138 



BULLETi:^r 711; U. S. DEPARTMENT OF AGEICULTUEE. 



The carriage has two sheaves, being light, simple, and strongly 

 constructed. On the bottom is a large hook, to which the chokers are 

 attached, and a small hook at each end, the haul-inline being attached 

 to one, the haul-back line to the other. The carriage (fig. 45), with 

 16 bj^ 3 inch manganese-steel sheaves, costs about $120. 



The blocks are much the same as those used in high-lead yarding. 

 The price of overhead blocks is given under " Loading." The fol- 

 lowing gives the number, types, and selling prices of blocks used 

 with this system at one camp : 



Net selling price. 



Type and size: 



1 14-mcli tree jack (fig. 46) $180 



3 large moving blocks 150 



2 yarding blocks 50 



2 IS-inch" trip or haul-back blocks 50 



6 14-inch trip or haul-back blocks 105 



2 tree shoes (fig. 47)^ 100 



Fig. 45. — Double-sheave over- 

 head can-iage. 



Fig. 46. — Tree jack. 



Fig. 47. — Tree shoe. 



Output. — The output with this system ranges from 50,000 to 100,000 

 feet per day. At one camp where the logs were moved 1,500 feet 

 down a steep slope the output averaged about 60,000 feet per day, 

 the logs averaging about 800 feet in volume. In the same camp 

 the output averaged from 85,000 to 100,000 feet per day on practically 

 level ground, when the hauling distance did not exceed 1,000 feet. At 

 another camp, where the logs were moved 2.000 feet down a steep 

 mountain side, the output averaged about 50,000 feet per day, the logs 

 averaging about 900 feet in volume. At still another camp, where 

 the logs were moved about 1,600 feet down a steep slope, the country 

 being badly broken up, the output ranged from 60,000 to 80,(X)0 feet 

 per day. In this latter case the timber was large, the logs averaging 

 2,000 feet in volume, and some of them containing 6,000 feet. 



1 A tree shoe is used to support the overhead cable at the tail tree. Since the ti^htcn- 

 int,' is genorally done at the head tree, the outer end of this cable is stationary, making 

 a hardwood shoe instead of sheaves practical. 



