« iepriekšējāTurpināt »
ton in the case of that engine was 46 lbs. Igine, with the above-mentioned proportions || the circumference of the wheel to twice the per square inch; and we have also seen is able, if in a good condition and with a stroke, thus the speed of the engine is that, in consequence of that resistance, the well-animated fire, to draw a load of 100 t., total pressure of the steam, when arriving tender included, with a velocity of 21, miles
Rd? / in the cylinder, was also necessarily 46 lbs. an hour. per square inch.
The same mode of calculation may serve or, putting for R its value found above, and The mass of water evaporated is 41.87 for any other load or any other engine. passing from the speed per minute to the cubic feet per hour, or 0.70 cubic feet per Thus, in general, making again use of the speed per hour, in multiplying by 60, minute. This water is immediately trans- letters already employed in our research of
V=60 formed, in the boiler, into steam, at the the resistance on the piston, viz.
(F+M+nM) D+pd' effective pressure of 50 lbs. per square inch M representing the number of tons of
It must be remarked that 60 8 equal or at the total pressure of 65 lbs. per square the load. inch.
n the resistance of the load per ton.
to S, or the evaporating power per hour; But we know the volume of the steam
that is to say, that by employing this value
F the friction of the engine without load. generated under a determined pressure. its additional friction for each to of the and the reckoning will be simplificd in its
it is no longer necessary to multiply by 60, Tables of that volume have been formed load. from experiment, and one will be found be
D the diameter of the wheel. low, $ 11. According to these tables, the
The formula will then be,
d the diameter of the cylinder. steam, generated under a total pressure of
m PSD I the length of the stroke.
V= 65 lbs. per square inch, occupies 435 times And p the atmospheric pressure per unit
[F+(8+n)M]D+pdel the space of the water which produced it. of surface.
This will consequently be the general Thus the water transformed into steam at the total pressure of 65 lbs. per square
expression of the velocity of the engine per
R=(F+0M+nM) inch, and spent each minute in the motion,
hour; expression in which everything is dol
known by measures taken on the engine, formed a volume of
will be the pressure of the steam per unit even the evaporating power S, which results 0.70 c. ft. X 435 = 304 cubic feet. of surface in the cylinder as above demon- from the extent of the heating surface comThis steam, penetrating into the cylin-strated (Chap V. Art. II.)
puted as above. m, which is the volume ders, is then reduced to a pressure of 46 lbs.
of the steam generated under the pressure Its temperature, however, remains the same,
P express the total pressure of the steam in P, is found in a table like the one below
the boiler; because the pipes that conduct it to the
(Chap. V. Art. V. $ 11.) cylinders and the cylinders themselves are
s, The effective evaporating power of the By means of this formula, and by measimmersed in the boiler, or surrounded by engine expressed by the number of cubicures simply taken on the engine, it will the flame that comes out of the fire-place. feet the boiler is able to evaporate in a therefore be easy to determine immediately We know that the space occupied by the minute at the pressure P,
the effect we may expect from it. steam, when its temperature remains the
And m the ratio of the volume of steam, In that expression, the evaporating power same, augments in an inverse ratio to the at the degree of pressure P, to the volume S being expressed in cubic feet the resulting pressure. At the moment it arrives in thel of water,
speed will also be expressed in feet. If we cylinders, that same mass of steam occu
wish to have it in miles, as a mile contains pies consequently a greater space in the
2580 ft., it will be sufficient to divide by that proportion of 65 to 46.
will be the total volume of steam generated number, and the result will be the speed of Thus its total volume is then
in a minute at the pressure P of the boiler. | the engine in miles per hour.
The steam, arriving in the cylinder passes 65
We shall see further on that the produce 304 x 430 cubic feet. from the pressure P to the pressure R, and mP is almost invariable; and consequently 46
changes its volume in an inverse ratio to the we learn by the inspection of this formula, Now, the area of the two cylinders is
pressures ; so that 190 square inches or 1.32 square foot ;
that the velocity of an engine with a given thus the above volume of 430 cubic feet of
lead increases with the heating surface and R
the diameter of the wheel, and diminishes, steam, passing through the cylinders in a ininute, must necessarily cross them with is the space occupied by the steam when
on the contrary, when the diameter of the a volocity of arrived in the cylinders.
cylinder and the stroke of the piston aug
This volume of steam, crossing the cyl326 feet
inders in a minute, if we divide it by the § 2. Analytical expression of the Load
area of the cylinders, we shall have the that an Engine can draw at a given which gives us, consequently, the velocity speed it must necessarily have, and conse
Velocity. of the piston in feet per minute with the
quently the velocity it will communicate to supposed load.
