Name/Title
Print, PhotographicEntry/Object ID
A1092.14Description
Small photo of a motorized suction dredge excavating the open, unlined section of the L.A. Aqueduct between the intake and Alabama Gates. There is a transformer float trailing behind dredge. Photo 2012.20.3 is likely the same dredge from a different position.
Information from Engineering Record, Vol. 62, No. 1, 1910:
"The suction dredges are both practically the same in design and construction. They have a steel hull 55 ft. long 20.5 ft. beam and 6 ft. deep which is divided by transverse bulkheads into four compartments. A 12" Eclipse horizontal shaft side suction centrifugal sand and gravel pump built by the United Iron Works of Oakland Cal is installed on each hull for dredging. These pumps were designed specially for this work each of them having a very heavy cast iron shell instead of containing the usual replaceable liners. The pump is located 15 ft. from the rear end of the hull with its shaft coinciding with the longitudinal center line of the latter. With this arrangement an entirely straight suction line extending to a ladder at the forward end of the hull is secured. The pump is driven by a 75 hp continuous speed three phase 60 cycle 2300 volt Westinghouse motor to which it is connected by a Morse rocker joint silent chain. The suction line of the dredge pump is joined at the forward end of the hull by means of a coupling to a flexible suction hose carried by a structural steel A frame ladder hinged on a shoe mounted on the hull. The ladder also carries a cutter used to loosen the materials so they will flow into the suction of the pump readily. The outer end of the ladder is hung by a 12" plow steel cable rove through a block and fall harder and tougher deposits were reached it difficult to make progress with them investigation led to the conclusion that the of the cutters was such that they hammered tenacious material rather than cut it proximity also magnified this hammering to some extent. The decision therefore made to equip each dredge with a single cutter larger size and to operate this cutter at 20. The results obtained with the new have been quite satisfactory. The cutter firm clay rapidly in pieces of such size that will pass through the pump without difficulty. At the same time they loosen soft readily so the pump is kept working to at all times. The new cutter head is a steel casting by means of a flanged coupling on a 415 16 steel shaft. The latter extends back plain bearings with grease cups to the rear end the ladder where it is geared to a jack driven by a 40 hp 440 volt three phase 60 Westinghouse motor. The connection the latter and the jack shaft is a Morse joint chain which permits the motor to be close to it and insures the utilization of the power available. When stiff tenacious material is by the suction dredges the cutter tended to about 25 per cent of the mass. The concrete is laid to a minimum thickness of 6 in and all over breakage in the excavation is filled with it. Two hydroelectric developments on Division Creek having a combined output of 725 kw were built originally to generate the current to operate the two suction dredges employed on the Owens Valley division. The first of these developments with a capacity of only 125 kw was installed to operate one of the dredges. The results obtained were so satisfactory that a 600 kw unit was placed adjacent to it. The output of the two developments is more than sufficient to operate the three dredges in service so a transmission line was extended from them to connect with a third development on Cottonwood Creek. From this latter development the transmission line continues along the entire upper 150 miles of the aqueduct delivering power for construction purposes wherever work is in progress."
From accession record: Digging aqueduct. Taken south of Independence Depot road, showing Lank and Keough ranch in distance. Drilled the aqueduct with old suction dredge.
(T)Collection
Allie Robinson Collection