DIPPER DREDGES 155 



along a circular track, of varying diameter, reaching to 20 ft. on 

 the larger dredges. The turntable is provided with a horizontal 

 groove around which passes a chain or rope wound around the 

 drum of a reversible engine. By paying the rope in or out the 

 turntable is turned, carrying with it the boom. 



The dipper handle is made of wood reinforced at the sides with 

 iron wearing plates. In small dredges the lower side is provided 

 with a cog rack which travels on pinions mounted on the boom. 

 These pinions are connected with a wheel controlled by a brake so 

 that the dipper can be held in any position. In large dredges the 

 dipper handle is held in place by a yoke and sliding plates arranged 

 in such manner that it can be held in any desired position. The 

 dipper handle is inserted in the slot of the boom and it is made of 

 different lengths, depending upon the depth at which the dredge 

 is designed to work. 



The dipper or bucket is similar to the one used on steam shovels. 

 The sides are built up of heavy steel plates riveted to angle irons, 

 while the bottom is only hinged to the back, forming a trap door, 

 which is kept closed by a spring latch. The latch is easily opened 

 by simply pulling a chain, but closes automatically as soon as the 

 dipper is lowered again. When the dredge is designed to work in 

 loose soils the front edge of the bucket is reinforced with a steel 

 cutting edge which can be easily renewed when worn out, but in 

 dredging through compact soils the front edge is reinforced by steel 

 projecting teeth. The capacity of the dredge is always given in 

 terms of the capacity of the bucket, thus, for instance, a 6-cu.yd. 

 dipper dredge is a dredge of the dipper type in which the capacity 

 of the bucket is equal to 6 cu.yds. Fig. 45 shows a dipper dredge 

 of 6 cu.yds. for dredging through loose soils, built by the Bucyrus 

 Co. of South Milwaukee, Wis. Buckets are made of different 

 sizes varying between 1 and 12 cu.yds. A bucket of 6 cu.yds. capac- 

 ity seems to be the most convenient and is preferred by engineers 

 and contractors. The bucket can be provided with a heavy cast- 

 steel bail, or the boom line may be attached directly to chains 

 stretched between the sides of the bucket. The bucket can be 

 fixed to the handle in different ways, which vary with the different 

 manufacturers. The boom line operating the bucket is attached 

 to the bail, passes over a large grooved sheave on top of the boom, 

 and passing over and along the upper side of the boom and over a 

 second large grooved sheave on the turntable, is wound around the 



