S TR
477
STR
Telford commenced his experiments upon iron byV|,l g what force would pull asunder, lengthwise, pieces of
8l °n$
(ijj 1 | r °m 1^ inches to 5 ^th of an inch in diameter. The, Pernnents were made upon those of the largest diameter,tb e ttleans °f an excellent hydrostatic machine, and in those ofitii> ^ aller by attaching weights perpendicularly, and repeat-® mem at various times.
f rQ y e then made several experiments upon different diameters,fg^^jth to J,th of an inch drawn horizontally, and with dif-p, ■ 1,1 degrees of curvature; and this was performed betweentw" 8 ^25, 140, and 139 feet 6 inches apart, and was„„ ? a ted 200 times. In the experiments made upon ^th ofti I j ) lnc h and under, the wire was drawn over pulleys; some-0tli es both ends were fixed, and sometimes one end only, thet-g> er having weights attached perpendicularly, to show thePart 8 w h en compared with those loaded upon the curved' °f the wire; these last were disposed at A and f divi-^ of the distance over which it was stretched. These^■ments being completed, it was ascertained what blowat j-1 break the wire when stretched nearly horizontally andfroJ aerent -curvatures, which was done by dropping weightsUib a . 8* ven height. The several wires were weighed, and' v eight of 100 in length of each noted.tr la ]j le result of the experiments was, that a bar of good® ft ble charcoal iron, 1 inch square, will suspend 27 tons,Oat an ' ron wire, ^,th of an inch in diameter, 200 feet in,r| (f I’ We ‘gbing 3 pounds 3 ounces, will suspend 700 pounds;Pa rt 1 'at the latter, with a curvature or versed sine of jfcth|i eil ,°f the chord line, will support ^th of the weight sus-j t | perpendicularly, when disposed equally at -J, andMnV en gth, and with a curvature of 4th of the chord, it8ijjji] ear sof the aforesaid perpendicular weight disposed in atij,] ar ' va y. A wire, 4th of an inch in diameter, drawn verybetween points, 31 ft. 6 in, apart, resisted the impulse ofguilds weight, falling from a height of 7 ft. 9 in.
*%e a S (n ‘5 English malleable iron, 1 inch square, willj from 27 to 30 tons before it breaks, and will bear4c Ur ^ to 16 tons before its length is at all extended. With^'ti Vatar e of 55th of the length, malleable iron, besides itsAt, .' Ve 'gbt, sustained j of what broke it perpendicularly.
* mr wou ^ therefore bear j of 15 tons without‘Uat . g ' n S its parts; but it is better in practice to assume,ll > inch square in action should only bear 4 tons.
Table showing the Cohesive Force of Iron.
Cohesion of squareinch in pounds.
Experimentalist.
Iron Wire .
93,064
Telford.
Swedish Iron.
72,064
Rennie.
Do.
64,960
Telford.
61,600
Telford*
Do.
66,000
Barlow.
Cast Iron, specific gravity , 7.716
82,700
Bevan.
Do.
19,488
Rennie.
Table showing the Extension, by a suspended Weight, of aWrought-iron Bar, 10 feet long and 1 inch square.
Tons.
Observedextension interms of thelength.
Computedextensionassumeduniform atTOoftoG
of the lengthper ton persquare inch.
Correspond-ing extensionin fractionsof the lengthcomputed at
per ton persquare inch.
Observedpermanentset in termsof thelength.
Observedperma-nent set infractionalparts ofthe
length.
1
.000689
.0008
T
T2350
2
.000156
.00016
bAb
3
.000238
.00024
ihs
•00000513
TffsW
4
.000319
.00032
I
3125
•00000283
33I&77
5
.000399
.00040
2^55
.00000356
531^35
6
. 00048
.00048
.00000427
23351S
Table showing the Extension and Permanent Set of a Cast-ironRod, 10 feet long and 1 inch square, drawn in the directionof its Length.
Tons.
Extension per Ton.
Total Extension.
Total permanent Set.
1
.01976
.01976
. 00579
2
.02027
.04155
.001860
3
.02171
.06515
.003954
4
.02318
.09274
.007543
5
.02479
.12397
.012619
6
.02727
.16363
.020571
'dji,
e lowing the Extensions of Cast-iron Rods, 10 feet long andpared with observed Compression of Bars of the same Ir
1 inch square, deducedfrom numerous Experiments, and com-•ons and the same size, cast with them for comparison.
Extension.
Compression.
Weights laid
on, with the corresponding Extensions, and
Mean Weights laid on, with corresponding Mean Compres-
Sets in Inches.
sions. Sets and Ratios of Weights to Compression.
Of
•u
Weights.
(w)
Extensions.
M
Sets.
(w)
(«)
Number ofExperi-ments.
Weights.
(w)
Compressionsin Inches.
(d)
Sets in Inches.
O)
(d)
1053.77
.0090
117086
8
2064.745
.01875
.00047
110120
1580.65
.0137
.00022
115131
8
4129.49
.03878
.00226
106485
2107.54
.0180
.000545
113309
8
6194 24
.05978
.00400
103617
3161.31
.0287
.00107
110150
8
8258 98
.07879
.00645
104823
4215.08
.0391
.00175
107803
8
10323.73
.09944
.00847
103819
5268.85
.0500
,00265
105377
8
12388.48
.12030
.010875
102980
6222.62
.0613
.00372
103142
8
14453.22
.14163
.01405
102049
7376.39
.0734
.00517
100496
8
16517.97
.16338
.01712
101102
8430.16
.0859
.00664
98139
8
18582.71
.18505
.02051
100420
9483.94
.0995
.00844
95316
8
20047.46
.20624
.02484
100114
10537.71
.1136
.01062
92762
8
24776.95
.24961
.03220
99263
11591.48
.1283
.01306
90347
8
28906.45
.29699
.04300
97331
12645.25
.1448
.01609
87329
7
33030.80
.35341
.06096
93463
13699 83
.1668
.02097
82133
7
37159.65
.41149
.08421
...
14793 10
.1859
.02410
79576
...
...
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