ICO PONCELET AND MORIN’S WEIGHING MACHINES. [Class V.
Portugal.
'i
Tuscany.
Total.
Sub-
division.
—
2
c
Medals.
1
'« 3
5 'C
y - a
3
— | ; «
’5 3
c «, ■-
8 | y 3
1 Met
•2 ri
3 «
aU.
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a a
Meduls.
c £
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y a.
No. 1 -
Commercial weighing in- 7struments — - -
i
i
- i - ' -
-
17 17
- 6
No. 2 -
Instruments of measure —
4 4
— -
No. 3 -
Counters and tell-tales - -
-
-
- - 1
1
-
- -
- -
—
V f i
- -
Gauges - - — -
4 4
— —
Indicators — - - -
3 3
- -
..
.
Total - - -
1
l
- - 1
1
-
i
- -
-
40 40
— : 7
Among the instruments exhibited in this Section aresome dynamometrical machines hut little known in thiscountry, but which have been applied in France , withgreat success, to determine the most favourable conditionsfor the construction and working of machines, withrespect to the economy of power. The machines here-tofore used for this purpose have been the steam-indicatorof Watt and the friction-break of Prony. The formerserves to determine the work done by the steam uponthe piston of a steam-engine during any single stroke;and the other, being applied to a driving-shaft when allother work is thrown off it, serves to measure the workby which that shaft is driven, from whatever source itmay be derived. It is the object of these dynamome-trical instruments to determine the work transmitted tothe whole or any part of a machine, not for a single strokeonly of a piston, but continuously, through any givenperiod; and to do this without absorbing—as the friction-break does—the whole work to be measured, but whilstthe machine is performing its customary work. Theamount of work necessary to yield given useful results isthus determined, independently of the influence of anyother parts of the machine than those which operatedirectly on the result.
Every such admeasurement is a manufacturing constantof great value, capable of being employed to determinethe cost of production under other and widely differentcircumstances. Such constants as have yet been thusdetermined, science owes chiefly to the labours of French engineers.* These dynamometers have been used notonly to determine the power transmitted by machineryfrom steam-engines and water-wheels, but to manuallabour, as applied to the workiug of pumps and drivingmachinery by cranks, and to the traction of horses. Everyeffort of a team of horses through successive days oflabour, and journeys as long as that from Amiens , Nancy,and Le Mans, to and from Paris , lias thus been measuredand recorded, and the work expended on such effortsestimated, aggregated by the machine, and registered innumbers.
The invention of these machines is due to GeneralPoncelet. They were constructed under the direction ofColonel Morin.
The following are the dynamometers exhibited:—
1. The “ Dynamometre de rotation,” for determiningthe work transmitted by a revolving shaft.
2. A dynamometer for determining the manual labourof driving the handle of a pump or a crank.
3. A dynamometer for registering the work of thesteam on the piston of an engine through any number ofstrokes. Constructed on the principle of the constantindicator, made in the year 1841 for the British Associa-tion of Science, and described in their Report for thatyear.
It will be sufficient to describef the rotation dynamo-
* They have been collected by Colonel Morin in his“Aide Memoire de Mecanique Pratique.” Fifth edition,1849, Matthias. Paris .
t It is not easy to make this description clear without adrawing. For a more intelligible explanation, the reader is
meter, which is that used by the Jury in its experimentson the centrifugal pumps.
Upon an axis, having cast-iron supports, capable ofbeing fixed by screws upon the floor, are placed twopulleys, which we will call a and b, the one, a, is fixedon the axis; the other, b, is moveable upon*it betweenlimits hereafter to be specified. Let it now be supposedthat the machine, the power employed in driving whichis to be measured, is worked by means of a strap passingover two drums, one of which is upon a shaft connectedwith the engine, or other motive power, which we willcall the driving-shaft. Let this strap he removed, andthe dynamometer being conveniently placed and screwedfirmly to the floor, let a strap from the drum on thedriving-shaft be passed over the drum, a, and one fromthe drum on the machine over B; then it is plain that ifb were fixed to the axis as a is, the strap passing over bw’ould transmit the motion of the driving-shaft on to themachinery; so that the latter would be driven as it wasbefore, except that the work would now be transmittedthrough the dynamometer, which before it was not. Tocause the axis to carry*the drum b round with it, a spring,fixed in the axis, passes between knife edges, fixed nearthe circumferences of the wheel b. This spring beingcarried round by the axis, and pressing on one of theknife edges of the drum b, carries it round with it, firstdeflecting under the resistance until the force with whichit tends to recover itself is equal to that resistance. Thisdeflection being measured, measures the resistance to heovercome to drive the machine, and the space travelledby the point where it is applied, measures the spacethrough which that resistance is overcome.
The registration of these measurements, under everychange of resistance and motion to which the machinemay be subjected, is effected as follows:—
A radial frame, fixed to the axis, carries three rollers,r, q, s, round which passes a long strip of paper, winding(when the rollers are put in motion) off r and vns t passing,between them, over q. To put them in motion a bevelwheel, whose axis—at right angles to the axis of the dy-namometer—has its hearings fixed to the frame, so as to becarried round with the axis of the dynamometer, engageswith another bevel wheel, which runs loose on the axisof the dynamometer, and which is held at rest by a fixedbracket. The bevel wheel carried round by the frameand engaging in this fixed bevel wheel, carries with itthe roller r, and obviously communicates to it, and there-fore to the strip of paper, a motion proportional to that ofthe point where the spring presses on the knife edge.The roller s is made to take up the paper thrown off byr, by means of a spiral spring inclosed in it. The stripof paper being thus understood to pass over the roller qwith a motion proportional to that of the point of appli-cation of the pressure which drives the machine, let it beobserved that on an arm of the drum b is fixed a style,carrying at its extremity a pencil, which is pressed by aspring upon the paper passing over the roller q. Whenthe strap which the drum b drives is taken off, that drum
referred to the “Lemons de Mecanique Pratique,” of M.Morin.