DESCRIPTIONS OF CLAMSHELL PREDGES 181 



six upright capstans on deck for handling lines and scows. The 

 stern engine had 8x10 in. cylinders and drove the three friction 

 drums for the stern anchors and two capstans on deck. Each cap- 

 stan was fitted with independent friction, brake and rackets. 



Steam was supplied to all three engines by two Roberts water 

 tube boilers. Each boiler had 46 sq.ft. of grate surface and 1200 

 sq.ft. of heating surface and was built for 250 Ibs. steam pressure, 

 although they were run at 125 Ibs. pressure. All the engines were 

 piped to a Wheeler admiralty condenser and also to a free exhaust 

 pipe, so that they could be run either condensing or non-condensing. 



The coal consumption was estimated from four to five tons per 

 day. The machine was operated by a crew of ten men. Jn regard 

 to the efficiency of the machine it worked one bucket a minute in 

 65 ft. of water. Its average work was the loading of ten or eleven 

 scows per day, the capacity of each scow being about 400 cu.yds. 

 The dredge often loaded scows in 30 and 40 minutes, and in soft 

 clay repeatedly loaded a pocket containing 60 cu.yds. with four 

 buckets in 4 minutes in 60 to 70 ft. of water. 



The dredge has worked very satisfactorily, working quickly, 

 easily and smoothly, with plenty of power and abundance of strength 

 in all its parts and with great steadiness. 



The Clamshell dredge "Champion" a new departure, namely 

 the opening and closing of a clamshell bucket by means of com- 

 pressed air, was designed by Mr. W. H. Arnold and used in the dredge 

 "Champion" of the W. H. Beard Dredging Co. of New York. It was 

 described in the Engineering News, May 2, 1901, from which the 

 following condensed description was taken: 



The pneumatic clamshell dredge bucket is an innovation 

 which promises to have a wide field of usefulness. As engineers 

 familiar with this type of dredging apparatus know, the ordinary 

 chain-closed clamshell has serious defects. The bucket can be 

 closed only after it has come to rest on the bottom, and the pull of the 

 closing chains reduces the effective digging weight of the buckets 

 owing to their lifting action. To avoid these objections several 

 attempts have been made to devise buckets closing by the action 

 of liquid pressure in a cylinder, but so far none of these devices 

 has gained much favor. The bucket illustrated here is one of the 

 latest of the devices and has given very good results. In it the 

 opening and closing of the bucket is performed by air pressure 

 operating through a cylinder and piston, the action being wholly 



