DIPPER DREDGES 157 



operates the different engines by means of levers, all located in the 

 captain's room on deck. The dipper dredges of large capacity are 

 usually provided with a deckhouse containing the kitchen, dining- 

 room, sitting-room, staterooms, bathroom and office; but these 

 conveniences vary in class of work done. 



The dipper dredge is a stationary machine and consequently 

 is entirely without propelling apparatus or engine. It is able, however, 

 to move from place to place so as to follow the progress of the work 

 without any help from tugboats or from the anchoring chains. 

 When the dredge is to be moved so as to attack a new bed, the 

 spuds are lifted, the dipper handle fully extended is lowered so as 

 to engage the soil as in dredging, the handle is then withdrawn and 

 this effort causes the vessel to move forward. By repeating 

 the same operation the machine slowly advances to the required 

 point. Then the spuds are lowered again, the boat is made 

 firm and the dredging operations are resumed. It takes less than 

 two minutes to lift the spuds, to move to a new place to be dredged 

 and lower the spuds again. The machine can be moved also laterally 

 by rotating around one spud. This is done by the stern spud being 

 held fast to the bottom while the two others are lifted; the vessel 

 will move either to the right or the left by the same operation of the 

 dipper engaging the soil, then the stern spud is lifted while one of 

 the fore spuds is lowered, and the dredge rotating now around this 

 new point will be moved laterally; and repeating the same operation 

 over and over the dredge can be moved the required distance, when 

 all the spuds will be lowered, the machine made fast, and the 

 dredging resumed. 



The output of the dipper dredge is an average of one bucket per 

 minute, and for this reason contractors have continuously requested 

 manufacturers to increase the capacity of the bucket. Thus there 

 are to-day dredges with buckets of 15 cu.yds., but the great cost of 

 these mighty machines and their high running expenses so increase 

 the cost of excavation that the work of these dipper dredges cannot 

 be compared with that of other large machines of different type. 

 However, dipper dredges of small capacity working under certain 

 conditions are still considered the most efficient and economical 

 machines. 



The output of the dipper dredge assumed at the rate of one 

 bucket per minute gives a fair idea, for rough estimates, of the work 

 to be obtained from the dipper dredge- under ordinary circumstances. 



