Highland Boy Aerial Tramway

The method of conveying ore from the mines that are difficult to reach by a surface line, by means of buckets or carriers traveling on a suspended cable down to lower ground, where it can be handled or shipped, is one that has become quite common through some parts of the West. The line to be described is about as good an illustration as can be found to show the value of this method.

The Highland Boy Gold Mining Co.'s property is located in the western part of the Bingham Camp. The ores are quite rich in copper, and a large tonnage is shipped out. The workings are located in Carr Fork, the principal fork of Bingham Canyon. The locality would be difficult to reach with a steam road, the fall of the gulch being rapid and development being difficult.

The ore was formerly hauled down to the railroad in wagons. With the enlargement of the properties and production of the company, it was decided to build an aerial tramway, after complete surveys had demonstrated that a surface line was hardly practicable.

The Bleichert system of cable carriage is used, and the line was built and all equipment furnished by the Trenton Iron Co., of Trenton, N. J. The line is on tangent throughout. The original length was 2-1/3 miles, but by a change in the location of the loading terminal it was reduced to 2-1/4 miles. The profile, drawn to natural scale, shows the mountainous route and also the location and height of the towers for supporting the cables. The ground elevation ranges from less than 5,900 ft. at the lower end to about 6,900 ft. at the upper one. The spacing between the towers varies from 152 ft. to about 870 ft. Where several towers are required to round off an abrupt change in grade they are spaced from 15 to 75 ft. The height of the towers varies from 14 to 70 ft. The greatest height of the cable above the ground is over 200 ft. There are 44 towers on the line.

The plans for the 25-ft. tower, about the average height, are practically standard for all. They show the side supports for the cables. Planks are laid on the sills and loaded with stone, to anchor the towers against swaying or tipping over.

The original design of spacing and heights of towers has proven to be excellent, with only one change being needed. Just north of the anchorage station (next described) the great length of span, combined with the steep incline, caused too sharp a turn in the cables, with resultant wear. So the two towers just north of the station were lowered 3 or 4 ft., while an additional tower was put in about 125 or 150 ft. further down. This effected the desired improvement.

At about one mile from the lower end is located an anchor station. Here the track cables from the opposite directions are anchored to a strong framework. By pulling in opposite directions they nearly counterbalance one another. They pass over supports and down on an incline to the anchor. The gap on the line between the supports is filled by an iron hanger bar. The traction cable is continuous.

At about 0.6 mile further up a tension station is located. Here each track cable coming in passes over a sheave to a tension weight below. The horizontal pull in opposite directions is nearly balanced by connecting the two. Provision for a varying length of the track cable is necessary because of the effect of heat and cold.

There are two track cables, one for the loaded buckets and one for the empties. Originally these were 1-1/8 ins. and 7/8-in. diameter, respectively, but when the tonnage was ta be increased the 1-1/8-in. cable was left on for the empties and the 7/8-in. one was displaced by a 1-1/4-in. cable for the loads. They are of the patent lack-coil track cable type. A 3/4-in. Langley traction cable is used. The track cable is supported at the ends of an arm at top of the tower and the traction cable runs on pulleys 6 ft. lower down.

The loading terminal is located so that tram cars loaded with ore, after being run out of the working tunnel of the mine, are run on a trestle into the building' and dumped into ore bins directly over the loading track. The traction cable makes two turns around a bull-wheel by which friction enough is secured to allow of control of' the cable by the wheel. Power can be applied by means of a horizontal shaft in the room below, beveled gearing on it engaging beveled gearing on the vertical shaft of the bull-wheel. Ordinarily no power is needed, but brakes have to be applied for regulation of the traction cable. This is because of the great excess of weight on the loaded side, acting by gravity through the 1,000-ft. fall to the discharge terminal. In starting up or when the buckets are all empty, power has to be applied.

