RESISTANCE OF TUBES TO COLLAPSE. ps BF 
and bottom with heavy ribbed covers, screwed to strong flanges on the 
cylinder, calculated to sustain great pressure. The tube to be experimented 
upon was fixed in the position shown at D, having cast-iron ends riveted 
and soldered to it to render it perfectly water-tight. The small tube m, 
communicating with the interior of the tube D, was for the purpose of 
allowing the escape of the contained air at the moment of collapse. The 
whole of the experiments were effected by means of the hydraulic pump, by 
which water was forced into the cylinder C; and the air, driven in a com- 
pressed state into the upper part, became highly elastic as the pressure was 
progressively increased until rupture took place. At very high pressures, 
the air in the cylinder C was permitted to escape, and collapse effected by 
water pressure only. 
The tubes upon which the experiments were made varied from 18 inches 
to 60 inches in length; from 4 inches to 183 inches in diameter, and from 
*043 to ‘25 inch in thickness of metal. They were composed of plates of 
riveted sheet-iron, and the thinnest were carefully brazed at the joints to 
make them tight and prevent the entrance of water under pressure. 
The results of the experiments may be stated under three heads: strength 
as affected by length, as affected by diameter, and as affected by thickness 
of metal. 
I. Strength as affected by Length.—The results under this head are sin- 
gularly interesting and conclusive. Within the limits of from 1°5 foot 
to about 10 feet in length, it is found that the strength of tubes similar in 
other respects, and supported at the ends by rigid rings, varies inversely as 
the length. 
Thus, taking the four-inch tubes of different lengths, we have the following 
mean results derived from experiment :— 
(1.) Resistance of four-inch Tubes to Collapse. 
Diameter. Thickness of Plates. Length. Collapsing Pressure. 
ins. ins. ins. Ibs. per sq. in. 
ART ROD) croc ee ciate as LUD Act ae CR 137 
Rea coare one OFS SUP TS aes 60 43 
4 POS Te ace © EUW eiene aor Se 65 
The remarkable differences which exist in the resisting powers of the above 
_ similar tubes will be at once apparent. Assuming the experiment upon the 
19-inch tube, 
tube 60 inches long to be correct, we may easily calculate the strength of 
the other 19- and 40-inch tubes, by the above-stated law of inverse pro- 
portion. 
Thus, for the 40-inch tube, we have 40 : 60::43:27=641bs. And for the 
19 : 60:: 43 : z=135 lbs., 
where the calculated differ from the experimental results by ;/;th in one case, 
and ;2,ths in the other. 
13 
(2.) Resistance of six-inch Tubes to Collapse. 
Diameter. Thickness. Length. Collapsing Pressure. 
ins. ins. ins. Ibs. per sq. in. 
eee Pl Os a 55 
2.) chia tears eee eM tanrenas (sete iets NO eis e-issaOer 
Here, from the data of experiment (1.), we may calculate the strength of a 
_ tube similar to that in experiment (2.) 
* 
“ 
7) 
59 : 30 :: 55 : e=28 lbs., 
where the calculated differs from the experimental result by 3th. 
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