CHAPTER XV 



AERIAL TRAMWAYS 



Aerial tramways are used for carrying logs and other forest 

 products up or down steep slopes, where other forms of trans- 

 port are not feasible. 



The most common type used in the United States has a sta- 

 tionary main cable which is stretched between the terminals of 

 the tramway and may consist of a single span or be supported at 

 frequent intervals on trestles. The trolleys carrying the loads 

 run on this cable. 



On gravity trams the route need not run in a direct line 

 provided there are stations at each sharp angle where trolleys 

 can be switched from one cable to another. Where power 

 is used to move the loads the line must be straight, or else 

 separate power must be provided for each straight section 

 of cable. Vertical curves are permissible when sufficient mo- 

 mentum or power is available for carrying the loads over 

 depressions. The average grade for gravity tramways is from 

 25 to 30 degrees. 



A single-wire tramway constructed in Tennessee to bring logs 

 from a plateau to a railroad in the valley had a |-inch main 

 cable with a distance between terminals of 3700 feet. The 

 grades conformed to the general slope of the land. The upper 

 end of the cable was fastened to a tree on the edge of the plateau 

 and ran in a straight line to a railroad located at the lower ter- 

 minal in the valley. The cable was supported at intervals of 

 from 150 to 250 feet on brackets of varying lengths which were 

 fastened to trees. The cable rested, without fastening, in a slot 

 in a casting bolted onto the end of the brackets, except in de- 

 pressions where one end of a piece of strap iron was riveted to 

 the outer side of the casting and the other end passed over the 

 cable and was nailed to the bracket. 



