The Mechanical Handling and Storing of Material

COAL TIPS OR HOISTS 543 daily, the capital expenditure for such a tip is fully warranted from a commercial standpoint. The tip shown in Figs. 758 and 759 is the same, but on a larger scale. Here the small bogey is let down over an inclined portion of the track at an angle of 30°, and the truck is raised up this incline with the end door closed, and this is not opened until the curved tipping portion of the track is reached. In this particular case the coal is dis- charged into an elevated receptacle. It has been found that coal trucks can be raised at an angle of 30° with the greatest safety, and no shifting of the coal takes place at this incline, neither is there any additional pressure against the end door. The expenditure of power is '7 kilowatt per 10 tons of coal handled, so that, inclusive of labour, the cost of handling 10 tons is a fraction over twopence, and when handling more than 7,000 double loads (of 20 tons each) per annum, the expenditure on the installation is justified; at 7,000 the total expense, including the capital account, is equal to that of hand labour. An interesting installation on the same principle is shown in Figs. 760 and 761. An ore pocket holding 60 tons is here filled by the trucks, and such a tip almost answers the same purpose as a hydraulic coal tip, but the initial cost is very considerably less. The weight of the truck is balanced by a weight which is seen at the back of the structure. The capacity of this plant is twelve 20-ton trucks per hour, and a 68 H. P. motor manipulates the tip. Figs. 762 to 764 show the winding gear which can be used as a capstan to draw the wagons near, and revolve the turntable as well as lifting the load. The power consumption for a 20-ton truck at the rate of 150 tons per hour is 1'5 kilo- watts. Such an installation becomes commercially economical when handling over 275 tons per day. A further and most useful development of the Aumund system is a portable tip, which may be handled in the same manner as ordinary rolling stock ; it may therefore form one of the units of a mineral train, and be used for unloading at the destination of the train. For this purpose the tip is mounted like a turntable upon a low carriage, and fitted with motors according to local circumstance’, taking the power from existing mains, or fitted with a primary motor of the oil or petrol type coupled to a dynamo. Figs. 766 to 769 are diagrams of electrically-driven tips of this description. Their use is precisely similar to those already described, with the exception that the turntable (driven by a separate motor) is used when the truck on the tip has been raised to an angle of 30°, and when the table has been turned to an angle of 90° with the line of rails, the end door is opened and the lift completed to an angle of from 45° to 55°. When the truck has discharged its load the turntable is used again, continuing in the same direction for another 90°, so that the truck may now leave the tip at the opposite end to that at which it entered. If used in this way the whole mineral train can be unloaded truck by truck, and the empties reunited for the return journey. These tips are self-propelling, and can therefore be used in a variety of ways, even dispensing with the locomotive when the mineral train has only a short distance to travel. The wheel base and the distribution of the load upon the permanent way does not exceed the usual limits, so that these tips can be used in the way described on all sidings where ordinary railway engines travel. Eight trucks of 10 or 20 tons can be tipped per hour. The lifting motor is of 25 H.P., whilst those manipulating the turntable and for self-propelling are of 8 H.P. each. The power consumed is ‘5 kilowatt per every 10 tons handled. One driver and two labourers are necessary, and the cost of unloading by these tips in Germany is reckoned to be just under l^d. for every 10 tons of coal handled. Such tips are economical if the amount handled annually exceeds 6,300 trucks of 20 tons; for quantities below this they are not more economical than hand labour.