This book is included in the Self Reliance Transportation section.
Preface
The following Elementary Lessons in Steam Machinery, were prepared for the Naval Cadets in H.M.S. "Britannia," and represent a systematic course of simple instruction preparatory to a more thorough study of the whole subject.
The syllabus of subjects dealt with is based on the plan adopted by the Science and Art Department.
The aim of the earlier lessons is to lay a sound basis of instruction in the elements of construction and mechanism, also in those mechanical details which students are usually expected to learn by workshop experience, and are not found in Steam Engine text-books.
Nothing is stated except the conclusions arrived at by experience, and the simplest examples are given to illustrate the various details of Marine Engines. Untried experiments are not referred to, but the information given is up to date, and obsolete ideas have been as far as possible avoided.
The notes on construction of a Battleship will serve as an introduction to the large subject of modern ship construction, treated of more fully in the Text Book of Naval Architecture, which has been prepared by order of the Admiralty.
J. LANGMAID.
H. GAISFORD.
October 1893. Table of Contents CONSTRUCTION LESSON I Measurements, etc. — Exact measurements necessary for machinery to ensure interchangeability of parts, obtained by use of standard rules and gauges. Use of calipers. True plane surfaces necessary, ensured by use of straight edges and surface plates. Definitions of strain and stress. Meaning of tensile and compressive forces, ultimate or breaking strength, factor of safety, safe working load. LESSON II Metals used in Machinery and Ship Construction.—Cast-iron: composed of pure iron and 3 to 5 per cent carbon; crystalline in structure, easily melted and run into moulds prepared from patterns; is brittle; strong to resist compressive, comparatively weak to resist tensile forces; relative strengths 50 tons and 9 tons per sq. in. respectively. Wrought - iron: purest form of iron, fibrous in structure, difficult to melt, can be welded; used for forgings; can be rolled into sheets and drawn into wire; rapidly magnetised and demagnetised; tensile strength 20 to 22 tons per sq. in. with grain, 18 to 20 across grain. Steel: used for cutting instruments, etc., called tool steel; mixture of iron with from 1 to 1-1/2 per cent carbon; made red hot and cooled gradually remains soft; made red hot and cooled suddenly becomes very hard. Hard steel can be tempered by reheating, temper shown by colour on surface; very strong to resist tensile and compressive forces; can be permanently magnetised. Mild Steel: mixture of iron with about 1/5 per cent carbon and a small amount of manganese; almost exclusively used for ship -building and boiler - making; very tough; cannot be tempered; tensile strength 27 to 30 tons per sq. in.; no grain; equally strong in all directions. Malleable Cast-iron. LESSON III Metals used in machinery and ship construction.—Metals (continued)—Copper: red colour; can be rolled into sheets and drawn into wire; not so much tensile strength as iron, but can be worked cold; used for making pipes for steam, water, etc.; oxidises slowly; used for sheathing ships; good conductor of electricity; used in the alloys gun metal or bronze, and brass; tensile strength 15 tons per sq. in. Tin: a white metal, used pure to coat iron, copper, etc., to prevent oxidation, and mixed with copper to form gun metal. Zinc: a white metal, used to coat iron, etc., to prevent oxidation—galvanised iron; mixed with copper to form brass, etc.; also for protection from galvanic action. Gun Metal or bronze: mixture 88 per cent copper, with 2 per cent zinc, and 10 per cent tin; makes castings of good tensile strength and non- oxidisable. By addition of phosphorus, phosphor bronze obtained, and by addition of manganese, manganese bronze, both haying much greater strength than gun metal. Tensile strengths, gun metal 15 tons per sq. in., rolled phosphor bronze 26 tons per sq. in. Brass: common brass, mixture of 70 per cent copper, 30 per cent zinc. Naval brass, 62 per cent copper, 37 zinc, 1 tin ; tensile strength 20 tons per sq. in. LESSON IV Riveted Joints.