CARGO SLINGS

283

legs are doing the same amount of work and relieve them of half

10'9

their load so that each leg supports ——=545 cwts.

2

C
Fig. 27.

8

Calculation.—Having found the length of the half diagonal AC
to be 2-83 feet, the triangle ACD may be solved as follows:—
Cosec Q=— = -—^a-^S •"• e==23° 51'-
In triangle DFJS, given /. 8=23° 51'. DE=W cwts,, ^.^=90°.
Find DF the tension on the sling.
DF=DE sec. 0=10. sec. 23° 51'=10x 1-09=10-9 cwts being
the tension on two legs, or 545 cwts on each of the four legs.
Ships* Cargo Lifting Blocks.—The following extracts are taken, by
permission of the British Engineering Standards Association, from
British Standard Specification No. 4X38, Ships' Cargo Lift/ing Blocks,
official copies of which can be obtained from the Director of the Associa-
tion, 28 Victoria Street, London, S W.I, price 2s. 2d. post free. The
specification is issued for the guidance of manufacturers who make
steel or iron cargo blocks and wish to subject them to tests preliminary to
their being guaranteed as British Standard Blocks. The principal
conditions of the tests are as follows:-
Definition.—"Block" shall apply to aB ships' blocks (except malleable
iron and wooden blocks) used for lifting piirposes and shall include