EXCAVATING MACHINERY USED IN LAND DRAINAGE. 19 
In the smaller drag-line machines the boom is generally constructed 
of two channels with cross bracing, while for the larger machines two 
cross-braced lattice girders are used. The lower ends of the two 
main members of the boom are spread apart to give stability, while 
at the upper end the two members are joined, at which point one or 
more sheaves are placed. 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 while the 
upper end is guyed to the rear corners of the platform. 
The bucket most frequently used on drag-line excavators is of the 
scraper type, although the clam-shell and orange-peel buckets are 
sometimes used for special work. The scraper bucket is connected 
to the main engine by two steel cables called respectively the hoist- 
ing and drag-line cables. The bucket is filled by being pulled toward 
the machine, and when full is raised by the hoisting cable which 
passes from the bucket over the sheaves in the end of the boom and 
down to the hoisting drum. There are many patented devices for 
quickly dumping the bucket, a feature that is important in digging 
sticky material. The capacity of the scraper buckets range from 
about five-eighths cubic yard to 3 cubic yards. 
The crew necessary to operate this type of machine consists of two 
men, an operator and a fireman on the steam machine, or an operator 
and an oiler on the gasoline or electrically-driven machines. In 
addition to these, two or more trackmen are required, except in the 
case of the so-called walking type. 
For movement over the ground the drag-line excavator may be 
mounted on either wheels, rollers, caterpillar tractors, trucks, or 
walking shoes. 
Where the ground is uneven or cut up with old channels and sur- 
face ditches, it is necessary in the case of all traction or roller exca- 
vators which are not of the rotary type to block or bridge across the 
depressions and to lay heavy timbers on which to move the machine. 
Where the machine weighs 25 tons or more the expense of providing 
a solid foundation becomes quite great. In the rotary type of exca- 
vator the machine can be revolved and can build its own foundation 
of earth. 
Drag-line excavators vary greatly in weight, not only with the 
capacity of the machine but with the manufacturer. Some of the 
five-eighths-yard stationary types weigh no more than 12 tons. 
There are a few standard makes of drag-line excavators which, 
although they may differ in details of construction, are operated in 
the same manner. They vary in weight from 25 tons to about 110 
tons. It is especially noteworthy that in all makes the heavier 
machines are mounted on wooden rollers or on trucks to run on a 
track. Wheels and caterpillar traction are used only on the fighter 
