The Mechanical Handling and Storing of Material

246 THE MECHANICAL HANDLING OF MATERIAL Fig. 346 represents a colliery tub taken up an incline by means of a link chain with special attachments which engage with the axle of the tub, and thus convey it up the incline. The endless chain travels over two polygon terminals, one of which is fitted with tightening gear. There are many similar devices; the one here illustrated is manufactured by Messrs Coulson & Co., Ltd., of Spennymoor. Endless Rope Haulage.—This is of far greater importance than chain haulage. 1 The speed of haulage de- pends largely on the state of the running track ; a well-laid line with properly constructed onsetting point (where the trucks are joined to the rope) can be worked quite satisfactorily up to a speed of 5 miles an hour, and at that rate 1,000 to 1,200 trucks per hour can be handled. With a rough track which may be laid on spoil banks or tailings dumps, the speed should be reduced to about 2 miles per hour, at which rate trucks can be handled with ease and safety. Where curved wheels are used to work haulages around corners, a high rate of speed is not desir- able, as even with the best con- structed track there is always a great ils in negotiating the small curves which the radius of the curve wheels necessitates. The amount of deflection off the straight for a curve wheel should be between 15° and 30°. If the angle at the inter- section is too flat the rope is likely to leave the wheel, and, on the other hand, should the angle be too acute, the curve, which by necessity has usually about a 3-ft. radius, Fig. 345. Chain Haulage for Hand Carts. deal of wear and tear on both the truck and the Fig. 346. Example of Chain Haulage for Collien- Tubs. is too sharp for the truck to work around with any degree of safety. As a support to the rope, a roller fitted to a swinging arm should be placed on the on-coming side of the wheel, and as a further precaution against the rope leaving the wheel, the latter should be slightly elevated on the off-going side of the rope. In running inclines a grade of 1 in 8 (12| per cent.) is about the limit for a fast travelling haulage, although at a lesser speed inclines 1 in 6 can be worked. The grade to a large extent is limited by the speed of the haulage, as with a fast rope and a steep 1 Extract from the very complete paper by Mr H. G. Kay, entitled “ Rope Haulage,'’ and read before the Chemical, Metallurgical, and Mining Society of South Africa.