POWER SKIDDING 



197 



foreman before felling operations begin, must be straight and 

 sound, and should have a minimum diameter of 18 inches at 

 60 feet above ground. In order to make the spar more stable 

 the trees are topped before the rigging is placed. 



In recent years a cableway skidder with a heavy steel spar 

 mounted on a skidder car has been placed on the market. This 

 spar replaces the head spar tree required by the earlier type and 

 is so constructed that it can be lowered to facilitate moving the 



Fig. 52. — A Steel Spar Cableway Skidder showing Loading Boom in Front. 



skidder from one set-up to another. The adjustment of the 

 blocks and the guying of the steel spar require only from one to 

 two hours, while a day is needed to take down the tackle, move 

 the skidder and adjust the blocks to a new head spar. The 

 great weight of the machine prevents its use on light or poorly 

 constructed track. 



Tail trees, which are also chosen before felling begins, are 

 located from 150 to 250 feet apart and should be at least 18 inches 

 in diameter at 30 feet above ground. 



