CHAPTER II.
EXAMINATION OF FIRST-CLASS GUNNERS.
(_a_) THE AZIMUTH INSTRUMENT AND DEFINITIONS.
Q. What is an angle?
A. An angle is the divergence of two intersecting lines.
In Fig. 57 the two intersecting lines SA and XA form the angle SAX, and when measured on the circle with A as the center it is found to be equal to 80°.45 (eighty and forty-five hundredths degrees).
Q. Into how many degrees is a circle divided?
A. 360.
Q. How is each degree divided in the U. S. Artillery service?
A. Each degree is divided into one hundred equal parts.
Q. Define a circle.
A. A circle is a plane figure bounded by a curve, every point of which is equally distant from a point within called the center. Fig. 57 represents a circle with _A_ as the center.
Q. What is the vertex of an angle?
A. The point where the two intersecting lines cross. As in Fig. 57, _A_ is the vertex of the angle _SAX_.
Q. Define an azimuth angle.
A. It is a horizontal angle measured from zero degrees at the south in a clockwise direction.
Q. What is meant by a horizontal angle?
A. One whose intersecting lines or sides are parallel with the level of water at that point.
Q. What is a vertical angle?
A. One whose sides lie in a plane of a plummet.
Q. Can an azimuth angle be greater than 90°?
A. Yes. See Fig. 51. _SAT_ = azimuth of target (less than 90°); _SAT'_ = azimuth of target (greater than 90°, but less than 180°); _SAT''_ = azimuth of target (greater than 270°). (All these azimuth angles are read in a _clockwise direction_ from zero at the south.)
Q. When is a gun or an instrument said to be set in azimuth?
A. When it reads zero and points south.
Q. What is an azimuth-instrument?
A. A device for measuring horizontal angles.
Q. Point out the following parts of the instrument:
1. Telescope-tube. 2. Telescope-trunnion. 3. Trunnion clamp-screws. 4. Focusing-knob. 5. Sunshade. 6. Dew-cap. 7. Objective-cell. 8. Objective. 9. Eyepiece-adapter. 10. Eyepiece. 11. Eye-lens. 12. Field-lens. 13. Cross-wire holders. 14. Cross-wire. 15. Brashear-Hastings erecting-prism. 16. Prism-holder. 17. Prism-cap. 18. Cross-wire adjusting-screw. 19. Instrument-base. 20. Leveling-screws. 21. Spindle-head. 22. Worm-gear. 23. Graduated circle. 24. Worm-screw. 25. Worm-box. 26. Worm-box spring. 27. Worm-box pivot. 28. Worm-box adjusting-screws. 29. Worm-box eccentric-crank. 30. Index-disk. 31. Index-pointer. 32. Disk-crank. 33. Worm adjusting-screw. 34. Reading-opening. 35. Azimuth-clamp. 36. Azimuth slow-motion screw. 37. Telescope-yoke. 38. Yoke-caps. 39. Levels. 40. Level-holders. 41. Level-adjusting screws. 42. Plumb-bob. 43. Plumb-bob chain. 44. Tripod-head. 45. Tripod-cap. 46. Tripod-thumbscrew. 47. Tripod-legs. 48. Pier-mounts.
A. See Fig. 58.
Q. Describe how to set the azimuth-instrument up for use.
A. First: Set the graduated circle and index-disc to read the known azimuth of a visible object and clamp (the eccentric-crank being in gear).
Second: Set the eyepiece slightly to the left of the reading-opening and tighten the azimuth-clamp.
Third: Raise the whole instrument by grasping the tripod, and turn it so that the telescope points approximately in the direction of the visible object whose azimuth is known, being careful to set the plumb-bob over the home station at the same time and not destroy the setting of the graduated circle and index-disc.
Fourth: Level the instrument. (This is done by loosening the azimuth-clamp and setting one level parallel to two opposite leveling-screws, then turn these two screws either _both inward_ toward the spindle-head or _both outward_ until the bubble comes in the middle. Perform the like operation with the other two leveling-screws and the instrument is level.)
Fifth: Release the azimuth-clamp and set the telescope as nearly as possible on the object, then clamp and set the vertical cross-hair exactly by turning the azimuth slow-motion screw. Verify the setting of the index-disc and the levels. The instrument is now set in azimuth. Azimuth instruments for mounting on the parapet have turned on their levelling screws so as to bring reading opening convenient to the eye.
Q. How is the azimuth of any other point read after the instrument is set up?
A. By turning the index-disc crank until the vertical hair cuts the object. Read the even degrees on the graduated circle, and hundredths of a degree on the index-disc. (In order to make a considerable change in azimuth-reading, much time is saved by releasing the eccentric-crank, turning the telescope approximately on the object, throwing the eccentric-gear again and reading accurately by turning the index-disc till the vertical hair cuts the object.)
Q. Why are _not_ azimuth-circles on guns, mortars, etc., always graduated so that their zeros will _point_ south?
A. If this were always done, the azimuth indicator-plate or subscale would have to be directly under the muzzle of the gun--a very awkward and inconvenient place. These azimuth sub-scales are therefore placed on the side, and when the gun or mortar points south the subscale points at zero on the azimuth-circle.
Q. Give some rules for caring for the azimuth instrument.
A. Never allow any of the leveling-screws to become so tight that they cannot be _easily_ turned by hand. When setting the instrument up over a concrete floor make little holes in the concrete for the points of the tripod-legs to set in. Never wipe the lenses with anything having the least sign of dirt or grit upon it. A perfectly clean chamois is always best. See that all screws are firmly clamped before putting the instrument away in the wooden carrying-box. In removing it from the box, pick it up by placing the hands underneath the worm-gear. Never clamp the instrument too tightly to the tripod-head. After the instrument is once leveled avoid jarring or leaning upon it.
Q. In case the azimuth-instrument will not stay level after performing the usual operation of leveling, how do you adjust the levels?
A. Set one level parallel with two opposite leveling-screws, and bring the bubble to the center by turning these two screws either both inward or both outward. Reverse the telescope through 180°. If the bubble is not in the center, this level is out of adjustment. Now correct one half of the error by using the small steel pin on the little adjusting-screws on the levels, and the other half by using the two opposite leveling-screws referred to above. Now turn the telescope 180° again. If it is still out of level, continue the above method of correction until, on reversing the telescope, no change in motion of the bubble can be observed.
Q. Give a rule for finding the least count of a vernier.
A. Divide the value of the smallest division on the limb or main scale by the number of divisions there are on the vernier. The result is equal to the least count on the vernier.
Q. How would you focus the telescope.
A. Focus the eyepiece until the cross-wires appear rough.
Then turn the telescope on some distant object and focus the objective by means of the focusing-knob until the intersection of the cross-wires remains on the same point, when the eye is moved up and down and to right and left.
Q. Set up the azimuth instrument over a given point; level, orient, and focus it.
(This should be practiced frequently.)
EXAMPLES.--I. The number of divisions on a vernier = 25. The value of the smallest division on the main scale = 25 yards. What is the least reading of the vernier?
_Ans._ 25 ÷ 25 = 1 yard.
II. The value of the smallest division on the main scale of the mercurial barometer = 1/10 of an inch. The number of divisions on the vernier = 10. What is the least count of the vernier?
_Ans._ 1/10 ÷ 10 = 1/100 of an inch.
_Note._--The following scheme for accurately counting seconds has been found valuable to gunners who have no stop-watches; it is also used by many photographers in timing pictures. When ready to start to count the time of flight, for example, trail your gun or instrument on the target, stop traversing, and count to yourself: One _one thousand_, two _one thousand_, three _one thousand_, four _one thousand_, etc., until finished, saying _one thousand_ after each number. The time required by the average man to say one _one thousand_ or eight _one thousand_ is equal to one second. With but little practice a gunner can be trained to count as high as 20 seconds accurately. In such cases stop-watches are not necessary.
(_b_) THE PLOTTING-ROOM.
Q. Point out or describe the following parts of the Whistler-Hearn plotting-board: The table, the azimuth-circle, azimuth graduations for primary and secondary stations, base-line arm, base-line plate, primary station, secondary station, primary arm, secondary arm, directing-gun arm, directing-gun azimuth-circle, base-line verniers, directing-gun vernier, base-line-arm verniers, azimuth-indices for primary and secondary stations, auxiliary arm, connecting-bar, clamp for arm index-clamp, gun-arm clamp, reading-opening for directing-gun azimuth-circle, index for gun azimuth-circle, speed-scale for range, speed-scale for azimuth or azimuth-travel devices, range correction-device, azimuth correction-device, micrometer, the "targ, tally dials."
A. See Figs. 59, 60, 61, and 62. These figures show by steps the "evolution of the Plotting Board."
Q. Describe how to obtain the range of a target from the primary or secondary station when the azimuth-angles from the primary and secondary stations are given to you.
A. First: Set the auxiliary-arm index to read the number of even degrees the target is from the secondary station, setting the arm-clamp in the V-shaped notch on the azimuth-circle corresponding to that number of degrees.
Second: Set the index-disc to read the hundredths by turning the index-knob and clamp the index. The auxiliary arm is now set; therefore the secondary arm is set automatically in azimuth by virtue of its always remaining parallel to the auxiliary arm.
Third: Set the primary arm to read the number of degrees and hundredths the target is from the primary station. (The point of intersection of the fiducial or bevel edges of the primary and secondary arms is the position of the target on the plotting-board.)
Fourth: Slide the metal intersection-block or "targ" along the secondary arm until it touches the edge of the primary. The range in yards can now be readily read on the scales marked on these arms. (Fig. 62.)
Q. How are the range and azimuth for the directing-gun obtained for the same target?
A. Move the gun-arm up to the intersecting edge of the targ, and read the range from the scale on the gun-arm. The degrees of azimuth are read through the reading-opening, and the hundredths are read on the index-disc for the gun-arm.
Q. Suppose the range must be corrected for, say, 150 yards more, and the azimuth for 1·78 degrees less, how can the corrected range and corrected azimuth be automatically read on the gun-arm?
A. Turn the pinion on the gun-arm to move the scale of the range correction-device until 2150 is set. (The _zero_ of this scale = 2000.) (By doing this it is readily seen that the gun-arm range-scale is just 150 yards _nearer_ the gun center; consequently all ranges read on this scale will be 150 yards more than if the range correction-device were at zero.) The azimuth correction is set by turning the micrometer until the number of even degrees of the azimuth correction (in this case one degree less) is read on the main scale, and the hundredths on the micrometer. (Thus it is seen that the gun-arm will read as many degrees and hundredths more or less than the true azimuth as the number of degrees and hundredths of the azimuth correction determined.)
