Logging; the principles and general methods of operation in the United States . STEM This comprises a main wire cable, from i inch to i| inches indiameter, suspended between two supports known, respectively,as the head spar tree and the tail tree. These are usuallylocated from 600 to 750 feet apart, although the span is some-times as great as 1500 feet. The greatest efficiency cannot beobtained at the latter distance, because lighter loads must behandled. Head spar trees are located along the logging railroad atintervals of approximately 1000 feet. They are selected by the ig6 POWER SKIDDING 1
Logging; the principles and general methods of operation in the United States . STEM This comprises a main wire cable, from i inch to i| inches indiameter, suspended between two supports known, respectively,as the head spar tree and the tail tree. These are usuallylocated from 600 to 750 feet apart, although the span is some-times as great as 1500 feet. The greatest efficiency cannot beobtained at the latter distance, because lighter loads must behandled. Head spar trees are located along the logging railroad atintervals of approximately 1000 feet. They are selected by the ig6 POWER SKIDDING 197 foreman before felling operations begin, must be straight andsound, and should have a minimum diameter of 18 inches at60 feet above ground. In order to make the spar more stablethe trees are topped before the rigging is placed. In recent years a cableway skidder with a heavy steel sparmounted on a skidder car has been placed on the market. Thisspar replaces the head spar tree required by the earlier type andis 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 theblocks and the guying of the steel spar require only from one totwo hours, while a day is needed to take down the tackle, movethe skidder and adjust the blocks to a new head spar. Thegreat weight of the machine prevents its use on light or poorlyconstructed track. Tail trees, which are also chosen before felling begins, arelocated from 150 to 250 feet apart and should be at least 18 inchesin diameter at 30 feet above ground. 198 LOGGING One end of the main cable is passed around the tail tree at aheight of 25 or 30 feet and is then carried to a stump or tree inthe rear to which it is made fast. The tailtree is braced with this cable and also withan additional guy rope. The other end ofthe main cable terminates in an eye nearthe head spar tree and is connected, bymeans of a clev
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisheretcet, bookyear1913
