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EQUIPMENT AND INSTRUMENTS 



4631 



ranging from 500 to 1,500 r. p.m., operating- on 110-volt direct current. Speed is 

 controlled by a Cutler-Hammer field rheostat with 12 to 14 steps of field control and a 

 no-voltage release which automatically turns the control arm to slow speed if, for any 

 reason, the current is cut off. 



Power transmission has been by gears, a silent chain, or a V-shaped belt. The 

 V-belt drive, on account of its silence, is preferable when it can be used. 



The operation of the machines is simple. When the control handle is vertical, the 

 reel is in neutral and is free to turn, and the wire will run out. To stop the wire running 

 out, the handle is moved to one side, shifting the reel to where it engages the brake. If 

 the control handle is moved to the opposite side the reel will engage the clutch. The 

 engagement with either brake or clutch may be abrupt or gradual according to the force 



Fn.uKE so.— Dccii-sca olectric sounding machine. 



applied to the handle. The clutch should always be idling at slow speed — never 

 stopped — at the time the reel engages it. 



Deep-sea sounding machine. — Each survey ship has at least one deep-sea sounding 

 machine. The reel of this machine has a mean circumference of about 1 fathom and 

 will hold about 6,000 fathoms of piano wu^e. The reel is usually made of duralumin 

 because its lightness reduces the momentum of the revolving reel, but some reels have 

 been made of cast steel. This machine is almost invariably electric-powered. The 

 weight of this machme complete with duralumin reel, electric motor, frame, base, etc., 

 is about 1,275 pounds. 



The machine is usually installed on the bridge, the wii-e being led outboard over the 

 ship's side by fair-leads on a boom (see 4633). There is usually a revolution counter, 



