 1902. It is a more durable and dust-free enhancement of simple compacted stone macadam surfaces invented by Scottish engineer John Loudon McAdam in the early 19th century.
This method involved spreading tar on the subgrade, placing a typical macadam layer, and finally sealing the macadam with a mixture of tar and sand. Tar-grouted macadam was in use well before 1900 and involved scarifying the surface of an existing macadam pavement, spreading tar, and re-compacting.
Coal tar is produced through thermal destruction of coal.Its composition varies with the process and type of coal used – lignite, bituminous or anthracite. [13]Coal tar is a mixture of approximately 10,000 chemicals, of which only about 50% have been identified.
Coal was originally used in America in the 1300s by the Hopi Indians as a way to cook their food, warm themselves and fire their clay. Coal did not resurface in the United States until 1673.
Weatherproof covers were added to hopper cars, creating the covered hopper. Early production emphasized two-bay cars very similar to open coal hoppers and suitable for materials of similar density, like Portland cement or rock-salt. Some cars were available in the 1910s, and became more common by the 1940s.
Mules hauled the empty coal tubs to the summit and were sent down in the last batch of cars; the return trip required 4–5 hours. The road would send down groups of 6–8 coal cars under control of a brakeman, and once 40–42 cars were down, send down the special "mule cars" with the draft animals, thus having just enough animals to return ...