CONDENSED INSTRUCTIONS.
1. Excessive charging must be avoided. A battery should not be undercharged, overdischarged, or allowed to stand completely discharged.
2. Keep the electrolyte at the proper height above the top of the plates.
3. The daily and weekly readings should be regularly and accurately taken and recorded.
4. Inspect each cell of the battery carefully at regular intervals.
5. If any low cells develop do not delay in bringing them back to condition.
6. Do not allow the sediment to get up to the plates.
7. Do not allow impurities, either solid or liquid, to get into or remain in the cells.
8. Have the battery room well ventilated, especially while charging.
9. Never bring an exposed flame into the battery room during or shortly after the gassing period of a charge.
10. Keep the floor and other parts of the battery room clean and dry.
11. Keep the iron, copper, or other metal work about the battery room free from corrosion.
12. Keep all connections clean and tight.
13. Post a copy of these condensed instructions in a conspicuous place.
APPENDIX NO. 4.
SUBMARINE MINE CABLE.
Submarine mine cable is shipped on reels having an outer sheathing for protection in transit, with at least 12 feet of both ends of the cable brought out and coiled on the head of the reel for test purposes. If the cable is not for immediate use, it should be moved to the cable tank, and by means of the overhead trolley and cable tongs put in its position in the tank, the two ends being properly tagged and firmly fixed so as to allow it to be tested. In arranging the multiple cable in the tanks that which is to be used first should be most readily accessible.
The cable tank should be provided with a cover to keep it clean, as well as to lessen as much as possible variations of temperature. Enough clean water to cover by several inches the outer sheathing of the cable reels should be kept in the tanks, but in climates where the water in the cable tanks would normally freeze to a depth exceeding 2 feet, the water should be let out of the tanks before ice begins to form and not again admitted until the following spring. In localities where the tanks may become a breeding place for mosquitoes, as a preventive measure, salt water from the ocean or bay should, when practicable, be used for filling the tanks, or where it is necessary to use fresh water sufficient salt should be added to produce a 3 per cent solution. No oil or kerosene should be used in the tanks.
The methods of recording tests and of classifying and transferring submarine mine cable are prescribed by orders from the War Department. The tests of submarine mine cable at posts will consist in determining the insulation and conductor resistances.
The insulation surrounding the conductor of a cable is supposed to be uniform in regard to quality of material, density, and thickness. The resistance which it offers to the passage of a current through it will then vary inversely with its length. In comparison the insulation resistance of 1 mile of cable is taken as the standard. This insulation has a large negative temperature coefficient; that is, an increase of temperature lowers its resistance. It is customary to reduce all insulation resistance to that at a standard temperature of 60° F., and for this purpose reduction factors applicable to the particular insulation compound should be furnished with the cable. (Note: It has been found that for most compounds, if the logarithms of the resistance are plotted as ordinates against the temperature in degrees F. as abscissæ, the resulting curve will be very nearly a straight line.)
The ordinary methods of measuring resistance—that is, by means of a Wheatstone bridge, or by fall of potential, or by voltmeter—can not be used in measuring resistance as high as that of the insulation of a submarine cable. For this the direct deflection method is employed.
In brief, this consists of the following steps:
First. The deflection produced in a galvanometer by a current from a battery through a known resistance, usually 100,000 ohms, is determined, whence is calculated the resistance through which this same battery would produce a deflection of one point using the unity shunt. This is expressed in megohms and is called the galvanometer “constant” under the conditions.
Second. The deflection produced by the current from the same battery through the insulation of the cable is determined, whence, from “First,” the corresponding number of megohms is calculated.
Third. This multiplied by the length of the cable in miles and corrected for temperature gives the required insulation resistance per mile.
This testing can be made most satisfactorily on dry days, but a close adherence to the instructions herein given relative to the preparation of the cable ends, the insulation of the cable lead and of the battery, and the drying out of the test room and instruments should enable satisfactory work to be done under adverse conditions of weather or climate. The following apparatus is required: Reflecting galvanometer, universal shunt, special testing key, 100,000-ohm resistance box, battery of dry cells giving approximately 100 volts, and stop watch.
[Figure 16] shows diagrammatically the arrangement of the apparatus for testing a reel of cable. As a rule the instruments should be so placed that one person may manipulate the key and the shunt while at the same time observing the galvanometer.
The 100,000-ohm box, as a protection to the galvanometer in testing, is always kept in the circuit and its value should be subtracted from the resistance determined, except in the case of high insulation resistance when it will not be necessary to make the subtraction.
The universal shunt is always employed with the galvanometer and is used both to vary the current through the latter and to protect it from a violent throw at the instant of making or breaking the circuit at the testing key. This last is accomplished by having the shunt on zero at such times.
The galvanometer being a very sensitive instrument must be solidly supported so as to be free from jars or vibrations.
The special testing key, shown diagrammatically in the figure, has its binding posts plainly marked. It is a double-throw key and has two positions upon each side. When completely closed to the right, the cable is charged through the galvanometer from the positive pole; when to the left, from the negative pole of the battery. In each case the deflection of the galvanometer is in the same direction. When partly closed on either side, the cable is discharged to earth through the galvanometer. (Note: It will be observed that the connections are such that the galvanometer is always connected to the cable core and never to the ground. With this connection, so long as the lead PX is free from leaks or grounds, the galvanometer measures only the current actually passing through the core and not that leaking through any imperfect insulation in the battery and leads.)
