(bucket); some extra valves, so that new ones can at once be substituted for the broken parts. BURSTED PIPES. When a pipe bursts, place a piece of sheet iron smeared well over with white or red lead, over the crack and wrap it tightly all over with copper wire. In case of steam pipes use clamps-in halves—in addition to wire wrapping. These are only a few of the many break-downs which may happen at sea under the best of management, and are only intended to give the learner a general idea of what is to be done in similar cases. Engineers, like poets, are born not made, and a born engineer is always ready for any emergency -still prevention is better than cure in engineering as well as in physics; so prevent all the breakdowns you can. REPAIRS TO BOILERS AT SEA. Owing to imperfections in the iron, small cracks often appear in the crown-sheet, flues, and back connections. If in the crown-sheet, and not more than two inches in length, drill a hole, cutting the crack out, cut a taper thread, and insert a wrought-iron pipe plug (a number of which of different sizes should be carried for that purpose) smeared with white lead. If in a flue, drill a number of small holes, and put in small rivets, hammering the heads out so as to cover the crack. If the crack is more than two inches long, or if it be a large hole which cannot be plugged, then you must put on a hard patch, and if the patch cannot be riveted on, then put it on with tap-bolts screwed into the sheet; care must be taken to admit water to the patch, else the fire will soon destroy it. Hard patches should be used on all parts of the boiler reached by the fire; and soft patches on the shell, and every other part not exposed to the fire. . The difference between a hard patch and a soft patch is, that a hard patch is riveted on or put on with tap bolts-bolts screwed into threaded holes both in the patches and sheet. A soft patch is put on with bolts and nuts. The best way to put on a soft patch is to first make a pattern of the patch needed out of sheet lead. Then take a piece of boiler plate and forge a patch as near like the lead pattern as possible, and lap over edge all around. Then drill as many 34 holes as are necessary about 3 inches apart in the sheet first and corresponding ones in the patch afterwards: the holes should come true. Next mix some boiler-makers' cement which is composed of equal parts of white and red lead mixed with enough iron borings to make a stiff putty. Cover the inside of the patch with this putty and it is ready to go on. Now wrap some 5% bolts with lampwick smeared with plain white lead, pass the bolts through from the inside and set up the nuts tight, placing a washer between each nut and the patch. Should the patch be so situated that the bolts cannot be put through with the hand then they must be fished through. To fish a bolt you must take a long piece of wire, pass it through the bolt-hole and out through the hand-hole, then tie the bolt to the wire with a piece of strong string, giving about an inch slack, haul out the wire and the bolt will come out nicely in its place. LEAKY TUBES, AND HOW TO PLUG THEM UP. Let us suppose the tube is 3 inches in diameter, and 7 feet long. We take two white-pine plugs 3 inches in diameter, tapering off to 2 7-8inches, and about 4 inches long. Next, bore a 3-4 inch hole through the centre of the plug. Take a 5-8 inch bar, 7 feet 4 inches long, with a thread cut two inches in length on each end. Run the bar through the tube, put in the pine plugs, and drive them in flush with the tube. Place a saucer-shaped washer filled with red lead, putty, or boiler-maker's cement, on each plug, and screw up tight with nuts. The following cut will show at a glance how this is done: FIG. 72. BEAM ENGINES (SIDEWEEL STEAMERS). Let us suppose the eccentrics loose upon the shaft, and the toes loose upon the rock-shaft ; now, also, let us suppose the engine should have 10 feet stroke, and we wish to cut off at halfstroke, that is, at 5 feet. We set the upper steam-valve first. To do this we measure off, on the slides from the top of the stroke, the distance of 2 1-2 feet, and then secure the cross-head just at that point. Next, block up the lifting rod with the upper valve its proper lift (1-4 its diameter), and secure it there by setting up on the binders. Next, secure the pin in the rock-shaft arm, about midway in the slot; then hook on the eccentric rod, and turn the eccentric forward its full throw, and then turn the toe on the rockshaft up until it just touches the upper toe on the lifting-rod; secure the eccentric and toe on rock-shaft, and the upper valve is set to cut-off at half-stroke. To set the lower steam-valve, you merely turn the engine back until the eccentric gives its full throw backwards, and then blocking up the lower steam-valve to its proper lift, you turn the other toe on the rock-shaft up until it just touches the toe on the lifting-rod, and secure it, and both your steam-valves are set. To set the exhaust-valves you place the engine on the centre, secure the pin in the rockshaft arm, and also the toes, and then turn the eccentric around until it gives the proper lead, and then secure it. The steam-valves on a beam engine require no lead. They should be set so as to just begin to lift as the crank passes the centre; but the exhaust-valves should have some lead. Poppetvalves set in this way as regards lead will give satisfaction. The precaution must be taken in setting a Stevens cut-off not to raise the pin in the rockshaft arm so that the eccentric will throw in a straight line, otherwise a break-down must follow. By lowering the toes on the rock-shaft arm it cuts off shorter; by raising them the steam follows further. After altering the position of the toes to give a different cut-off, the pin in the rock-shaft arm must be raised (or lowered as the case may be) to preserve the proper lift for the valve; and the eccentric moved forward to open the valve at the proper time. A Stevens cut-off will not cut-off equally from both ends. |