Grapple Dredges
General Description.—A grapple dredge is, in principle, a derrick mounted on a float and swinging a grab bucket. Any derrick lighter may perform the operation of dredging by simply attaching a grab bucket to its fall. This, however, is merely a makeshift, and by no means constitutes a dredge. The operation of the bucket is […]
Gold Dredging & Sluice Box
The Metallurgy of Dredging: The gold-saving appliances of a dredge consist respectively of screens, tables, and sluices. The essential duty of the screen is to classify the material prior to concentration, it also serves to disintegrate or break up the material passing over or through it, so that particles of gold may not be carried off […]
Gold Dredges & Gold Dredging
We are the first and only concern in this country to devote its whole attention exclusively to the designing and building of gold dredges; therefore, we are especially well equipped to do this work much better and more quickly than other concerns; for with them, dredge building is only a side line, and their principal […]
Dredging Alluvial Gold
The only minerals of any importance which are found in alluvial deposits are gold and other precious metals, tinstone, and those gems which by reason of their hardness and power of resisting chemical changes are preserved in their original state even after being scoured by water for long periods. It is now generally conceded that […]
Clamshell Dredge
The grab, or “ clamshell ” type of dredge, consists of a self-filling and discharging scoop or bucket, with the necessary engine power for working this from a crane. Well-known makers of this form of dredge are Messrs. Rose, Downs, & Thompson, Limited (see illustration), and Messrs. Priestman Bros. Both firms recommend, for this purpose, […]
Dredge HP Horse Power Requirements
In calculating the horse-power consumed by suction and by bucket dredges, figures have been taken from the various official reports on the mining industry in New Zealand, dates and pages in each instance being given. The calculations are made in theoretical horsepower, and for easy references are given in tabular form. The difference in the […]
Suction Dredge
These machines consist essentially of a floating structure, supplied with a powerful pump of centrifugal type, raising sand and water through a suction pipe. Characteristic types of suction dredges are the Ball and the Welman. The Welman patent pump is in many respects similar to a centrifugal pump; the runner, however, is differently constructed, the […]
Bucket Dredge
The bucket dredge may be described as a continuous dipper dredge, the material being raised by a revolving chain of dippers or buckets, which scoop or dig into the deposit. The principle and system of raising material in these machines are almost identical with those of harbour dredges. The favourite type of bucket dredge is […]
Types of Dredges
The type of a Dredge is defined according to the Nature of the Work they do. Under this heading bucket dredges may be classed as: River dredges; paddock dredges. The river dredge is designed to work with some depth of water underneath it, and is not called upon to cut its own flotation. It is, therefore, not […]
Electric Dredge
Small electric dredges are great where water power is available within reasonable distance, electricity may be generated and transmitted by cable to the dredge, proving an economical substitute for steam, especially in localities where fuel is dear. The small space, too, occupied by the plant, and the ease with which it is handled, make electricity […]