EXCAVATING MACHINERY USED IN LAND DRAINAGE. 3 



In late years the so-called dry-land excavators of various types have 

 been developed and have reduced the cost of excavation under con- 

 ditions to which floating dredges are not adapted. The growth of 

 the drag-line scraper excavator has been especially prominent. At 

 present this machine probably has a wider field of usefulness than any 

 other type of excavator made. 



The cost of all kinds of excavation has now reached a very low 

 figure as compared to the prices prevailing for work by machinery 

 only a few years ago. This has mainly been brought about by the 

 entrance into the contracting field of many men equipped with 

 modern machinery who, through the keen competition, have taken 

 contracts at prices permitting only a small margin of profit. 



THE FLOATING DIPPER DREDGE. 



The floating dipper dredge is probably the oldest and most widely 

 used type of machine for the excavation of drainage ditches. The 

 essential parts are the hull, engines, boiler, A-frame, swinging circle, 

 spuds, boom, and dipper. With the exception of the dipper theseparts 

 appear in some form on every type of floating dredge used for ditching. 

 Various manufacturers have different patented details of construction, 

 but the general principles of construction and operation are the same 

 on all floating dipper dredges. 



ESSENTIAL FEATURES OF CONSTRUCTION. 



The hull may be either of wood or of steel; the use of the latter 

 material will undoubtedly constantly increase in the future owing to 

 the ever-increasing cost of timber that is suitable for building hulls. 

 The many difficulties met with in the operation of the earlier machines 

 have taught manufacturers that certain fixed relations exist between 

 the dimensions of the hull and the positions and weights of the other 

 parts of the dredge. Unless these relations are considered in the 

 design of the hull much trouble will result in the operation of the 

 dredge. The smaller dredged ditches are generally constructed by 

 machines with from 1 to 1^ yard dippers. The machinery necessary 

 for operating these sizes being comparatively light, the hulls are 

 of such dimensions that they can easily be floated in the smaller 

 channels, although the width of hull used for a machine of given 

 capacity varies somewhat with the different manufacturers. Some 

 dredges are so designed that the thrust of the dipper, when digging, 

 is carried directly from the A-frame through the spud arm to the 

 spud shoe and the bank of the ditch. By this arrangement a slightly 

 narrower hull can be used than is necessary where the machine is 

 differently designed. 



