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Continuous track, also called tank tread〔 or caterpillar track, is a system of vehicle propulsion in which a continuous band of treads or track plates is driven by two or more wheels. This band is typically made of modular steel plates in the case of military vehicles and heavy equipment, or synthetic rubber reinforced with steel wires in the case of lighter agricultural or construction vehicles. The large surface area of the tracks distributes the weight of the vehicle better than steel or rubber tyres on an equivalent vehicle, enabling a continuous tracked vehicle to traverse soft ground with less likelihood of becoming stuck due to sinking. The prominent treads of the metal plates are both hard-wearing and damage resistant, especially in comparison to rubber tyres. The aggressive treads of the tracks provide good traction in soft surfaces but can damage paved surfaces. Special tracks that incorporate rubber pads can be installed for use on paved surfaces to prevent the damage that can be caused by all-metal tracks. Continuous tracks can be traced back as far as 1770 and today are commonly used on a variety of vehicles including bulldozers, excavators, tanks, and tractors, but can be found on any vehicle used in an application that can benefit from the added traction, low ground pressure and durability inherent in continuous track propulsion systems. == History == There have been theories that perhaps the oldest implementation of something resembling continuous tracks was in prehistoric erection of large stone monuments, when megaliths may have been slid atop rounded wooden logs. The logs were grooved near their ends to be held in alignment and rotation by belts out past the edge of the megalith and lubricated by some means, probably organic. The logs are carried from the back of the procession to the front in an endless chain, like continuous track. The system is a precursor to development of the axle, which keeps a rotating cylinder fixed relative to its cargo. But the logs were likely often separate and each log was carried by men from the back to the front. In modern times, continuous track propulsion systems can be traced back to a crude continuous track system designed in the 1770s by Richard Lovell Edgeworth. Polish mathematician and inventor Józef Maria Hoene-Wroński conceived of the idea in the 1830s.〔(【引用サイトリンク】title=Josef-Maria Hoëné de Wronski )〕 The British polymath Sir George Cayley patented a continuous track, which he called a "universal railway". In 1837, a Russian inventor Dmitry Zagryazhsky designed a "carriage with mobile tracks" which he patented the same year, but due to a lack of funds and interest from manufacturers he was unable to build a working prototype, and his patent was voided in 1839. Although not a continuous track in the form encountered today, a dreadnaught wheel or "endless railway wheel" was patented by the British Engineer James Boydell in 1846. In Boydell's design, a series of flat feet are attached to the periphery of the wheel, spreading the weight. A number of horse-drawn wagons, carts and gun carriages were successfully deployed in the Crimean War, waged between October 1853 and February 1856, the Royal Arsenal at Woolwich manufacturing dreadnaught wheels. A letter of recommendation was signed by Sir William Codrington, the General commanding the troops at Sebastapol.〔(【引用サイトリンク】title=Boydell Artillery Wheel )〕 Boydell patented improvements to his wheel in 1854 (No. 431) - the year his dreadnaught wheel was first applied to a steam engine - and 1858 (No. 356), the latter an impracticable palliative measure involving the lifting one or other of the driving wheels to facilitate turning. A number of manufacturers including Richard Bach, Richard Garrett & Sons, Charles Burrell & Sons and Clayton & Shuttleworth applied the Boydell patent under licence. The British military were interested in Boydell's invention from an early date. One of the objectives was to transport Mallet's Mortar, a giant 36" weapon which was under development but, by the end of the Crimean war, the mortar was not ready for service. A detailed report of the tests on steam traction, carried out by a select Committee of the Board of Ordnance, was published in June 1856, by which date the Crimean War was over, consequently the mortar and its transportation became irrelevant. In those tests, a Garrett engine was put through its paces on Plumstead Common. The Garrett engine featured in the Lord Mayor's show in London, and in the following month that engine was shipped to Australia. A steam tractor employing dreadnaught wheels was built at Bach's Birmingham works, and was used between 1856 and 1858 for ploughing in Thetford; and the first generation of Burrell/Boydell engines was built at the St. Nicholas works in 1856, again, after the close of the Crimean war. Between late 1856 and 1862 Burrell manufactured not less than a score of engines fitted with dreadnaught wheels. And in April 1858, "The Engineer" gave a brief description of a Clayton & Shuttleworth engine fitted with dreadnaught wheels, which was supplied not to the Western Allies, but to the Russian Government for heavy artillery haulage in the Crimea, in the post-war period. Steam tractors fitted with dreadnaught wheels had a number of shortcomings and, notwithstanding the creations of the late 1850s, were never used extensively.