Cable testing is a very simple operation, but extreme care is necessary in all operations.
FIG. 16.—CABLE TESTING.
The following is a detailed description:
I. Preparing the cable for testing.—1. Closely examine each conductor end. Look particularly for unusually hard or brittle insulation and for torn, pinched, or punctured insulation, especially near the ends of the armor wires. If any of the ends are not in perfect condition, cut off enough cable to secure good ends. (Caution.—Do not cut off more than enough to secure good ends, for after three or four tests it may be necessary to unreel the whole cable to secure enough of the inner end above water.)
2. Verify the tagging. Remember that the “shore end” is the end from the outer coils on the reel and is numbered clockwise. The other end is numbered contraclockwise.
3. The “ground” should be made by taking several turns of bare copper wire around the armor of the cable to be tested and soldering them in position. One such ground in each tank is sufficient. Whenever “ground” or “earth” is subsequently spoken of, this ground in the tank is meant, and not a connection to ground at some point outside the tank.
4. The leads PX and BY ([fig. 16]) should be of loading or other heavily insulated wire. They must be carefully insulated from each other, from the ground, and from the walls or other parts of buildings. This is especially true of the cable lead PX. In damp weather porcelain-knob insulators and porcelain tubes (the latter for use in passing through walls or partitions) may not be sufficient to afford proper insulation for the cable lead. In such case the latter should be suspended in the air from the testing switch to the cable tank by means of several chains of paraffined porcelain insulators suspended by marline or protective tape which has been boiled in paraffin. These suspensions should be in each case under cover and should be kept as dry as possible. The length of the leads is immaterial. If loading wire is used, the distance between supports should be short (not over 50 feet), as this wire stretches considerably from its own weight, pulling out the insulation and giving a very thin wall, particularly at points of support. Extreme care should be taken to tighten up on the knob insulators, in case they are used, just enough to hold the wire without pinching the insulation.
5. Using a double connector, join the lead BY to the ground wire on the cable above the surface of the water. Put a connector on the end of the other lead so that it can be readily attached in turn to each conductor.
6. Any protective covering, such as armor, jute, etc., should be removed from the ends of the conductors for a distance of about 12 inches, thus laying the insulation coating bare. This latter should not be handled and must be kept scrupulously clean. With a clean dry knife prepare each conductor of the cable to be tested by cutting off about 1 inch of the insulation from each end of the wire and then tapering the end of the insulation for about 1 inch, leaving a perfectly clean surface. In damp weather dip each end of each conductor into melted paraffin (not boiling, but heated above 212° F.). Secure one end of the cable so that it is well separated from the surrounding objects and separate the conductors so that no ends are touching.
7. Take one strand of a loading wire about 4 feet long and wrap it two or three times around the projecting copper end of each conductor at the other end of the cable, then connect it to earth. See that the conductors at this end are dry. Leave the lead PX disconnected and suspended in the air.
II. Setting up the testing apparatus.—1. Select a light, dry room as near the cable tank as practicable.
2. Use dry cells for the battery. The voltage of the battery should be such as to give a full scale deflection of the galvanometer through the resistance employed for taking the constant (with shunt at ¹/₁₀₀₀). Large galvanometer throws are essential for reliable results.
Set up the cells on shelves in a small closed closet or box, with narrow strips of wood or heavy cardboard laid between each row of cells, lengthwise and crosswise. The height of each strip should be about half the height of a cell, so that the two layers of strips will come nearly to the tops of the cells and keep them well separated. Wire the cells in series and bring the terminals out to a double-pole single-throw switch, which should be on a heavy porcelain or slate base and rated for at least 250 volts. (It may be found desirable to install some electric lamps in the closet to keep the battery dry.)
If difficulty is experienced in eliminating grounds from the battery set up in this manner, the battery box should be suspended in air by means of chains of paraffined cleats.
3. Set up the galvanometer on a pier or on a window sill if the building is of masonry. It should be insulated by placing its feet on a slate or ebonite slab, or in glass insulators. Remove the cover. Adjust the level until the suspended coil hangs freely. Maneuver the suspended coil, by means of the knob at the top of the tube, until its face is parallel with the face of the instrument. Then adjust the level until the upper suspension hangs in the center of the supporting tube, and the air gap between the coil and armature is symmetrical. Replace the cover. Put on the scale and the telescope. Turn the mirror so that it reflects the 0 of the scale approximately, getting exact adjustment by moving the scale. Be careful (particularly in dry weather) not to touch the glass of the cover or to do anything which will produce a static charge on the glass.
The galvanometer scales are usually graduated in equal divisions corresponding to 1 millimeter on the circumference of a circle whose radius is 1 meter. Each tenth division is usually marked with a number. This number is sometimes 1 instead of 10, 2 instead of 20, and so on. The number of divisions to read and record is the number of smallest (millimeter) divisions. Do not try to read closer than ½ of one division. The larger the throw the less the personal error. No accurate conclusion can be drawn from a very small throw.