—Rivets. Forms of rivet heads and points in ordinary use, pan-shaped heads, countersunk, conical and snap pointed rivets. Rivet holes drilled or punched, holes in two plates brought exactly in line. Riveting done by hand work or machine, machine work best. Rivets used red hot, on cooling contract and hold plates very firmly. Screw rivet. Single or double rows of rivets used. Lap Joints used for edges of plates; sketch of section of lap joint showing either form of rivet. Butt Joint with butt strap for connecting ends of plates, sketch of section of butt joint showing either form of rivet; double butt straps used for boiler joints, and three rows of rivets. Joint of two plates not in one plane by angle- iron (or steel) joint, or by flanged joint (sketch sections of both). Proportion of strength of single and double riveted lap joint to that of solid plate 56 and 70 per cent respectively LESSON V Screw Threads and Fastenings.—Formation of screw thread. Kinds of threads used: V thread, square thread, rounded and buttress threads. Screw threads formed on cylindrical surfaces by screwcutting lathe, by dies and taps. Bolt and nut. Pitch of screw thread. To distinguish right and left handed threads. Sketches of V and square threaded screws showing thread right or left handed. Single, double, etc., threaded screws. Pitch estimated by number of threads to the inch for ordinary fastenings. "Whitworth" or common threads; fine or gas threads. Bolt heads and nuts made hexagonal, turned by spanners. Use of studs. Methods used to prevent a nut screwed up from slackening back, lock nuts, guards, and set screws. MECHANISM LESSON VI Transmission of power by shafts, etc.—Shafts, Bearings, etc. Cylindrical shafts of wrought-iron or mild steel used for transmission of power. Shafts are subjected principally to twisting forces. Strength of solid shafts to resist twisting, proportional to diameter. Advantage of using hollow shafts. Two shafts joined by flange coupling (sketch). Universal joint. Method of securing centres or bosses of wheels, etc., to shafts by sunk. keys. Disconnecting gear and clutches. Bearings. Supports of shafts called bearings. Sketch of ordinary pedestal bearing; parts of shafts resting in bearings called journals, use of liners. Use of wood bearings, description of bearing for stern shaft of ship lined with lignum vita?. Joints of working rods. Knuckle joint, use of bushes ; marine engine connecting rod showing brasses, etc. for crank pin bearing LESSON VII Conversion of Motion.—Explanation of method of converting reciprocating into rotatory motion, illustrated by crank and connecting rod of steam engine, with outline sketch. Meaning of dead points: fly-wheel used with single cylinder engines; two engines with their cranks at right angles, or three engines with cranks at 120°, used in ships. Crank shaft (sketch). Explanation of conversion of rotatory into reciprocating motion by means of eccentric, eccentric strap and rod (sketch). Irregular reciprocating motion obtained from rotatory motion by use of cams LESSON VIII Toothed Gearing.—Toothed wheels necessary to transmit power, short description of spur wheels, bevel wheels with outline sketch, mitre wheels, mortice wheels, pinion, rack and pinion, helical gearing. Trains of wheels used in machines for raising weights, for obtaining increased or decreased velocity ratio in two shafts, or for changing direction of motion. Worm and worm wheel, outline sketch. LESSON IX Friction.—Resistance to one part of machine sliding over another due to friction. Friction lessened by making surfaces in contact smooth, by making surfaces working together of different metals, by use of lubricants. Action of lubricant in lessening friction, steady supply of lubricant necessary. Sketch of bearing fitted with siphon lubricator. Friction lessened by mechanical means by friction wheels, etc. Heat due to friction. Hot bearings. Examples where friction is useful. Weston's friction clutch (sketch) Brakes. Sketch of winch fitted with band brake LESSON X Stuffing Boxes and Packing, joints of pipes, etc. —Explanation of method of making piston rod of steam engine work steam-tight in cylinder end by stuffing box, gland, and packing (sketch of section). Packing used made of canvas and india-rubber or asbestos. Metallic packing used for high pressure steam glands. Metallic packing rings used for steam engine pistons, etc. Method of keeping ram of hydraulic press wafer -tight by cup leather (sketch section). Double cup leather packing used for hydraulic pistons. Steam pipes, etc., joined together by flanges and holts, kept from leaking by red lead cement, etc. Riveted joints caulked LESSON XI Valves and Cocks, used in machinery for regulating or controlling the admission or discharge of steam, water, etc.