The Economy of Workshop Manipulation A logical method of learning constructive mechanics. Arranged with questions for the use of apprentice engineers and students.
Minor changes to the text are noted at the end of the book.
A LOGICAL METHOD OF LEARNING CONSTRUCTIVE
ARRANGED WITH QUESTIONS
FOR THE USE OF
APPRENTICE ENGINEERS AND STUDENTS.
AUTHOR OF "A TREATISE ON THE CONSTRUCTION AND OPERATION OF WOOD-WORKING
MACHINES," "THE OPERATOR'S HANDBOOK," "WOOD CONVERSION BY
MACHINERY," AND OTHER WRITINGS ON MECHANICAL SUBJECTS.
E. & F. N. SPON, 48 CHARING CROSS.
NEW YORK: 446 BROOME STREET.
[All rights reserved.]
Entered, according to Act of Congress, in the year 1875, by
In the Office of the Librarian of Congress, at Washington.
The contents of the present work, except the Introductionand the chapter on Gauges, consist mainly ina revision of a series of articles published in "Engineering"and the Journal of the Franklin Institute,under the head of "The Principles of Shop Manipulation,"during 1873 and 1874.
The articles alluded to were suggested by observationsmade in actual practice, and by noting a "habitof thought" common among learners, which did notseem to accord with the purely scientific manner inwhich mechanical subjects are now so constantlytreated.
The favourable reception which the articles on"Shop Manipulation" met with during their serialpublication, and various requests for their reproductionin the form of a book, has led to the presentedition.
The addition of a few questions at the end of eachchapter, some of which are not answered in the text,it is thought will assist the main object of the work,which is to promote a habit of logical investigation onthe part of learners.
It will be proper to mention here, what will be morefully pointed out in the Introduction, that althoughworkshop processes may be scientifically explainedand proved, they must nevertheless be learned logically.This view, it is hoped, will not lead to anythingin the book being construed as a disparagementof the importance of theoretical studies.
Success in Technical Training, as in other kinds ofeducation, must depend greatly upon how well the generalmode of thought among learners is understood andfollowed; and if the present work directs some attentionto this matter it will not fail to add something tothose influences which tend to build up our industrialinterests.
10 John Street, Adelphi,
|I.||PLANS OF STUDYING,||6|
|III.||ENGINEERING AS A CALLING,||17|
|IV.||THE CONDITIONS OF APPRENTICESHIP,||18|
|V.||THE OBJECT OF MECHANICAL INDUSTRY,||25|
|VI.||ON THE NATURE AND OBJECTS OF MACHINERY,||28|
|X.||MACHINERY FOR TRANSMITTING AND DISTRIBUTING POWER,||42|
|XI.||SHAFTS FOR TRANSMITTING POWER,||44|
|XII.||BELTS FOR TRANSMITTING POWER,||48|
|XIII.||GEARING AS A MEANS OF TRANSMITTING POWER,||51|
|XIV.||HYDRAULIC APPARATUS FOR TRANSMITTING POWER,||53|
|XV.||PNEUMATIC MACHINERY FOR TRANSMITTING POWER,||55|
|XVI.||MACHINERY OF APPLICATION,||57|
|XVII.||MACHINERY FOR MOVING AND HANDLING MATERIAL,||60|
|XIX.||THE ARRANGEMENT OF ENGINEERING ESTABLISHMENTS,||71|
|XX.||GENERALISATION OF SHOP PROCESSES,||74|
|XXII.||PATTERN MAKING AND CASTING,||90|
|XXIX.||FITTING AND FINISHING,||118|
|XXXI.||PLANING OR RECIPROCATING MACHINES,||128|
|XXXIV.||BORING AND DRILLING,||136|
In adding another to the large number of books which treatupon Mechanics, and especially of that class devoted to what iscalled Mechanical Engineering, it will be proper to explain someof the reasons for preparing the present work; and as theseexplanations will constitute a part of the work itself, and bedirected to a subject of some interest to a learner, they areincluded in the Introduction.
First I will notice that among our many books upon mechanicalsubjects there are none that seem to be directed to theinstruction of apprentice engineers; at least, there are nonedirected to that part of a mechanical education most difficult toacquire, a power of analysing and deducing conclusions fromcommonplace matters.
