36 “BULLETIN 300, U. S. DEPARTMENT OF AGRICULTURE. 
BOOM. 
In the smaller drag-line excavators the boom is generally con- 
structed of two channels with cross bracing (Pl. IV, Fig. 1), while in 
the larger machines two cross-braced lattice girders are used (Pl. V, 
Fig. 1). The lower ends of the two main members of the boom are 
spread apart to give stability, while at the upper end the two mem- 
bers are joined, and at that point one or more sheaves are placed. On 
some of the smaller machines the top of the boom is guyed to the top 
of the A frame, which is located near the front of the main engine. 
The lower ends of the A frame are bolted to the platform; the upper 
end is guyed to the rear corners of the platform. The length of the 
boom for drag-line excavators varies from 30 to 150 feet. On most 
machines it is suspended by a cable running to a drum on the plat- 
form. For raising or lowering the boom this drum may be operated 
either by power or by hand. 
BUCKET. 
There are various forms of scraper buckets made for use with drag- 
line excavators. A type of bucket in common use is shown in Plate 
VI, Figure 2. This bucket can be operated with two lines, a loading 
and a hoisting line. For holding the bucket horizontal when hoist- 
ing, a patented device is used which consists of a cable secured to the 
top of the bucket at its front end, which, after passing through a 
sheave at the hoisting connection, runs down to the loading bail. 
With the loading line kept taut the bucket maintains a horizontal 
position. To dump the bucket, the loading line is merely released. 
The sizes, weights, and approximate prices of this bucket of stand- 
ard type are shown in Table 14. 
TABLE 14.—Weights and prices of scraper buckets. 
Width | Weight 
Ca- of : ; 
; without Price. 
pacity.| cutting teeth. 
edge. 
Cu.yds.| Inches. | Pounds. 
3 
3 36 2, 200 $660 
1 45 2, 500 698 
14 45 2, 800 780 
ie 48 3, 200 862 
2 51 4850 | 1,043 
2h 57 5,850 | 1,191 
3 60 6,550 | 1,357 
3h 60 7,000 | 1,510 
Many operators experience trouble with scraper buckets of the 
smaller sizes from their failure to clean themselves when working 
in sticky clay. To obviate this a skeleton scraper bucket has been 
made for very sticky clay. This bucket cleans itself more readily in 
