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BASIC MACHINES AND HOW THEY’ WORK Prepared Naval Dover by Bureau of Personnel Publications, New York Inc. Published in Canada by Gemml Publishing Company, Ltd., 30 Lesmill Road, Don Mills, Toronto, Ontario. Published in the United Kingdom by Constable and Company, Ltd., 10 Orange Street, London WC 2. This Dover edition, lint published in 1971, is an ilnabridged and unaltered republication of the work originally published by the United States Government Printing Office in 1965, under the title: Basic Machines. This work was prepared by the Bureau of Naval Personnel, Department of the Navy, as Navy Training Course NAVPERS 10624.A. t*.imaiiwzoi Standard Book Number: O-486-21709-4 Library of Congress Catalog Cord Number: 77.153739 Manufactured in the Uniti States of America Dover Publications, Inc. 180 vatick street New Yodi, N. Y. 10014 PREFACE Basic Machines is written as a reference far the enlisted men in the Navy whose duties require knowledge of the fundamentals of machinery. Beginning with the sim&_t .,i machines-the lever-the book proceeds with tiie discussicn of block and tackle, w!xel and axle, inclined plane, screw and gears. It explains the concepts of work and #aver, and differentiates between the terms “force” and “pressure, ” The fundamentals of hydznstatic and hydraulic mechanisms are discussed in detail. The final chapters include several examples of the combination of simple mechanisms to make complex machines. As one of several basic Navy Training Courses, this book was p-pared by the Education and Training Support Service, Washington, D. C., far the Chief of Naval Personnel. CONTENTS Page CHAPTER 1 1. Levers ....................... 2. Block and Tackle 3. The Wheel and Axle 4. The Inclined Plane and Wedge. ........ 23 5. The Screw 26 6. c&i-s. 7. Work ......................... 39 8. -r,.wr 46 9. Force afid Pressure 10 ................. 16 ............... ..................... 30 ........................ ........................ 50 .............. ... . 56 and Basic Mechanisms . . . 69 10. Hydrostatic and Hydraulic Machines 11. Machine Elements 12. Complex ?&whines ................ 13. Internal Combustion 14. Power Trains 15. Basic Computer Mechanisms Engine 87 ......... .................. NDEX......................................... ......... 106 ~ . 130 . . 150 158 vii CREDITS Figures Source Underwood Corporation Figure 12-4 through Figure 12-16 iJ. S. Naval Institute: Naval Auxiliary Machinery Naval Turbines Pigure Q-6 Figure 11-2 . ““l CHAPTER 1 LEVERS hammer, a screwdriver, a ship’s wheel. A machine is any device that helps you to do work. It ‘may help by changing the amount of the force or the speed of action. For example, a claw hammer is a machine-you can use it to apply a large force for pulling out a nail. A relatively small pull on the handle produces a much greater force at the claws. We use machines to TRANSFORM energy. For example, a generator transforms mechanical energy into electrical energy. We use machines to TRANSFER energy from one place to another. For example, the connecting rods, crankshaft, drive shaft, and rear axle transfer energy from the automobile engine to the rear wheels. Another use of machines is to MULTIPLY FORCE. We use a svstem of oullevs (a chain hoist for example) to lift a heavy road. The pulley system enables us to raise the load by exerting a force which is smaller than the weight of the load. We must exert this force over a greater distance than the height through which the load is raised; thus, the load moves more slowly than the chain on which we pull. A machine enables us to gain force, but only at the expense of speed. Machines may also be used to MULTIPLY SPEED. The best example of this is the bicycle, by which we gain speed by exerting a greater force. Machines are also used to CHANGE THE DIRECTION OF A FORCE. For example, the signalman’s halyard enables one end of the line to exert an uuward force on a sisnal flag as a downward fdrce is exerted on the other end. There are only six simple machines-the LEVER, the BLOCK, the WHEEL a.dAXLE, the INCLINED PLANE, the SCREW, and the GEAR. However. uhvsiciste reccumlze that there are only two bask! prlnclples I% machines; namely, the lever and the inclined plane. The wheel and YOUR HELPERS Ships have evolved through the ages from crude rafts to the huge complex cruisers and carriers of today’s Navy. It was a long step from oars to sails, and another long step from sails to steam. With today’s modern nuclearpowered ships another long step has beentaken. Each step in the progress of shipbuilding has involved the use of more and more machines, until today’s Navy men are specialists in operating and maintatning machinery. TheBoatswainoperates the winches to hoist cargo and the anchor; the men in the engine room operate pumps, valves, generators, and other machines to produce and ,, control the ship’s power; men in the weapons department operate shell hoist, and rammers; elevate and train thegunsandmissilelaunchers; the cooks operate mixers and can openers; men in the CB rates drive trucks, operate cranes, graders, and bulldozers. In fact it is safe to say every rate in the Navy uses machinery some time during the day’s work. Each machine used aboard ship has made the physical work load of the crew lighter. You don’t walk the capstan to raise the anchor, or heave on a line to sling cargo aboard. Machines have taken over these jobs, and have simplllied and made countless others easier. Machines are your friends. They have taken much of the backscbe sod drudgery out of a sailor’s life. Reading this book should