184 A TREATISE ON DREDGES AND DREDGING 



cord which, rotates the reel in the reverse direction and winds the 

 hose onto it as fast as it comes out of the water. Both the unwind- 

 ing and rewinding actions are wholly automatic and require no 

 particular care on the part of the operator. 



On the dredge " Champion " a double or Siamese hose was used, 

 one barrel of which supplied air to the bottom of the piston and the 

 other to the top of the piston. A pressure of 100 Ibs. per sq.in. was 

 used. The admission of the air to the cylinder and its exhaust 

 were controlled by a three-way cock on each of the two lines of 

 pipe leading to the hose, these cocks being placed in the operator's 

 cabin close to the hand of the dredge operator. 



The main dimensions of the bucket used on the dredge ''Cham- 

 pion" were: Capacity, 3 cu.yds.; diameter of cylinder, 16 in.; area 

 of piston, 200 sq.in. ; length of stroke, 4 ft. ; working pressure of air, 

 100 Ibs. per sq.in. ; total pressure on piston, 20,000 Ibs. ; total weight 

 of reciprocating parts, 9000 Ibs.; total closing force on material, 

 29,000 Ibs. ; actual weight of bucket, 24,000 Ibs. This bucket was 

 designed for hard digging. For soft material a larger bucket is 

 employed and for handling blasted rock the bucket shell is replaced 

 by grapples. 



The advantages claimed for this form of clamshell over chain- 

 closing buckets are: Closing and opening independent of use of 

 frictions; bucket can be lowered into scow well and dumped on the 

 doors without dropping the load; a gain of about 10 ft. in width 

 of cut is made owing to the fact that the chain-closed bucket will 

 fall off in opening. The entire weight of the bucket is on the bottom 

 while closing, and finally the ability to close the bucket at a given 

 depth enables the dressing off of the bottom of the cut at the required 

 depth without excess excavation. 