_Note._--Having determined by the ballistic board the range and azimuth corrections, they will usually answer for some time and thus avoid continual setting of these corrections on the gun-arm.
Q. What is the object of the travel-devices for range and azimuth correction on the gun-arm?
A. These are to determine the amount of change of range and azimuth between each observation of the target. The results thus obtained are given to the range- and deflection-board operators, who use it in finding the total range correction and the total azimuth correction.
Q. What are all plotting-boards principally used for?
A. For finding the position of a target whereby the range and the azimuth of it from any other point (as a directing-gun of a battery) can be determined.
Q. What is meant by the scale of a plotting-board?
A. By the scale of a plotting-board is meant, one inch on the board is equal to one, two, or so many yards on the ground; e.g., a scale of "one inch equals 300 yards" means, one inch distance on the board equals 300 yards on the ground.
Q. How can you determine the distance between two points on a plotting-board?
A. By using the range-arm that is constructed for the scale to which the board is drawn, setting the zero on one point and reading the number of yards on the arm where the point cuts the scale-edge.
Q. How is the longitudinal deviation measured on the plotting-board?
A. Measure the distance from the gun to the target, and from the gun to the splash. Subtract the lesser from the greater, and this will be the longitudinal deviation, according to the meaning given in drill regulations.
Q. How is the lateral deviation measured?
A. Read the azimuth of the target and splash from the directing-gun. Subtract the lesser from the greater: result = lateral deviation. If the azimuth to the target be greater than that to the splash, it is seen that the deviation will be to the left and _vice versa_.
Q. How are open sights on rapid-fire guns used?
A. The same as on small-arm pieces; i.e., the range in yards or elevation in degrees and minutes is set on the rear sight according to how the sight is graduated, and the gun is elevated and traversed until the target, front sight, and rear sight all come in line.
Q. Describe the 5" R.F. sight.
A. It consists of a sight-bar graduated in degrees and minutes (lowest reading being six minutes), with a sliding scale at the top for deflection right or left, the deflection-scale reading to three minutes. A range-drum is also geared to the sight-bar, and moves with it in such a manner that when the piece has a certain elevation it will shoot to a distance equal to the range on the drum. This avoids using any range-table.
Q. Describe the 6-pdr. R.F. sight.
A. A simple bar-sight graduated to yards with a deflection-scale reading to three minutes.
Q. How is the deflection-scale set on open sights when it is desired to fire to right or left?
A. To fire right, move the peep-hole to the right; to fire left, move the peep-hole to the left.
Q. From what line is all elevation measured?
A. From the axis of the bore. (See Fig. 63.)
Q. Define sight elevation.
A. The angle between the axis of the bore before firing and the line of sight. (See Figs. 63 and 64.)
Q. In case shot strikes to the right or left, and as gunner you had the sight on the target when the shot struck, how could you correct your error with a telescopic sight or open sights?
A. Stopping traversing at the instant shot strikes, move the vertical hair rapidly to the splash. The sight is now corrected for the error, and its setting will be correct for the next shot.
THE RANGE-BOARD.
NOMENCLATURE. (See Fig. 65.)
_The Frame._--The outside frame, or box, of the instrument.
_The Board._--That upon which the charts are pasted. _K-K._
_The Ruler._--The balance wooden strip to which the metal scale and slides are attached. _X-X._
_The Scale._--The fixed graduated scale on the ruler. _m-m._
_The Bar._--The metal rod or bar which slides on the _top_ of the scale.
_The Register._--The fixed point in the center of the bar. _a._
_The Trammel._--The pointer which slides on the bar. _b._
_The Pointer._--The pointer at the top of the trammel.
_The Index._--The lower point on the trammel.
_Normals._--The straight vertical lines in each set of curves.
_The String._--The cord on the right side of the board used in determining travel.
_The Travel-scale._--Scales for setting the string.
_Prediction-scale._--Vertical lines on the right side of the board, used in determining the travel during the observing interval.
ADJUSTMENT.
Adjust the ruler by means of the adjusting-screw on the left, so that its upper edge coincides with the parallel lines on the board.
OPERATION.
The bar is clamped by means of the screw near the left end of the ruler.
The bar must be held firmly while moving the trammel. In making corrections for artillery fire the following data, as obtained at the opening of the action, will usually suffice for the entire action.
_Density of the air_, _Velocity of the wind_, _Azimuth of the wind_, _Height of tide_.
The range effects and deviating effects of the wind must be obtained for each shot. Tide should be changed at least every half-hour. As soon as the density of the air is ascertained the computer will insert a pin, or set the pointer at the top of the corresponding curve. The same will be done for height of tide.
The muzzle velocity to be used for the first shot will be marked in a similar manner as directed by the range officer. The wind-component device having been set for the azimuth and velocity of the wind and the azimuth of the target, the computer will note the reference-number and set the pointer at the top of the wind-curve having that number.
As soon as he receives the travel reference-number he will set the string accordingly, using the scale for the _observing interval_ used.
_To determine correction._--As soon as the approximate range is received, the computer sets the ruler for the range and the index at zero; he then slides the trammel to the left until the pointer is opposite the atmosphere curve as indicated by the pointers _e_, _f_, _g_, etc., holding the bar in place with the left hand. He then slides the bar until the pointer is at normal for atmosphere; this completes the correction for atmosphere.
He then proceeds in the same manner for _wind_ and _tide_, always sliding the trammel until the pointer is at the indicated curve, holding the bar in place with the left hand and then sliding the bar until the pointer is at normal.
If the muzzle velocity is normal, no correction is made for velocity. If, however, the muzzle velocity is not normal, he makes a correction for muzzle velocity in a similar manner as for other data.
The above corrections are made before the travel is received. The computer clamps the bar and then waits until he receives the travel.
As soon as the travel is received, he sets the string, slides trammel until the pointer is opposite the string, unclamps the bar and moves it until the pointer is opposite the normal; this adds the correction for travel during the time of flight.
He then notes the total travel during the observing interval, which is indicated by the position of the string on the travel-scale corresponding to the observing interval used. He slides the trammel so that the pointer will be at the vertical line corresponding to the total travel during the observing interval, and then slides the bar to the normal; this adds the travel during the observing interval. He now clamps the bar. _The register now indicates the total correction to be applied to the arm._
_Trial-shots._--The gun is laid so that the shot should have a certain range, all corrections having been determined as described above, except of course that for travel.
The bar is set with the index at zero, and the trammel is set at the muzzle velocity used in the computation for the shot.
The gun is fired and the range of the shot is plotted. The range officer determines how much the shot has fallen short or gone beyond, and announces the result as plus or minus so many yards. The computer moves the bar plus or minus the number of yards announced, using the scale for this purpose.
The pointer now indicates the muzzle velocity to be used in computing the next shot. The velocity pointer is moved accordingly.
If a second trial shot is used, the corrections are computed as before, using, however, the new muzzle velocity as determined from the first shot.
In determining a second corrected muzzle velocity the bar should be moved for but half the longitudinal deviation of the shot from the expected range; the pointer then marks the velocity to be used for the next shot.
In case a third trial shot is used the process is the same except that the bar is moved for but one third of the longitudinal deviation.
The curves are given for every ten yards of range, for every ten per cent of weight of air, and for every ten miles of wind, etc.
For conditions in which the values lie between these readings, the trammel can readily be set by the eye sufficiently close for all practical purposes.
EXAMPLE: Range 7000; atmosphere 20; wind 70; velocity 2260; travel 400; tide +10. Find the correction to be applied to the gun-arm.
SOLUTION: I. Set ruler _XX_ at 7000 on scale _KK_.
II. Set pointer _a_ at 2000 on scale _MM_.
III. Set pointer _e_ at 20; _f_ at 70; _g_ at +10; _h_ at 2260, string _cc_ at 400 on 20-second interval line, and scale _dd_ such that the number 400 cuts the intersection of the string with ruler _XX_.
IV. Set pointer _b_ at 16 (atmosphere normal); move slide _z_ till _b_ cuts the 20 curve of atmosphere.
V. Set _b_ at 50 (zero wind) and slide _z_ till _b_ cuts the 70 curve.
VI. Set _b_ at 0 tide and slide _z_ till _b_ cuts +10.
VII. Set _b_ at 2200 I. V. and slide _z_ till _b_ cuts 2260.
VIII. Set _b_ at 400 on scale _dd_ and slide _z_ till _b_ cuts 300 (normal) on scale _dd_.
The range correction is now found on scale _mm_ opposite pointer _a_. This number is now set on the gun-arm of the plotting-board and each next plotted position will read on the range-scale of the gun-arm just that many yards more or less than the true range, i.e., the corrected range.
See Fig. 65.
THE DEFLECTION-BOARD.
NOMENCLATURE.
_Platen._--The rectangular sliding frame.
_Wind-arm._--The arm pivoted to the board on the left of the platen.
_Wind-component Scale._--The scale above the movable end of the wind-arm.
_Drift-curve._--The curved edge of the metal plate attached to the left end of the platen.
_Travel-arm._--The arm pivoted on the platen.
_Azimuth Correction-scale._--The sliding scale below the platen.
_Deflection-scale._--The fixed scale immediately above the azimuth correction-scale.
_Travel-scale._--A scale for making corrections for angular travel of the target; there are two, one below the azimuth correction-scale and one on the platen.
_"T" Square._--The sliding "T" square having the time graduations at one edge, corresponding to given ranges.
OPERATION.
Place the travel-scale on the platen in the lower or upper position according as the observing interval is 10 or 20 seconds.
As soon as the wind-component device is set note the deflection reference-number indicated, and set the wind-arm to the corresponding reading on the wind-component scale.
Set the platen so that the point of the drift-curve corresponding to the given range will be accurately over the right-hand edge of the wind-arm.
As soon as the reference-number indicating the _angular travel_ of the target during the observing interval is announced, set the travel-arm (right edge) for that travel by the travel-scale on the platen and set the azimuth correction-scale for the same travel by means of the travel-scale below it.
Set the "T" square so that the point of its scale corresponding to the given range will be accurately over the right edge of the travel-arm.
The azimuth correction to be applied to the gun-arm in all cases is then read from the azimuth correction scale at the bevel edge of the "T" square.
When Case I or II is being used the deflection to be sent to the guns is read from the deflection-scale at the bevel edge of the "T" square.
After the second observation the corrected range determined is used in setting the platen and "T" square.
See Fig. 60.
