The Airplane Propeller

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U.S. Government Printing Office, 1921 - Propellers, Aerial - 337 pages
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Page 3 - BY ORDER OF THE SECRETARY OF W.AR: PEYTON C. MARCH, General, Chief of Staff.
Page 320 - ... weight or spring cease to act, the oscillations of the pendulum soon come to an end. The rate of movement of the wheels is entirely controlled by the pendulum ; thus to the same clock we might attach a pendulum vibrating seconds, or one vibrating half-seconds ; and its rate, the weight being the same, would be twice as great in the latter case as in the former, since the teeth of the scape-wheel are allowed *~ pass twice as fast.
Page 320 - FIG. 190. counter would be twice as great in the latter case as in the former. In order to make the instrument recording, it remains only to transform the motion of the counter into a proportionate angular rotation of the pointer on the dial. Then the angular deflection of the pointer and counter would be moved the same distance as though the speed of revolution had been constant and equal to the average speed over the whole period and no indication of the assumed variation in speed would be given...
Page 315 - ... the wind. The recording device is shown in Fig. 14 and diagrammatically in Fig. 13. It has the ordinary clockwork drum and pen. These are described elsewhere. The gauge consists of two movable circular plates SI and S2, rigidly connected by a rod ab. The plates form the tops of the bellows fl and f2.
Page 316 - Figs. 15 and 16 are shown views of a very widely used combination of the Foxboro indicating box and the Zahm Pitot-Venturi tube (now adopted as standard by the Signal Corps). The pressure lead of the Pitot enters the small cylinders located in the indicating case which in itself is made air-tight by a gasket under the cover. The, suction of the Venturi is transmitted to the case itself. When a difference of pressure exists between the inside and outside of the two cylinders, they elongate or contract....
Page 315 - The link bc carries on one end the marking pen g; on the other a counter weight for the movable parts of the instrument. At the end of this link is fastened the spring R, whose tension balances the pressure of the pen. This spring is so placed that the displacement of the pen is nearly proportional to the wind speed. The recording apparatus is enclosed in a box about 9 in.
Page 124 - The dryer the air, the more rapid will be the evaporation, and, consequently, the greater the difference between the "wet-bulb" and "dry-bulb
Page 315 - The Venturi is carefully proportioned to give the maximum possible suction with a given air speed. The antenna is supported by a long, slender, hollow arm of light wood which contains the tubes transmitting the pressure to the recording device as shown in Fig. 12. It is fastened to this arm by a light, adjustable clip, in order that the antenna may be turned directly into the wind. The recording device is shown in Fig. 14 and diagrammatically in Fig.
Page 78 - DD, which separate all fine mist from the air but allow the air to pass through freely in a saturated condition. These baffles may be made up of boards in convenient sections. Copper nails or wooden dowels should be used. They should fit tightly, as any leakages will allow the spray to get through to the steam pipes, which would spoil the humidity regulation. H represents the heating pipes, which are concentrated toward the center.
Page 313 - I'itot and Venturi. — To increase the pressure differences, and thus get practicable forces on the gauges, the Venturi tube is coupled with the pressure part of the Pitot. Such a combination is shown diagrammatically in Fig. 9. Here the velocity at the throat will be considerably greater than that acting on the suction side of a Pitot, and therefore has a considerably greater effect. The mathematical theory of the Venturi is a little more complicated than that of the Pitot and the theoretical suction...

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