If, on the contrary, we wish to know the the piston. To deduce from that the speed of the
load a given engine can draw at a deter
Now the area of the two cylinders is mined speed, it is sufficient, in the foregcing engine in miles per hour, we must observe that an hour contains 60 minutes, and thus | #do; thus the velocity per minute will be, equation, to consider V as known and to that the speed per hour will be 60 times as
draw from it the unknown quantity M. great ; a mile containing 5280 ft., the pro
It will then be,
επd R duce must be divided by that number in In order to effect that division, the area of
F m PSD-pd21 V
M= order to have the speed expressed in miles;
(0 +n VD
sen and finally the speed of the engine, accord the cylinders ought necessarily to be exing to the proportion of the stroke to the pressed in units similar to those of the vol
After the manner that the calculation has diameter of the wheel, is 5.887 times that
The area of the cylinders must be been established, it is clear that the value
then expressed in square feet and not in we shall find for M, will be the number of We shall consequently have
inches; and the same condition is conse- tons of the total load, that is to say, tender
quently required also for R, P, and p. So included. 326 X 60 X5.837=21.83 miles, velocity of in the calculation we must express the
sures in lbs. per square foot, which putz $ 3. Of the Heating Surface that must be the engine per hour. them at the same rate as if expressed in the
adopted to obtain from an Engine a deThus we see that the evaporation sup- usual manner.
termined Velocity with a given Load. posed above, must necessarily produce a Passing from this exprossion to the velo The same equation may also serve to velocity of 214 miles per hour for tho en-city of the engino, we know that it is to the determino any one of the indeterminato gn:; that is to say, that a locomotivo, en velocity of the piston in the proportion of quantities in the general problem of loco.
m X 8
of the piston.
motive engines. Thus, for instance, it will ||tion of the velocity of the engine to that of||tion will, in that case, give for the diamet show the extent of heating surface, or the the piston, the result will naturally be the of the wheel evaporating power necessary to enable an relative speed of the engine. engine to draw a known load at a fixed We also see that in the case of a maxi
(P-p.da 1 speed. For that, we have only to draw mum load, the pressure of the steam in the
(8+n) M+F from the general equation the value of S. cylinder will be the same as in the boiler,
It is understood that this method can It will be,
and that its velocity will be the very veloc-only succeed within certain limits, and that V [18+) MDnF D +p da l].
ity at which the steam is generated in the the diameter of the wheel cannot be reduced S =
boiler; results which besides are, of them- beyond certain dimensions, fixed by the m PD
selves, evident to an attentive mind, and other requisites of the business. The result thus obtained will be the ef- which have already been pointed out. fective evaporating power of the engine in
$ 9. Of the effective Pressure necessary in
In regard to the limit of speed with small cubic feet of water per hour; and as we loads, the engine-men never urge it so as
the Boiler of an Engine, the Dimensions have seen (Chap. V. Art. IV. 93) that the to risk an accident, by too great a velocity
of which are already fired, in order that effective evaporating power is equal to 16 in tho motion of the piston, or other parts
the Engine may draw a certain Maxi
mum Load. of the heating surface expressed in square of the mechanism. Only one single infeet, we shall easily obtain the last by mul- stance, in the experiments we shall relate
Finally, if the length of the stroke, the tiplying the result by the fractional num- below, will be found, in which the engines diameter of the cylinders, and that of the
attained a speed of 35 miles an hour. This wheel are already fixed, we may calculate $ 4. Of the Maximum Load of an En- velocity is the greatest that has been ob- what is the pressure that must be produced
gine with a given Pressure. served, until the present moment, except in the boiler to enable the engine to attain We found above ($ 2) the expression of during some extremely short intervals. the maximum load required. The same the load an engine is able to draw at a giv- When the train is too light, the engine-men equation resolved in that case, in regard to en velocity; and the less the velocity, the take care partially to shut the regulator, the quantity P considered as unknown, more considerable may be the load.
and not to animate the fire to its highest gives must, however, add that in all cases, for pitch, as we shall mention hereafter.
