Page 353 



EQUIPMENT AND INSTRUMENTS 



4461 



4461. Description of Large Taut-Wire Apparatus 



The large taut-wire apparatus (fig. 75) consists of two principal parts, (1) a heavy standard A to which is attached a heavy reel 

 C containing the wire, an unreeling mechanism D, and a brake and tension adjusting mechanism E; and (2) a long metal stand B 

 which contains the measuring apparatus consisting of a cyclometer wheel F and revolution counter G, a dynamometer H, and suit 

 able rollers and fair-lead sheaves to lead the wire over the measuring apparatus and toward the ship's stern. 



Figure 75.— The large taut-wire apparatus. 



The standard A is permanently mounted on deck by through bolts to a structural member of the ship's hull. The standard 

 has a horizontal spindle J to the after end of which is affixed a detachable flyer arm B, on one end of which a wheel K is mounted 

 at an angle of about 45° with the axis of the spindle, and on the other end of which is a counterpoise weight L. A brake drum E, 

 enclosed by a split trake tand, is attached to the forward end of the spindle. The brake is operated by wing nuts Mthat work 

 against springs on two bolts coimecting the two sides of the band, which are used to adjust the tension on the wire. The flyer arm is 

 detachable so that the reel, containing the wire, may be secured to and removed from a bracket on the standard. The reel is secured 

 to the bracket by a center consisting of a central ring and three arms. The central ring is held to the bracket by a heavy setscrew 

 and the end of each arm carries two setscrews that fit against a pad which engages a recess in the inner circumference of the reel. 

 The center should be secured to the reel before it is attached to the bracket on the standard. 



The reel, when fully wound, contains approximately 140 nautical miles of 0.0285-inch diameter (No. 21 B and S gage) piano wire 

 having a tensile strength of approximately 190 poimds. The wire should not be galvanized for this would cause erratic operation 

 of the apparatus. Any splices should be securely and neatly made so they will pass through the measuring apparatus without part- 

 ing or catching. The reel must be mounted on the standard so that the wire will be unreeled by clockwise revolutions of the flyer 

 arm. 



The measuring apparatus is mounted on a metal stand which is slightly more than 8 feet long and 2 feet wide at the base. The 

 forward end of the measuring apparatus contains two pairs of rollers A'', mounted at right-angles to each other, whose important func- 

 tion it is to eliminate the rotary motion of the wire as it is unreeled from the reel. From between these rollers the wire takes a three- 

 quarter turn around the circumference of the cyclometer wheel F, which is mounted between the horizontal members of the stand P. 

 A six-figure revolution counter G registers each complete revolution of the cyclometer wheel. This wheel, over which the wire passes, 

 is constructed with a circumference intended to equal one-thousandth part of a nautical mile. 



The wire passes vertically upward from the forward edge of the cyclometer wheel, crossing the horizontal lead to the wheel, and 

 over a fair-lead sheave mounted on the forward vertical member of the stand so that the wire will cross without interference. 

 From the forward fair-lead sheave the wire passes under the sheave // of the djTiamometer. 



The dyncmcmeter is an apparatus that indicates the tension of the wire. It consists of a sheave mounted in a frame iJ, that slides 

 on two round vertical guide reds with springs at their lower ends. The frame is free to slide up and down on the guide rods and the 

 tension on the wire is indicated by the position of a pointer attached to the frame relative to a calibrated scale on the forward side of 

 the angle iron uprights. The wire passes around the lower side of the dynamometer sheave and from the lift of the sheave and frame, 

 the tension on the wire is indicated on the scale. 



After the wire leaves the dynamometer sheave it passes up over the after fair-lead sheave S, mounted on the after vertical member 

 of the stand. Three rollers T, two vertical and one horizontal, are mounted aft of the fair-lead sheave and from between these, the 

 wire passes into the water astern of the ship. If the wire does not lead fair into the water, additional rollers must be provided on 

 the stern to lead it over the taffrail. 



One spare reel is generally provided so that it may be sent to the wire manufacturer for refilling while the other reel is in use. 



The operation of- the apparatus is simple. After the end of the wire has been 

 anchored and a tension has been placed on it by the ship's forward motion, the pull of 

 the wire causes the flyer to revolve around the reel, lifting and unreeling the wire from 

 the reel. The rotational velocity of the flyer depends directly on the forward speed 

 of the vessel over the ground, and on a straight course over level bottom the length 



