538 



AGRICULTURAL ENGINEERING 



size of pulley upon which the rope should be used is also 

 given. The working strength, or the greatest load the rope 

 should carry with safety, is given as about one-seventh of the 

 breaking load. 



Strength of different sizes of three-strand Manila rope, and size of pulley 



to use. 



Diameter 



Weight per 

 100 lbs. rope 



Safe load 



Breaking load 



Diameter of 

 pulley 



Inches 



Pounds 



Pounds 



Pounds 



Inches 



M 



3 



55 



400 



2 



H 



5 



130 



900 



3 



Vi 



7.6 



230 



1620 



4 



5 A 



13.3 



410 



2880 



5 



% 



16.3 



520 



3640 



6 



% 



23.6 



775 



5440 



7 



l 



28.3 



925 



6480 



8 



Good Knots. The three qualities of a good knot have been 

 stated as follows: "(1) Rapidity with which it can be tied; 

 (2) its ability to hold fast when pulled tight; and (3) the 

 readiness with which it can be undone." In Kent's Mechan- 

 ical Engineer's Pocket Book it is stated, "The principle 

 of a good knot is that no two parts which would move in 

 the same direction if the rope were to slip 

 should lay along side of, and touching, each 

 other." 



Parts of the Rope. For the sake of clear- 

 ness in the discussion of knots which is to 

 follow, the student should understand what 

 is meant by the following parts of a rope : 



The standing part is the long unused 

 part of the rope, as represented by A, 

 Fig. 324. 



The bight is the loop formed whenever the rope is turned 

 back upon itself, as B. 



324. 



Fig 

 parts of a 



The 

 rope: 



A, standing part; 



B, bight; C, loop; 

 D, end. 