Our text-books, such as are available for apprentices, consistmainly of mathematical formulæ relating to forces, the propertiesof material, examples of practice, and so on, but do not dealwith the operation of machines nor with constructive manipulation,leaving out that most important part of a mechanicaleducation, which consists in special as distinguished from generalknowledge.
The theorems, formulæ, constants, tables, and rules, which aregenerally termed the principles of mechanics, are in a sense onlysymbols of principles; and it is possible, as many facts willprove, for a learner to master the theories and symbols ofmechanical principles, and yet not be able to turn such knowledgeto practical account.
A principle in mechanics may be known, and even familiar toa learner, without being logically understood; it might even besaid that both theory and practice may be learned without thepower to connect and apply the two things. A person may, forexample, understand the geometry of tooth gearing and how tolay out teeth of the proper form for various kinds of wheels, howto proportion and arrange the spokes, rims, hubs, and so on; hemay also understand the practical application of wheels as ameans of varying or transmitting motion, but between thisknowledge and a complete wheel lies a long train of intricateprocesses, such as pattern-making, moulding, casting, boring,and fitting. Farther on comes other conditions connected withthe operation of wheels, such as adaptation, wear, noise, accidentalstrains, with many other things equally as important, asepicycloidal curves or other geometrical problems relating towheels.
Text-books, such as relate to construction, consist generally ofexamples, drawings, and explanations of machines, gearing, tools,and so on; such examples are of use to a learner, no doubt, butin most cases he can examine the machines themselves, and onentering a shop is brought at once in contact not only with themachines but also with their operation. Examples and drawingsrelate to how machines are constructed,but when a learner comes to the actual operation of machines, anew and more interesting problem is reached in the reasons
The difference between how machineryis constructed and whyit is so constructed, is a wide one. This difference the readershould keep in mind, because it is to the second query that thepresent work will be mainly addressed. There will be anattempt—an imperfect one, no doubt, in some cases—to deducefrom practice the causes which have led to certain forms ofmachines, and to the ordinary processes of workshop manipulation.In the mind of a learner, whether apprentice or student,the strongest tendency is to investigate why certain proportionsand arrangement are right and others wrong—why the operationsof a workshop are conducted in one manner instead ofanother? This is the natural habit of thought, and the naturalcourse of inquiry and investigation is deductive.
Nothing can be more unreasonable than to expect an apprenticeengineer to begin by an inductive course in learning and reasoningabout mechanics. Even if the mind were capable of sucha course, which can not be assumed in so intricate and extensivea subject as mechanics, there would be a want of interest and anabsence of apparent purpose which would hinder or preventprogress. Any rational view of the matter, together with asmany facts as can be cited, will all point to the conclusion thatapprentices must learn deductively, and that some practiceshould accompany or precede theoretical studies. How dull andobjectless it seems to a young man when he toils through "thesum of the squares of the base and perpendicular of a right-angletriangle," without knowing a purpose to which this problem isto be applied; he generally wonders why such puzzling theoremswere ever invented, and what they can have to do with thepractical affairs of life. But if the same learner were to happenupon a builder squaring a foundation by means of the rule "six,eight, and ten," and should in this operation detect the applicationof that tiresome problem of "the sum of the squares," hewould at once awake to a new interest in the matter; what wasbefore tedious and without object, would now appear useful andinteresting. The subject would become fascinating, and the learnerwould go on with a new zeal to trace out the connection betweenpractice and other problems of the kind. Nothing inspires alearner so much as contact with practice; the natural tendency,as before said, is to proceed deductively.
A few years ago, or even at the present time, many school-booksin use which treat of mechanics in connection withnatural philosophy are so arranged as to hinder a learner fromgrasping a true conception of force, power, and motion; theseelements were confounded with various agents of transmission,such as wheels, wedges, levers, screws, and so on. A learner wastaught to call these things "mechanical powers," whatever thatmay mean, and to compute their power as mechanical elements.In this manner was fixed in the mind, as many can bear witness,an erroneous conception of the relations between power andthe means for its