26 



BULLETIN 440, U. S. DEPARTMENT OP AGRICULTXJEE. 



on the machines after they arrive in the woods. Three types of 

 efficient spark arresters are in use, varying in price from $12 to $45. 



Because of the increase in size of yarding engines, there is a ten- 

 dency to use heavier wire rope for yarding. At present the most 

 satisfactory sizes for main lines are 1 inch for the small yarders, 

 1 1 -inch for all ordinary yarders, and IJ-inch for the larger yarders 

 in rough country with uphill hauls. The universal back line is 

 five-eighths inch, except for very small machines, upon which one- 

 half inch is sometimes used. Dolbeers are commonly equipped with 

 seven-eighths-inch main line and three-eighths-inch back line. 



Wire rope for logging is commonly quoted at list prices upon which 

 certain discounts are allowed, varying from time to time with the 

 price of steel. There are two grades, plow steel and extra plow steel. 

 Most logging rope is the latter grade. Yarding rope is commonly 

 composed of 6 strands of 19 wires, each about a hemp center. On 

 account of its greater pliability, rope having 8 strands of 19 wires 

 each is preferred for chokers. Table 4 gives approximate net prices 

 in 1914 per linear foot for standard logging wire rope f. o. b. San 

 Francisco. 



Table 4. — Approximate net prices for standard logging wire rope in 1914 at San Francisco. 



Diam- 

 eter. 



Weight 

 per foot. 



Plow 



steel, 

 6 by 19. 



Extra 

 plow 

 steel, 

 6 by 19. 



Extra 



plow 



steel, 



8 by 19. 



Inches, 

 h 



f 

 a 



1 



H 



li 



If 



li 



Pounds. 



Per foot. 

 $0.06 

 .085 

 .115 

 .15 

 .19 

 .24 

 .29 



Per foot. 

 $0.08 

 .11 

 .15 

 .19 

 .245 

 .30 

 .37 

 .44 

 .54 



Perfoot. 



0.62 

 .89 

 1.20 

 1.58 

 2.00 

 2.45 

 3.00 

 3.55 



SO. 12 

 .17 



.27 

 .33 

 .40 



.48 

 .58 



.41 



Usually four or five chokers are kept on hand at each machine. 

 Each consists of a piece of cable from 15 to 30 feet in length, having 

 a loop on one and a choker hook on the other. They may be made 

 of old yarding cable or new 1-inch 8 by 19 strand. 



The proper block equipment for a yarder consists of two "Tommy 

 Moores" or "Jumbos" for the yarding line, and one head or tail block 

 and about six 10 or 12 inch trip-hne blocks for the back line. 

 Shackle yarding blocks are still used in a few mstances but are 

 rapidly being supplanted by the "Jumbos," since the latter permit 

 the passage of the butt hook and chokers on the outward trip. A 

 moving block is sometimes added to the equipment of a yarder, 

 though usually one of the "Jumbos" is used for moving. Table 5 

 gives the approximate cost of the best grade of logging blocks f. o. b. 

 San Francisco. 



