ELECTRICAL POWER FOR DREDGES.

Otago Witness, Issue 2762, 20 February 1907, Page 27

ELECTRICAL POWER FOR DREDGES.

With such a copious and continuous supply of water as exists in the Molyneux River and its tributaries, and the many torrential streams in its neighbourhood, it might leasonably have been expected that sonu thought and attention wou.d have been given to the question of harnessing these waters and driving gold-winning dredges by electricity, more so for the reason that many in Otago are, or were, in such inaccessible and out-of-the-way places for the delivery oi coal. The carting and boating of coal to dredges, more particularly to those in the gorges, has been a very heavy item of expense to many companies, and frequently the cause 01 considerable loss of time. The only dredge in Otago on which electricity is used as motive pirwer is the Eamscleugh Company's Xo. 3 machiHe, near Alexandra, one of tlie largest and most powerful machines on the goldiieids. The- source of the water supply i& the Fraser River gorge, about 3^ miles from the dredge, and for one mile- and a-ha.f of tEat distance tha water is conveyed through a 24in pipe lin« to the powerhouse, where 200 brake horse-power is at present developed. The pipe line is capable of developing three times that amount. At the powerhcu&e electricity is generated by means of a peliton wheel, coupled direct to a 200 hcr^e-power generator, and. thence conveyed by fneans of overhead wires at 5000 volts, being subsequently transformed down to the dredge, at 250 volts. A 100 horse-power motor drives the main buckets, screen, and pump, and & 2ft borse-poiwer motor the winch. A second 20 horse-power motor drives the elevator, which is 128 ft long. The mcrtor is placed at the top end of the elevator under housing, and is found to work admirably. Tho Earnscleugh Company's No. 3 dredge- has now been driven by electricity for a period of about four years. The initial outlay for the electric plant was very heavy as compared with what a steam plant would run into. With electricity, however, working expenses are only about one-third of what it would cost to run the dredge with a steam-driven plarrt. Only three men are required on each shift, one man at the powerhouse- and two on board the dredge. The actual running cost is covered by about 16oz, whereas if equipped with a steam plant the dredge, being a large one, wou'd absorb from 21oz to 220z per week for woiking expenses. The cost of the pipe line, together with construction aud laying down, W39 something like £5000, while tha origin*! outlay for electric plant was £ZSQO. The screen of the Earn--cieugh No. 3 dredge is tho largest in the co'ony, being no less than 17ft in diameter. The Earnscleugh Company purposes putting into commiseion another dredge on ground adjoining the old Fraser Flat claim. This will likewise bs driven by electricity. but will bo a very much more powerful machine than the No. 3. The e'evator will be on* of the. largest yet placed, on a dredge, its actual length bteing 160 ft. The main ladder will be 90ft long. The capacity of the dredge will ba somewhat similar to that of the No. 3, but po&sib"y the buckets may travel more speedily. Altogether it will he a, very large and powerful machine. Ths ground which it will have to treat is practically terrace ground, aad will average over 120 ft in depth. The elevator will be driven by a 30 horse-power motor, the winch by a SO horse-power, the- silt wheel by a 12 horse-ppw-er. the screen by a 12 hor&e-power, the pump by a 60 horse-power, aud the buckets by an 85 horse-power motor. The polton wheel in connection with this dredge is being designed and 'constructed by Messrs Cosseus and Black, and. the- contract to supply generators and motors has keen let to the General Electric Company of U.S. The Earnsclepgh Company's No 2 dredge has about 14 or 15 months' work ahead of it The Xo. 1, a small machine, constructed in 1896. has been closed down for some 18 months. TKe Xo. 3 :<? working m vugin giound. Altogether, the company lias a very considerable area, of ground in front of it, and is likely to h*ve a long life. Ihe operations of tbe comoany aa a wbo'e. are under ■the supervision of Mr Charles Weaver, managing dire-tor.