The Mechanical Handling and Storing of Material

88 THE MECHANICAL HANDLING OF MATERIAL belt and drums of sufficient diameter no separation of the plies has so far been experienced. It will, however, be well to wait before giving a final decision on this subject, until installations with multiple pulley drives have been in use for a sufficient number of years, to see whether the life of a belt under these conditions is as long as with the ordinary terminal drive. At any rate, the ability to drive the conveyor from either terminal is of the greatest advantage. Frequently, two conveyors working in the same direction, one from the other, or from the same point in opposite directions, have been driven by one motor by the latter being situated at the junction of the two conveyors. Driving Power.—The power required for driving belt conveyors is comparatively small; in fact, there is probably no conveyor system which is so economical on this point. The calculation is influenced by a great number of considerations, of which the number of plies and, consequently, the stiffness of the belt, the distance apart at which the supports are placed and the nature of the driving arrangement form the principal items, in addition to the load, length, and speed of the conveyor. The method of lubrication and the state of the atmosphere also influence the power consumed, and, as this latter as well as other conditions cannot be considered as permanent, it appears of little use to give formulas for elaborate calculations, as these would only be right for certain specific conditions. Opinions of experts also differ so much on this subject— which was shown during the discussion on the interesting papers of Messrs Titcomb, Baldwin, and Peck, read before the American Society of Mechanical Engineers—that it will probably be better, more to the point, and more useful to the user to give a table of horse powers calculated to give a sufficient margin of power for small contingencies. This table gives the power required for horizontal conveyors, which will be less for a downward and more for an upward incline. Horse Power required for Belt Conveyors 100 ft. long running at a Speed of 100 ft. per Minute, and with a Normal Load of the Different Materials Width of Belt in Inches. For Handling Heavy Ore. For Handling Coal. For Handling Grain. H.P. Consumed by Conveyor. Additional H.P. Consumed by each Throw-off or Tripper. H.P. Con- sumed by Conveyor. Additional H.P. Consumed by each Throw-off or Tripper. H.P. Con- sumed by Conveyor. Additional H.P. Consumed by each Throw-off or Tripper. 10 •775 •25 •540 •25 •486 •25 12 ■961 •50 •675 •50 •594 •25 14 1147 ■50 •840 •50 ■702 •25 16 1-550 ■50 i-oso •50 •810 •50 18 2-013 •75 1-316 •50 •952 •50 20 2-343 •75 1-512 ■75 1-092 •75 22 2-838 TOO 1-792 ’75 1 -358 •75 24 3-636 1-25 2-250 •75 1-740 •75 i 26 4-320 1 -50 2-670 1-00 1-925 •75 28 5-040 1-75 3-090 roo •2-118 •75 30 5-760 2-00 3-540 1'25 2-310 roo 32 6747 2-25 4’096 1-50 2-707 1-oo 34 7’254 2-50 4-416 1-75 2-950 roo 36 8-151 3-00 4-768 1'75 3-200 1-25 38 9-348 3 25 5-635 2-00 3-815 1-50 40 10-168 3-50 6-355 2-00 4-130 1-75 42 10-906 3 75 6'405 2-25 4-725 1-75 44 11-644 4-00 7'790 •2-50 5-320 2-00 46 12-505 4 25 7-175 2-75 5-915 2-25 48 13-366 4-50 7-560 3-00 6-895 2-50