66 A TREATISE ON DREDGES AND DREDGING 



vidual dredges, but a general idea can be obtained from the 

 following data: 



Elevator or ladder dredges with small buckets, that is from 4 to 

 10 cu.ft., will excavate from 150 cu.yds. of hard material to 2000 

 cu.yds. of soft material in a 10-hour day. Working in average 

 earth under ordinary conditions about 1000 cu.yds. can be exca- 

 vated. With buckets from i to f cu.yd. capacity the output will 

 vary from 500 cu.yds. in hard material to 3000 in soft mud. In 

 average earth from 1500 to 1800 cu.yds. can be handled in a 10-hour 

 day. With buckets from J to 1 cu.yd. from 1000 to 6000 cu.yds. 

 can be excavated, doing in average earth in a 10-hour day, about 

 3000 cu.yds. 



Dipper dredges are seldom made with buckets of less than 1 cu.yd. 

 capacity. A comparison of a large number of records of dipper 

 dredges of various sizes shows that machines of this type working 

 in soft mud will excavate just about twice as much as in hardpan 

 and such soils. When logs and boulders are encountered less than 

 this amount is excavated. 



A machine with a 1 cu.yd. dipper will excavate from 300 to 

 800 cu.yds., doing in average earth about 500 cu.yds.; with a 

 3-cu.yd. dipper from 1000 to 1000 cu.yds. can be excavated ; and in 

 average earth about 1500 cu.yds. With a 6-cu.yd. dipper 5000 cu.yds. 

 of average earth should be excavated in 10 hours. With dippers 

 having a capacity of from 9 to 10 cu.yds. about 8000 cu.yds. should 

 be excavated in average earth, in 10 hours. 



With grapple dredges there is generally a less output than with 

 dipper dredges, as they are generally used in deeper water, and then 

 too the movement of the bucket is slower. With small buckets 

 working in hard material, such as hardpan, some records show as 

 small an output as 180 cu.yds. in 10 hours. The " Fin MacCool," 

 described later in this treatise, with a 10-cu.yd. clamshell bucket 

 excavating in deep water, dug 2800 cu.yds. in 10 hours. However, 

 there are some records with smaller buckets of 4000 to 5000 

 cu.yds. per day. 



Hydraulic suction dredges must have their work gauged by the 

 size of the pump, depth of water, and length of discharge pipe. Pipes 

 up to 2000 and 3000 ft. are very efficient; over this distance the 

 friction in the pipes is great, but many dredges are designed to-day 

 to pump material from 4000 to 5000 ft. The longest pipe line known 

 to the writer was 2J miles. The smallest record for a day's work 



