The Viaduct Works' Handbook

93 the whole of the working mechanism, with the exception of the top slides, driving pullies, and fly wheel. This arrangement is very com- pact, and allows free access to the work being rivetted without danger of accident from the working machinery; the mechanism is got at from a pit below. The slides, which carry the rivetting snaps, are of wrought-iron, and are made to project upwards, so as to stand higher than the top of the machine, and each slide is provided with two sockets, one above the other, the snaps being used in either socket according to the class of work which is to be rivetted. These slides work in dovetailed grooves, on the top of the main casting, and are moved backwards and forwards by wrought-iron levers, to which they are attached by links. The levers are worked by cams fixed on shafts, each carrying a spur wheel 3 feet 5 inches in diameter, these wheels gearing into each other, and one of them also gearing into a 54-inch pinion fixed on the driving shaft gear, which carries the fly- wheel and actuates the whole arrangement. It will be noticed that the cams only force the levers and slides to their work ; to bring them back the ends of the levers are prolonged, and chains are attached to them, which pass over small pulleys, the ends of these chains being connected with a weight which is heavy enough to bring the levers into their proper position ready for the next stroke. To regulate the varying strain on the dies, the bearings of the levers are fixed against powerful steel springs, adjustable by set screws. When considered desirable the machine can be made single acting, by fastening back one of the levers, and taking off one of the chains. A small pair of shears is provided at the end of the machine for cutting off the red-hot iron as described above; the cutters being worked from an eccentric fixed on the driving shaft. One of these machines has been in use for several years at the Viaduct Works, Crumlin, and has given unqualified satisfaction, turning out a large quantity of girder and other work with a rapidity and precision before unattainable. It is particularly adapted for bridge work, as the cross girders and many of the main girders can be rivetted entirely by this machine. The usual practice adopted at the Crumlin Works is to rivet the angle irons on to the web-plates, with the snaps in the lower sockets of slides; the snaps are then re- moved to the upper sockets, and the girder under operation is turned over on its side, in such a position that the top flange to be rivetted is situated between the two dies, whilst the web and the other flange