Q. How do the divisions on the azimuth-subscale and the deflection-scale of the sights compare with one another?
A. They are equal--the least reading on the former = 5 hundredths, and on the sight-scale one point or division = 5 hundredths or 3 minutes.
Q. How are the predicted range and predicted azimuth obtained?
A. It is now, under the new system of fire direction, obtained by means of the travel correction on the range correction and azimuth correction-board. If these new boards are not yet issued, the use of a range-keeper's range prediction-scale and a gunner's azimuth prediction-scale determines them at the gun. The old method was by plotting several positions of a target on the plotting-board and using a prediction-ruler, whence the _predicted point_ was obtained.
Q. Define quadrant elevation.
A. The angle between the axis of the bore before firing and the horizontal plane. (See Figs. 63 and 64.)
Q. What is the difference between quadrant and sight elevation?
A. Where the gun is above the target, sight elevation equals quadrant elevation plus the angular depression of the target. Where the gun is below the target, sight elevation equals quadrant elevation minus the angular elevation of the target.
Q. How is the gunner's quadrant used?
A. It is used principally in giving elevation to mortars by first setting the movable arm such that the knife-edged tooth engages in an even-degree mark on the rack, and by moving the sliding level to read the exact number of minutes. Then it is placed on its seat at the breech, being careful to see that the arrow points in the direction of the line of fire, and by elevating or depressing the piece until the bubble comes in the middle the mortar or piece will be set at the elevation set on the quadrant. (See Fig. 67.)
Q. Point out the following parts of the telescopic sight: Telescope, objective, eyepiece, erecting-prisms, trunnions, leveling-lug, leveling-screw, cross-level, elevation-arc, elevating-screw, vernier, focusing-collar, deflection-screw, deflection-scale, micrometer, disc, and telescope-level. (See Fig. 68.)
Q. How is deflection set on it?
A. By moving the deflection-screw the vertical cross-wire moves.
Q. How is deflection set to fire right and to fire left?
A. Move the vertical hair to the right to fire left, move it to the left to fire right, by turning the deflection-screw.
Q. How is elevation set on it?
A. Set the zero of the vernier opposite the mark on the limb representing the number of even degrees of the given elevation. Then turn the micrometer-disc by turning the elevation-screw until the given number of minutes is read on it. The sight is then set on the trunnion-bracket and the piece elevated till the bubble comes in the middle for quadrant elevation or till the horizontal cross-hair cuts the water line of target for sight elevation. The gun then has the elevation set on the sight.
Q. What is the lowest reading of the vernier on the elevation-arc?
A. Two minutes.
Q. What is the lowest reading of the deflection-scale?
A. Three minutes.
Q. Why is it necessary to elevate the gun till the bubble on the telescope-level comes in the middle, to set the gun for quadrant elevation?
A. Because by definition quadrant elevation is the angle between the axis of the bore and the horizontal plane, and when the bubble is in the center of the level the telescope is horizontal and the axis of the gun makes an angle with it equal to the elevation set on the arc.
Q. Name and point out the following parts of the rapid-fire sight: Telescope, objective, eyepiece, interior and exterior deflection-scales, micrometer-head, deflection-screw, open sights, dew-cap, lugs, and thumb-screws.
A. See Fig. 70.
Q. What is one point on the deflection-scale equal to at the target?
A. One five-hundredth of the range in yards; thus one point equals 2 yards at 1000 yards, 4 yards at 2000 yards, and so on.
Q. EXAMPLE: The range is 5000 yards, and the drift for that range is found in the range-table to be 12 minutes; how would you set your deflection-scale on the telescopic sight?
A. "_Fire left_" 12 minutes, or 4 points.
Q. Why?
A. Because drift in our service is always to the right, and to overcome this drift and make the projectile hit the target we will have _to fire to the left_ this 12 minutes due to drift.
Q. EXAMPLE: The range is 5000 yards, and the component of the wind perpendicular to the line of fire is 20 miles, giving from the range-table correction for drift equal to 12 minutes and wind 6 minutes. The wind is blowing from right to left. How would you set your sight?
A. "_Fire left_" 6 minutes.
Q. Why?
A. Because, as shown above, the drift alone would require the sight to be set at "_Fire left_" 12 minutes, and if the wind correction is 6 minutes and is blowing from right to left, to overcome this wind and make the projectile hit the target we would have to "_Fire right_" 6 minutes. Therefore, if the total setting of the sight is to be "_Fire left_" 12 minutes plus "_Fire right_" 6 minutes, the final or resultant setting should be "_Fire left_" 6 minutes.
_Note._--The corrections for wind and drift are usually found at the same time from a chart, correction-board, or table.
Q. EXAMPLE: The time of flight is 10 seconds (this is found from the gun commander's range-table, knowing the range); how would you determine the correction for travel with a telescopic sight?
A. Set the sight at zero. Traverse the gun until the vertical hair cuts the target. Signal: "Stop traversing," and count the number of seconds time of flight (10), moving by the right hand the deflection-screw, to keep the vertical hair on the target. When 10 seconds are counted stop turning the deflection-screw. Where the vertical hair now rests is the correction for "travel during time of flight." Since to "_Fire left_" we move the vertical hair to the _right_, this correction for travel found will have to be set for "_Fire left_," or on the other side of the scale, if the target is moving from _right_ to _left_. If it is moving from _left_ to _right_, the correction found will have to be set "_Fire right_." In other words, always set the cross-hair in the opposite direction from the motion of the vessel in making the correction for travel. This also applies to open sights.
Q. EXAMPLE: If you were given the range, a gun commander's range-table, a correction for wind and drift equal to "_Fire left_" 9 minutes, and the target were moving from right to left, how would you proceed to determine the setting of your sight?
A. First, determine by the above method the correction for travel during time of flight (time of flight being found in the gun commander's range-table). Set this on the sight. Suppose it were "_Fire left_" 3 minutes.
Second, use this position of the vertical hair as a new zero, and move the vertical hair to "_Fire left_" 12 minutes. That is, "_Fire left_" 3 minutes plus "_Fire left_" 9 minutes equals "_Fire left_" 12 minutes.
If the travel had been "_Fire right_" 3 minutes, then by moving the scale "_Fire left_" 9 minutes, the final setting of the sight would have been "_Fire left_" 6 minutes.
Q. From the table on page 129 find the number of yards 3 points on the telescopic sight are equal to at 7000 yards range.
A. 18 yards.
2. Point or describe the location of the following parts of the telescopic sights, Model 1904:
Eye-lens cover. Gear-case cover and cover for Dial. range drum. Focusing ring. Telescope lamp-holder. Peep-sight. Sight-shank elevation-scale. Eye-end telescope clamp. Elevation-guide. Deflection worm knob. Sight-arm. Telescope tube. Yoke-shaft. Elevation rack. Bearing for yoke. Cell-end telescope clamp. Yoke. Objective shutter. Lamp-bracket for range drum Cradle. and elevation-scale. Cross sight. Elevation worm. Yoke-cap. Focusing sleeve nut. Deflection-pointer bracket. Deflection scale. Fulcrum. Elevating gear-shaft. Elevating wheel and hub. Deflection worm. Sight-bracket. Eye-lens. Plug connection for lamps. Field lens. Lamp-holder for deflection Cross-wire ring. scale. Cross wires. Range drum. Erecting prisms (Porro). Objective.
A. See Figs. 71 and 72.
TABLE OF VALUES IN YARDS OF POINTS OF DEFLECTION.
------------------------------------------------- Min. | 3 | 6 | 9 | 12 | 15 ------------------------------------------------- Points. | 1 | 2 | 3 | 4 | 5 ------------------------------------------------- Range. | Value of Points in Yards. ------------------------------------------------- 1000 | 1 | 2 | 3 | 4 | 5 2000 | 2 | 4 | 6 | 8 | 10 3000 | 3 | 6 | 9 | 12 | 15 4000 | 3 | 6 | 9 | 12 | 15 5000 | 4 | 8 | 12 | 16 | 20 6000 | 5 | 10 | 15 | 20 | 25 7000 | 6 | 12 | 18 | 24 | 30 8000 | 7 | 14 | 21 | 28 | 35 9000 | 8 | 16 | 24 | 32 | 40 ------------------------------------------------- 10000 | 9 | 18 | 27 | 36 | 45 -------------------------------------------------
_Note._--This table is only _approximate_. It is true within 1 yard, which is sufficiently accurate for all firing under Case II.
Q. Where is the sight placed under cases one, two, and three?
A. On the trunnion for case one, to give both elevation and direction. On the sight standard for case two, to give direction only (quadrant elevation is set by the elevating-arc). It is not intended to be used at all in case three, but, of course, it could where the quadrant elevation is to be set by the sight instead of by the elevation-arc. It will then have to be placed on the trunnions.
Q. Define cases one, two, and three.
A. Case one, where direction and elevation are given by the sight on the trunnion. Case two, where direction is given by the sight, and elevation by the quadrant or elevating-arc. Case three, where direction is given by the azimuth-circle, and elevation by the quadrant or arc.
Q. What is the difference between the axis of the bore and the line of departure?
A. The jump. (See Fig. 63.)
Q. What is the line of sight?
A. Line joining the target, the point of the front sight and the peep of the rear sight; or with telescopic sights, the line joining the target and the intersection of the vertical and horizontal hairs in the sight. (See Fig. 63.)
Q. Define time of flight.
A. The time it takes the projectile to leave the bore till it strikes.
Q. What is a _tangent_?
A. A straight line which touches but one point on the circumference of a circle and is perpendicular to the radius at that point.
Q. Define angle of fall.
A. It is the angle which the tangent to the trajectory at the point of impact makes with a line parallel to the line of sight at this point.
Q. What is the line of departure?
A. The prolonged axis of the bore at the moment the projectile leaves the muzzle.
Q. What is the line of fire?
A. The prolonged axis of the bore before the gun is fired.
Q. What is the axis of the bore?
A. The line passing through the centre of the bore from breech to muzzle.
Q. What is the angle of departure?
A. The angle included between the _line of departure_ and the horizontal plane.
Q. Define drift.
A. It is the deviation due to the rifling in the gun to the right or left of the vertical plane passing through the axis of the bore, or plane of fire. It is always to the right in the U. S. service.
Q. To what in a telescopic sight does the front sight on an open sight correspond?
A. The intersection of the cross-hairs.
Q. To what does the rear sight correspond?
A. The eye-lens.
Q. What is the trajectory?
A. The path of the projectile in the air.
Q. How is the velocity of the wind determined?
A. By the anemometer. First take the reading of the discs on the anemometer and note the time. After six minutes have elapsed read the scales. Take the difference of the scales and multiply by 10, which gives the velocity. (See Fig. 73.)
