WEST COAST DREDGES

Press, Volume LXXII, Issue 21808, 13 June 1936, Page 13

WEST COAST DREDGES

MODERNITY QUESTIONED A GENERAL CRITICISM A correspondent, signing himself “Modern,’' suggests in a letter to the Editor of “The Press,” that gold dredges in use on the West Coast are cut erf date. “As one who has been connected with gold dredging in New Zealand and of latter years in other countries, on the latest modern dredges, dredging to a depth of 130 feet from water level,” he says, "I was surprised on making an inspection of some of the dredges now operating on the West Coast to find that they were far from being modern, as I was gxven*to understand. The only machinery that is modern on these dredges is the closeconnected type of buckets and tumblers. As to the rest of the machinery it is no better than the machinery that existed on the dredges 30 years ago, and this applies to some of the dredges now being constructed. Even some of the modem buckets and bottom tumblers are not of the proper design for the nature of the ground that is being dredged, and the quantity of material it is desired to be treated an hour. This means heavier stresses on all the dredge and machinery than is necessary, and consuming that extra power that is net required, and which does not lower the costs. “Simplicity of design on a dredge should always be aimed at, and complicated gearing and designs more often than not lead to lost time and expense, extending much beyond their usefulness. There are many factors to be taken into consideration when getting out specifications for bucket dredges, and I am surprised that the directors or the consulting engineers of these companies have not given these specifications more consideration. “There are many details I could go into in keeping down the costs of these dredges, which these companies have not provided for, or have probably been overloked for want of practical knowledge. . , „ , „ . “I was also surprised to find that many of these dredges were operating with elevators, which are not required. This is another matter which has not been taken into consideration. All modern dredges to-day, when they have no overburden of any height above water level to contend with, have no elevators to stack tailings. These modern dredges have tables after the style of the sluice-box type, as you call them in New Zealand. It is a Cheaper method of dredging, and the soil can be put back on top of the tailings, and the ground left level, ■when, as with the elevator type of dredge, it only leaves a heap of stones and the ground useless for all time. In some parts of the West Coast this land, under this method of dredging, would become more valuable than at present in its virgin state. “I should like to mention that op the latest modern dredges, dredging land bearing top soil, a chute is provided that extends well over the stern of the dredge. When stripping the ground the soil is brought up in the buckets, and discharged into this chute. Therefore no soil in a muddy state is going over gold-saving appliances, and the screen and most of the machinery are out of action. This means a great saving in power as well as costs, and you are not wearing out machinery that serves no useful purpose. This is a simple arrangement that can be installed at very little cost, and I am surprised that this method has not been adopted on some of the dredges in New Zealand. “It may be of interest to New Zealand to know that these dredges are managed by New Zealanders. I was informed that a company operating on the West Coast, near Greymouth, was dredging to a depth of 150 feet in Siam. That is not right, as there are no dredges in that country dredging to more than a depth of 60 feet. “There is another matter I would like to refer to, and that is the number of men that are employed on some of these dredges, and who are not required. I have been informed that one company carries a dredgemaster and manager to control or manage one dredge. Many a mining company has had a short life through nothing else but overhead expenses, and this is another matter to be taken into consideration. My advice to the shareholders or direcors of companies in geting out specifications to build modern dredges is to see that every detail is modern. In this year of 1936 there is no justification for some of the machinery that exists on some of these dredges, and the same applies to those ciredges being constructed. In the days when dredge engineers and operators were less enlightened than they are now, this machinery served its purpose well. “Finally, when inviting applications for the position of dredgemaster, appoint the dredgemaster on his merits, but not by the cut-and-dried method that has been adopted lately, as I have been informed, in several instances. This is a great mistake, and is not in the interests of the shareholders.”

Local Engineer’s Reply A Christchurch mining engineer, who has had extensive dredging experience in the South Island and abroad, challenged most of the statements contained in the above letter when it was shown to him. He thought the writer could have been more explicit and explained just where the recently-erected dredges on the Coast did not conform to modern principles. This engineer said that there were pronounced improvements on the dredges of 30 years ago. It was worth noting as an indication of this that a dredge transferred only last year from the Malay to the Coast—which would scarcely have been transferred had it not been fairly modem—was scarcely as up-to-date as some of laose recently constructed locally. “Modem’s” contention that elevators were unnecessary when they had no overburden to lift was against successful practice. In deep ground, reliance on the sluice box alone would mean that the buckets would have to lift the material higher, but, more important also, the water for washing: and the pump for this purpose was a great consumer of power. Tailings on an average were deposited a third higher than the original surface level, provided there was no stream of water to carry them away, and this made it impossible to do without elevators when the ground was deep. The dredge to-day was a fairly simple machine, and there had been a definite improvement on 30 years ago in the quality of the material used. There was one dredge on the Coast now in course of construction by a Sydney firm which had to do with the construction of the Bulolo dredges, he said, and the sensational returns of these machines scarcely suggested that they lacked anything in the way of modernity. Electrical winches, with the winchman on the top deck and everything under his eye, were a great advance on the winches of the old days, when practically all that the winchman saw was the ladder well near him. There was no comparison between the electrically-driven machine and that of .years ago, with the then difficulty of getting coal over bad roads, or when 10 or 12 men had to be kept cutting wood and carting it for the steam-driven plants. The statement that the soil chute was something new was wide of the mark. A machine to do this worked in Southland 25 to 30 years ago on good land, and it made a perfect job of It The levelled and resoiled tailings were about as high as the surrounding fences, and actually improved the quality of the soil The reason the device was not in use on the Coast was that most of the dredges I were operating there on beach leadg.