MACHINERY. 



The pracllcal application of mechanics to t!ic conllrudlion 

 of machinery, is a liibjoft of the utmoll impiirtance to the 

 welfare of our country, depending fo materially a3 it does 

 upon commerce, wliich is derived chiefly from our manu- 

 factures ; and thefe owe the pre-eminence they have over 

 other nations to the general introduftion of machinery, 

 which has taken place within thele forty years, to abridge 

 manual labour in every department, and in every trifling ope- 

 ration : it is to this foiirce we mud look for the increafe 

 of property of every defcription, as the introduftion of 

 every machine is a real creation of all the work it will per- 

 form, without the addition of farther increafe of human la- 

 bour. An idea is very generally entertained, that machinery 

 is prejudicial to the interefl: of mankind, as far as it tend? to 

 diminidi the value of that labour by which the lower clalfes 

 of focicty can alone purchafe the means of fubfutcnce : 

 this idea is, however, founded on error, as applied to any 

 fuppcfcd injury fociet)' in general can fullain, though indi- 

 viduals whole labours are fuperfeded by machines, will 

 fuffer inconvenience for a time, yet it is only for a time, and 

 fo long as they, or others more intelligent, fliall difcover a 

 new channel for the exertion of their induftry. As ma- 

 chines tend to increafe the quantities of thoie luxuries and 

 neceflaries of life which mankind are fo anxious to obtain, it 

 only requires that an equitable divifion of thefe benefits 

 fhould be made to obviate every objeflion, and really im- 

 prove the condition of all c'afles ; a retiofpecl of the lail 

 forty years fliews the truth of this obfervation, for though 

 fo many machines have been employed in all trades and ma- 

 r.ufaclures as probably to do more vvork than the whole po- 

 pulation could do previous to that period, yet the value of 

 Tiuman labour has, notwithllanding, increafed in the fame 

 proportion as other articles have advanced in price. 



We fliall, in this article, enter into fome general obfer- 

 vations upon the conllruction of machinery, and particu- 

 larly point out fuch contrivances as feem applicable to 

 other purpofes than thofe for which tht-ir inventors have 

 employed them ; and we fliall give, as examples of praftical 

 machinery, a defcription of the famous block machines at 

 Portfmouth, which contain many new contrivances. We 

 were unable to introduce thefe under the article Block, 

 as the machines were not erected at the time that article was 

 printed. 



The grand objeft of all mechanifm, or machinery, is to 

 convey and modify the motion of the firlt mover of the ma- 

 chine, and communicate it in a proper manner to tlie fubjeft 

 to be operated upon : thus, the flow rotative motion of a 

 water-wheel is, by the machinery of cranks, levers, and 

 toothed wheels, converted into a rapid reciprocating mo- 

 tion for working fawing machines, and the velocity of the 

 motion is increafed or diminiflied, as ihe occafian requires 

 either great power or great fpeed. In like manner, the reCli- 

 iinear motion of the piftoii rod of a tteam engiiie is, by the 

 machinery of parallel levers, working-beam, connefting-rod, 

 crank and fly-wheel, converted into a rotative motion ; and 

 this motion can ajain, by the machinery of wheel-work, be 

 adapted, either in velocityor power, to work grinding-llones, 

 circular faws, threfhing-mills, and other fimilar machines 

 which require great velocity ; or fl.itting mills, boring ma- 

 chines, rafping machines f^r logwood, lead-pipe drawing 

 machines, &c. which require great power to give them mo- 

 tion, and are, therefore, performed with a lefs vel city. 

 Machinery is, therefore, the organs by which motion is 

 altered in its velocity, its period, and direflion, and thus 

 adapted to any purpofe. All machinery will be found, 

 upon minute invefligation, to be only modifications of the 

 fix mechanical powers : the greateft number will be found to 



conflll chiefly of parts wliicK have a tttotion of rotatiot 

 round fixed axes, and derive all their energy from levers 

 virtually contained in them : thus the pulhes, wheel and 

 axle, are only modifications of the lever, and the fcrew 

 is compounded of the lever with a variety of the inclined 

 plane or wedge, fo that the number of mechanical powers 

 may be reduced to two, which alFume an infinite variety of 

 forms and motions. The theory and manner of calculating 

 their effefts will be found under Mechanics. 



In contriving any machinery, the engineer fhould always 

 remember that nothing contributes more to the perfection 

 of a machine, efpecially if it is maffive and ponderous, thafi 

 great uniformity of motion. Every irregularity of motion 

 waftes fome of the impelling power ; and it is only the 

 greatefliof the varying velocity which is equal to that which 

 the machine would acquire if moving uniformly throughout ; 

 for while the motion accelerates, the impi.liing force is 

 greater than what balances the reflftance then aftually op. 

 pcfed to it, and the velocity is lefs than wliat the machine 

 would acquire if moving uniformly ; and when the machine 

 attains its greatefl velocity, it attains it becaufe the power 

 is then not aiting againfl the whole reflllance. In both of 

 thefe fituations, therefore, the performance of the machine is 

 lefs than if the power and reflftance conflantly bore the fame 

 relation to each other, in which cafe it would move uni- 

 formly. 



Every attention fhould, therefore, be given to this, and 

 we fliould endeavour to remove all caufe of irregularity 

 through the whole machine. There are continual returns of 

 ftrains and jolts from the inertia of the different parts adding 

 in oppoflte dircttion. Although the whole mome!ita may 

 always balance each other, yet the general motion is hob- 

 bling, and the points of fupport are ilrained. A great 

 engine, lo conflruCied, commonly caufes the building to 

 tremble ; but when uniform motion pervades the whole 

 machine, the inertia of eaeh part tends to preferve this 

 uniformity, and all goes fmoolhiy. It is alfo defervmg of 

 remark, that when the communications are fo contrived, that 

 the uniform motion of one part produces uniform motion to 

 the next, the preffi'res at the communicating points remain 

 eonllant or invariable. Now the accomplifhing of this is 

 generally within the reach of n echanics, and the engineer 

 fhould adapt his machinery to the particular cafe before 

 him. 



In the machinery for modifying and adapting a rotatory 

 motion, the tirll which prefents itfVlf is the communication 

 by means of toothed wheels acting on each other. This is 

 tlie moif general method in machinery, becaufe it tranfmits 

 the motion with certainty and accuracy, and if the teeth 

 are properly formed, wheels, perhaps, coufume lefs force in 

 fri"'.ion than any other method ; but this is a fubject un- 

 derflood by few mechanics. Jn the treatifes on the con- 

 ftruftion of mills, and other works of this kind, are many 

 inllrucllons for the formation of the teeth of wheels, and 

 almoil every noted millwright has his own noitrums ; but 

 they are mofl of them defective in principle, or at Icaft they 

 are only corrett in certain cafes, which have by experiment 

 or theory been determined, and are extremely fallacious 

 when applied indifferently for all cafes, as is the millwright's 

 cullom. An inveltigation of this fnbjeft, as applied to 

 delicate mechanifm, where accuracy rath<T than 'Irergth is 

 the objeft, will be found in our article Clock IFori, and 

 we pr 'pofe to give fome further applications ot tfiole prin- 

 ciples to wheels of large dimenflons under Mill Il'ori. 



In the formation of the teeth of wheels, a fmall de- 

 viation from the perfect form is not, perhaps, of very 

 great importance, except in cafes where a very iarge wheel 



drives 