4. Place a table or low shelf conveniently to one side and place the shunt, the testing key, the ⅒ megohm box, and a voltmeter on it. The apparatus should be insulated by an ebonite or slate slab, or glass insulators. Fasten the shunt and the key securely to the table or the shelf. (The use of paraffin paper for insulating instruments is a makeshift at best. It soon gets soiled and creased, then it has to be replaced.)
The use of lamps to keep the apparatus dry may be desirable, or it may be found convenient to expose the apparatus to the sun for a few minutes before beginning the test on any day. The use in the testing room of a small stove or of a gasoline torch for two or three hours before the beginning of the testing will ordinarily prove very advantageous.
5. Wire up as in [figure 16], except that the leads from the testing key should be carried to the battery through the double-pole single-throw switch above referred to. (The battery switch should be opened whenever any connections are made or altered.) All leads used in connecting up the instruments should be of heavy copper, and stiff enough to hold permanently any shape to which they are bent. They should be supported at points of connection only, and should not lie on the table or within an inch of each other.
III. Testing the insulation of the apparatus.—1. Voltmeter test of battery insulation.—This is a rough test, but should be included. A serious ground can be much more quickly located with a voltmeter than with the galvanometer.
(a) Disconnect the battery leads at the battery switch; connect + lead of battery to + post of the voltmeter; connect the B end of the lead BY to - post of the voltmeter; - lead of the battery should be in the air. Close the voltmeter switch and read.
(b) Disconnect the voltmeter. Connect - lead of the battery to - post of the voltmeter. Connect the B end of the lead BY to + post of the voltmeter; + lead of the battery should be in the air. Close the voltmeter switch and read.
If any deflection is obtained in either case, the battery or its connections are grounded. Locate and remove the ground. (See Foster or some other practical handbook.)
2. Testing the battery voltage.—Connect the voltmeter across the battery terminals. Read and record the voltage. (If there is no voltmeter available which will read as high as the battery voltage, take the voltage of the battery in sections and add, or make a multiplier of one of the resistance coils in the ⅒ megohm box.)
3. Testing the battery and the apparatus for grounds with the galvanometer.—With a camel’s-hair brush go over all the instruments and carefully remove dust. See that the instruments and connections are dry. Do not blow on the instruments.
Open the battery switch. Connect the battery leads to the battery switch. Disconnect lead PX at P and connect the earth leads BY and EY to the key at “cable post.” (Y is grounded.) Both battery leads are left connected to the key. The shunt should be on 0. Close the battery switch. Close the testing key to the right. Turn the shunt gradually to the unity post. The galvanometer deflection should be zero. Turn the shunt to 0. Reverse the testing key. Turn the shunt to the unity post. The deflection should be zero. If any deflection is obtained, there is a ground in the battery, the apparatus, or the connections. The test of the cable should not proceed if a deflection is obtained in either position of the key.
In reporting the voltage + to earth and - to earth as “zero” on form, it will be understood that this means zero using the galvanometer, as herein described.
4. Insulation of leads.—Turn the shunt to 0. Open the battery switch. Connect the earth leads BY and EY to their proper posts. Connect the cable lead, PX, to “cable” post. See that the cable tank ends of the lead PX is disconnected at X and suspended in the air. Close the battery switch. Close the key and turn the shunt to the unity post. Deflections should be as small as possible and in any case must be steady and uniform for several trials. Turn the shunt to 0. Reverse the key, stopping at the discharge position. Turn the shunt to the unity post and wait until the galvanometer rests at 0, indicating that the leads are discharged. Turn the shunt to 0. Close the key all the way down. Turn the shunt to the unity post. The deflection should not differ materially from that noted above. If there is a deflection, the trouble is in the lead PX or its connections. Go over these, carefully examining for dust and moisture and noting particularly the proximity of all wires of opposite potential which cross or lie near each other. If there is a small deflection which can not be removed, a correction must be applied subsequently to the deflection obtained in the test for the insulation resistance of the conductor.
Using proper care, there are very few days when perfect insulation of the instruments can not be secured. The lead leakage with well-insulated wire put up properly will be noticed rarely.
5. Use of Price guard-wire.—As an additional precaution against surface leakage across the insulation at the ends of the conductor it will sometimes be advisable to install an additional lead (not necessarily as carefully insulated as PX) running from the testing switch to the cable under test. This lead should be connected in at the testing switch to the post carrying the lower blade between “D” and “C” ([fig. 16]); the tank end should be bare of insulation for a sufficient distance to enable the bare wire to be wrapped firmly, without pinching, around the insulation at each end of the particular conductor under test, just below the tapered portion.
The potential difference between the cable core and this guard-wire is thus made practically nil, so that any leakage will be from the guard-wire to the tank, consequently this leakage will not be measured by the galvanometer.
