When failure in angles was first noted, the recorded load was 653,500 lb., or slightly more than four times the computed basis of load, which would increase the above strains about one-fifth, giving a calculated flange strain when angle failed of some 15,000 lb. per square inch, and bearing area strain on end flange and web rivets about 80,000 lb. per square inch, neither of which could possibly be true, or the web would have torn out from the rivets, and the flanges be perfectly sound, well within elastic limits, although in the last case it is to be noted that the horizontal table of the flange was perfectly sound, the flange failure commencing primarily with a long split along the weld of the angle iron root, throwing the whole flange duty upon the vertical legs of the angle iron, when a rupture strain was quickly reached. Had the angles been rolled from a solid ingot, or on the German method of developing from a flat instead of from the ordinary welded pile, the strength of this beam would have been largely increased. The prime weakness in this beam was due, therefore, to the mode of manufacturing the angle irons, which were weak along the weld at the root. This was also shown in the end bracket angles uniting the beam to the posts. The writer deduces from this experiment that a plate web is an exceedingly stiff member, much stiffer than is commonly supposed; that the customary method of proportioning rivets—viz., the horizontal component between any two given points divided by allowable bearing pressure per square inch equals number of rivets required—is not true, and that the friction due to power riveting has enormous value. This beam was reported to the company interested as practically safe by the writer, on general considerations, before the experiment was made, and the opinion reaffirmed after the experiment.
London Bridge cost $10,000,000. It is 900 feet long and 54 feet wide. 100,000 persons pass over it every twenty-four hours. The lamp posts are made from cannon taken during the Peninsular War.
HYDRAULIC TUBE PRESS.
Forming metal tubes from circular plates by pressing or forcing them, by the aid of mandrels, through dies or annular rings, though comparatively a modern manufacture, is carried on to a considerable extent, and with the improvements that are almost daily being made in it, and the rapidly extending use of such tubes, this extraordinary process bids fair to become a most important manufacture.
The press illustrated here was designed and made by Messrs. Henry Bessemer & Co., of Sheffield, for Mr. Samuel Walker, of Birmingham, for the manufacture of tubes of large size, and also for making hollow steel projectiles.
The press is made entirely of Bessemer steel, and is of the three-column construction, a strong casting of triangular form serving as a base of the press; into this casting the three columns fit, and carry on their upper ends a like casting, forming a top or entablature. Into this top casting the main cylinder is fixed mouth downward,
concentric with the machine. Two small cylinders for giving the return or upward stroke rest mouth upward in the bottom casting at opposite sides. The two rams of these cylinders pass through the ends of, and carry, a crosshead, upon which the main ram rests. The two lifting rams are made long enough to pass through holes in the top casting, and thus form guides to the crosshead and mandrel.