118 BULLETIN" 711, U. S, DEPARTMENT OF AGRICULTURE. 



One companj^ has found that the base of the spar tree should be 

 from 14 to 20 feet from the center of the track. To insure the work- 

 men against injury certain precautions are taken. The main-line 

 lead block is hung in a 2-inch strap, the pins and shackles of these 

 blocks being extra large. A " safety " guy is rigged under the bight 

 of the main line in such a way that the main line will be deflected 

 in case any of the rigging breaks. The bark on the spar tree is 

 removed for several feet at the point where the lead block strap is 

 attached, thus preventing it from being dislodged when yarding 

 is in progress. 



The general method of using a saw or ax to cut off the tops of 

 trees selected for spars is both tedious and dangerous work. One 

 company is using dynamite instead. The head rigger puts on a pair 

 of long-spurred climbing irons and ascends the tree to the desired 



height, taking several sticks of dynamite 

 with him. The dynamite, which is tied to- 

 gether end to end, like a string of sausages, 

 is fastened securely around the tree at the 

 point where he desires to remove the top. 

 A detonating cap, to which a long piece 

 of fuse is attached, is inserted in one of 

 the sticks of dynamite. The rigger de- 

 scends 20 feet or so, lights the fuse, and 

 makes his way to a safe place on the 

 ground some distance from the tree. After 

 a few minutes the dynamite explodes, the 

 tree top leaps into the air and comes 

 crashing down. This way of removing the 

 tops is only in the experimental stage at 

 present. 



EQUIPMENT. 



The equipment used in high-lead yard- 

 ing differs little from that used in ground 

 yarding. 



Yarding engines. — Any kind of two- 

 drum yarding engines may be used. To take full advantage of 

 Ihe system, however, an engine with higher drum speeds than that 

 of standard yarding engines should be used. One company, work- 

 ing on good ground and in second-growth timber where the logs 

 average about 600 feet in volume, has purchased yarding engines 

 designed especially for this system. These machines are simple 

 geared, with 11 by 17 inch cylinders. Both main and trip drums 

 are driven directly from pinions on the crank shaft without the 

 interposition of counter shafts or idlers. The drums are narrow 

 and of large capacity. The increased length of stroke compensates 



Fig. 35. — Auto-lubricatini 

 high-load block. 



