The ore house and head frame which the writer recently designed for the Henry Adney gold mine, Cripple Creek, Colo., and which are now in process of erection, present several features of interest, as differing from ordinary, conventional types.
The plant which is displaced was very wasteful, and could not have been operated at any profit on medium or low-grade ores. The head frame, when completed, will be the highest structure of this kind in the Cripple Creek district, and has a height from the collar of the shaft to the center of the sheave of 101 ft.
An automatic bucket dumper is used, and dumps the ore into the storage bin, of 20 tons capacity, near the top of the head frame. Immediately below the lever gate, for discharging this bin, is a revolving spout.
This spout, when placed in one position directs the ore to the nearest grizzly, and when turned 90°, directs to the farther grizzly. The bucket for hoisting ore is to be displaced by a skip in the near future. The storage bin is intended to accomplish several important results:
First, to enable the ore-sorter to regulate the operation of screening the crude ore much better than it can be done by merely dumping the bucket on the grizzly.
Second, to avoid the danger of the ore-sorters being struck by flying rock when the bucket is dumped into a nearly empty bin with frequency. The additional storage in this bin also reduces the liability to interruptions to the work of sorting, caused by trifling delays in hoisting.
While the extra height of head frame for this bin adds some initial expense, it has several features of value. It gives an easy angle for winding the hoist rope, and it makes possible, by placing a dumper and chute at the west, opposite the ore dump, to dump waste rock, without any tramming, for a long period of time.
The crude ore bins below the grizzlies are of 30 tons capacity each, and the screenings bins and sorted ore bins are also of 30 tons each. All bin floors slope 45°, and the grizzlies and screens have the same inclination.
The washers at the mouths of the crude ore bins are chutes having metal bottoms, with 0.375-in. perforations, and having lever gates at their lower ends, through which the sorter draws the washed ore and waste to the sorting table, where they are separated.
The ore is dropped through the square vertical spouts into the bin below, and the waste is thrown into a car and taken to the dump. The water for washing the ore is pumped by a centrifugal pump, direct-connected to a 5 h. p. induction motor.
The pump draws water from the two slime tanks, and forces it through two spray pipes extending the whole length of each washer, and spraying the entire exposed surface of the ore.
However, one will understand when it is said that the main feature of the plant is of coarse the shaft house, which is the central portion of the structure. It is 40 feet square and 75 feet high, and contains all the powerful machinery used every day in lifting the 300 tons of ore from the depths of the mine.
Drains and launders return the water and slimes to the tanks, where the slimes settle and are shoveled out periodically to the slime drier. The drier is a plate 9 ft. by 10 ft. in size, and heated by exhaust steam. Chutes extend from the screenings bins through the corners of the sorted ore bins, bringing the screenings gates parallel with the ore gates, which deliver ore near the top of the door of the ordinary box car.
By the use of swinging spouts, ore or screenings can be loaded, with little or no shoveling, into box cars. All posts are set on concrete pillars with dowel-pins, which prevent dislocation.
All diagonal braces for ore house and head frame are of 2" x 6" stuff, well spiked. Some designers use rods for sway-braces, but they are open to the objection that they loosen when the timber shrinks, and if they are unequally tightened, the structure is thrown out of perpendicular.
The 2" x 6" braces, well spiked together where they cross, sustain both tension and compression, which the rods will not do. Gains are used freely, but no tenons, in this structure. Bolts and rods are used at joints liable to considerable tension.
The method of trussing the main brace is rather unusual, and has the merit of being less expensive and cumbersome than braces connecting to the main frame, which, on account of their length, would have to be trussed in two directions.
The form of brace here adopted leaves a wide space clear between itself and the posts. The saving accomplished by this plant, over the previous arrangement, will be considerably above $1 per ton of ore shipped.