For example: Suppose at 10:05 A.M. the reading is 62 miles, and at 10:11 A.M. the reading is 63 miles. If in six minutes it goes one mile, in sixty minutes it will go ten times, or ten miles per hour.
Q. How are the components of the wind in the direction of the line of fire and in a lateral direction determined? (See Fig. 74.)
A. First: Set the arrow on the disc to read the azimuth of the wind. (This is done automatically.)
Second: Set the little lever-arm at the azimuth of the line of fire.
Third: At the point on the lever-arm reading the velocity of the wind as determined by the anemometer, run the finger or a pencil along the nearest line toward the arrow, and where this line cuts the arrow is read the longitudinal component or the component in the direction of the line of fire.
Q. How are the wind components determined by the "new method"?
A. 1^o _target-pointer_ to velocity of wind on target-arm.
2^o Set _ring_ to azimuth of wind.
3^o Set _target-arm_ to azimuth of gun.
4^o Components are now read on the dial from the point indicated by the _target-pointer_. (See Fig. 75.)
Fourth: From this same point on the little lever-arm run a pencil along the nearest line parallel to the arrow, and where it intersects the diameter of the disc perpendicular to the arrow is read the component in the direction of deflection or the lateral component.
Q. What is a difference chart?
A. One that determines the differences in azimuth and range between the directing-gun and the gun for which it is constructed. It consists of a board having drawn on it circles of different diameters, which are the azimuth difference circles (the amounts being written on each circle). (See Fig. 77.)
Q. How is it used?
A. First: Set the range-arm on the given azimuth.
Second: Run the finger to the given range on the range-arm.
Third: The azimuth difference is read on the nearest circle that cuts the point where the finger last rests, and the range difference is read on the scale in red ink along the azimuth circle of the board. (See Fig. 77.)
Q. What is meant by muzzle velocity?
A. The number of feet per second a projectile is moving at the time it leaves the muzzle of the gun. It is also called Initial Velocity.
Q. From the following gun commanders' range-scale find the time of flight, sight elevation, and quadrant elevation for 4120 yards range.
GUN COMMANDERS' RANGE-SCALE. I. V. 2200. 8-inch B. L. R. Smokeless powder.
---------------------+---------+-----------------------+------------------- Quadrant Elevation. | | Sight Elevation. | ----------+----------+ Range. +------------+----------+ Time of Flight, | | | | | Seconds. Degrees. | Minutes. | | Degrees. | Minutes. | ----------+----------+---------+------------+----------+------------------- +4 | 16 | 4100 | -1 | 3 | 6-1/5 +4 | 18 | 4120 | -1 | 1 | +4 | 20 | 4140 | -0 | 58 | +4 | 23 | 4160 | -0 | 56 | 7-2/5 +4 | 26 | 4180 | -0 | 54 | +4 | 28 | 4200 | -0 | 51 | +4 | 31 | 4220 | -0 | 49 | 8-2/5 ----------+----------+---------+------------+----------+-------------------
A. 6-1/5 seconds, about; 1° 1' minus (depression); 4° 18' plus (elevation).
THE ATMOSPHERE-BOARD.
Q. Describe the atmosphere-board.
A. This is merely a graphic table by means of which the reference-numbers to be recorded on the atmosphere-aeroscope indicator can be determined from the readings of the barometer and thermometer. The arguments are barometer and thermometer readings, and the reference-numbers are indicated by diagonal lines. The thermometer axis is horizontal and the barometer axis is vertical. To increase the ease and rapidity of reading the barometer scale is graduated on a movable T square.
The method of construction is shown in Fig. 79.
_Operation._--Set the T square for the thermometer reading and note the diagonal line which intersects the fiducial edge of the T square the nearest to the barometer reading. The atmosphere dial is graduated to ½ per cent. The reading of the board should be taken to the nearest half reference-number.
SPECIAL APPARATUS FOR MORTARS.
Q. Point to the following parts of the Mortar Gun-arm:
Movable gun-arm. Yards range. Overlap. Elevations. Time of flight. Zones.
A. See Fig. 80.
SET-FORWARD RULER.
Q. Describe the set-forward ruler and explain its use.
A. First find the travel in yards per minute. Set the pointer (_a_) on the slide (_b_) at the number of yards on the scale of "yards travel per minute (_c_)." Then on gun-arm get time of flight for that point. The "set-forward point" will be the reading opposite time of flight on the scale of "yards travel during time of flight +1 minute (_d_)." (See Fig. 81.)
EXAMPLE.--After taking four observations on a target we find that in one minute's time it has traveled 200 yards. Set the pointer (_a_) at 200 yards on the scale (_c_). On the gun-arm we see that the time of flight for this point is sixty seconds. Therefore our set-forward point is 400 yards, as this is the reading exactly opposite the time of flight on scale (_d_). (See Fig. 81.)
Q. Describe and explain the use of the prediction scale.
A. The prediction scale is graduated in the same manner as the gun-arm (1" = 300 yards), and is used for finding the _predicted point_. After having marked four points on the board, showing the course of the target, place the prediction scale so that zero (0) is on the last point, or reading, and then mark off as many yards in advance of the last point as the first reads from zero. This point is known as the predicted point, and is used by the range officer only. As soon as the predicted point is found he sets his azimuth instrument at the given azimuth and when the target crosses the vertical wire in the instrument, he gives the signal "Fire." (See Fig. 82.)
DEFLECTION SCALE.
Q. Describe the deflection scale and explain its use.
A. The deflection scale is used to determine azimuth corrections for mortars. After the "set-forward point" has been obtained, the plotter sets the gun-arm on it and by means of the _indicator_ determines the zone, range, and elevation of the target. The operator reads the straight azimuth from the gun-azimuth scale and gets the zone and elevation from the plotter. He then sets the elevation scale-pointer at the given elevation, turns crank moving small azimuth pointer to the azimuth he obtained from gun-arm scale; then by referring to the large azimuth scale-pointer he reads the corrected gun-azimuth, which he sends to the pits together with zone and elevation. Should it become necessary to make a correction for drift, turn the deflection-scale knob, either to right or left, as the case may be, as 3 = normal. (See Fig. 83.)
_Note._--This apparatus depends upon the fact that the drift is the same for the same elevation in every zone except the eighth. In this zone the instrument cannot be used as now constructed.
WARSHIPS.
Q. State the general appearance, average length, beam, draft, speed, tonnage, thickness of belt and deck armor of battleships, armored cruisers, protected cruisers, torpedo-boat destroyers, and torpedo boats.
A. See Table "A."
Q. Point from Figs. 84 and 85 the following:
Sloop. Schooner. Ship. Bark. Barkentine. Brig. Brigantine. Steam yacht. Revenue cutter. Gunboat. Protected cruiser. Armored cruiser. Battleship. Torpedo-boat destroyer. Torpedo boat. Submarine. Monitor.
TABLE A.--TABLE OF WARSHIP CHARACTERISTICS.
----------------------------+-----------------+----------------+ | | | Characteristics. | Battleships. | Armored | | | Cruisers. | ----------------------------+-----------------+----------------+ |Large, massive |High freeboard, | | appearance, | fine | | low freeboard, | lines, fairly | General Appearance. | large, turrets, | heavy guns | | heavy | and turrets, | | guns, heavy | great | | armor, | length as | | moderate | compared | | speed. | to beam, | | | high speed. | ----------------------------+-----------------+----------------+ Average length | 400 feet | 500 feet | Average beam | 75 feet | 67 feet | Average draft | 29 feet | 28 feet | Average speed | 17 knots | 21 knots | Average tonnage | 15,000 tons | 11,000 tons | Aver. thickness, belt armor | 13 inches | 5 inches | Aver. thickness, deck armor | 3 inches | 3-1/3 inches | ----------------------------+-----------------+----------------+
----------------------------+-----------------+--------------+------------- | | Torpedo | Characteristics. | Protected | Boat | Torpedo | Cruisers. | Destroyers. | Boats. ----------------------------+-----------------+--------------+------------- | High freeboard, | Very long, | Small size, | moderate | narrow | long, | size, very | beam, | narrow, General Appearance. | fine lines, | high | not as | light armament,| bow, low | many | narrow | freeboard, | smokestacks | beam. | many | as a | | smokestacks.| destroyer. ----------------------------+-----------------+--------------+------------- Average length | 350 feet | 250 feet | 175 feet Average beam | 50 feet | | Average draft | 22 feet | | Average speed | 22 knots | 31 knots | 28 knots Average tonnage | 5000 tons | 350 tons | 200 tons Aver. thickness, belt armor | none | | Aver. thickness, deck armor | Protective | | | deck 2 ins | | ----------------------------+-----------------+--------------+-------------
Q. What vessels are unarmored?
A. Gunboats, torpedo-boats and destroyers.
Q. What is the best part of a ship to attack at long range?
A. The decks.
Q. What part should rapid-fire guns attack at short range?
A. Sides, ends, and small turrets, and guns protected only with shields. These rules, however, may vary with height of battery, form of attack, and class of ships attacking.
Q. How are ships of the U. S. Navy distinguished, knowing their names? (See Fig. 86.)
A. Battle-ships are generally named after States (except the Kearsarge), cruisers after large cities, gunboats after historical cities as a rule, coast-defense monitors have Indian names, torpedo-boats and torpedo-boat destroyers are named after heroes of wars. (The above rules have a few exceptions.)
Q. From the silhouettes on Fig. 86, Ships of the U. S. Navy, find a battle-ship, a high-speed cruiser, a gunboat, a coast-defense monitor.
A. Signal numbers 20, 30, 23, 6.
Q. Find from Figs. 86 to 93 inclusive, a battle-ship, cruiser, monitor, and gunboat of the navies of Germany, France, England, Japan, and Russia.
Q. What thickness of Krupp cemented armor will a six-inch gun penetrate at 5000 yards? An eight-inch gun? A ten-inch gun? A twelve-inch gun, model 1895? A twelve-inch, model 1900?
A. Six-inch penetrates 3 inches; eight-inch, 5 inches; ten-inch, 7 inches; twelve-inch '95, 10 inches; twelve-inch 1900, 12 inches. (See Armor-attack Sheet, Fig. 87.)
EXAMINATION FOR TORPEDO-COMPANY GUNNERS.
SECOND-CLASS GUNNERS.
_Ammunition, Nomenclature, and Service of Piece._
_Note._--In the following series of questions and answers the new and adopted system only is included.
