136. BULLETIX 111, U. S. DEPAETMENT OF AGKICULTUEE. 



Rigging. — The rigging consists of a main cable siis]Dended between 

 a head tree (fig. 43) and a tail tree (fig. 44). Upon this line the car- 

 riage travels. Ttvo lines only are required to operate the carriage; 

 one to haul it in, the other to haul it back. The main cable, leading 

 from a drum on the logging engine, passes through a block suspended 

 near the top of the head tree, thence out to and over a tree shoe 

 suspended on the tail tree, and then down to a stump, where it is 

 made fast. The haul-in line, leading from a second drum on the en- 

 gine, passes through a block on the head tree in the same way as the 

 main cable, and thence to the front end of the carriage, where it is 

 made fast. The haul-back or trip line, leading from a third drum 

 on the engine, passes along one side of the run, then through a block 

 on the tail tree, and thence to the back end of the carriage. 



The distance between the head and tail tree depends, of course, 

 on the yarding distance, which in turn may be fixed hy the practical 

 range of the system. The system has been used successfully to yard 

 logs a distance of 2,500 feet. The tail trees are from 150 to 300 feet 

 apart, depending on conditions. 



Operation. — The haul-back line hauls the carriage out along the 

 main line to the point where the log is to be hooked on. Then the 

 main cable is slackened sufficiently to lower the carriage to the ground, 

 the haul-back line being, used to pull the carriage to the log when 

 the log lies to one side of the center of the run. ^'^Tien the choker or 

 chokers have been attached to the carriage, the main cable is tightened 

 until the front end of the load is raised far enough from the ground 

 to clear obstructions. Powerful brakes on the main drum cable hold 

 the main cable taut while the carriage with its load is pulled in. 

 TTlien the load is brought to the landing place, the main cable is 

 lowered and then the load unhooked. The main cable is then tightened 

 and the operation repeated. As logging on a run progresses, the cor- 

 ner trip block has to be shifted. 



Logs can not be j^arded from behind the tail tree, and it is difficult 

 to yard logs on the outer edge of a wide strip near the tail tree. More 

 power is required to raise the logs from the ground than with S3^s- 

 tems having a taut oveihcad cable, since the engine has to raise the 

 cable as well as the log. 



Changing lines. — One head tree is all that is required at each set- 

 ting of the engine. The tail tree is changed each time a strip is 

 logged, the new. tail tree being selected and guyed before the old one 

 is deserted. In changing lines, the lines are first drawn in to the 

 head tree. The straw line, which is run before the change is started, 

 is then used to run out the trip line. This operation takes from one 

 to two hours. 



Equipment. — The equipment is much the same as that used with 

 other systems of o^■erhead logging. 