There are 116 buckets used on the line at once. Each has a capacity of 4-1/2 cu. ft., weighing about 290 lbs. complete, and carrying about 700 lbs. of ore. They are spaced about 205 ft. apart, and travel at a rate of about 350 ft. per minute. Ordinarily about 105 loads per hour are run over the line. About 500 tons per day of 15 hours (1-1/2 shifts) is the usual day's work for the line.

The buckets have a strong and elaborate grip-ping device, which they are fastened to the traction cable. By a swivel connection between this and the bucket, the latter maintains an up-right position when the track cable is on an in-cline of as much as 500 from the horizontal.

On entering the loading terminal building the handle of the grip of each empty bucket strikes a projecting arm and is forced upward, and so the grip is released. The bucket here leaves the cable and runs on to a hanger bar (a continuation of the track cable), around which it travels by momentum to the loading place. The bucket is filled through one of the ore chutes, operated by an attendant. It is then pushed forward to the outgoing track cable. The spacing of the buckets is regulated by the revolutions of the bull-wheel actuating certain mechanism that rings a bell at the required intervals, at which an attendant fastens the grip and starts the bucket on its journey. During the cold weather the entrance and exit sides of the line are each provided with folding doors, opened by the bucket striking against converging arms and forcing them apart, and closed by springs as soon as the bucket passes through.

The pull of the cable on the bull-wheel is opposed by diagonal bracing and also by a cable leading back to a dead-man.

At the discharge terminal each bucket runs on to an unloading track. The grip is released by its handle striking a projecting arm, an attendant causes the load to be dumped, and the bucket runs around on the hanger bar to the position for starting on its return journey.

The traction cable makes the turn around a horizontal sheave mounted on a tension carriage. This slides back and forth, according to the tension of the cable, a chain leading from it over a vertical sheave and down to a weight.

The track cable at the terminal is 35 or 40 ft. above the ground. To raise coal up to its level (for transportation to the mine) the following ingenious method is employed: At the top of the shaft of the cable sheave is a beveled pinion which engages a beveled gear on a short horizontal shaft. The latter shaft is hollow, and it can be keyed, to an inside shaft and made to rotate the same. The key fits and slides in a slot cut length-ways of the inner shaft, so that, as the outer shaft and cogs are moved back and forth by varying- tension, the outer shaft--sliding on the inner one--is still connected by the key sliding in the slot. The inner shaft has at its further end (about 35 ft. distant) a sprocket wheel and endless chain, by which coal from below is raised up an incline to coal chutes, from which the buckets on the cable can be filled. The power is furnished by the excess of weight on the loaded cable, acting through the 1,000-ft. fall.

To give even wear on the track cable, twice a week it is gone over and given one-eighth turn at each tower by means of pipe wrenches. To control its position, a clip or clamp, fastened by a bolt and nut, is used, reaching from which is a lever arm whose further end is held between the branches of a double arm that runs longitudinally out from the top of the tower. To oil the traction cable, a bucket is specially fitted up; a spout sticks out in front, being regulated for a certain feed, and this oils the cable in front of the bucket as it moves along. The linemen travel in the buckets at their line work, jumping on and off at the different towers.

The tramway has been in operation about three years. The track cable has been partly renewed during this time. Some parts of the cables have worn out. A splice is made by slipping a sleeve, in shape like a frustum of a cone, over the end of each section and kneading the end. A right and left screw sleeve is then made to connect these, and by screwing up the ends of the cones are brought together.

The cost per .ton of ore transported over the line during the latter part of the time has been not over 9 cts. per ton, including all labor and repairs, and this low cost is obtained without credit being given for the coal and other supplies carried over the line to the mine. It is estimated that to build and equip a railroad for economical operation would have cost about four times as much as for the aerial tramway. Figures as to the exact first cost of the tramway complete, with all equipment, are not obtainable, but is it thought to have been about $35,000.

The terminal stations were designed for the company by Geo. K. Fischer, M. E. For the data from which this description has been prepared the writer is indebted to Mr. R. H. Channing, General Manager of the Highland Boy Gold Mining Co., Salt Lake City.