IV. Take the galvanometer constant as follows: Open the battery switch.
With a short piece of wire connect the hinge post of the testing key marked “cable” to either “earth” post of the key, the leads to the cable tank being disconnected at E, B, and P. Turn the shunt to 0. Examine the ⅒ megohm box and see that all the resistance coils are in the circuit. Close the battery switch and the testing key. Turn the shunt to the ¹/₁₀₀₀ post. Watch the swing of the galvanometer and when it has come to rest, read and record. Turn the shunt to 0. The galvanometer should return exactly to 0. If it does not, readjust and repeat until it does. The galvanometer constant is numerically equal to the total throw in smallest divisions of the scale multiplied by 100. Remove the connecting wire and replace the leads to the tank.
If at any subsequent time during the test the galvanometer adjustment is disturbed—that is, if it does not return accurately to zero when the shunt is at 0—the constant should be redetermined.
Testing the cable.—1. See that the testing key is open and the shunt at 0. Connect the earth lead to ground on the cable armor. Remove the earth connection from No. 1 conductor and connect the cable lead to this conductor; in wet weather the connector joint should be dipped in melted paraffin. (In using paraffin to insulate joints or ends bring it just above 212° F. to evaporate any moisture present. It should not be boiling. The paraffin coating should be at least as thick as the rubber insulation and extend back over the rubber for an inch or more.)
2. Close the testing key to the left (+ to earth), stopping at the discharge position, and turn the shunt to the unity post. There should be no deflection. If there is, it is due either to a charge on the cable, which will disappear after a moment, or to earth currents. (It is assumed that the testing apparatus has been thoroughly tested for insulation.) If due to earth currents, the conductor is probably a poor one. Earth currents are readily recognizable by their fluctuating character. Before assuming that the trouble can not be removed, the joint between the lead and the conductor should be examined again. Moisture on the cable end will give a path for earth currents. Note the value and direction of the throw of the galvanometer and record it.
3. Turn the shunt to 0, close the testing key all the way down (+ to earth), noting the time to the second, or starting the stop watch at the same time, if one is available. The time must be accurately noted. The insulation resistance at the end of one minute’s electrification is the resistance to be reported.
4. When 35 seconds have elapsed, turn the shunt to the ¹/₁₀₀₀-post and watch the galvanometer throw; if small, move the shunt successively to the ¹/₁₀₀-post, to the ¹/₁₀-post, and to the unity post. This operation must be completed before 45 seconds have elapsed from the time the key was closed. With good cable the unity post will always be reached without danger of throwing the galvanometer reading off the scale. Remember that each successive post should give 10 times the throw of the preceding post.
5. At the end of one minute read the deflection, correct for the leakage of the leads and the earth currents, and record. (See example following.)
6. At the end of two minutes read the deflection, correct and record it. For good cable it should be less than the deflection observed at the end of one minute.
7. Turn the shunt to 0, and reverse the key, stopping at the discharge position. Turn the shunt on gradually until the unity post is reached and wait until the reading is 0, indicating that the conductor is discharged. If earth currents are present, 0 will not be reached or will be passed. In this case proceed as before described. A submarine mine cable conductor a mile long will discharge ordinarily in about three minutes.
8. Turn the shunt to 0, stop and start the stop watch; at the same time close the key all the way down (- to earth).
9. After 35 seconds, start turning the shunt, ceasing at 45 seconds. ([See paragraph 4, above].)
10. At the end of one minute read the deflection, correct and record it. For good cable it should be substantially the same as the deflection observed at the end of one minute with + of the battery to earth.
11. Turn the shunt to 0, and reverse the key, stopping at the discharge position.
12. Disconnect No. 2 conductor from ground. Disconnect No. 1 from the lead and connect up No. 2. Connect No. 1 to ground. It is not necessary to wait for No. 1 to be discharged completely before disconnecting it.
13. Proceed with No. 2 as with No. 1 and repeat with each conductor.
14. On the completion of the test all conductor ends should be carefully taped.
15. To determine the correct value of the insulation resistance it is essential that the negative pole of the battery be connected to the core of the cable, otherwise the products of electrolysis will tend to seal up any fault which may exist and will cause the conductor to appear better than it really is. With the negative pole of the battery to the core the tendency is to deposit copper on the core and thus to lay bare any fault. The insulation resistance of any conductor is therefore found by multiplying the corrected deflection at the end of one minute, with + of battery to earth, by the denominator of the shunt used, and then dividing the galvanometer constant by this product. The resistance of the ¹/₁₀-megohm box is neglected unless the insulation resistance determined is very low, say, under 1 megohm, when the 100,000 ohms should be subtracted from the above quotient.
16. To determine the insulation resistance per mile at 60° F., multiply the actual insulation resistance found by the length of the cable in miles, and this result by the multiplier furnished by the torpedo depot for the particular make of cable, corresponding to the temperature of the water in the tank observed during test.
Example.—Leakage of the leads found to be one-half division. Earth currents found to give 1½ divisions in a negative direction from 0 of the scale. Galvanometer throw at the end of one minute (+ to earth), 15 divisions. The corrected deflection is, 15 - ½ + 1½ = 16 divisions.