〔 In August 1858, more than two years after the end of the Crimean War, John Fowler (agricultural engineer) filed British Patent No. 1948 on another form of "Endless Railway". In his illustration of the invention, Fowler used a pair of wheels of equal diameter on each side of his vehicle, around which pair of toothed wheels ran a 'track' of eight jointed segments, with a smaller jockey/drive wheel between each pair of wheels, to support the 'track'. Comprising only eight sections, the 'track' sections are essentially 'longitudinal', as in Boydell's initial design.〔(【引用サイトリンク】title=Burrell-Boydell Tractor )〕 Fowler's arrangement is a precursor to the multi-section caterpillar track in which a relatively large number of short 'transverse' treads are used, as proposed by Sir George Caley in 1825, rather than a small number of relatively long 'longitudinal' treads. Further to Fowler's patent of 1858, in 1877, a Russian, Fyodor Blinov, created a tracked vehicle called "wagon moved on endless rails" (caterpillars).〔(【引用サイトリンク】title=The inventor of the tractor )〕 It lacked self-propulsion and was pulled by horses. Blinov received a patent for his "wagon" in 1878. From 1881 to 1888 he developed a steam-powered caterpillar-tractor. This self-propelled crawler was successfully tested and featured at a farmers' exhibition in 1896.〔 Steam traction engines were used at the end of the 19th Century in the Boer Wars. But neither dreadnaught wheels nor continuous tracks were used, rather "roll-out" wooden plank roads were thrown under the wheels as required. In short, whilst the development of the continuous track engaged the attention of a number of inventors in the 18th and 19th centuries, the general use and exploitation of the continuous track belonged to the 20th Century. A little known American inventor, Henery T. Stith, developed a continuous track prototype which was, in multiple forms, patented in 1873, 1880, and 1900. The last was for the application of the track to a prototype off-road bicycle built for his son. The 1900 prototype is retained by his surviving family. Frank Beamond, a less-commonly known but significant British inventor, designed and built caterpillar tracks, and was granted patents for them in a number of countries, in 1900 and 1907.〔(【引用サイトリンク】title=Invention of the Caterpillar Track: Frank Beamond and his Patents )〕 An effective continuous track was invented and implemented by Alvin Orlando Lombard for the Lombard Steam Log Hauler. He was granted a patent in 1901 and built the first steam-powered log hauler at the Waterville Iron Works in Waterville, Maine, the same year. In all, 83 Lombard steam log haulers are known to have been built up to 1917, when production switched entirely to internal combustion engine powered machines, ending with a Fairbanks diesel powered unit in 1934. Undoubtedly, Alvin Lombard was the first commercial manufacturer of the tractor crawler. At least one of Lombard's steam-powered machines apparently remains in working order.〔(【引用サイトリンク】title=Lombard Log Hauler and Model T Snowmobile Show Route 175 Thornton, NH )〕 A gasoline-powered Lombard hauler is on display at the Maine State Museum in Augusta. In addition, there may have been up to twice as many Phoenix Centipeed versions of the steam log hauler built under license from Lombard, with vertical instead of horizontal cylinders. In 1903, the founder of Holt Manufacturing, Benjamin Holt, paid Lombard $60,000 for the right to produce vehicles under his patent. There seems to have been an agreement made after Lombard moved to California, but when previous track patents were studied, discrepancies arose concerning how this matter was resolved. At about the same time a British agricultural company, Hornsby in Grantham, developed a continuous track which was patented in 1905.〔British Patent No. 16,345 (1904)〕 The design differed from modern tracks in that it flexed in only one direction, with the effect that the links locked together to form a solid rail on which the road wheels ran. Hornsby's tracked vehicles were given trials as artillery tractors by the British Army on several occasions between 1905 and 1910, but not adopted. The patent was purchased by Holt. The Hornsby tractors featured a track-steer clutch arrangement, which is the basis of the modern crawler operation, and some say an observing British soldier quipped that it crawled like a caterpillar. The word was shrewdly trademarked and defended by Holt. American James B. Hill, working in Bowling Green, Wood County, Ohio, patented what he termed "apron traction" on September 24, 1907. Caterpillar Tractor Company began in 1925 from a merger of the Holt Manufacturing Company and the C. L. Best Tractor Company; an early successful manufacturer of crawler tractors. Caterpillar brand continuous tracks have since revolutionized construction vehicles and land warfare. Track systems have been developed and improved during their use on fighting vehicles. During World War I Holt tractors were used by the British and Austro-Hungarian armies to tow heavy artillery and stimulated the development of tanks in several countries. The first tanks to go into action, the Mark I, built by Great Britain, were designed from scratch and were inspired by but not directly based on the Holt. The slightly later French and German tanks were built on modified Holt running gear. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Continuous track」の詳細全文を読む スポンサード リンク
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