Scientific American Supplement, No. 312, December 24, 1881 — John Shaqi
Scientific American Supplement, No. 312, December 24, 1881Various
Science
Scientific American Supplement, No. 312, December 24, 1881
Various
Science -- Periodicals
The most striking features of the crane are, the great range of all
the motions, the large radius, and the method of providing for the
latter by a horizontal jib suspended from a king-post. It was at first
intended to have a straight inclined jib, and to alter the radius by
pivoting this round its lower end, as is commonly done; it occurred,
however, to Mr. Matthews, M.I.C.E., representing Sir J. Coode, that
the plan eventually adopted would be in many ways preferable; the
crane was therefore constructed by Messrs. Stothert & Pitt with this
modification, and as far as can be judged from the trial with proof
load, the arrangements can hardly be surpassed for quick and accurate
block-setting. In cranes with "derricking" jibs it is necessary to
connect the derrick and hoisting gears in such a manner that a
variation of the radius may not affect the level of the load; this
plan answers sufficiently well for ordinary purposes, but for
block-setting it is requisite to have extreme accuracy in all the
movements and great quickness in changing from one to another; the
arrangements adopted in foundry cranes, in which all the motions are
entirely independent of one another, seems therefore more suited for
this kind of work. Other not inconsiderable advantages are also
secured by the adoption of the foundry crane type, the amount of clear
headway under the jib being much increased, and the difficulty avoided
of making a jib sixty feet long sufficiently stiff without undue
weight.
The principal dimensions of the crane are, total height of lift 46
feet, radius variable from 25 feet minimum to 45 feet maximum, height
from rail to underside of jib 22 feet 23/4 inches, radius of tail to
center of boiler 22 feet, working load 15 tons, proof load 19 tons.
The general arrangement consists of a truck on which is fixed a post,
round which the crane revolves; the jib is supported midway by an
inclined strut, above which is placed the king-post; the strut is
curved round at the bottom and forms one piece with the side frames,
which are carried right back as a tail to support the boiler and
balance weight.
The hoisting gear consists of a double system of chains 13/16 in. in
diameter placed side by side; each chain is anchored by an adjustable
screw to the end of the jib, and, passing round the traveling carriage
and down to the falling block, is taken along the jib over a sliding
pulley which leads it on to the grooved barrel, 3 ft. 9 in. in
diameter. In front of the barrel is placed an automatic winder which
insures a proper coiling of the chain in the grooves. The motive power
is derived from two cylinders 10 in. in diameter and 16 in. stroke,
one being bolted to each side frame; these cylinders, which are
provided with link motion and reversing gear, drive a steel crank
shaft 23/4 in. in diameter; on this shaft is a steel sliding pinion
which drives the barrel by a double purchase.
Public-domain text, read in full here on John Shaqi.
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