help you recoguixe and uuderstand the operations of many of the machines 9ou see about you. WI&T IS A MACHINK? A5 you look you, you probably see half a dozen mxhtnes that you don’t recognize as such. Ordinarily you think of a machine au a complex devtce-a gasoline engine or a tgpevriter. They are machinea, but M) is a 1 BASIC MACHINES The amount of weight and the distance from the fulcrum can be varied to suit the need. Another good example is the oars in a rowboat. Notice that the sailor in figure l-3 applies his effort on the handles of the oars. The oarlock acts as the fulcrum, and the water acts as the resistance to be overcome. In this case, as in figure l-l, the force isappliedon one side of the fulcrum and the resistance to be overcome is applied to the opposite side, hence this is a first-class lever. Crowbars, shears, and pliers are common examples of this class of lever. axle, the block and tackle, and gears may be considered levers. The we.lge and the screw use the principle of the inclined plane. When you are familiar with the principles of these simple machines, you can readily understand the operation of complex machines. Complex machines are merely combinations of two or more simple machines. TIIE LEVER The simplest machine, and perhaps the one with which you are most familiar, isthe LEVER. A seasaw is a familiar example of a lever in which one weight balances the other. There are three basic parts which you will find in all levers; namely. the FULCRUM (F), a force or EFFORT (El, and a RESISTANCE CR). Look at the lever in figure 1-1. You see ihe pivotal point F (fulcrum); the EFFORT (El which you apply at a distance A from the +~lcrum; and a resistance (R) which acts at a distance a from the fulcrum. Distances A and a are thr le-er arms. Second-Class The second-class lever (fig. 1-2B) has the fulcrums at one end; the effort is applied at the other end. The resistance is somewhere between these points. The wheelbarrow in figure 1-4 is a good example of a second-class lever. if you appljj 50 pounds of effort to.the handles of a wheelbarrow 4 feet from the fulcrum (wheel), you can lift 200 pounds of weight 1 foot from the fulcrum. If the load were placed farther back away from the wheel, would it be easier or harder to lift? Both firstand second-class levers are commonly used to help in overcoming big resistances with a relatively small effort. CLASSES OF LEVERS The three classes of levers a,re shown in fiire 1-2. The location of the fulcrum (the ,fixed or pivot point) with relation to the resistance (or weight) and the effort determines the lever class. First-Class Levers Levers FULCRUM A In the first-class lever (fig. LWL), the fulcrum is located Setcseen the effort and the reststance. As mentioned earlier, the seesaw is a good exampIe of the ftret-class lever. EFFcm WElSHl L. CLASS 1 LEVER ECFom FULCRVY t A YElG"T 1. 2 CLASS LEVER Fv- ermw e.CLAU a LCVCR F@ure 1-L-A simple lever. 131..l Flguro l-S.-Three 3 classes of lsverr. 5.30 Chapter l-LEVERS ,~,,,,, ,,,,,, ::i:,,,, !$,,Z,@ pr::, Figure I-3.-Oars 131.2 are levers. other end, with the effort applied at some point between. You can always spot third-class levers because you will find the effort applied between the fulcrum and the resistance. Look at figure l-5. It is easy to see that while point E is moving the short distance e, the resistance R has been moved a greater distance r. The speed of R must have been greater than that of E, since R covered a greater distance in the same length of time. Levers I~%;& Third-Class ~,~:@~ :>>:,f There are occasions when you will want to ;t;;y,:,; :’ ,, speed up the movement of the resistance even ,,,:, ,, ,’ though you have to use a large amount of effort. Levers that help you accomplish this are third-class levers. As shown in figure 1-2C, the fulcrum is at one end of the lever and the weight or resistance to be overcome is at the Your arm (fig. l-61, is a third-class lever. It is this lever action that makes it possible for you to flex your arms so quickly. Your elbow is the fulcrum. Your biceps muscle, F 131.3 kes it easier. Figure 3 1-5.-A third-class lever. 131.4 BASIC MACHINES (RI (F) Figure l-7.-Easy Figure I-6.-Your does it. 110.4 This leaves a B-foot length of bar from the fulcrum to the point where you pnsh down. The B-foot portion is three times as long as the distance from the fulcrum to the renter of the But you lifted a load three times as crate. great as the force you applied-3 x 100 = 300 Here is an indication of a direct pounds. relationship between lengths of lever arms and forces acting on those arms. You can state this relationship in general terms by saying-the length of the effort arm is the same rmmber of times greater than the length of the resistance arm as the resistance to be overcome is greater than the effort yorl Writing these words as a mathemust apply. matical equation, it looks like this- arm is a lever. effort; and your hand some 16 inches from SabtgpullatEto resbtance at R. yoursel( of thts principle, try by pu6htng on it about three from the hiages MuImyum). The ‘t use third-cIass levers to do L-R -_1 E in which, L = ler&h of effort arx. 1 =,le@tb of resistance arm. R’= resistance weight or force. ,,E = effort force. Remember that all distances must be in the 66me ,<&nrch as ,feet, +nd all, forces mud be In the.clame, untt6&3Ucb~~a6~pound6. Now, kik6, another problem’tind 680 how it work6 wt. ,6uppore y,ou ‘tint to pry up t,he lid of ,P’ paM can, (f@. f-,8) ,:wtth 6 84nch,file remper, and yti know that the average force If the distance holdtng ,the ,lld, ,t6 50 pounds. from the edge of the patat can to the edge of 4