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.
[Illustration]
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.
The main ram is 24 in. in diameter, and has a stroke of 12 ft. The press
is worked at a pressure of 3 tons per square inch, giving a down force of
1,300 tons. The two lifting rams are each 8-1/2 in. in diameter, and give an
upward force of 300 tons. This large upward force is required for
stripping the tubes off the mandrels, in addition to raising the main ram
crosshead, etc.
Referring to the engraving, the main cylinder is seen at the top with the
main ram carrying the crosshead, to which are connected the two lifting
rams, the cylinders for which extend below ground. By this arrangement a
reciprocating motion is obtained, rams only being used, the central ram
giving the downward thrust, and the two smaller side rams giving the
upward stroke.
Mr. Walker has this press in operation, and from a disk of steel 3 ft. in
diameter, having a mean thickness of about 4 in., he has raised a tube or
cylinder with a solid end to it 3 ft. 6 in. long and 12 in. in diameter,
of a uniform thickness of about 1 in., and sanguine hopes are entertained
of producing greater results. Messrs. Bessemer & Co. are now making a
larger press of similar construction.--_Engineering._
TIMBER, AND SOME OF ITS DISEASES.[2] By H. MARSHALL WARD.