THE CROSBY SLING CALCULATOR

If the below calculator does not appear, or the version number is not 5.1please use the link below and choose open to install the latest version.Install Version 5.1

LING ANGLES

Sling Angle Degrees (A) Load Angle Factor = L / H 90 1.000 60 1.155 50 1.305 45 1.414 30 2.000

LOAD ON EACH LEG OF SLING =(Load 2) x LOAD ANGLE FACTOR

ANSI B30.9 recommends against the use of a horizontal sling angle smaller than 30

2 Measure the length of the sling. For example, imagine a sling that measures 3 feet in length.

3 Measure the vertical distance that the sling covers. This is the distance between the crane's hook and the load. For example, imagine that this distance is 2 feet.4 Divide the vertical distance by the sling's length: 2 3 = 0.67.Find the inverse cosine of this ratio using a scientific calculator: cos-1 (0.67) = 47.9 degrees. This is the angle between the sling and the vertical.

Wire Rope Sling Calculations

There are several calculations that may be of use to enable the load taken by a sling to be calculated. Single Leg Slings(a) Single PartThe load in the leg of a single leg sling is equivalent to the load to be lifted. To obtain the required breaking load of the rope to be used this must be increased by the Factor of Safety which is normally 5.i.e. Load in Leg = Load to be Lifted (W).... Required Rope breaking load = W x Factor of Safety. (b) Double Part and Grommet LegsWithin the scope of BS 1290 the required rope breaking load is calculated by:

Load to be lifted (W)0.3

For single leg slings, the calculations to determine the required rope breaking load must be adapted where the sling configuration is other than a straight lift, i.e. basket hitch, choke hitch etc. Where these types of lifts are to be used consultation with the supplier is recommended. Multi Leg Slings(a) Uniform Load MethodWhere the Uniform Load Method of rating is used the following calculations are applicable: Included Angle: 0-90o 90o-120o 2 Required Rope = W x F of S W x F of SLegs Breaking Load 1.4 1 3 Required Rope = W x F of SLegs Breaking Load 2.1 4 Required Rope = W x F of S W x F of SLegs Breaking Load 2.1 1.5

Where W = Load to be lifted F of S = Factor of Safety applicable (b) Trigonometric MethodWhere sling assemblies are to be rated at a specific angle i.e. 30o, 45o, 60o, etc. the following calculations apply. 2 Legs Required Rope Breaking Load = W ________ x F of S 2 cos B 3 Legs Required Rope Breaking Load = W ________ x F of S 3 cos B 4 Legs Required Rope Breaking Load = W ________ x F of S 4 cos B Where B = 2 x angle of operation W = Load to be lifted F of S = Factor of Safety applicable It must be pointed out in all the above calculations that the load lifted is assumed to be static. Where a load is 'snatched', as a general rule the load to be lifted must be assumed to double.

CHOKER HITCH CAPACITY =

SLING CHOKER ANGLE ADJUSTMENT

TYPE OF SLING CHOKER FACTOR

WIRE ROPE 70-75 % FIBER ROPE 50 %

FIBER WEBBING 75-80 CHAIN 75 %

1/2" 6 x 19 XIPS IWRC WITH A CHOKER ANGLE OF 85 DEGREES CAPACITY IS 5000 PNDS X .7 X .74 = 2590 POUNDS

RESULTANT FORCEFORCE = TENSION x ANGLE FACTOR CAPACITY x CHOKER FACTOR x