D[(8+n)M+F]. the motion to be possible, the resistance on $ 6. Of the Diameter that ought to be giv
d'1 the piston must not be greater than the force en to the Cylinder, to render an Engine
This pressure will be expressed, accordthat is to move it. Consequently, the re capable of attaining a fixed Marimum ing to the adopted measures, in pounds per sistance we have expressed by R must, at
square foot, but, by taking the ti part of it, most, be equal to P. This observation
we may reduce it to the usual expression fixes the limits of the possible load, with a concluded above ($ 4) the limit of possible
The same equation from which we have of pounds per square inch. determined pressure. Beyond that point loads with a given pressure, may
The same would take place in regard to
also serve the equation may continue to give results, to determine the diameter that ought to be easily found ;-we shall not stop any longer
other research. These deductions are but they will no longer suit the question, given to the cylinders of an engine to ren on this point. It is scarcely necessary to The limit of the load with the pressure Pder it capable of drawing a fixed load at a add, that the values given by those equawill thus be known by the equation R=P;
tions are only applicable to the questions, D [F + (8 + n) M]
d=/D[(8+n) M+F]. in as far as they are not in opposition to the d? +p=P,
practical rules of construction. Thus, the This diameter will be expressed in feet, pressure determined above must in no case (P-pd1
according to the manner the calculation was exceed the resistance of which the metal of
made. It will be easily reduced to the the boiler is capable ; neither must the di(6 + n) D common expression in inches.
ameter of the wheel be large enough to put This equation will give the maximum
the engine in danger in going off the rails, load' of the engine, including the weight of $ 7. Of the Length that ought to be given nor small enough to destroy its speed, &c. the tender, subservient, however, to the to the Stroke of the Piston of an Engine, &c. conditions of adhesion explained hereafter, the Cylinders of which have already a in Chap. VIII.
fixed Diameter, so as to enable that Én- | $ 10. Synoptical Table of the preceding $5. Of the Velocity of the Engine corresgine to draw a certain Maximum Load.
Formula. ponding with the Maximum Load.
In the same manner, also, if the diameter In a view to facilitate practical researchPutting that value of M in the formula of the cylinder has already been chosen ones, we shall collect here those different forthat gives the speed, we have the speed account of some other consideration, we formulæ into a table. corresponding with the maximum load. may, in a certain degree, produce the same The signs employed having the following After the necessary reductions we find effect; that is to say, render the engine significations, viz. :
m S D V=
able to attain the maximum load required, M, representing the number of gross tons d'I
by adopting for the stroke of the piston a of the load, tender included. If we write this expression under the fol- suitable length. In that case the equation |n, the resistance per ton of the load, or aclowing formgives
cording to the determination already
made, n = 8 lbs. V
I-D[(+n) M+F] **d?
F, the friction of the engine without load,
(P-p) d? we shall perceive at first sight, that it is
taken, according to the average of the exactly the speed produced by the
This measure of the stroke will be ex above experiments, in case the engine is
passage in the cylinders of the steam of the boiler, pressed, according to the adopted meas not yet constructed ; that is to say, at when that steam undergoes no reduction
ures, in feet and decimals of feet; one may 15 lbs. per ton of its presumed weight. m S transform it, as usual, in inches.
In case the engine is already constructed, of pressure. In fact,
and one wishes to obtain a very accurate § 8. Of the Diameter thal ought to be giv. of steam produced at the pressure of the
en to the Wheel of an Engine, so as to
result, F must be determined by a direct boiler, divided by the area of the two cyl
enable it to draw a fixed Maximum Load. || , the additional friction of the engine per
experiment made on the engine itself. inders ; that is to say, the speed which its
We may also obtain the same result by passage in the cylinders, without alteration, reducing, in a suitable proportion, the di
ton of load, or according to the determin
ation hereabove, 0 = 1 lb.; and, conseproduces for the piston; and multiplying ameter of the wheel, by which the speed of
quently, (8 + 1) = 9 lbs. that quantity by -which is the the engine will be diminished, and a great-i D, the diameter of the wheel, expressed in
er power of traction given to it. The equa feet.
is the mass
d, the diameter of the cylinder, also ex lected, that the reduced heating surface We must remark that these formulæ ar
pressed in feet and decimals of feet. itself consists of the sum of the heating not such as are called empiric ones ; tha 1, the length of the stroke, in feet and deci surface of the fire-place, more the third is to say, imaginary suppositions, corresmals of feet.
part of the heating surface of the tubes.),ponding more or less exactly with experiP, the total pressure (or atmospheric pres- ||m, being the ratio of the volume of the ence. They are, on the contrary, rigorous
sure included) of the steam in the boiler, steam at the total pressure P, to the vol-deductions from the most solid principles expressed in pounds per square foot ; ume of water that has produced it, accord- of mechanics; their elements have been that is to say, 144 times the pressure per ing to the known tables, one of which determined by direct experiments, and their square inch
will be found in one of the following par-results will soon be confirmed in the same p, the atmospheric pressure expressed in agraphs.
