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时间: 2019年12月14日 13:02

Minnie seized on the opportunity, which chance had afforded her, to introduce the matter she wished to speak about. In 1913 the Gnome Monosoupape engine was introduced, a model in which the inlet valve to the cylinder was omitted, while the piston was of the ordinary cast-iron type. A single exhaust valve in the cylinder head was operated in a manner similar to that on the previous Gnome engines, and the fact of this being the only valve on the cylinder gave the engine its name. Each cylinder contained ports at the bottom which communicated with the crank chamber, and were overrun by the piston when this was approaching the bottom end of its stroke. During the working cycle of the engine the exhaust valve was opened early to allow the exhaust gases to escape from the cylinder, so that by the time the piston overran the ports at the bottom the pressure within the cylinder was approximately equal to that in the crank case, and practically no flow of gas took place in either direction through the ports. The exhaust valve remained open as usual during the succeeding up-stroke of the piston, and the valve was held open until the piston had returned through about one-third of its downward stroke, thus permitting fresh air to enter the cylinder. The exhaust valve then closed, and the downward motion of the piston, continuing, caused a partial vacuum inside the cylinder; when the434 piston overran the ports, the rich mixture from the crank case immediately entered. The cylinder was then full of the mixture, and the next upward stroke of the piston compressed the charge; upon ignition the working cycle was repeated. The speed variation of this engine was obtained by varying the extent and duration of the opening of the exhaust valves, and was controlled by the pilot by hand-operated levers acting on the valve tappet rollers. The weight per horse-power of these engines was slightly less than that of the two-valve type, while the lubrication of the gudgeon pin and piston showed an improvement, so that a lower lubricating oil consumption was obtained. The 100 horse-power Gnome Monosoupape was built with nine cylinders, each 4鈥?3 inches bore by 5鈥? inches stroke, and it developed its rated power at 1,200 revolutions per minute. [Pg 246] CHAPTER XII. � Although successful heavier-than-air flight is less than two decades old, and successful dirigible propulsion antedates it by a very short period, the mass of experiment and accomplishment renders any one-volume history of the subject a matter of selection. In addition to the restrictions imposed by space limits, the material for compilation is fragmentary, and, in many cases, scattered through periodical and other publications. Hitherto, there has been no attempt at furnishing a detailed account of how the aeroplane and the dirigible of to-day came to being, but each author who has treated the subject has devoted his attention to some special phase or section. The principal exception to this rule鈥擧ildebrandt鈥攚rote in 1906, and a good many of his statements are inaccurate, especially with regard to heavier-than-air experiment. 亚洲免费无码中文在线|一区二区三区高清视频|偷自拍亚洲视频在线观看|免费啪视频观试看视频 � That theory of eclecticism was altogether impracticable. It was as though a gentleman should go into the House of Commons determined to support no party, but to serve his country by individual utterances. Such gentlemen have gone into the House of Commons, but they have not served their country much. Of course the project broke down. Liberalism, freethinking, and open inquiry will never object to appear in company with their opposites, because they have the conceit to think that they can quell those opposites; but the opposites will not appear in conjunction with liberalism, free-thinking, and open inquiry. As a natural consequence, our new publication became an organ of liberalism, free-thinking, and open inquiry. The result has been good; and though there is much in the now established principles of The Fortnightly with which I do not myself agree, I may safely say that the publication has assured an individuality, and asserted for itself a position in our periodical literature, which is well understood and highly respected. At the same time, however, though it was at the time difficult to pick out, there was very real progress being made, and, though a number of 鈥榝reak鈥?machines fell out by the wayside, the pioneer designers of those days learnt by a process of trial and error the right principles to follow and gradually succeeded in getting their ideas crystallised. There is one story of 1914 that must be included, however briefly, in any record of aeronautical achievement, since it demonstrates past question that to Professor Langley really belongs the honour of having achieved a design which would ensure actual flight, although the series of accidents which attended his experiments gave to the Wright Brothers the honour of first leaving the earth and descending without accident in a power-driven heavier-than-air machine. In March, 1914, Glenn Curtiss was invited to send a flying boat to Washington for the celebration of 鈥楲angley Day,鈥?when he remarked, 鈥業 would like to put the Langley aeroplane itself in the air.鈥?In consequence of this remark, Secretary Walcot of the Smithsonian Institution authorised Curtiss to re-canvas the original Langley aeroplane and launch it either under its own power or with a more recent engine and propeller. Curtiss completed this, and had the machine ready on the shores of Lake Keuka, Hammondsport, N.Y., by May. The main object of these renewed trials was to show whether the original Langley machine was capable of sustained free flight with a pilot, and a secondary object was to determine more fully the advantages of the tandem monoplane type; thus the aeroplane was first244 flown as nearly as possible in its original condition, and then with such modifications as seemed desirable. The only difference made for the first trials consisted in fitting floats with connecting trusses; the steel main frame, wings, rudders, engine, and propellers were substantially as they had been in 1903. The pilot had the same seat under the main frame and the same general system of control. He could raise or lower the craft by moving the rear rudder up and down; he could steer right or left by moving the vertical rudder. He had no ailerons nor wing-warping mechanism, but for lateral balance depended on the dihedral angle of the wings and upon suitable movements of his weight or of the vertical rudder. For some hour and a half this dictation went on, with interruption when heads of departments brought in reports, or when Keeling had to send for information as to some point in his correspondence. He noticed that on these occasions she sat with her pencil in her hand, so as to be ready to proceed as soon as he began again. Once she{78} corrected him about a date that had occurred previously in a letter, and was right.