Q. What guns are usually assigned to torpedo companies?
A. R. F. guns, principally 3-inch.
Q. Give a rough outline of the general operation of the system of submarine mines.
A. A submarine mine is a ball-shaped iron case filled with high explosive. Several of these are _planted_ across a channel and held below the surface of the water by heavy anchors. From each mine is run a single-core cable. All these cables join the wires of a multiple-core cable which runs to the "mining casemate." In this building are electrical devices for firing the mine either when it is struck by the enemy's ship (called "contact-firing,") or at the mine-commander's will ("observation-firing"). This firing is accomplished by sending an electric current through the cable to the mine. Inside the mine is an electric fuse. The return-circuit is by ground. (The details of electrical and engineering features and wiring are not required of a second-class gunner.)
Q. What ammunition is used in the 3-inch R. F. gun?
A. A cartridge case of solid drawn brass about 23 inches long containing a powder charge in the base of 5 pounds of smokeless and a projectile weighing 15 pounds in the top. Armor-piercing shell and shrapnel are also used. The saluting charge weight, 2 pounds.
Q. What primer is used?
A. The Frankford Arsenal 110-grain igniting. (See No. 2, Fig. 97.)
Q. Name the principal parts of this primer.
A. Body, obturating-cup, vent-closing disc, primer charge, end-closing wad. (See No. 2, Fig. 97.)
_Note._--The following data is given for general information only:
Weight of the piece, 1722 pounds. Length, 154·5 inches. Length of bore, 50 calibers. Number of grooves, 24. Twist of rifling, 1 in 50 calibers at the breech and increasing to 1 in 25 at the muzzle. Kind of powder, smokeless. Weight of charge, 5 pounds. Weight of projectile, 15 pounds. Muzzle velocity, 2600 feet per second. Muzzle energy, 702·9 foot-tons. Penetration in steel, at the muzzle 5·37 inches; at 1000 yards, 3·82 inches; at 2000 yards, 2·72 inches; at 3000 yards, 1·94 inches.
Q. Point out the following parts of the breech-block:
Block. Carrier plate. Carrier plate ring. Locking spring. Lever handle. Threaded sectors. Slotted sectors. Extractor. Firing pin.
A. See Figs. 17 and 19.
Q. What acts as the gas check?
Q. How should a 3-inch R. F. breech-block be cared for--kind of oil, etc.
A. Same as for any other heavy gun. (See first part of book.)
Q. Describe how the extractor and firing pin work.
A. (This will have to be done at the gun.)
Q. Describe the action of the lever handle.
A. (Do this at the gun.)
Q. Point out the following parts of the gun and mount (masking parapet mount):
Outer base. Inner base. Counterweights. Recoil-cylinder. Piston-rod. Pivot. Pivot yoke. Trunnions. Traversing clamp. Elevating clamp. Range drum. Cradle. Elevating gear. Sight. Night Sights. Ratchet lever. Lever pawl. Ratchet-wheel pawl. Pivot socket and clamp. Shield. Muzzle. Breech. Bore. Chamber.
A. See Figs. 17 and 19.
Q. How are rapid-fire guns cared for and kept in working order?
A. Same as the 12", 10", 8", 6", etc. (Given under heading for second-class gunners, Gun-companies.)
Q. How many men constitute a gun detachment for the 3-inch R. F. gun (masking parapet mount) and give the posts of each?
A. Chief of detachment, gun-pointer, and 5 men.
POSTS. Chief of detachment, 2 yards to the right of the carriage, facing it.
Gun-pointer, immediately in rear of the shoulder piece, facing to the front.
No. 1, 2 feet to the right and rear of the breech facing it.
No. 2, 2 feet to the left and rear of the breech facing it.
No. 3, on the right of the gun, near the elevating clamp, facing to the front.
No. 4, 3 feet in rear of the breech facing it.
No. 5, near the ammunition recess, facing the gun.
The posts of the gun detachment as given above are for inspection and preparatory to the service of the gun.
The men resume their posts on the completion of any duty requiring them elsewhere.
The chief of detachment and gun-pointer go wherever their presence is necessary.
Q. Give the duties of the gun commander, chief of detachment, and gun-pointer.
A. _The gun commander_ indicates the target, repeats the commands "Commence firing" and "Cease firing," announces the kind of projectile to be used, the order of fire, and, in restricted fire, the number of shots and the firing interval. He is responsible to the battery commander for the condition of the material and the efficiency of the personnel of his command, sees that the guns, magazines, equipments, and implements are properly secured after the day's drill.
_The chief of detachment_ is responsible that the gunner identifies the target. He is particularly charged with seeing that his piece is properly loaded and that the precautions for safety in case of misfires are carried out. At the command "Cease firing" he will cause the breech to be opened.
_The gun-pointer_ is responsible for the proper regulation of the current for the lights of the night sights. He adjusts the sight in its seat and sets the elevation and the deflection scales for the indicated range and deflection. He aims the gun and fires as soon after the command "Ready" as the piece is aimed. He will observe the splash of his shots if possible and when necessary make the proper correction on his sight. In connection with the gun commander he determines the deflection correction for travel of target, using the deflection scale for the purpose.
Q. Give the duties of the members of the detachment for loading and firing.
A. _The chief of detachment_ indicates the target and range and commands: 1. _No_. --, 2. _With_ (such projectile), 3. _Commence firing_ (or, so many rounds, _commence firing_).
He repeats the command _cease firing_.
After the first round the projectile is named only when a different kind is ordered and the gun is loaded without command immediately after it is fired.
_The gun-pointer_, when the gun has the proper elevation, commands and signals _clamp_. He fires by lanyard and in simulated firing calls out _fire_ when he pulls the lanyard, as a signal to load.
_No. 1_ opens the breech, closes it as soon as the cartridge is inserted, and calls out _ready_ as soon as he is clear of the recoil.
(If there is any difficulty in opening or closing the breech, he examines the threads of the _breech-block_, wipes off any dirt found, and oils the mechanism.)
_No. 2_ receives a round of ammunition from No. 5 and inserts it in the chamber.
(If there is difficulty in opening or closing the breech, he examines the threads of the _breech recess_, wipes off any dirt found, and oils the threads if they become dry.)
_No. 3_ clamps the gun in elevation at the gun-pointer's command and unclamps immediately after the gun is fired.
_No. 4_ receives the empty cartridge case as it is ejected and lays it aside.
_No. 5_ brings a round of ammunition of the designated kind from the recess and passes it to No. 2.
MATERIAL AND DUTIES OF THE LOADING-ROOM.
(Except electrical principles involved.)
Q. What apparatus is used in making a Turk's head?
A. A navy knife and tool-box "D" is required. Besides the tools the box should be equipped with a supply of Turk's head collars and marline.
Q. What is used in making a telegraph-joint?
A. A pair of pliers, navy knife, and, where insulation is desired, okonite tape.
Q. What is used in making a joint to be used under water?
A. A navy knife, tool-box "D," junction-boxes in which to clamp the Turk's heads, and the material for making okonite joints or the cores. These materials are, okonite tape, cement, Manson tape and tin-foil. A torch is needed for vulcanizing the joint. Brass jointers are sometimes used in making the joints.
Q. Point out all the parts of an assembled mine.
A. See Fig. 98.
Q. Point out the following parts of a compound plug: circuit-closers; transformer; loading-wire; fuse-wires; fuses; fuse-can; bursting-charge; set-screw for fuse-can; lead or graphite gasket for same; rubber packing; brass washers; fuse-can cap; lower tube set-screw; gland; lower tube; plug proper; loading-wire.
Q. Name some of the duties in the loading-room.
A. Loading mines with explosives; assembling them complete to the single-core cable; preparing compound plugs, cables, and raising-ropes; in other words, preparing a mine for planting in the harbor, except attaching the anchor and mooring-rope.
Q. Make a telegraph-joint.
A. See Figs. 99 and 100.
Q. Make a Turk's head.
A. See Fig. 101. Trim the ends square: 15 inches from it place a wrapping of a few turns of marline overlapping each other and secured by a square knot. Slip on the collar, flat side against the stop of the marline; bend the iron wires back over the collar and cut off 4 inches from one and 6 inches from the next, alternately. Bend the wires with the pliers as so to closely fit and crimp the collar. Beginning at the Turk's head, wrap closely with marline so as to bind the wires to the cable. The jute covering and serving maybe bent back over the wires, or it may be cut off: in cutting turn the edge of the knife away from the cable.
Q. Make a taped joint, place it in salt water for 30 minutes and test.
A. 1^o Bare the two ends of wire about ¾ inch.
2^o Join by brass jointer, then crimp.
3^o Cover with rubber cement.
4^o Wrap with tape, about five or six layers.
5^o Wrap with tin-foil.
6^o Wrap with Manson tape.
7^o Vulcanize for about 30 seconds and unwrap tin-foil and Manson tape and rewrap with new Manson tape.
Q. How is a taped joint vulcanized when in the "distribution-box boat"?
A. By tying a piece of waste soaked in kerosene to a wire lighting, and using this as a torch for heating the joint.
Q. Explain the method of preparing a compound plug.
A. This will have to be learned by practice and constant instruction at the loading-room.
_Note._--The transformer, fuse, can, etc., on the compound plug are still in a state of experimentation and no method for the assembling of the latest design has been adopted as yet.
Q. How do you test the transformer?
A. With a circuit detector or galvanometer and a dry cell, as shown in figure.
_Note._--In case of a break in the coil, Fig. 102, there would be no current flowing in galvanometer and no deflection of the needle would be indicated.
The wires that should show _closed_ circuit are the two red wires and the black wire and transformer case. Those that should be _open_ are the black, and either red wire. (See Fig. 102.)
Q. How are fuses tested?
A. With a dry cell and a circuit detector. A closed-circuit test is all that is necessary. This should always be done under the supervision of an experienced electrician.
Q. What apparatus is used in preparing a compound plug complete?
A. Bench vise, S-wrench, large monkey wrench, screw driver, small pliers, navy knife, loading wire, cotton-braided wire, priming charge, fuses, rubber packings, brass washers, followers, lead washers, set screws, red lead or ruberine, circuit detector, brass jointers, rubber tape.
Q. What is the method of numbering mines?
A. Facing in the direction of the expected approach of the enemy's ships, mines are numbered from left to right, beginning with No. 1.
