Improvements in Gold Dredges in America.

Progress, Volume I, Issue 4, 1 February 1906, Page 79

Improvements in Gold Dredges in America.

The development of the gold dredge 15 erne of the most irr>p&rlanl features of modern minang and its effect \>]M>r> ihe world's output of the pifecjpus metal is important (says a writer in th^ NJew York *' Engtnttnng *ti<} Mwwg jowrn*} ") The effiuency oi the <lf<:<lg^ o( Urge electrical pow^r has be^n demonstrated 50 successfully tlut «h« demand for the machines is now very large 1 h<r« is hardly a concern making these gold dredges which is not working overtime trying to catch up With orders, a considerable proportion of which arc for export. The gold dredge has developed rapidly in the past ten years ihe type once established, inventors and manufactures have tried to increase 'he size and capacity Improvements in these duecijpns are charac«tns(;c oi the newest machines A number of big dredges are now in course of completion for lht Klcndyke. where \hey wjJI be operated m cpjjnection with a cower plant at Dawwn City TUfse wiU average a total o( 500 horse power for each machine, divided into separate units of from 7 to 100 horse power induction motors These dredges vMI be among the largest in use, and they will be equipped with the most recent improvements. The power house at Dawson City will contain a kilowatt turbo-generator, driven by a 600h.p steam turbine This will represent one of the first instances of a steam turbine used Jpr mining purposes \\\ the Klondyke. Similar g&jd dredges are being built >» thas country for operation in Australia South Africa South Am«tici and different parts o( oat Picifvc Coast Five large dredges are now in course of construction for a Californian mining company These will hav< 75 buckets in line, with a capacity of 7 cubic feet e 4 ch ; the total weight of th« machines, exclusive o( framework and hull, will aggregate 2000 tons Heretofore, the largest dredges Constructed have had only 65 buckets, with a capacity of 6 cubic feet e&ch The tendency to build larger and more, pawerju] boats is noteworthy. The earhrst forms of gold dredges »n use were operated by steam, but it was fou»d that they could be use^ proMablv only where the oTe \va^ nth The w,ork of developing th« d"re<fge was rcUrded for a tim< and it was not until cheap cUctrtc power was supplied thii the present movement assumed great headway California has been among th? first in the field, both m developing long-distance electrical transmission and also in the utilisation gf current for extensive mining purposes Starting with boats that would dig 20,00 cubic yards of earth per month, they have gradually increased m size and capacity until the largest m operation to-day dig from 50,000 to 7<i,oc>c> cubic yards of material per month But even th^ « not considered the limit Several that are now >» coiuse oi construe! >&» will I>e capable at haneffrng upwards <j{ too,aoo cvtb*c yards oY a mouth The tit bucket has been considered the standard for these machines in the past few years, but, as smacked, a few have been in operation with 6ft. buckets and now a number will shortly be launched in California with 7ft. buckets With increase in the size of buckets, and with more of these on the endless chain, a corresponding increase in the size of the motors and hulls of the ship follows The standard hull of the larger class of boats is 50ft by 90ft., but the newer rraft will reach 50^ tt?)^oJi and some are Ulkmg pJJaunching trail SoJl l>y 150 ft. On the Janei boals j5O fc p rnowK wtii be trqwred ii>i iiiggmg. And /< h p motors for driving the centrifugal pumps Corresponding increase m the size of the motors for operating th* dtcU wwiches, stackers, declc pump^, and screens will follow. The size o{ the boat and its general outlines must be proportioned carefully to the number and size of the motors, for the strain of handling the gravel and screeni»g is tremendous The harmonising of all parts oJ the boat has been a problem worked out by ttogintrTs and inventors, so ihM a)] parts now balance we)] Of the more than ha)i a hundred boaU kj> ppr?»l>Du in CahfoT v»fc n>bs^ i>J A recent report of a machine expert showed that the gdld boits w«r« being manufactured in a s^gre of different shops throughout the country, an<i that the output wjs about one machine 1 w««U This limit was dy« entirely to lack of facilities for increasing the manufacture. Provision is b<mg made to increase the output. Orders have been placed for enough machines to keep the present shops busy ' for the ntxi five years. '