We illustrate the new dredger Ajax, recently built for Mr. Geo. F. Smith,
of Stockton, Cal.
The dredger has now been working for two weeks at Wakefield, and, we are
informed, is giving entire satisfaction; having been repeatedly timed to
be discharging clay at the rate of 220 cubic yards per hour.
[Illustration: THE NEW DREDGER AJAX.]
The Ajax is almost a duplicate of the last dredger designed by Mr. Ferris
for levee building on Roberts Island, with such modifications and
improvements as have suggested themselves in the two years it has been
working.
The hull, oval in plan, is 36 ft. 10 in. by 60 ft. over all; it has four
solid fore and aft bulkheads, and a well hole 5 × 12 ft. at one end for
the bucket ladder.
The main engine is 10 × 24, operating, by bevel gearing and a 3½ in.
vertical shaft, a 4 sided upper tumbler with 21 in. sides. This engine
works also a gypsy shaft for swinging, and the conveyer that carries the
mud ashore. A steam hoist with 6 × 11 engines raises and lowers the
bucket ladder. The buckets, at 4 foot centers, have a struck capacity of
5 cubic feet, and are speeded to deliver from 18 to 20 a minute,
according to the character of the material being handled. They are of
boiler iron, with a 5 in. steel nosing. The links are of wrought iron,
with cast bushings. The lower tumbler is hexagonal, on a 4 in. shaft.
The conveyer, projecting 72 ft. from the center of the boat, consists of
a 5 ply rubber belt 36 in. wide; running over iron drums at each end and
intermediate iron friction rollers at 3 foot centers. Ratchet and pinion
on each side of conveyer ladder give means for taking up the slack of the
belt and adjusting the drums to maintain them parallel.
This conveyer is the important feature of the dredge. It is entirely
satisfactory in its working and delivers its material, as nearly as may
be, in a dry state upon the levee. It was feared the rubber belt would be
shortlived, but a 4 ply belt ran continuously for over two years on the
Roberts Island dredge before it needed replacing.
The boiler is of the marine type, 52 in. by 10 ft. 6 in., with 3 in.
tubes and 14 in. flues; and burns about 1,400 lb. of steam coal in a day
of 12 hours. There are three pumps aboard--a hand force pump for washing
boiler, a plunger pump for boiler feed, and an Evans steam pump to throw
a jet of water into the delivery hopper when digging in any very
tenacious material. All three are connected with the boiler.
Water tanks below deck serve to trim the boat and furnish a supply for
the boiler. The dredger cuts by swinging on a center spud 16 in. in
diameter, and moves forward from 8 to 10 ft. at each fleet.
The Roberts Island dredger, of which the Ajax is an improved copy,
handles steadily 700 yards per day of 12 hours, in the stiffest and most
tenacious clay in which it has been worked; and ranges from that average
to 1,500 yards per day in soft, peaty mud.
The Ajax was built by Farrington, Hyatt & Co., of the Stockton Iron
Works.
This type of dredger can be built for about $12,500, and we are informed
can be relied on for a monthly average of 26,000 yards in any material
met with in the overflowed lands near Stockton, delivered 50 ft. ashore,
at a height of 10 or 12 ft. above the ground line.--_Min. and Sci.
Press_.
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