Q. How are groups numbered?
A. In the same manner. No. 1 group on the left, No. 2 next toward the right, etc.
Q. How are the mooring-ropes prepared, and what are the rules for length of mine cables and of mooring-ropes?
A. The mooring-cables are cut off with square ends and the ends passed through the holes in the mooring-sockets. The strand and wires are untwisted and spread out for a length equal to the length of the socket-hole. The rope is then pulled back until the loose ends are about flush with the top edge of the hole; a piece of marline is tied about the rope below the socket. If necessary to hold the socket a piece of burlap may be wrapped around below the socket and a fold allowed to fall over the hand. Generally means can be found to set the socket upright while pouring full of alloy. Great care must be taken to see that there is no water or surplus oil on the socket or mooring-rope before pouring the alloy. (Nine parts lead, 1 part antimony.)
Mines are planted with a submergence of 5 feet below mean low water.
Where ordinary anchors are used the mooring-ropes must be prepared for depths obtained by sounding. If sockets are used, the ropes for No. 32 cases are but 10 feet less than the ascertained depths at mean low water. This allows 5 feet for submergence and 5 feet for mine, mine bail, sockets, shackles, and anchor. For the larger mine cases an additional allowance must be made for the length of the cylindrical part of the case. Finally each mooring-rope is tagged at each end with the number of the corresponding mine.
Mine cables are cut to the following lengths, plus twice the approximate depth of the water:
Feet.
No. 1 1425 No. 2 1225 No. 3 1025 No. 4 825 No. 5 725 No. 6 625 No. 7 525 No. 8 475 No. 9 425 No. 10 375 No. 11 425 No. 12 475 No. 13 525 No. 14 625 No. 15 725 No. 16 825 No. 17 1025 No. 18 1225 No. 19 1425
Each end of each cable is tagged with the number of the corresponding mine.
MATERIAL FOR AND DUTIES ON THE WATER.
Q. What apparatus is taken out on the distribution-box boat?
A. One distribution-box, 1 buoy for same, 1 mooring-rope for attaching buoy to distribution-box, 1 anchor sufficiently heavy to hold distribution-box boat, 1 anchor buoy (keg), and rope for same, 2 anchor shackles (1 for anchor and 1 for box), 1 pair field glasses, alcohol, 2 alcohol lamps, cable tags, Turk's head, collars, cotton waste, 2 files, 2 hammers, 2 heavy lines, knives, marline, 2 marline spikes, 1 megaphone, 2 monkey wrenches, 2 pliers, protective tape, rubber cement, rubber tape, 2 scissors, tin-foil, telephone, brass connectors, lashings.
The planter may locate the distribution-box boat anchor, and in that case it, together with its buoy, would not be taken out in the distribution-box boat.
Q. How and in what way are the cores of cable numbered?
A. They are numbered by the non-commissioned officer in charge of the boat, who establishes communication with the casemate, using the boat telephone, and working under the instructions of the casemate electrician.
Nos. 1, 13, and 19 are easily selected by means of their special marking; No. 19 is the center core; No. 13 is the marked core in the inner row of six; and No. 1 is the marked core in the outer row of twelve.
In the seven-cored cable there are no marked cores, the cores being numbered under the instructions of the casemate electrician.
Q. How is multiple cable laid?
A. It is transported to the planter by tramway, hoisted by steam-derrick to the _forward jacks_; it is then joined to the "shore ends" of the cable; the planter then steams to the distribution-box buoy and passes the end of the cable to the distribution launch, where a Turk's head is made and all is ready to receive the single-core cables for planting.
PLANTING OF MINES.
Q. How are single-core cables prepared?
A. 1^o If the single-core cable has not been cut and coiled in loading-room, place reel on jacks, cut 20 feet off the end, unreel to lengths given previously, cut and tag with mine number.
2^o Carry cable No. 19 on port side to after deck, keeping tagged end forward and coil in figure eight, keeping tagged end on bottom.
3^o Make Turk's head on each end, first slipping tagged end through a mine cap.
4^o Continue the operation above in the following order:
Nos. 1 to 9 starboard side.
Nos. 10 to 19 port side.
Q. Describe how to place mines aboard and to attach to cables preparatory to being planted.
A. 1^o Place mine buoys, anchors, mooring-ropes, raising-ropes, shackles, sister hooks, etc., aboard forward and in convenient places.
2^o Place loaded mines aboard last, nine on starboard and ten on port.
3^o Cut to proper length the loading wire, make a tapped joint with S. C. conductor with Turk's head, previously prepared through mine cap.
4^o Fasten mine cap on mine, lash cables to bales, shackle mooring-rope to mine, and anchor, lash mooring-rope to mine cable every 5 feet (not done if automatic anchor is used).
5^o Cut raising-ropes 50 feet plus depth of water and attach one end to anchor by anchor knot, the other end to mine cable by two half hitches and a serving of marline, secure at a few other points.
6^o Attach about 60 feet small rope to mine buoys and mark this rope every 5 feet, slip free end through maneuvering ring, and tie to buoy. (The mines, anchors, cables, raising-ropes, and mine buoys are now ready to be planted.)
Q. Explain how to sling the mine and anchor, and prepare it to "let go."
A. 1^o Mouse upper hooks of differential blocks and lash well with marline the tripping hooks.
2^o Sling the anchor to the tripping hook on the differential block of the forward davit, swing clear of rail, and lower close to water.
3^o Perform similar operation with mine from after davit.
Q. Describe the method of planting.
A. The planter now moves to the distribution-box boat, the latter to the port, No. 10 cable is passed to the same, planter now moves to No. 10 buoy, and when mine is abreast, the command "let go" is given.
The tripping hook of the mine is released first, and that of the anchor immediately after. The planter now circles to starboard, passes to the rear, and comes up to the distribution-box boat to the starboard. No. 9 is now passed, and planter moves forward to the position of this mine, plants it, and returns to distribution-box boat to repeat the operation till the group is planted.
CAUTIONS TO BE OBSERVED.
Men operating tripping hooks keep their feet free from all cable. Men on after deck must keep entirely free of all cable while being spent when planter is passing from distribution-box boat to mine buoy.
If dynamite is used as explosive all mines should be covered with paulines or burlap to protect them from the direct rays of the sun.
Q. Name the apparatus on the boat used in planting mines.
A. Derricks, catheads, snatch-blocks, steam-winches, insulated cable, cable-drum frames, circuit detector, boat-hooks, sounding-lines graduated to feet, davits, differential blocks, mooring-ropes, raising-ropes, buoyant mines and anchors, shackles and extra split pins for same, lashing-rope, alcohol, 2 alcohol lamps, 1 cable cutter, cable tags, Turk's head, collars, cotton waste, 4 files, 4 hammers, 6 heaving-lines, knives, marline, 2 marline spikes, 1 megaphone, 2 monkey wrenches, 4 pliers, protective tape, rope, rubber cement, rubber tape, 2 scissors, 1 set of stencil numbers, tin-foil, and a measuring line which has marks every 100 feet, with double marks at 300 and 600 feet.
Q. Give a method for marking the positions at which mines are to be planted.
A. The distribution-box is located first, a buoy and anchor being used as the mark. The center point of the group is located next, then the two ends of the group. The launch is directed over the spot selected from the map for the distribution-point by means of base-end instruments at the primary and secondary stations (these two instruments being set at the azimuth of the selected spot), and by signals from these stations the launch drops the anchor and buoy when it is at the intersection of the vertical cross-wires of each instrument. The launch marks the center of the group by moving approximately perpendicular to the line of mines to the desired distance. The line of mines is then determined by taking bearings and objects on shore (previously determined from the map) or by a similar method to that of locating the distribution-box buoy. Small planting-buoys are used for this purpose. The distribution-box buoy is usually a large keg or vinegar-barrel.
Q. How are soundings made?
A. By starting from either end of the "located group" and making a sounding at every 100 feet.
SMALL BOAT DRILL.
Q. Explain how a small boat used for marking and locating is managed, and give the commands necessary.
A. Upon leaving wharf, "Shove off!" performed by designated man.
To raise oars preliminary to rowing: "Up oars!" all oars being held vertically, opposite rowlocks, blades athwart boat.
To lower oars into the water: "Let fall!"; all oars are dropped easily into the water, without splashing, and quickly adjusted into the rowlocks, and then held in position of "Oars!" (See below.)
To move the boat forward: "Stand by to give way together!--GIVE WAY TOGETHER!" the boat being propelled forward at the latter command, all the men taking a slow uniform stroke, being guided by No. 1, feathering their oars as they come out of the water and move forward.
To cease rowing temporarily: "Oars!"; at this command the oars are raised out of the water to a horizontal position, blades parallel with the surface of the water.
To rest without taking oars from rowlocks: "In oars," when oars are drawn in and placed with handles under gunwales on opposite side of boat from rowlocks.
To move backward a short distance: "Back water!" executed opposite to "Give way together!"
To stop boat: "Hold water!"; the oars are held rigidly in the water, blades vertical.
To stop boat quickly, as if running on a rock: "About face! hold!" when the oarsmen turn about and hold blade in water, stopping momentum of boat.
To turn to port: "Pull starboard, back port!" (To turn to starboard, the opposite).
To make a landing: "In bow!"; the bow oar is raised vertically, then lowered into its place in the boat, and the bow man takes the boat-hook and guides boat gently into its place.
To cease rowing: "Way enough!"; the oars are raised vertically, shoved properly in place.
CORDAGE.
Q. Name the important knots used in mine-work.
A. Anchor-knot or fisherman's bend, square knot, clove-hitch, bowline, stopper, whipping, and short splice. (See plate of knots for gun-companies.)
THE U. S. MAGAZINE RIFLE.
See Examination for Second-class Gunners, for Gun-companies.
FIRST-CLASS GUNNERS.
CARE AND PRESERVATION OF MINE MATERIAL.
Q. How are mine-cases preserved and cared for?
A. They are painted light gray on the outside, and the screw-threads covered with a mixture of lard-oil and white lead (4 parts of tallow to 1 white lead). They are also either painted or covered with protective material on the inside. They are then stored on suitable racks inside a "torpedo storehouse."
Q. How are all bearing surfaces, such as screw-threads, prepared for storage?
A. By first thoroughly cleaning them with brushes, kerosene, waste, etc., and then covering with the above mixture of white lead and tallow.
Q. How is the motor-generator cared for?
A. Fill all oil-holes, and keep all parts free from dust and foreign material; see that all connections are tight; see that all brushes are in good condition, and replace worn ones by new ones. Use very fine _sandpaper_ for slight inequalities of the commutator.
Q. How are the mine-panel and the switchboard cared for?
A. See that all bolts to busses are tight, that all lamps are screwed home, that all contacts are clean and free from gum or dirt, that all switches work properly and all contacts correctly made.
