EXCAVATING MACHINERY USED IN LAND DRAINAGE. 24 
TABLE 11.—Clearance of dredges fitted with telescopic or convertible spuds. 
Overhead clearance. | Width clearance. 
Ca- 
pacity | ] ; 
Ante Telescopic Vertical | eS, Telescopic ankical 
spud. spud. | spud. spud. spud. 
Cu.yds.. Feet. Feet. Feet. Feet. Feet. 
3 18 18 143 14 to 16 20 to 22 
Seale erat eek | ae meee o de NE a 3 ao he 
1 18 20 174 16 to 21 24 to 29 
14 19 22 20 20 to 26 28 to 34 
2 | 20 24 202 26 to 32 32 to 38 
24 | 21 26 21 31t037 | 37t043 
3 | 22 30 22 35to42 | 41048 
ae lea eae les |r eee ee 235i sees eee eee Peace sake 
4 22 S4e leee assis 39to46 | 45to5l 
5 22 Sora lPeree eee: 43 to 55 49 to 61 
The overhead clearance is figured from bottom of hull to top of 
cabin, with A frame lowered and with spuds unshipped. Figures for 
width clearance are for minimum and maximum lengths of boom. 
When designing a ditch the engineer should always have in mind 
the limitations of the type and size of machine adapted to the work. 
Consistent with other considerations a ditch system should be so de- 
signed as to give the contractor the greatest amount of excavation for 
a given size of dredge. This point may be illustrated by a practical 
example: Suppose a ditch is designed with a bottom width varying 
from 16 to 46 feet and a cut of 7 feet throughout the length of 15 
miles. The ditch as planned is too wide at its lower end to be con- 
structed by a dredge of ordinary size, unless it be equipped with tele- 
scopic or convertible power spuds. By making the cut deeper at 
the lower end the width of the ditch can be made considerably less, 
and a dredge of ordinary size can dig the ditch throughout. To use 
two dredges of different sizes on such a comparatively small job 
would increase the unit cost. 
If ditches are planned for one machine to do all the work the cost 
of construction will be reduced, but the time required to do it all with 
one machine may be so great that the district would rather pay the 
additional cost involved in installing two plants. 
A contract may include a number of ditches, all but one of which 
are suited to a given size of machine, this one being too wide to be 
cut by the dredge at one cutting, with yardage insufficient to justify 
the installation of another dredge. That difficulty may be overcome 
by making a double cut, which, however, requires the use of either 
vertical or convertible spuds. 
Parallel small lateral ditches, each having a separate outlet into a 
large main canal, are difficult to construct. The dredge required to 
excavate the main ditch is too large for the economical construction 
Le ee ee eS OE oO ewETET 
