UG 1045 1045 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 ^Ax^2)-V^ WASHINGTON GOVERNMENT PRINTING OFFICE 1921 Wak Department Document No. 1045 Offlce of The Adjutant General kliflARY OF CONQJ^ESS \ eeeuMgNTs d. vision g WAR DEPARTMENT, Washington, November ^4? ^920. The following publication, entitled " Operating Equipment for U. S. Army Observation Balloons, Tension Meters, Maneuvering Blocks, Maneuvering Spiders, Danger Cones and Clamps, Valve Testing Device, Sand Bags," is published for the information and guidance of all concerned. [062.1, A. CO.] By order of the Secretary of War : PEYTON C. MARCH, Major General, Chief of Staff. Official : ' P. C. HARRIS, 7' he Adjutant General. OPERATING EQUIPMENT FOR ARMY OBSERVATION BALLOONS. TENSION METERS. 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 is 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. 2). The greater the tension on the coil the more this spring must be com- pressed in order to balance the thrust (W) on the roller. The com- pression of the spring is indicated hj graduations on the container by means of which the tensions in kilograms are indicated. The pressure (W) in the roller R in the direction of the arrow (Plate I, fig. 1) is 2 T COS. a. If the angle (a) remains constant, the pressure (W) is in direct pro- portion to the tension (T). In the French tension meter the plunger supporting the roller has a mark which must at all times coincide with a fixed mark on the frame. This insures a constant angle (a). The spring pressure is regulated by means of a handwheel on the upper end of the plunger stem. It is obvious that if the tension changes while the instrument is in place the spring must be read- justed in order to bring the plunger back to position. This type of meter was used extensively by both the French and American armies in France. Another type of spring-pressure tension is shown in Plate I, fig. 3. In this instrument there are no adjustments to be made after the in- 5 6 OPERATING EQUIPMENT FOR ARMY OBSERVATION BALLOONS. strument is once placed on the cable. Any fluctuation in tension is immediately indicated by the movement of the plunger ; however, in this case the angle (a) varies. At (0) tension this angle is at its greatest. A spring as a measuring device, however, will not give complete accuracy. Two springs made at the same time from the same stock and hardened simultaneously may have a variance of 5 per cent. This could be overcome to a certain extent by graduating each indi- vidual meter to suit its particular spring. Should the spring become r//V^/CA7-/A* " horizontal. (4) The instrument is accurate to about one- twentieth of the reading. MANEUVERING BLOCKS. DESCRIPTION AND USE OF. The maneuvering block or sheave is a pulley constructed in such a manner that it may be opened and placed upon the balloon cable while Plate V. — Photograph of maneuvering blocks. the balloon is in ascension. It is generally used in connection with a maneuvering spider to haul down the balloon, if for any reason it becomes necessary, as for instance, when the winch becomes inopera- tive. If it becomes desirable that the balloon ascend from some other point than the winch site the maneuvering block is passed around the cable and is anchored at the desired point. In maneuvering across country innumerable conditions present themselves where the maneu- vering block is made use of. These conditions will not be presented here as they are fully covered in instruction manuals on maneuvering. There are three different models of maneuvering blocks illustrated herewith which present the types most used by the Army Balloon Service. They are all built to withstand stresses of from 10,000 to 14,000 pounds. The workmanship is of the very best for the purpose ; all parts are buffed and polished. All blocks are constructed mostly of bronze, of the following composition : Eighty per cent copper, 10 per cent phosphorus tin, and 10 per cent lead. OPERATING EQUIPMENT FOR ARMY OBSERVATION BALLOONS. 13 M/INEC/l^^/?/A/G SLOC/r Plate V.— Standard types of maneuvering blocks used during war by U. S. Army. 14 OPERATING EQUIPMENT FOE ARMY OBSERVATION BALLOONS. The sheave wheel is highly polished in the groove which is deep to keep the cable from flattening. The groove is designed to fit the cable Plate VI. — Burton maneuvering block (improved type). (Open.) snugly, but not tightly enough to cause wear on the sides of the cable ;. care should be exercised to avoid any rough spots in the groove, as OPERATING EQUIPMENT FOE ARMY OBSERVATION BALLOONS. 15 there is no quicker way to destroy a cable than to have a rough sheave groove. One of the blocks shown is provided with a compression grease cup. This makes a good sheave for use where the sheave is Plate VI. -Burton maneuvering block (improved type). (Closed.) anchored, as high speed is developed requiring proper lubrication. For ordinary maneuvering purposes this grease cup is not required, and is a disadvantage, as their stems are easily broken. It is ap- 16 OPERATING EQUIPMENT FOR ARMY OBSERVATION BALLOONS. Plate VIII. — Standard type of maneuvering spider. 'I'l^TB IX.— View showing maneuvering blocli attached to cable and anchored to ground by anchorage spider. Note the screw pickets at the ends of the spider cables. OPEEATING EQUIPMENT FOR ARMY OBSERVATION BALLOONS. 17 parent from the cuts how each type opens for placing on the cable. The very best of care should be accorded the maneuvering block, much depending upon its proper operation and strength when required, as it is under emergency conditions that its use is most often necessary-. MANEUVERING SPIDER. DESCRIPTION AND USE OF. The maneuvering spider is made up in various forms, two of the most common being illustrated herewith. Its purpose is to provide 18 OPERATING EQUIPMENT FOR ARMY OBSERVATION BALLOONS. means for the men to apply their force to the maneuvering block, also to provide a ring from which to suspend sandbags to overcome the vertical component of the forces acting upon the maneuvering block when in use with the spider in hauling down balloons. Any rope with a loop spliced into the end, and of length sufficient to allow the required number of men to distribute themselves along same, will serve the purpose. However, under most conditions the types shown will be found most convenient, due to the men being able • 7b J4i^/?c/7. Cod/e. /Vo./ Sond to apply their force more directly to the maneuvering block, espe- cially where the ground is uneven. The size rope used is usually 1 inch in diameter, this size giving sufficient strength when in good condition and being of cross section sufficient to afford the men good hand hold. The spliced loop at the block should be of ample length to accommodate all the sandbags, required to be attached thereto without necessitating some of the bags being hooked onto the ropes of other sandbags. When this practice has to be resorted to, the — 7b /^/7