manufactures.

PART T.

machinery.

Manufac- (1.) In order to follow out the plan sketched in the preced-tures. ing'Introductory Chapter.it is necessary,before we proceed

---' to describe the processes of different Manufactories, that

we should explain and illustrate the fundamental prin-ciples of the Machines by which these processes areconducted, and also such simple Machines as are ofcommon apphcatmn and use ; for it is obvious thatunless these are properly understood in their simplelorms, it will be impossible to comprehend their opera-tion m the complicated and combined forms in whichthey are employed in the various Manufactories we shallhave to describe.

Definition Amongst the Ancients, the term Machine was ap-i*l a Ma- plied to every tool or instrument employed in the per-i-lime. formance of any work: with us it is more restrictedbut it is still of uncertain application ; the best defini-tion of Machine , as it relates to manufacturing processes,seems to be, that it is a construction combining dif-ferent mechanical powers with a view to the productionof some ulterior and definite object, and is, exceptso far as custom has in a few cases made a sort ofdistinction, synonymous with Engine. The EmHish,for instance, always say Steam-engine, but the French call this a Machine , Machine a vapeur. I n fact, thereare a number of cases in which Machine or Engine isused with perfect indifference; as for example, Pianino-Engine or Planing Machine, Boring Engine or Borin”Machine, Dividing Engine or Dividing Machine, &c!The same definition may therefore be applied both toEngine and to Machine, the application of one term orthe other being rather a matter of custom than expressiveof an intrinsic difference, in those cases where the oneor the other is employed.

The object intended to be effected m every Machineis to transmit a certain power or force applied on onepart, called the applied point, to another part, calledthe working point, in order there to produce somemechanical operation. We shall first, therefore, inquireinto the nature of those forces or powers by which motionis communicated, generally designated motive forces;secondly, of those which, from the imperfect nature ofMachinery , have a tendency to counteract and impedethis motion, called therefore retarding forces; and lastly,of those which are introduced to modify and regulatethe motion resulting from the variable difference of thetwo former, and which may therefore be termed regu-lating forces.

I. Of Motive Forces.

First Motive forces or first movers may be divided into the

'Hovers. following Jive classes :

1. The muscular power of men.

2. The muscular power of horses and other animals.

3. The power or force of the wind.

4. The weight and moving force of water.

5. The expansive force and rapid condensation of steam.

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(2.) In order to form a comparison between the effects Machinery produceable from these different sources of motion, it isat least convenient, if not necessary, to have one common Dynamicstandard of reference, or one definite dynamic unit. In unit,this Country we employ what is called a horse-power,and it was perhaps at first intended to represent themedium effort of a horse. Several recent experi-ments, however, some of which were attended by thewriter of this Essay, prove most distinctly that thenominal horse-power very far exceeds the actual powerof the strongest horse, to continue working day by day,and much more the medium power of horses in general.

This however is immaterial, so that the amount of what Horse -is called a horse-power is properly understood. The power,horse-power, then, may be defined to be a force, fromwhatever source it arises, which is competent to raise33,000 pounds one foot highin a minute, or more precisely,a force such that the weight raised by it in a minute,multiplied by the number of feet to which it is raised,shall produce the above number, 33,000, abstractingfrom every kind of resistance but the load itself. Thisdistinction leads us to another consideration, namely, themaximum power of a horse for useful mechanical effect.

When we state that 33,000 pounds raised a foot highin a minute is a horse-power, it is obvious that to raisethis power unaided by Machinery is inconsistent with themuscular power of the animal; on the other hand, toraise I pound to the height of 33,000 feet is inconsistentwith his speed. The number 33,000 must therefore bedivided into two factors, one representing the weightin pounds and the other the number of feet per minutehe is able to raise it, so that the product of the two maybring out the number required, and such that both theweight and speed may be best adapted to the power ofthe animal.

It has been ascertained from a number of well-directedexperiments, that the speed at which a horse can move,so as to produce the maximum mechanical effect, is 2$

English miles per hour, or 220 feet per minute; at whichrate, taking the horse-power at what is above stated, he willconstant 1 )’ oppose a resistance or weight of 150 pounds;but from observations made on the resistance of canalboats, which are frequently drawn at about the rate of 2|miles an hour, it does not appear that a horse can be ad-vantageously opposed to more than 100 pounds; andmoreover, that being opposed to that resistance andmoving with the velocity of 2J miles per hour, or 220feet per minute, or 3f feet per second, the best effect isproduced. It appears, therefore, that the actual mediumpower of a horse does not exceed 22,000 pounds a foothigh in a minute.

(3 ) In order to show the great economy in the employ-ment of horses by adjusting the speed and weight to thenature of the animal’s physical powers, we may take thecase of our quick day-coaches ; in these it is well knownthat proprietors consider it necessary to employ a horse

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