The galvanometer constant (450 divisions through ¹/₁₀ megohm, shunt at ¹/₁₀₀₀), 45,000 megohms. That is, the battery will give ¹/₁₀ of 450 divisions = 45 through 1 megohm, the shunt at ¹/₁₀₀₀; or, what is the same thing, one division through 45 megohms, the shunt at ¹/₁₀₀₀; therefore with the shunt at unity the battery will give one division through 45 × 1,000 = 45,000 megohms. The insulation resistances = 45,000 ÷ 16 = 2,813 megohms. If the cable is three-fourths mile long, the insulation resistance in megohms per mile is 2,813 × ¾ = 2,110 megohms.
Manufacturer, Safety Insulated Wire & Cable Co.
Temperature of water in tank, 80° F.
Multiplier, 1.7056; 2,110 × 1.7056 = 3,599 megohms insulation resistance per mile at 60° F. This result is recorded on the form.
VI. Copper resistance.—1. The drop of potential method is quicker than the bridge method under the usual conditions and should be used if the apparatus is available.
Apparatus required.—(a) Source of power (110 volts D. C. lighting circuit, casemate battery or generator); (b) a double-pole single-throw switch to which the power leads are attached; (c) a bank of ten 110-volt lamps in parallel; (d) a D. C. ammeter of not more than 0-25 scale; (e) a D. C. voltmeter, 0-150 scale.
Place the lamp bank and the ammeter in one side of the power line from the switch to the conductor, and the other end of the conductor to the other side of the power line. Connect the voltmeter across the ends of the cable so as to measure the drop of potential between the ends of the conductor being tested. Close the switch, take simultaneous readings on the voltmeter and the ammeter and calculate the resistance. With the apparatus described a conductor 1 mile long will receive about 2½ amperes and show a drop of about 50 volts. The lamps are inserted as a safety precaution. In no case should the current through the conductor exceed 6 amperes. If the cable has been tested for insulation resistance and all the conductors show high insulation, the lamps are not necessary, provided the cable is at least a mile long.
2. The copper resistance found is reduced to that at 60° F. by multiplying by the coefficient found in the following table with the temperature of the water in the tank at the time of the test as an argument:
| Reduction of copper resistance to 60° F. | |||
|---|---|---|---|
| Temperature. | δ | Temperature. | δ |
| °F. | °F. | ||
| 10 | 1.1252 | 55 | 1.0113 |
| 11 | 1.1224 | 56 | 1.0090 |
| 12 | 1.1196 | 57 | 1.0068 |
| 13 | 1.1168 | 58 | 1.0045 |
| 14 | 1.1141 | 59 | 1.0023 |
| 15 | 1.1113 | 60 | 1.0000 |
| 16 | 1.1086 | 61 | .9978 |
| 17 | 1.1059 | 62 | .9956 |
| 18 | 1.1032 | 63 | .9933 |
| 19 | 1.1005 | 64 | .9911 |
| 20 | 1.0978 | 65 | .9889 |
| 21 | 1.0952 | 66 | .9867 |
| 22 | 1.0925 | 67 | .9846 |
| 23 | 1.0899 | 68 | .9824 |
| 24 | 1.0873 | 69 | .9802 |
| 25 | 1.0846 | 70 | .9781 |
| 26 | 1.0820 | 71 | .9759 |
| 27 | 1.0794 | 72 | .9738 |
| 28 | 1.0769 | 73 | .9717 |
| 29 | 1.0743 | 74 | .9695 |
| 30 | 1.0717 | 75 | .9674 |
| 31 | 1.0692 | 76 | .9653 |
| 32 | 1.0667 | 77 | .9632 |
| 33 | 1.0641 | 78 | .9611 |
| 34 | 1.0616 | 79 | .9591 |
| 35 | 1.0591 | 80 | .9570 |
| 36 | 1.0566 | 81 | .9549 |
| 37 | 1.0542 | 82 | .9529 |
| 38 | 1.0517 | 83 | .9508 |
| 39 | 1.0492 | 84 | .9488 |
| 40 | 1.0468 | 85 | .9468 |
| 41 | 1.0443 | 86 | .9448 |
| 42 | 1.0419 | 87 | .9428 |
| 43 | 1.0395 | 88 | .9408 |
| 44 | 1.0371 | 89 | .9388 |
| 45 | 1.0347 | 90 | .9368 |
| 46 | 1.0323 | 91 | .9348 |
| 47 | 1.0300 | 92 | .9328 |
| 48 | 1.0276 | 93 | .9308 |
| 49 | 1.0252 | 94 | .9288 |
| 50 | 1.0229 | 95 | .9269 |
| 51 | 1.0206 | 96 | .9250 |
| 52 | 1.0182 | 97 | .9231 |
| 53 | 1.0159 | 98 | .9211 |
| 54 | 1.0136 | 99 | .9192 |
The true length of a cable should be that of its center conductor.