—1. Valves opened and closed by hand. Description of ordinary stop valve, with conical seated valve (outline sketch of section). Lift need not exceed one fourth diameter of opening. Usually fitted to close with right-hand motion. 2. Valves opened and closed by self-acting mechanism. Description of slide valve of steam engine. 3. Valves opened and closed by the pressure of a fluid. Description of india-rubber disc valve (sketch section). Description of non- return valves, ball valves, safety valves, escape valves. Cocks. — Description of ordinary straight-way cock (sketch), sideway cock, threeway cock. Position of score on end of plug tells whether cock is shut or open. LESSON XII Pumps.—Explanation of working of lift pump, outline sketch, limit of working. Explanation of working of force pumps, outline sketches of single and double-acting force pumps. Hydraulic jack. Explanation of working of centrifugal pump, its advantages and disadvantages. Outline sketch, showing direction in which vanes revolve. Air fans. Ejectors THE MARINE STEAM ENGINE BOILERS AND BOILER MOUNTINGS LESSON XIII Boilers.—Advantage of cylindrical over square form. Names and uses of parts: shell, front, back, furnaces, combustion chamber, tubes, heating surfaces, tube plates, furnace bars, grate surface, ash pit, bearing bars, furnace door, ash pit door or draught plate, bridge, water line, steam space, water space, stays, stay tubes, manhole doors, mud-hole doors, smoke box, uptake, funnel, damper, air casing, lagging. Sketch (section through furnace, etc.) of cylindrical "return tube" marine boiler LESSON XIV Boilers (continued).—Sketch (section through furnace, etc.) of "Through tube" boiler. "Double-ended" return tube boiler, "Locomotive" boiler, fusible plug. Tubulous boilers. Preservation of boilers LESSON XV Combustion.—Composition of coal, definition of combustion, supply of air necessary; how obtained, natural draught, steam blast, forced draught, air-pressure gauge, funnel exhaust, boiler tube ferrules, description of laying and lighting tires LESSON XVI Evaporation.—Latent heat of steam. Total heat of evaporation. LESSON XVII Fittings of Boilers.—Description and uses of internal steam pipe, stop valve (sketch section of automatic stop valve), auxiliary stop valve, safety valves (sketch section), glass water gauges (sketch), test cocks, Bourdon pressure gauge (sketch), main and auxiliary feed valves, blow-out and brine valves. Density of water in boilers. Hydrometer. LESSON XVIII Main Steam Pipe, Expansion Joints (sketch section), Separator (sketch section) MARINE ENGINES LESSON XIX Sectional elevation of vertical direct acting marine engine, with names and description of parts.— Engines. The cylinder and its fittings, sketch of piston and its parts. Piston rod, guide block, guides, piston rod crosshead, connecting rod, crank, crank shaft, main bearings, sole or bed plate LESSON XX Sketch of section of cylinder, with movable piston and slide valve, description of working of single ported slide valve, description and advantages of double ported slide valve, and of piston valve. Balance piston. Method of working slide valves by eccentrics, eccentric straps and rods, meaning of lap, lead, and angular advance. Go-ahead and go -astern eccentrics, etc., necessary. Sketch and description of link motion and reversing gear LESSON XXI Condensation of steam, vacuum, vacuum gauge, surface condenser (sketch section); use of air, circulating and feed pumps. Changes in steam passing from boiler through engine and back to boiler. Jet condenser. Advantage of surface over jet condensation LESSON XXII Expansion of steam; advantage of using high pressure steam expansively; compound and triple expansion engines. Sketches and description of engines of H.M. ships "Sappho" and "Scylla" LESSON XXIII Explanation of Work and Horse Power.—The Indicator and Indicator diagrams LESSON XXIV Propulsion by Screw Propellers.—Sketch and description of screw propeller. Sketch and description of thrust bearing. Meaning of pitch and slip. Advantages of twin screws. Efficiency of the marine steam engine Short Description of the Construction of a Battleship Index End of Preview.
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