A recent visit to the Portland mine at Victor, Colo., revealed a number of ingenious and interesting devices for eliminating labor and reducing expenses. One of the most interesting is the third rail system of electric haulage, which is used around the mill and throughout the tunnel, through which rock is hauled from some of the shaft workings to the outside.
The cars are built on a wooden framework and have two three-inch axles to which are attached (one to each axle), a 10 horse power Crane type or railway type motor by means of single reduction gearing and equipped with standard rheostatic control.
Each car will carry from five to seven tons of rock and travels eight miles per hour. The cut herewith show clearly the construction of the cars.
The third rail consists of a 1¼ x ¾-inch bar of iron, fastened by means of screws to a 2 x 6 plank laid on the ties about 12 inches inside of one rail and banded by means of copper wire fastened into holes drilled in the ends of the bars. Throughout the tunnel and where much moisture is liable to accumulate, the plank on which the rail is laid is boiled in oil, which gives a fairly decent insulation and protection against leakage from the inside to the outside rails.
Current is furnished at 110 volts from the D. C. side of a motor generator set supplied with current from the plants of the Pueblo Suburban Railway Co. The maximum horse power required is on curves and amounts to 40 horse power for a short time only.
It is stated that $25 per year will cover the maintenance cost of the system. The voltage is of course low, but as the maximum distance the car travels on any one track is less than 1,000 feet, there is no question that the choice of voltage was wise.
The leakage from a higher voltage circuit, as well as the danger from shocks, would probably prohibit a higher voltage.
The contact shoe is simply a heavy piece of cast iron sliding along the surface of the third rail and attached to the car by a simple link arrangement.
Red lights are thrown on in the tunnel when the car is moving as a warning to pedestrians to seek places of safety, and at times when the car is not operating a switch throws the current off from the track, thus eliminating the leakage of current during that time.
It is not claimed that the system is applicable to all places requiring haulage, but for conditions similar to those found in this mine there is no question of its efficiency.
The lost cost of maintenance is particularly noticeable when contrasted with trolley systems of other mines. It is very seldom that bars or other pieces of metal are dropped across the track, as the miners are required to be cautious, but when this does happen the current breaker opens and prevents damage.
Another interesting device found in the mill and designed by Mr. Lamos is a scheme for dumping rock from the skip into either of two bins and controlled by the engineer.
This is shown in Fig. 2, and consists of a structure mounted on wheels and having two sloping surfaces. This is run on a track which spans the ore bin and the place for the mill dirt.
On the underside of this structure is mounted a rack which meshes with a pinon mounted on a shaft spanning the track and by a belt-driven motor.
The engineer starts the motor from his station at the hoist in the direction he wishes it to go, and this moves the structure into proper position for shooting the load from the skip into the ore or mill dirt bin.
A switch at either end is opened by the structure as it reaches its limit, the current shut off and the motor stopped. This little device is saving the company $100 per month wages originally paid a man for arranging the trap for proper dumping.