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STRANDS OF COPPER WIRE.

OOPPER WIRES are laid up into concentric strands

u or into ropes of seven strands. A rope of seven strands each composed of seven wires, is called a seven by seven rope, and is usually written 7x7. The number of wires that can be made into a strand is limited hy the capacity of the stranding machinery. Two hundred wires is the usual limit of a concentric strand, and one hundred and thirty-three wires of a rope.

In a strand of circular milage, C. M., composed of n wires of diameter d, with a weight per 1 000 feet w, then we have

C.M.=d2 x n.

de C. M.

N n

w=.00305 X C. M. The weights of strands are calculated about one per cent. heavier than a solid wire of the same circular milage, while the resistance is calculated for the solid wire.

In specifying how a strand shall be made, the number of wires to be used or the diameter of each wire may be given. In the first case the wire usually has to be specially drawn, and this will delay an order, especially

the size wires B. &. S. G., of which the strand is to be made,

The diameter of a strand may be calculated by multiplying the diameter of one wire by the factors given in the table at the bottom of the opposite page, according to the number of wires composing the strand.

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Circular mils.

1 17

12

19

27

| 37 | 48 | 61 | 75 | 91 | 108 | 127 | 147 | 169

192

217 | 7x7 7x19

Diameter of each wire.

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1 000 000 1 000. | 377. | 288.7 | 229.4 | 192.5 164.4 | 144.3 | 128. | 115.5 | 104.8

950 000 974.6 368.4 | 281.4 223.6 / 187.6 | 160.2 140.7 124.7 112.6 102.1
900 000 948.6 358.5 273.9 | 217.6 182.6 155.9 136.9 121.4 | 109.5 99.5
850 000 921.9 348.4 | 266.1 | 211.5 177.4 | 151.5 | 133.1 | 118. | 106.5 96.6
800 000 894.4 | 338. | 258.2 | 205. 172.1 | 147. 129.1 | 114.5 | 103.3 93.7

96.2 93.8 91.3 88.7 86.1

82.5 80.4 78.3 76. 73.8

84.1

76.9 74.9 72.9 70.9 68.7

72.2
70.3
68.5
66.5
64.5

67.8
66.1
64.4
62.5
60.7

142.9 139.2 135.5

86.7
84.5
82.2

79.9
| 77.5

81.8

79.3

127.8

866. 836.6 806.2 774.6 741.6

327.3 250. 198.6 166.7 142.3 125. 110.8 i 100. 316.3 241.5 191.9 161. 137.5 120.8 107.1 96.6 304.7 232.7 | 184.9 | 155.2 | 132.5 | 116.4 | 103.2 93.1 292.7 | 2:23.6 | 177.6 I 149.1 | 127.3 | 111.81 99.1 89.4 1 280.3 214.1 | 170.1 | 142.7 | 121.9 107. 94.9

94.9 85.6

58.8 | 123.

7
56.7 119.5
54.7 115.

2
52.5 | 110.7
50.3 106.

75. 72.5 69.9 67.1 64.2

53.5

90.7 83.3 76.8

| 62.5 87.7 80.5 74.2 69. 64.3 60.4 84.5 77.6 71.5 66.5 162. 58.2 81.2 1 74.5 | 68.7 | 63.9 59.5 | 55.9 77.7 71.4 65.8 61.2 57.1 74.1 68. 62.7 58.3 54.3 51. 70.3 64.6 59.5 55.3 51.6 48.4 66.3 60.9 56.1 52.2 48.6 45.6 62. 56.9 52.6 48.8 45.5 42.7 57.4 52.7 48.6 45.2 42.1 39.5

90.5

750 000
700 000

600 000
550 000

500 000
450 000
400 000
350 000
300 000

707.1 267.2 670.8 | 253.5 632.4 239. 591.6 223.6 547.7 207.

204.1 | 162.2 / 136.1 | 116.2 193.7 | 153.8 129.1 | 110.3 182.6 145. 121.7 103.9 170.8 | 135.7 | 113.9 | 97.2 158.1 125.6 105.4 90.

96.8 91.3 85.4

80.9 75.7 70.1

81.7 77.5

73.1 |

68.3 | 63.2

48. 45.5 42.9 40.1 37.1

101. 61.3 95 8 58.1 90.4 | 54.8 84.5 51.2 78.3 47.4

250 000

500. 1 189.

144.3 / 114.7 | 96.2

82.1 | 72.2 | 64.

57.7 | 52.4 | 48.1

44.3

41.2

38.4

36.1 | 33.9

71.4 | 43.3

DIAMETERS OF WIRES IN STRANDS.—(Continued.)

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