AERIAL TRAMWAYS 223 



A log was carried by a pair of trolleys, each having two sheave 

 pulleys which ran on the upper side of the cable. Two short 

 chains each having a ring on one end and a "grab" on the other 

 were used for attaching the logs to the trolleys. 



Five sets of trolleys were joined together by a |-inch cable, 

 which was wound around a drum equipped with a friction brake. 

 This drum was placed at the head of the tramway and served 

 both to control the speed of the descending load and to return the 

 empty trolleys to the head of the tramway. Power for the 

 latter purpose was supphed by a 15-horse-power gasoline engine. 



The logs were loaded on the tramway from a set of balanced 

 skids which were placed so that one end was directly under the 

 main cable. Horses brought the logs to the base of the skids 

 on which they were rolled. The grabs were then driven and 

 the skids elevated until the rings on the grabs could be fastened 

 in the hook on the trolleys. 



The maximum capacity of the tramway was 6000 feet log 

 scale per turn, and approximately thirty minutes were consumed 

 in making one round-trip. 



A similar tramway has been used in the Northwest for getting 

 logs upon plateaus from canyons. The cable is suspended 

 between two points and the loaded trolleys are hauled to the top 

 by a steam hoisting engine. 



A special adaptation of a single-wire tramway^ has been used 

 on an operation in the Northwest for lowering logs on grades 

 up to 60 degrees. The main cable was i| inches in diameter 

 and 1500 feet long. It was attached at the head of the tramway 

 to a large tree at a height of 75 feet. The tree was braced 

 securely on three sides with guy wires. A 16-inch sheave block 

 was spHced to the lower end of the main cable and through this 

 block a one-inch cable 150 feet long was passed. One end of the 

 latter was attached to a stump and the other to the drum of a 

 yarding engine, both stump and yarding engine being in front of 

 and equidistant from the sheave block. The main cable could 

 be hfted several feet above ground by tightening the secondary 

 cable with a few turns on the drum. The logs were attached by 



^ See The Timberman, Portland, Oregon, August, 1909, p. 24. 