From the size of the conductor and its copper resistance the length of the cable may be computed by use of the following wire table:
| Table of resistances of pure copper wire at 60° F. | ||
|---|---|---|
| Size B. & S. | Dia. in mils. | Ohms per 1,000 feet. |
| 1 | 289 | 0.11999 |
| 2 | 258 | .15130 |
| 3 | 229 | .19080 |
| 4 | 204 | .24058 |
| 5 | 182 | .30338 |
| 6 | 162 | .38256 |
| 7 | 144 | .48245 |
| 8 | 128 | .60831 |
| 9 | 114 | .76696 |
| 10 | 102 | .96740 |
| 11 | 91 | 1.21960 |
| 12 | 81 | 1.5379 |
| 13 | 72 | 1.9393 |
| 14 | 64 | 2.4453 |
| 15 | 57 | 3.0134 |
| 16 | 51 | 3.8880 |
| 17 | 45 | 4.9030 |
| 18 | 40 | 6.1827 |
| 19 | 36 | 7.8024 |
| 20 | 32 | 9.8316 |
| 21 | 28.5 | 12.397 |
| 22 | 25.3 | 15.625 |
| 23 | 22.6 | 19.712 |
| 24 | 20.1 | 24.857 |
| 25 | 17.9 | 31.343 |
| 26 | 15.9 | 39.535 |
| 27 | 14.2 | 49.839 |
| 28 | 12.6 | 62.848 |
| 29 | 11.3 | 79.250 |
| 30 | 10.0 | 99.932 |
The objections to the use of a bridge for measuring copper resistance are the difficulty of eliminating the resistance of the plug contacts and the time required to secure balance. The resistance of the plug contacts may often be as high as 20 ohms, particularly if used at the tank.
If the bridge is used at all, it should be placed in the testing room, and the same leads employed for testing insulation should be used. The resistance of these leads should first be determined by connecting them together and measuring; this resistance is subtracted from each resistance measured.
VII. General.—The key to success in cable testing is great care in every detail. The cable now being furnished is all tested with galvanometers having constants from 200,000 to 250,000 megohms. It has all been accepted after most careful test. The chances are that it is good when it arrives at the post, unless it has been mechanically injured in transit, which should be ascertained by careful inspection when delivered at the post.
Do not accept a single measurement if it shows low resistance, but repeat until certain of results. The time between trials on the same conductor should be as great as practicable. For example: Measurements showing low resistance made in the morning should be repeated in the afternoon; those made in the afternoon should be repeated the next day; the conductor being connected to earth during the interval between tests.
APPENDIX NO. 5.
CARE AND PRESERVATION OF
SUBMARINE MINE MATÉRIEL.
Frequent inspections of all articles of submarine mine equipment should be made, not only to check up the property, but also to determine the condition of all matériel, and especially to see if it has been affected by dampness. These inspections should be thorough and detailed, as only in this manner can there be impressed on those directly charged with the care of the property the importance of ventilation, dryness, and the proper use of preservatives.
The generating set, storage battery, motor-generators, casemate transformers, power panel, and operating boards will be installed in the mining casemate, and such tools, appliances, and materials as may be used when this apparatus is in commission will also be kept there.
The explosive will be kept in the magazines and tested and cared for in the manner prescribed in [Appendix No. 1].
The multiple and single conductor cable will be kept in the cable tanks as described in [Appendix No. 4].
All other articles of equipment will ordinarily be kept in the storehouse, and a noncommissioned officer will be placed directly in charge. It shall be his duty to keep the matériel in the best possible condition, using such details from the submarine mine detachment from time to time as may be necessary to assist him in this work. He shall check up all articles taken from the storehouse during practice and report at the end of the day’s work any shortage in tools or appliances that he may discover.
Paints and oils should be kept separate from other stores, and the floor where kept should be covered with 2 or 3 inches of sand, to be renewed occasionally. Sawdust should never be used for this purpose. Cotton waste which has become unfit for use should be promptly burned. Fuses must not be stored with other explosives.
Gasoline in considerable quantities should be stored in tanks underground and never inside of buildings. Small quantities should be kept outside of buildings in some safe place.
When oil engines or generators are out of commission, their bright parts should be covered with light slushing oil. Brass screw threads and parts of tools that are liable to rust should be covered also. In all cases the light slushing oil should be applied in a thin coat, since this is all that is necessary to give good protection. Before applying the light slushing oil to any surface it should be thoroughly cleaned, so as to be free from rust, water, kerosene and lubricating oil, as their presence will cause rusting underneath the slushing oil. The protected surfaces should be occasionally inspected and the coating of slushing oil renewed as often as required.
Screw threads of mine cases, steel screw threads of compound plugs, bolts, nuts and washers, and surfaces of flat joints should be kept coated with the light slushing oil or a mixture of machine oil and graphite.
No oils or grease should ever be placed on points where metallic contact of electrical instruments is necessary, nor on india rubber, ebonite, or slate.
Mine cases should rest on racks or skids, and where space permits should not be in contact with each other. In handling mine cases care must be taken not to damage the bails and bolts. They should be arranged so that the holes in the mine cases can be seen easily; these holes should be fitted with a wooden plug which has been thoroughly greased all over its surface. New mine cases, if galvanized, usually will not need painting until they have been in the water. When taken from the water they should be thoroughly dried, and if they should show signs of rust they should be gone over thoroughly with steel wire brushes until the rust is removed. Parts which can not be reached with the brush should be cleaned with three-cornered steel scrapers. A heavy coat of red lead should then be applied. Seven gallons of this paint can be made by mixing 100 pounds of red lead ground in oil with 5 gallons of raw linseed oil. This mixture should be applied within two or three weeks after mixing. One gallon of paint should give 10 mine cases one coat. After this coat has been allowed to dry there should be applied a coat of white lead toned down to a neutral gray. Seven gallons of this paint can be made by mixing 100 pounds white lead, 2½ gallons raw linseed oil, 2½ gallons turpentine, 1 gallon liquid drier, and adding about 1 pound of lampblack to tone down the mixture.
