14 BULLETIN 300, U. S. DEPARTMENT OF AGRICULTURE. 
well as the digging pull on the bucket, are practically the same for 
any one size of dredge on all three types of hoist, the variation in the 
cable speed being taken care of in the diameter of the hoisting drum 
and the ratio of the gears. Thus a single-line hitch requires heavier 
machinery and a higher gear-ratio, while a triple-line hitch has a 
lower ratio of gears and a greater cable speed than either of the 
other two types. 
The hoisting and backing machinery for all three types follows the 
same general design and construction. With a triple-line hitch the 
hoisting drum is mounted directly ahead of the main engines and is 
geared directly to the engine pinion, while with the single and 
double-line hitches the hoisting drum is compound-geared from 
the engines so as to decrease the cable speed and increase the 
pull. The engines are of double nonreversible type, throttle-con- 
trolled. On the larger sizes of dredge the hoisting and backing 
drums have grooved surfaces and are moved by steam-set frictions 
of the outside-band type, the cylinders for operating the frictions 
being attached to the spokes of the larger gears and connected to the 
friction bands by levers keyed to crank pins inserted through the 
gears near their rims. The entire mechanism is mounted on a struc- 
tural-stee] base and is kept in alignment by means of cross braces and 
gusset plates. 
Floating dipper dredges are designed with the pulls on the dipper 
bail shown in Table 5. 7 
TABLE 5.—Pull on dipper bail for various sizes of dipper. 
Capacity of 
machine. Pull. 
Cubic yards. Pounds. 
1 30, 000 
4 39, 000 
bo 
2 
7 : 
3 63,000 
4 , 
5 104/000 
The swinging engines are of the double-reversible type, compound- 
geared to either a single drum or to a long shaft which has a drum at 
each end for direct leads to the swinging circle. Only one lever is 
required to reverse and control the engine. On the small dredges, 
which have little deck space for machinery, the swinging is usually 
done by means of friction drums operated by either the main engine 
or the hoisting and backing engines. 
The machinery for operating the spuds varies both with the type of 
spud used and with the make of dredge. Telescopic bank spuds may 
be raised by a friction hoist and the pinning up of the dredge accom- 
