TIMBER SLIDES AND CHUTES 



237 



slides. The grade necessary to make logs run by gravity depends 

 on the character and condition of the shde, the kind and size of 

 the timber and whether the slide is used dry, greased or iced. 

 The greater the weight of the log the faster its speed, hence 

 large or long logs will run on lower grades than small or short 

 ones. Heavy hardwood logs will run on lower grades than 

 most soft-woods, and peeled logs will run on lower grades than 

 if unpeeled. 



Earth slides with a 25 per cent grade may be used during the 

 summer but if the grade is as low as 10 per cent they are used 

 to best advantage during cold weather when they can be iced. 



During the warm season, horses are often used to drag logs 

 in earth slides. Several logs are fastened together by grabs into 

 a ''turn" and a team is attached to the forward log. In cold 

 weather animals can be wholly or partially dispensed with. 



Iced timber sUdes are most efficient and therefore may be 

 used on the lowest grades; those lubricated with skid grease 

 rank next, while dry timber sHdes are the least efficient. 



The following table of grades for running timber slides is from 

 European practice:^ 



Grades of 25 per cent are considered best for dry running 

 timber shdes in which large logs are to be handled, although 45 

 per cent may be used on short stretches if the shde is built 

 strong and rigid. The minimum grade should not be less than 

 10 per cent. 



Timber sKdes with maximum grades of 80 per cent and an 

 average grade of 60 per cent have been operated, but are not 

 desirable because of the heavy loss through breakage. 



1 From Forest Utilization, by Karl Gayer. (Vol. V, " Schlich's Manual of 

 Forestry," p. 325.) 