Mines treated in this way, if kept in a dry storehouse, and not put in the water, should not require repainting for several years. Frequent inspection should be made, however, for in handling the cases and changing their positions on the racks, it will often happen that an abrasion will be made in the surface of the paint, which if neglected may serve as the starting point of a progressive corrosion, which may extend rapidly under the surface of the paint. Should loose paint or rust be seen the case should be repainted. A small wooden mallet may be used to tap the case at all points to loosen scales of rust or paint; then the surface should be thoroughly wire brushed or scraped and the cases repainted as stated above. The inside of mine cases must be inspected to see that the interior surfaces are kept free from rust.
Ground mines and ground mine buoys should be treated in the manner just described for buoyant mine cases.
If the oil engine has not been painted, it should be given a priming coat of red lead mixed in oil. This should be rubbed down with pumice stone and two coats of steel-colored paint applied. The second coat should be rubbed down and two coats of varnish then applied. After this the engine should not need repainting for a couple of years. When, however, repainting is necessary, the engine should be rubbed down until all the varnish is removed and a coat of steel-colored paint applied. This coat should be rubbed until no brush marks remain, and one or two coats of varnish should then be applied. The steel-colored paint should be applied flat; that is, the color which is ground in Japan should be mixed with turpentine. One gallon of this paint is more than sufficient to give an engine two coats.
The motor-generators and the casemate transformers usually will not need the priming coat of red lead, as they come from the factory painted. When it is necessary to paint them, one coat of the steel-colored paint and one of varnish will usually be found sufficient.
Anchors, distribution boxes, junction boxes, mooring sockets, shackles, sister hooks, and the ironwork of operating boards and power panels should be painted with asphaltum varnish.
Paint brushes when new, and before use, should be wrapped or bridled with strong twine and soaked in water to swell. After use they should be cleaned with turpentine and put away in water to keep them from drying and becoming unpliable.
Large ropes should be stored on skids, allowing a free circulation of air. Small ropes should be hung on wooden pins. Ropes should be uncoiled semiannually in dry seasons and stretched out for several days to dry. Wire rope must be stored in a dry place where it will not rust. Marline-covered wire rope should be stored where there is a fair circulation of air. The date of receipt should be stenciled on each reel. If not used at the end of five years it should be run through a bath of pure distilled tar oil. This may be done by setting up an empty reel 20 feet in front of the full reel and placing a tub of the tar oil midway between them. As the rope comes off the full reel it is passed through the oil and the surplus oil slicked off with a piece of burlap, thus returning the oil to the bath. The freshly oiled reel will continue to drip for several days, and sand should be put on the floor under the reel to take up the excess oil. After use in water the marline-covered rope should be thoroughly dried out and then reoiled as above described.
APPENDIX NO. 6.
INSTRUCTIONS FOR MASTERS OF
MINE PLANTERS.
The matter contained in this appendix is primarily for the information of the masters of those vessels which are called into service for mine planting purposes upon the outbreak or threatening of hostilities.
The master shall request to be supplied with a copy of Regulations for Mine Planters, U. S. Army.
To each vessel will be assigned a coast artillery officer, who shall be the commanding officer of the vessel. All orders for the vessel shall be given to and through him. He shall have general charge of its business and be responsible for the proper care and disposition of all stores aboard, leaving to the master of the vessel the full and unquestioned control and authority over all matters for which he is professionally responsible.
Any orders to be given by the commanding officer concerning the vessel or its crew will be given to or through the master, except that when planting mines or operating any of the mining appliances or machinery aboard the vessel, the commanding officer, or an officer designated by him, may give instructions directly to any of the vessel’s officers or to members of the vessel’s crew who have duties directly connected with the mining work.
The duties and responsibilities of the master of a vessel engaged in submarine mine work do not differ materially from those devolving upon him when his vessel is otherwise employed. With respect to every duty the vessel may be called upon to perform, it may be stated that explicit directions as to where the vessel is to go and just what maneuvers it is to execute in the mine field will be given by the officer aboard, and it is then incumbent upon the master to execute the maneuver according to his best judgment.
The duties that vessels employed as mine planters are likely to be called upon to perform are as follows:
- 1. To lay out the mine fields.
- 2. To lay the multiple cable.
- 3. To plant mines.
- 4. To take up mines (including replacing defective
- mines by good ones where necessary).
- 5. To take up the cable.
The commanding officer of the vessel is responsible for the proper equipment of the vessel with the necessary apparatus for mine planting, for the loading of all the matériel prior to the planting, and for the method of procedure under the above heads.
The master of the vessel will carry out the orders of the commanding officer and is concerned only in the handling of his boat to prevent accidents to it and to the boats engaged in the planting.
