History of Steam on the Erie Canal. UnknownЧитать онлайн книгу.
the utilized insignificantly small. A very intelligent captain of one of the best and most powerful steamers known to the Erie Canal, who had a full and carefully-kept log, stated that when his engine exceeded a hundred horse-power of steam, he could only equal twelve horses on the tow-path. Thus over seven-eighths of his power was wastefully developed in order to render one-eighth useful. But this occurred when he was moving only two loaded boats—the steamer and one in tow—but when moving four boats—three in tow—the percentage of utility was lessened, and he could not exceed eight to ten per cent. of his steam, as shown in slower movement, when fewer horses on the tow-path could equal him.
The steamer is a reservoir, and its rotatory power is free to be developed "inversely as its resistances." Hence, when fastened to a pier, it is all developed in its receding currents, and per contra when moving; if its machinery had a perfect fulcrum, it would all be developed in the run of the boat; consequently, on rivers and lakes, with fine-lined steamers, that cut the water like a knife, it is like standing in a small boat and pushing from a large one, but on canals, with their full bows, it is like standing in a large boat and pushing from a small one; the little one runs away with the power. The more than 100 square feet area of immersed section of the full bow represents the large boat, and the dozen square feet effective area of propeller blades, set at an easy angle for spiral motion and recession velocity, is the little one that squanders the power so extravagantly. Increase in number of boats increases this contrast. The propeller blades of a good canaller will move twelve to fifteen miles, in their line of spiral movement, to get two to three miles headway for the boat.
A correct scientific analysis can trace the developments of the eighty-five to ninety per cent. of the inherent power of the steam that is wasted on the common canal-boat, and that has no resultant effect whatever in the motion of the boat, just as positively as it can trace the co-developments of fifteen to ten per cent. that is utilized and that moves the boat.
The practical man sees the truths of these statements. He sees steam used with small, medium and large engines for canal purposes, and sees them all fail to meet the economy of transportation established by horses; but he would just as soon put men on the tow-path to compete with horses as to put horses into his elevators to compete with steam; and that, because in the elevators the power of the steam is chiefly utilized, whilst on the canal it is chiefly wasted.
It is therefore conclusive that there is an absolute necessity for a new mechanical system, for a radically different system of transmissive mechanism, for a system that can develop a considerable portion of the power of the steam in the movement of boats.
The variations of the old systems of propulsion that are being continuously tried are worthless, in the very nature of the case, because they are in no sense a remedy for existing inabilities, and because they do not, in any sense whatever, meet the difficulties.
STEAM IN 1871 AND 1872
Screw Propellers
Soon after the Act of April, 1871, to foster and develop the inland commerce of the State, the steam canal-boat Cathcart was tried. She is like the Niagara of 1859, and has not been continued in the trade.
The canal-boat George Barnard, afterward called the Andrew H. Dawson, was tried, and has run through the season of 1872. She has a common propeller in her bow, with a recess from the water-line inclined to twenty feet aft to the bottom. Her propeller, therefore, forces the current against this incline and along the bottom in retardation of its progress. Hence, she cannot be expected to excel former trials.
Конец ознакомительного фрагмента.
Текст предоставлен ООО «ЛитРес».
Прочитайте эту книгу целиком, купив полную легальную версию на ЛитРес.
Безопасно оплатить книгу можно банковской картой Visa, MasterCard, Maestro, со счета мобильного телефона, с платежного терминала, в салоне МТС или Связной, через PayPal, WebMoney, Яндекс.Деньги, QIWI Кошелек, бонусными картами или другим удобным Вам способом.