INTRODUCTION TO SONAR 



OUTPUT RACK 



INPUT SLIDE 



/INPUT RACK 



INPUT GEAR 

 TO RACK 



STATIONARY 

 PIN 



FOLLOWER 



FOLLOWER 



Figure 7-7. 



71.105 

 Flat cam and cam follower. 



12.91 

 Figure 7-6. — Screw multiplier. 



input B to have a value of 4. If B moves ahead 

 a value of 4 and input A remains stationary, 

 then the output value C is 2. If input A were 

 -1, and input B were +4, then output C would 

 be +1-1/2. For the type of lever differential 

 shown in figure 7-5 the output equals half the 

 algebraic sum of the inputs. 



A mechanical multiplier commonly used is 

 the screw type, shown in figure 7-6. It talces two 

 constantly chcinging input values, and produces 

 a single output that is the product of the two 

 inputs. If the input to the screws (point A) is 

 weapon time of flight, for example, and the 

 input to the rack (point B) is range rate, then 

 the output (point C) is predicted range. 



A cam is a device that produces a mechanical 

 output that has a nonlinear relation to its input. 

 Cams usually convert a rotary motion into a 

 linear output. Figure 7-7 shows a flat cam mounted 

 on a rotating shaft. A cam follower rides on the 

 outer edge of the cam, converting the rotary motion 

 of the input to a linear output. 



Other mechanical computing devices used in 

 fire control systems include such mechanisms 

 as integrators and component solvers. Integrators 

 solve problems pertaining to time and motion, 

 having two inputs and one output. One input may 

 be elapsing tim3, for instance, and the other 

 input range rate. The output of the integrator 

 will be total change of range at any instant of 

 time. 



A component solver provides solutions to 

 problems involving movemsnt in relation to the 

 target. The solver has two inputs (usually from 



differentials) and two outputs. When solving for 

 own ship movement, for example, the inputs may 

 be own ship speed and target relative bearing. 

 The outputs are own ship's horizontal motion 

 along and across the line of sight. 



Mechanical Noncomputing Devices 



In all types of computing instruments, certain 

 values or quantities must be limited insofar as 

 they pertain to minimum and maximum values. 

 Some computing components must have a limit 

 stop to protect them from too large or too small 

 an input value. Limit stops are mechanical safety 

 devices that prevent shafts from rotating farther 

 than they should. Friction drives, overrides, and 

 overdrives also are used to protect components. 



A mechanical stop is shown in figure 7-8. 

 Notice that rotation in the type illustrated is 

 limited to about 90°. Rotation is halted when 

 the shafts come in contact with the fixed block 

 at the top of the device. 



A friction drive absorbs the shock that other- 

 wise could damage a computing component. If 

 a motor overruns enough for the output to hit 

 a limit stop, or a handcrank is turned with too 

 much force, or the line driven by the crank hits 

 a limit stop and the crank still turns, the 

 friction drive slips and eases the strain on the 

 mechanism. 



A hunting tooth limit stop keeps values within 

 specified computation limits. It has two gears. 

 One is connected to the input shaft, and the 

 other functions when the hunting tooth engages 

 as a result of the quantities set on the input 

 gear. 



An override allows a computing mechanism 

 to accept larger quantities than the design speci- 

 fies. The override permits acceptance of only 



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