The following precautions will be observed by masters:
1. If current flows across the mine field the planting vessel, to avoid accidents, should always pass on the downstream side of the yawl boat holding the measuring line.
2. The greatest care should be taken that the measuring line and buoy ropes are not caught in the propellers. If the vessel has twin screws, the upstream propeller should be stopped as soon as the measuring line has been passed to the marking boat. In all cases a man with a boat hook should be posted near the anchor davits and another amidships, to hold the measuring line above the water and clear of the sides of the vessel. Keg buoys, and as much of the buoy rope as possible, should be held on the rail near the stern, letting the rope pay out slowly and under tension, until the propellers are past the rope, then the keg and the remainder of the rope may be thrown overboard.
3. A general rule is never to back either propeller when buoy ropes, measuring lines, or cables are being handled overboard at or near the stern of the vessel.
4. If it becomes absolutely necessary to reverse the propellers when paying out cable, men paying it out must haul it in taut and keep it above the wheel and clear of it. The planting vessel should not pass nearer than 25 feet to the distribution box boat when cable is leading out from the latter, nor should it pass over any cable, if it can be avoided, if the depth is less than 16 feet.
5. The vessel should proceed after passing the distribution box boat on such a course that cable will pay off smoothly without becoming entangled. If a cable becomes fouled and entangled, the end should be “let go” at once at the distribution box boat—the planter should proceed on, not stop nor back its propellers. Mine cable should never be made fast in the distribution box boat until after a mine is dropped. It is much better to drop the mine out of position than to endanger the propellers of the vessel. The propeller nearest the distribution box should be stopped the moment the bow of the vessel passes the distribution box boat on its course to drop a mine.
6. If, in planting, the vessel moves against the direction of the current, there is little danger of overturning the distribution box boat if ordinary caution is observed. Should it be necessary to plant against a cross current or with it, it is best to pass the cable end to the distribution box boat by a launch or small boat. In this way the planter need not pass within 50 or 75 yards of the boat.
7. To avoid getting foul of the buoy rope or mine after the mine is dropped, the helm should be put over so as to throw the stern away from the mine. The vessel should be under good headway so that the propellers may be stopped until they are well past the buoy and buoy ropes of the mine. These points are important; failure to observe them will result disastrously.
In laying multiple cable, the course of the vessel invariably should be against the current. Rather than lay cable with the current it is advisable to postpone laying the cable until a change of the tide causes a favorable direction of current. In the end, time will be saved by waiting. Cable should pay off on the upstream side of the vessel if any cross current is running. All care should be taken that the cable does not get caught in the vessel’s propellers. This is of the greatest importance.
As the cable pays out over a chock near the bow of the vessel a man should stand by with a 3-inch strap in readiness to stop the cable should it be necessary, and two men should manipulate brakes to prevent the cable from paying out too rapidly. This is especially necessary if the water is deeper than 50 feet.
Especial care is necessary in planting mines to avoid: (a) Colliding with yawl or distribution box boat; (b) picking up cable in the propeller; (c) getting the mine cable tangled; (d) drifting over the mine after it is dropped.
APPENDIX NO. 7.
MANUAL FOR SMALL BOATS.
The left-hand side of a boat or ship, looking toward the bow, is the port side, and the other is the starboard side. The men who row on the port side are called the port oars and those rowing on the starboard side are called the starboard oars.
Boats are called single or double banked, according as they have one or two oarsmen to a thwart.
Thwarts are the seats on which the crew sits; the space abaft the after thwart is called the stern sheet.
Floorings and gratings are the bottom boards of a boat. They prevent the weight from bearing directly upon the planking.
The gunwale of a boat is the upper rail.
The yoke is an athwartship piece of wood or metal fitting over the rudderhead.
Yoke lanyards are the small lines made fast to the ends of the yoke, by which the rudder is turned and the boat steered.
The stem is the upturned portion of the keel at the bow of the boat, to which the forward ends of the planks are secured.
Oars are said to be double banked when two men pull one oar.
The blade of an oar is the broad flattened part. The handle is the small part of an oar on the inboard end of the loom, which the oarsman grasps when pulling. The loom is the portion of an oar extending from the blade to the handle. The leather is the portion of an oar which rests in the rowlock. This is sometimes covered with canvas, but is usually covered with leather; hence the name.
Feathering is the term applied to the operation of turning the blades nearly flat to the water after the stroke, with the upper edge turned forward, especially valuable in rowing against a head wind.
Rowlocks are forked pieces of metal in which the leather of the oars rests while pulling. Swivel rowlocks are movable, a pin on the rowlock fitting into a socket in the gunwale.
Thole pins are pins set vertically in the gunwale and are used in place of rowlocks.
The steering rowlock is a peculiar form of swivel rowlock (fitted near the stern of a boat) in which the steering oar is shipped. This is sometimes called a crutch.
The painter is a rope secured in the bow for towing or for securing the boat.
Boat-falls are tackles made with two blocks and a length of rope; used for hoisting boats.
The plug is the wooden stopper fitted into a hole in the bottom of a boat to let water in or out.
A boat breaker is a small keg used for carrying fresh water.
A boat-recall is an understood signal made to order a boat’s return.