Q. How should electric lights be cared for?
A. They should be kept clean and polished. Any snap-switch that sparks badly should be replaced. No verdigris should be allowed to accumulate on any brass fittings. When a lamp becomes dull or black inside, a new one should replace it. When any fuse is blown out, new ones should be put in. (Never use copper wire as a substitute for a fuse.)
Q. How should transformers be cared for?
A. Simply kept clean and in a dry place. They should be tested with a circuit-detector once in a while.
Q. How is the charging-generator cared for?
A. Keep free from dirt or rust, fill all oil-holes, clean the commutator with a dry rag, keep the brushes set so as to make good contact, and when not in use cover with a rubber paulin.
Q. How is the oil-engine cared for?
A. The oil-engine should be kept clean and nicely painted, all oil-holes filled, the water-tank filled and free from mud and sediment, the vaporizer examined from time to time and kept free from packed carbon, the piston clean and well oiled, the poppet-valves tight and free from any clogging material, the starting-torch clean and free from soot.
Q. When putting a piece of machinery out of commission what is done?
A. All bearing surfaces are exposed, cleaned, and covered with white lead and lard-oil or a similar substitute preservative. All small loose parts are removed, covered with cosmic wrapped in burlap, and stored under cover. The machine should also be housed.
Q. Name some of the principal cleaning materials.
A. Steel scrapers, button and wire brushes, waste, pomade, sandpaper, emery and crocus cloth, gasoline, kerosene, and alcohol.
Q. Name some preserving materials.
A. Cosmic, white lead, red lead, raw linseed oil, turpentine, beef tallow, drier, lamp black, pumice stone, varnish, asphaltum varnish, paint brushes, shellac, graphite paint and insulac.
Q. Name some uses of each.
A. Cosmic: Covering bright parts of engines, generators, motors, etc., when out of commission.
White Lead: (4 pts. W. L. to 1 of tallow) Used on screw-threads of mine cases, steel threads, compound plugs, bolts, nuts, washers, surfaces of flute joints, etc.
Caution: _Never use this on a joint where electrical contact is to be made_.
Red Lead: (100 pounds red lead ground in linseed-oil with 5 gallons raw linseed added.) On mine cases after being scraped. As a preliminary coat for iron surfaces of engines, generators, etc.
Raw Linseed, Turpentine, Drier, and Lampblack, for making different kinds of paint. Turpentine is also used to clean brushes, etc.
Tallow: For mixing with white lead to form a preservative.
Pumice-stone: When powdered and mixed with oil is used to rub down surfaces, as the first coat of varnish on an engine.
Varnish: As a finishing coat for metal and wood surfaces not exposed to heat or water.
Asphaltum Varnish: For painting anchors, distribution-boxes, mooring-sockets, shackles, sister hooks, junction boxes, iron work of operating boards and power panels, etc.
Shellac: For covering decks, spars, etc.
Graphite Paint: For painting hot parts of engines, etc.
Insulac: For preserving insulation on electrical instruments, etc.
Q. How is an engine painted?
A. All hot surfaces should be painted with black graphite paint. All other surfaces after being thoroughly scraped and sand-papered should be given a priming coat of red-lead paint. This should be lightly rubbed down with powdered pumice and oil, then two coats of preferably steel color metal paint applied and rubbed. Two coats of varnish are now applied and rubbed with pumice as above, after each coat becomes thoroughly dry.
HANDLING HIGH EXPLOSIVES.
Q. Name some high explosives used in submarine mining.
A. Wet gun-cotton principally, dynamite, and other high explosives that can be readily purchased in commercial life in case of emergency.
Q. Why is wet gun-cotton to be preferred as a high explosive?
A. Because it is perfectly safe to handle. It can only be detonated by first detonating a small piece of dry gun-cotton placed near it.
Q. What are some important precautions to be observed when loading mines?
A. 1^o Always wear rubbers when entering the magazine to get the explosive. (The main supply is always kept in a cool magazine.)
2^o Never drop or slide along the floor boxes of high explosive.
3^o Do not expose high explosive to sun's rays or heat.
4^o Bring only one box to the loading-room at a time, then, when used, burn the box and sawdust in a safe place.
5^o Place canvas or burlap on floor of loading-room, then place mine on skids upon this.
6^o Use rubber gloves when handling dynamite.
7^o Sweep floor frequently and throw sweepings in water.
8^o After mine is loaded by use of funnel, carefully clean threads with a soft brush, then smear plenty of ruberine on threads.
9^o Never saw or bore a dry guncotton cake.
10^o Never open a mine loaded with dynamite without first consulting an officer.
11^o _Never thaw out dynamite near a stove._
Q. How is dynamite that is frozen thawed out?
A. Place the frozen dynamite in an open watertight can. Place this can in another can of warm water, such that the heat of the warm water only will do the thawing.
KNOWLEDGE AND USE OF THE PLOTTING-BOARD AND AZIMUTH INSTRUMENT.
Q. Describe the plotting board.
A. It is the same as that used for guns except the gun arm and its parts are not used. The scale is ordinarily 100 yards = 1 inch.
Q. How is it used for mine firing?
A. The ship is _tracked by plotting_ points of intersection of the primary and secondary arm every 20 seconds. After several positions are plotted a point is predicted at a certain interval of time ahead and by means of a "combination prediction and speed scale" the time of the arrival of the ship over the mine which was previously plotted on the board is obtained and this is the time of firing that mine. This is called "judgment firing."
Q. Describe and use the azimuth instrument.
A. See Examination for First-class Gunners for Gun-companies.
BATTERIES, GENERATORS, AND SEARCH-LIGHTS.
Q. Name the batteries used in mine work.
A. Casemate battery (storage--40 cells) and boat telephone battery (either storage or dry cells sufficient to give 15 volts).
Q. Describe the casemate battery. (See Fig. 103.)
A. This is a storage-battery of the standard chloride accumulator type. It is composed of 40 cells, type D-5 (D = size of plate 5, the number of plates). D-5 has two positive and three negative plates, each 6" × 6". Positive plates are of a brownish color, negative grayish. These plates are contained in a glass jar nearly filled with electrolyte (one part sulphuric acid to five parts distilled water by volume makes electrolyte of 1·210 specific gravity. _The acid must be poured into the water._)
These glass jars are placed in trays of sand and the trays rest on glass insulators. The normal charge and discharge rate of this battery is 5 amperes, although in starting the motor generator a much higher current is drawn from the battery. The voltage is about 80.
Q. What precautions are necessary to keep it in order?
A. 1^o Do not overcharge, overdischarge, or allow to stand completely discharged. (Battery should be charged when discharge is 1.8 volts per cell.)
2^o Keep plates covered with electrolyte about ¾ inch above top of plates. If not at proper height add distilled water.
3^o Keep cells free from sediment.
4^o A record of each cell (voltage and specific gravity) should be kept each time the battery is charged, and this should be done about once a week.
5^o The indications of a complete charge are: when positive plates have a deep chocolate color, negative light slate, cells gas freely, each cell reads about 2·5 volts, and 1.210 specific gravity, and when no perceptible rise in voltage occurs for a lapse of 10 to 15 minutes.
6^o If any low cells develop, bring them back into condition immediately.
(_a_) If voltage is very low, look for sediment or foreign matter, then charge separately.
(_b_) If specific gravity is very low take out some electrolyte and add 1.200 specific gravity electrolyte. (This used to be 1.400.)
7^o Keep battery-room well ventilated, especially while charging.
8^o Never bring an exposed flame into battery-room while charging. (The gases given off are explosive when mixed with air.)
9^o Keep the floor and all parts of the room clean, iron, copper, and metal work free from corrosion; keep all connections tight and clean; never allow verdigris to collect _anywhere_.
Q. Describe a searchlight.
A. It consists of an iron cylinder mounted on an iron pedestal in a yoke. The cylinder contains a parabolic mirror in the back, a series of glass strips in the front, and two "carbons" in the middle.
The electric current in passing through the carbons heats the points to a very high degree, producing a brilliant light. This light is reflected by the mirror towards the front, and the mirror, being of a curved form, also converges the rays of light. Underneath most searchlights are electric motors for traversing and elevating, and these motors are started or stopped by means of switches in a contrivance called a "controller," which is always placed at a distance from the light.
Q. Point out the following parts of a 36" searchlight: hand star-wheel for slow vertical movement; wheel for throwing out split nut used for connecting or disconnecting the drum from the base mechanism; wheel for slow horizontal movement; hand star-wheel for clamping turntable to center-pin for electrical control; wood handles on drum for moving drum by hand; hand-wheel for clamping hand star-wheel _A_ when electric control is used; controller-switch; controller-handle; controller fuse-box; controller-coupling for connecting cable from the projector; focusing-screw; socket for inserting wrench to operate lamp-switch used for cutting out feeding-magnet; socket for inserting wrench when feeding by hand; door used for adjusting the carbons and for cleaning the front door; door used when carbons are to be adjusted or changed; front door; door used when adjusting negative carbons or cleaning the mirror; horizontal peepsights; vertical peepsights; sliding case to be opened when lamp mechanism is to be inspected; projector main switch; latches for fastening base-sheeting; base-sheeting.
A. See Fig. 104.
Q. Describe the principal parts of the charging-generator?
A. The frame holds the field-magnets within which revolves an armature consisting of a winding of conductors and a commutator. Brushes made of carbon touch the commutator. The base rests on guides which permits of a motion of the generator to take up the slack of the belt.
Q. Point out the following parts of the generator: frame, base, field-coil, commutator, brushes, shaft, pulley, adjusting-screw, rocker-handle, magnet-frame bolt, brush-holder, brush stud-cable, rocker, bearing-cup, journal-box, pole-shoe, pole.
A. See Fig. 105.
Q. Point out the following parts of the oil-engine: cylinder-casing, vaporizer, vaporizer-cap, vaporizer-cover, vaporizer-cover lid, valve-box journal, valve-box sleeve, spray-nozzle, horizontal valve, horizontal-valve spring, vertical valve, vertical-valve spring, valve-box, valve-box screw-cap, valve-box coupling, overflow-glass, oil-pump can, oil-pump plug, oil-pump plunger, oil-pump plunger-spring, oil-pump plunger-head, oil-pump plunger-head guide, oil-pump gauge, oil-pump body, bed-plate, bearing-cup, splasher, oil-tank, oil-filter, filter-cock, worm-gear, gear-wheel, gear-guard, crank-shaft, crank-pin oiler, piston, connecting-rod, cam-shaft, governor-wheel, governor-pinion, governor-counterpoise, crank-shaft, governor-balls, governor-counterweight, air-valve cam, exhaust-valve cam, cam rollers, cam shifter, locking-handle, air-valve, exhaust-valve, cylinder-lubricator, cylinder-lubricator pulley, fly-wheel, fly-wheel key-guard, splasher.
