FLUMES AND LOG SLUICES 



395 



work must be done at some point below the flume, often leading 

 to increased cost of manufacture. 



LOCATION 



Flume routes are best located by engineers who have special- 

 ized on logging. The practice followed by some successful flume 

 builders is to locate the route with a transit and set stakes as 

 for a railroad survey. Levels are then run and plotted and the 

 grade line established, the latter being the cut-off height of the 

 trestle bent which is the bottom of the cap. Center stakes for 

 the bents are established at proper intervals, and foflowing this 

 the grade stakes are set for the batter-post mud-sifls. The 

 data for the base of each trestle bent are calculated for the use 

 of the constructors, and show the length of the two lower sash 

 braces, the distance along the batter posts, and the length 

 each batter post must extend below the first sash brace in order 

 that the trestle may stand plumb on the mud-siU. The calcu- 

 lation of the length of each sash brace is important because 

 it governs the batter of the posts and if it is not properly 

 calculated the spacing between the posts under the cap will 

 vary. 



Careful consideration must be given to curves and the maxi- 

 mum degree of curvature must be determined for the longest 

 material that is to be handled. The following table ^ of curva- 

 tures for flumes is regarded as safe. 



Curves at the base of steep grades should be avoided, because 

 jams will form which will not only damage the flume but will 



1 From Lumber Flumes, by Francis R. Steel, Bui. of the Harvard Forest Club, 

 Vol. I, 191 1. 



