Synopses & Reviews
Synopsis
Excerpt from Operating Equipment for U. S. Army Observation Balloons: Tension Meters, Maneuvering Blocks, Maneuvering Spiders, Danger Cones and Clamps, Valve Testing Device, Sand Bags; Prepared in the Office of the Chief of Air Service, November, 1920
In order to safeguard the observation balloon from damage due to high winds and also to protect the cable from excessive strains it is necessary to frequently measure the tension to which the cable is subjected.
There are two ways of obtaining this tension. First, the tension indicating device is built directly into the winch and is so arranged that the load on the cable is constantly indicated. If it is desirable, a registering device can be used, and thereby a graphic record of the tension throughout the flight is obtained for future use. However, this latter feature has not been deemed necessary in the United States Army Air Service.
Second, a portable tension meter is also in use. This weighs between 6 and 7 pounds; is temporarily applied to the cable close to the winch; a reading is taken and noted. The general principles of the tension meters are shown in figure 1. The cable is made to pass under three rollers, R, R' and R. The roller R 1s placed midway between the two rollers R' and R, so as to deflect the cable. This places a resultant pressure (w) against the roller R in the direction shown by the arrow. In the spring-type tension meter this pressure on roller R is resisted by means of a coil spring (see Plate I, fig. The greater the tension on the coil the more this spring must be com pressed ln order to balance the thrust (w) on the roller. _the com pression of the Spring is indicated by graduations on the container by means of which the tensions in kilograms are indicated.
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