A Treatise On The Principles And Practice Of Dock Engineering

538 DOCK ENGINEERING. These notches, which fix the stoppages of the traveller, are arranged at intervals of about 5 feet. On arriving at the position at which it is desired to lower the load, the engine is stopped, the hoisting drum thrown out of gear, and the traveller with its load commences to run backward under the action of a tail rope or overhauling gear until it cornes to a notch, in which it engages automatically, and, at the same time, releases the fall block, so that the load can be lowered with the brake in the usual manner. The outer projecting ends of the beams may be hinged, so that they can be drawn into a vertical position when out of use. The Transporter shown in figs. 555 and 556 is of a type used in France, and manufactured by Messrs. Daydé and Pillé, of Creil. It is formed of a vertical framework in the shape of the letter A, at right angles to which the transporting beam is set. The frame is free to travel along the quay on a line of rails, and is steadied by a second line of rails placed along the shed front, at some distance above the quay level, so as to prevent over- turning. The travelling beam can be set to any required inclination. The apparatus is worked by two independent winches, one of which controls the hoisting of the load and the other the travelling movement. Both these winches are driven by steam power from machinery at the foot of the frame, movement being communicated by means of shafts and bevelled wheels. The apparatus in question is adapted to loads of 30 cwts. Coal Tips and Lifts.—The process of loading a vessel with a cargo of coal is attended by some difficulty, owing to the brittleness of the material, which is such that, unless extreme care be taken, its value may be very seriously depreciated by breakage into minute fragments and dust. Coal is usually conveyed to port from the collieries in waggons, either end-tipping or with drop-bottoms. Waggons of the latter class are simply lifted and slewed bodily by a quay crane, and suspended over the hold while the coal is discharged. End-tipping waggons are tilted so that their contents are emptied into a shoot which directs them into the hatchway. Until a conical heap of sufficient height is formed, the operations in both cases are accompanied by considerable breakage of coal, owing to the great depth of the hold into which it has to fall. This can, to some extent, be remedied by the assistance of an anti-breakage crane, which forms an auxiliary feature of most coaling tips. For the first few waggon loads, the coal, after passing down the shoot, enters a skip placed to receive it, the skip being suspended from the crane, by which it is lowered carefully to the bottom and its contents there deposited. Even after the cone has attained a good height, it will be necessary to control the discharge from the shoot with the aid of flaps, or doors, as a rapid rush of material will frequently produce nearly as much damage as a long fall. If the railway tracks are at a sufficiently high level, the waggons may be discharged direct from that level, but, in the case of a low-level approach, it will be necessary to first lift the waggons to such a height as will clear