A. See Fig. 106.
Q. Name some important points to be observed in caring for the generator.
A. 1^o Keep it perfectly dry.
2^o Keep it perfectly clean.
3^o Do not let pieces of iron or steel come near it when running.
4^o Keep the belt adjusted.
5^o Keep the bearings well oiled.
6^o Keep commutator clean and smooth (use fine sandpaper only, then a soft cloth and some oil or vaseline, then dry thoroughly).
7^o Keep brushes in trim and making good contact.
8^o Do not allow armature to heat badly, or it will suddenly burn out.
9^o Keep brushes on neutral point to prevent sparking. There is usually a mark on the dynamo to show this, if not, rock brushes until sparking ceases.
10^o Keep covered when not using.
11^o Keep connections clean and tight.
12^o Never overload it.
CASEMATE APPARATUS.
Q. Point out the following parts of the power panel:
Milli-ammeter and its protecting lamp. Double pole circuit-breaker. Single pole reverse current circuit breaker. Direct current ammeter (two way). Direct current voltmeter. Alternating current voltmeter. Double-pole double-throw lever switches. Double-pole single-throw lever switches. Receptacles. Plugs. Lamps. D. C. busses. A. C. " Charging rheostat. Field " Resistance for reverse current circuit-breaker. Terminal strips. Fuses. Fuse clips.
A. This must be learned at casemate.
Q. Point out the following parts of the operating panel:
Signal-block. Master " Mine " Cable terminal block. Single stroke gong and its switch. Red lamp and white lamp, and use of each. Resistance coil and its use. Earth terminal. A. C. " D. C. " A. C. jaw. D. C. " Testing switch on master block. Firing switch. Jumper. Testing switch on mine block. Automatic switch. Mine switch. Power switch. Automatic switch release. Solenoid.
The terminal block is provided with binding posts and clips.
A. This must be learned at the casemate.
Q. What is a motor generator?
A. A combination of a separate motor and a generator connected to the same shaft.
Q. What kind of a motor generator is the one in the casemate?
A. It consists of a motor driven by direct current and a generator which delivers alternating current. It has about 1-1/3 H. P.
Q. What is the voltage of each?
A. 80-110 for the motor and about the same for the generator.
Q. What is the object of the casemate transformer?
A. To raise the voltage from about 80 to 500 alternating current.
Q. Describe the mine transformer.
A. This will be learned in the casemate.
Q. Explain what switches you would set on power panel for automatic firing, the board having been previously tested and found by the electrician to be in order.
A. 1^o Put D. C. on busses { (_a_) Close double-pole circuit-breaker { (storage-battery), or by { (_b_) Close S. P. reverse current { circuit-breaker and switch No. 2 { to the right (post power), or { (_c_) Close S. P. reverse current circuit-breaker { and switch No. 2 to the left (casemate generator).
2^o Read voltage by plugging in proper receptacle.
3^o Close switch No. 3 up.
4^o " " " 4 " (or down).
5^o " " " 9 " ( " " ).
6^o Read A. C. voltage by plugging in proper receptacle.
8^o Close switch No. 8 up.
Q. Explain how to set operating panel for automatic firing.
A. All contacts, connections, switches, etc., having been previously tested and examined by the electrician and found in order:
1^o Close up the testing, automatic, mine, power, and gong switches.
2^o Close firing switch. */
_Note._--If one or more automatic switches cannot be made to stay up, open the power switch for that mine before closing firing switch.
Q. How would you fire by judgment?
A. Conditions being as above, lift the automatic switch release of the mine to be fired at the command "Fire".
Q. How are mines tested?
A. 1^o Put D. C. on D. C. busses.
2^o Open power switches on all mine blocks.
3^o Unscrew all green lamps except on panel being tested.
4^o Close switch No. 3 down.
5^o Close power switch of each mine in succession and read milli-ammeter. This should be about 30 to 40 milli-amperes.
Q. Point out and describe the parts of a boat-telephone.
A. See Fig. 107.
Q. Describe how to connect up and use the boat-telephone.
A. 1^o Connect one wire of the casemate 'phone to either side of the battery, and the other to the ground (waterpipe is a good ground).
2^o The same end of the battery is connected to wire Nos. 1, 13, or 19 of the multiple cable leading to the distribution-box boat.
3^o Connect one wire of the 'phone in the D. B. boat to this same core (No. 19, for example).
4^o Connect the other wire to an earth plate which is overboard. (An earth plate is usually made of iron or copper.)
5^o The other terminal of the telephone battery has a permanent connection to earth. These connections then place the two telephones in parallel with the battery.
To call, press the push-button.
To talk, press the talking-switch.
Q. Point out and describe the parts of a wall-telephone composite artillery type.
A. See Fig. 108.
Q. Give the tests for telephones.
A. 1st. _Bell is not rung by its own magneto._
Analysis: 1. Short circuit on line. 2. Mechanical trouble in the bell. 3. Short circuit in the phone. 4. Open circuit in the phone. 5. Magneto does not generate.
Operator's test: With the receiver on the hook turn the magneto handle briskly.
If the bell does not ring and the magneto turns hard, (1. Short circuit on line) or (3. Short circuit in phone) is indicated, and the operator proceeds as follows, trying to ring after each step:
Inspect for contact of lightning-arrester carbons: a piece of writing-paper should pass between them easily. See that the ends of the line and ground wires do not touch any other part after passing through the binding-posts.
Disconnect the line and ground wires. If the bell rings now, (1. Short circuit on line) is clearly indicated, but if it does not ring and still turns hard, (3. Short circuit in phone) is indicated.
If the handle does not turn hard, the operator takes up (2. Mechanical trouble in the bell) and sees that the striker is not bound by the metallic cap over it or by the wood of the box, also that the armature can be moved by hand and that the striker will touch the gongs when the armature is so moved. The first trouble can be remedied; the others should be reported.
(4. Open circuit in the phone). Open the magneto box, see that contact is made between shaft and spring at _U_ and between the springs at _V_ when the handle is turned. The last may fail because the shaft is caught at some place, as where it enters the box or the collar on the shaft may have slipped or the springs may be bent. The spring at _U_ may be held against the end of the shaft with a pencil, during a test, to insure good contact. A spark seen at _U_ or _V_ indicates poor contact. If the operator cannot easily correct these faults, he should report as nearly as practicable what trouble he found.
Test for (5. Magneto does not generate) by moistening the tips of the fingers and touch terminals of magneto. Turn the handles, and if no shock is felt, a failure to generate is indicated.
2d. _Bell is not rung by distant magneto._
Analysis: 1. Home phone out of order.
2. Distant phone out of order.
3. Line out of order.
Operator's test:
(_a_) Test for (1. Home phone out of order) by detaching the line and ground wires and turning the handle.
(_b_) Test for (2. Distant phone out of order) at the distant phone in a manner entirely similar to (1. Home phone out of order).
(_c_) See expert's test for line troubles.
_Can hear but cannot be heard._
Analysis: 1. Local circuit at fault.
(_a_) Battery, (_b_) connections or wiring, (_c_) transmitter, (_d_) primary coil.
2. Distant receiver out of order.
3. Home secondary coil short-circuited.
Operator's test: Disconnect line and ground wires and connect binding-posts _R_ and _C_ with a piece of wire, thus short-circuiting the phone. Place the receiver to the ear and scratch gently with the finger-nail on the inside of the transmitter mouthpiece.
If this is distinctly heard, the local circuit and receiver are all right.
If no sound results, put the receiver to the ear, lower and raise hook lever, also open and close the two-way switch. If a distinct click is heard for each of these, the local circuit is all right but the transmitter may not be in good order and a report should be made.
If no sound results from above, make sure that the switch contact is good and no pivots are loose, that all contacts are good, that the connections at battery terminals are good with no green substance on the wires or posts, that the water in the jars is up to the prescribed point, about an inch from the neck of the cell, that the zincs and carbons are not touching, that the zincs are not eaten off, and that the zinc of one cell is connected to the carbon of the other, and that there are no crystals on the zincs and carbons.
The operator should correct any of these that he can, reporting the others.
For (2. Distant receiver out of order) the operator at the distant phone should try the tests above. If these give no sound in his receiver, he should try another receiver, if one is available. He may try a new cord or substitute two pieces of wire for it.
3d. _Can neither hear nor be heard._
Analysis: This indicates general trouble:
1. In the phones.
2. In the line.
Operators' test: Go over the phone carefully, looking for poor contacts, as when an insulated wire is put in the binding-posts, binding-posts not screwed down tight, ends of wires passing through post touching other parts, contacts at cells and condition of cells as noted before. Disconnect the line and ground wires and test out phones as indicated. See that ground wire is in the middle post. If there are fuses in the line, see that they are not burned out. If no trouble is found to exist when the line is disconnected, report line out of order.
Transcriber's Notes
Obvious errors of punctuation and diacritics repaired.
Both "defense" and "defence" are used and have not been changed.
Both "guncotton" and "gun-cottom" are used and have not been changed.
Hyphen added: hand[-]wheels (p. 8).
Hyphen removed: War[-]ships (p. 2).
P. viii: 8-inch Non-disappearnig -> 8-inch Non-disappearing.
P. 2: first or second-slass gunners -> first or second-class gunners.
P. 7: verticle angle -> vertical angle.
P. 31: Tetlautograph detail -> Telautograph detail.
P. 35: singals "Ready" or "Misfire," -> signals "Ready" or "Misfire,".
P. 77: Frankfort Arsenal -> Frankford Arsenal.
P. 89: right-handed sope -> right-handed rope.
P. 101: each pir of front and rear stakes -> each pair of front and rear stakes.
P. 110: Thong and Bush -> Thong and Brush.
P. 123: EXAGERATED DIAGRAMS -> EXAGGERATED DIAGRAMS.
P. 144: on dial -> on the dial.
P. 148, table, last column: 6 1 -> 6 1/5.
P. 156: TABLE A.--TABLE OF WARSHIP CHARACTERISTICS was split in two to fit within a reasonable width.
P. 160: (See Armor-attack Sheet, Fig. 86.) -> (See Armor-attack Sheet, Fig. 87.)
P. 168: 36 Imperieuse (34B Warspite) -> 36 Imperieuse (36B Warspite).
P. 184: 2 alochol lamps -> 2 alcohol lamps.
P. 187: free fram any clogging material -> free from any clogging material.
End of Project Gutenberg's The Gunner's Examiner, by Harold E. Cloke