Tackle Block Reeving THE REEVING OF TACKLE Ratio A Ratio B Number of Bronze Anti- BLOCKS Bushed Friction Parts of Line In reeving a pair of tackle blocks, one of which has more Sheaves Bearing than two sheaves, the hoisting rope should lead from one of .96 .98 1 the center sheaves of the upper block to prevent toppling 1.87 1.94 2 2.75 2.88 3 and avoid injury to the rope. The two blocks should be 3.59 3.81 4 placed so that the sheaves in the upper block are at right 4.39 4.71 5 angles to those in the lower one, as shown in the following 5.16 5.60 6 illustrations. 5.90 6.47 7 6.60 7.32 8 Start reeving with the becket, or dead end, of the rope. Use 7.27 8.16 9 a shackle block as the upper one of a pair and a hook block 7.91 8.98 10 as the lower one as seen below. 8.52 9.79 11 9.11 10.6 12 Sheaves in a set of blocks revolve at different rates of speed. 9.68 11.4 13 Those nearest the lead line, revolve at the highest rate of 10.2 12.1 14 speed and wear out more rapidly. 10.7 12.9 15 11.2 13.6 16 11.7 14.3 17 All sheaves should be kept well lubricated when in opera- 12.2 15.0 18 tion to reduce friction and wear. 12.6 15.7 19 13.0 16.4 20 Total Load To Be Lifted = Ratio A or B Single Line Pull (lbs.) After calculating Ratio A or B, consult the table to deter- mine number of parts of line. Examples To find the number of parts of line needed when weight load and single line pull are known and using Bronze Bushed Sheaves. 72,480 lbs. (load to be lifted) = 9.06 8,000 lbs. (single line pull) (Ratio A) Refer to ratio 9.06 in table or number nearest to it, then check column under heading “Number of Parts of Line”... 12 parts of line to be used for this load. To find the single line pull needed when weight of load and number of parts of lines are known and using Anti-Friction Bearing Sheaves. 68,000 lbs. (load to be lifted) = 9,290 lbs. 7.32 (ratio B of 8 part line) (single line pull) 9,290 lbs. single line pull required to lift this load on 8 parts of a line. HOW TO FIGURE LINE PARTS To find the lift capacity when the parts of line and single line To help figure the number of parts of line to be used for pull are known. a given load or the line pull required for a given load, the following ratio table is provided with examples of how 10,000 lbs. (single line pull) x 4.71 (Ratio B-5 parts of line)= to use it.: 47,100 lbs. (Lift capacity) 10,000 lbs. single line pull with 5 parts of line will accom- modate 47,100 lbs. lift capacity.