INPUT DESCRIPTIONS 



EXTRACTION COSTS 



Extraction costs are made up of the seven inputs shown in figure 1 . 



MBF/acre is a situation variable called density, which may be determined from a 

 timber cruise or from contractors' records. It is designated either "XBFPA" or "MBFPA" 

 in the computer program (see p. 14). Defect averaged 10 percent. 



LogS/MBF also is a situation variable and is readily judged by experienced contractors 

 Its program designation is "XGPMBF" or "LGPMBF. " Log lengths ranged from 16 to 40 feet. 



Hours/ cycle denotes production time and is generated by the following multiple- 

 regression equation: 



y = ^o+Vi+V2+V3' 



where Y ~ cycle (turn) time in hours 



x^ = skidding distance 



x^ = slope 



x = number of logs per cycle 



Briefly, the equation gives cycle time in hours based on the three most significant varia- 

 bles we found --skidding distance, slope, and number of logs skidded during each cycle. The 

 constants for this equation are as follows: 



Skidding type Regression (a ) Distance (a ) Slope (a ) Logs (a ) 



Crawler tractor, 



25-40 DBHP 



0.04293 



0.0018800 



0.0020339 



0.02415 



Crawler tractor, 











41-60 DBHP '■ 



.08071 



.0000953 



.0020964 



.02218 



Crawler tractor, 











61-80 DBHP 



.10518 



.0002705 



- .0020109 



.01257 



Crawler tractor, 











110-130 DBHP 



.10736 



.0004778 



.0013270 



.01502 



Rubber-tired vehicle, 











55-80 BHP 



.01222 



.0002291 



- .0007572 



.01912 



Rubber-tired vehicle. 











81-117 BHP 



.08941 



.0007040 



.0012269 



.01182 



High- lead, portable tower 



.04297 



.0000024 



.0009517 



.00807 



Idaho jammer 



.00535 



.0000475 



.0001651 



. 00000 



Shovel ( w/tongs) 



.01760 



.0002081 



- .0005169 



.00000 



The multiple-regression equation is shown in program statement 35, beginning with "RC" 

 (regression constant) and ending with "XLGPC" (number of logs per cycle). 



Delays are caused from equipment breakdowns, personnel "breaks," weather condi- 

 tions, etc. These vary among individual skidding operations. Delay averages as percents of 

 available operating times were established for the various skidding methods as follows: high- 

 lead, portable tower, 20 percent; Idaho jammer, 15 percent; shovel (w/tongs), 20 percent; all 



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