AERIAL TRAMWAYS 259 
The tramway was built with a standing line 1| inches in 
diameter which was suspended from spars, spaced from 500 to 
2000 feet apart, depending upon the configuration of the ground 
surface. The stationary return line for the trolleys was |-inch 
since the chief load which it had to support was the weight of 
the empty carriers. An endless f-inch traction line, run at a 
speed of 250 feet per minute, furnished the tractive force for moving 
the loaded and empty carriers. This traction line was driven by 
a 7- by 9-inch yarding engine, on the single-drum of which a 
capstan was bolted. The traction line was wound three times 
around the drum and then passed through three 10-inch blocks 
at the end of the line, so arranged that two of the blocks, spaced 
on either side of a central one, acted as spreaders and prevented 
too sharp an angle in the traction cable. The standing line was 
built in units 2000 feet in length, the ends of which were moored 
to stumps or trees. The ends of two sections of cable were 4 feet 
apart, the intervening space being spanned by a section of U- 
shaped metal track. There were curves as high as 43 degrees, 
the standing line at such places being supported on masts spaced 
100 feet apart. 
The logs were loaded from a skidway at which the elevation 
of the standing line was 4 feet. A choker, placed near each end 
of the log was caught in a slot on the lower part of a trolley, and 
the traction cable was placed on top of the choker in the same slot. 
Loads were spaced from 50 to 200 feet apart, the cable being 
stopped whenever a log was loaded. The capacity of this system, 
operated by a crew of 18 men, was 15,000 board feet per hour. 
The design of the hanger and trolley used on a line similar to 
that in Idaho is shown in Fig. 83. The trolley is made of cast 
steel and has two 12-inch sheave wheels hung on a frame pivoted 
at a so as to allow it to travel up and down the hanger segment 
o on which the standing line d rests. The endless traction line 
is shown at b and e. The hanger hook is pivoted at c in order 
to give flexibility to the suspended load so that it can swing in a 
forward or backward direction. The grip for holding the trac- 
tion line is shown at / and also at e, the weight of the load serving 
to hold the grip k against the cable. A chain is wrapped twice 
around the end of a log and caught in the hook m at w which 
is then closed as shown in the cut and locked with the clevis I. The 
release of the load is accomplished by raising the clevis I which allows 