way. pounds per square foot as above, that is V, finally, being the velocity of the engine
In all cases, these formulæ suppose the to say, p=2117 lbs. ; and, consequently in feet per hour, that velocity being ne- engine drawing its load on a dead level. If ( PP), the effective pressure of the steam in the boiler, being expressed in
cessarily expressed in that manner for it be required to apply them to the case of the same manner, viz., in pounds per
the general harmony of the calculation ; an inclined plane, it will suffice to take for but as a mile contains 5280 feet, it can M, not the nominal load of the engine, but
easily be reduced to the speed in miles, its real load ; that is to say, not merely the S, being the effective evaporating power of
and vice versa.
resistance of the wagons, but their resistthe engine per hour, or otherwise, accord These different signs being thus well un-ance in ascending the inclined plane in ing to
described experiments, S being derstood, and the letters n and 8 being re- question, as will be seen in Chap. VII. Art. the iss of the number of square feet in the placed by their values, 8 lbs. and 1 lb., the II. reduced heating surface. (It will be recol-formulæ above give the following table :- $ 11. Table of the Volume of the Steam
generated under different degrees of Pressure, necessary for the application of the Formula.
The use of the formulæ we have obtained, necessitating a knowledge of the volume of the steam at different degrees of pressure, we subjoin here a table which we have calcuted from 5 to 5 lbs. pressure.
The intermediate degrees may be easily filled up; but it would be an unnecessary operation, as we shall see that the pressure in the boiler has so little influence on the speed, that we may, in our calculations, take from the table the pressure nearest to the one we require, provided we also take the volume corresponding with that approximate pressure.
The reason of the little influence the pressure has on the result is, that in proportion as the pressure augments, the volume of the steam diminishes, so that the produce mP, that the equation contains, remains constant for such values of P as are very near to each other. We shall very shortly be witnesses of the fact, which will be explained in the calculation we shall make of the velocity of the engine at different pressure.
! V[(9 M+F)D+pdal]
(F +9 M)D+pda i V=
m PSD-pd? I V
D (9 M+F);
(P – p) da 1 Me 9 M+F:
SYNOPTICAL TABLE OF THE PRACTICAL FORMULÆ OF LOCOMOTIVE ENGINES.
TABLE OF THE VOLUME OF THESTEAM GENE
RATED UNDER DIFFERENT PRESSURES.
Total Pressure expressed.||
Volume of Correspond- the steam ing tempera- compared to
ture by the volume In Ibs. per In atmos
Fahrenheit's of the water pheres. thermometer that pro
QUESTIONS TO BE SOLVED.
1. Velocity which an Engine of known proportions will take, when working at a given
The result being the speed in feet per hour, the speed in miles will be obtained by di.
pressure, and drawing a determined load.
This lead will be expressed in gross tons, tender included :-
surface may be deduced by multiplying by the fractional number 10 :-
draw a known load with a fixed velocity.
This speed being expressed in feet, the speed per mile will be its zz'to part :-
that, if necessary, it may draw a certain maximum load.
This stroke will be expressed in feet, and may be transformed into inches, as above :-
- I foot
$ 12. Of the combined Proportions that ought|| 1254
Tlit surmuwi be 13 x =143 square, iak.
9 order that it may fulfil several conditions at ||of resistance occasioned by the nchina son Finally, this letgondition will be fulthe same time.
of the plane is, therefore, equai to the irac-Slied by giving, for instance, to the fireWe have given, above, separate from tion of 139 t. on a level. Consequentiy place a heating surface of 50 square fett, each other, the different practical formulæ the total traction on the rising sind will and to the tubes a swfuce of 280 square
fet. of locomotion; but we may also combinebe 139 t. + 100 t. 239 t. those formulæ with one another. To give
This example indicates sufficiently the an example of this, and at the same time || clined plane will be
Thus, in this case, the load on the in- manner in which the calculation is to be a practical application of the results ob- And the load on the dead level V" = 100 t. other combination that might occur. Evi
M' = 239 t. made. It would be the same with any tained hitherto, we shall suppose that it is
The engine being supposed to weigh tently, nothing is required but to bring drawing a certain given maximum load, ||.:2 t., with coupled wheels, will have a fric. together the different equations concerning drawing a certain given maximum load, || tion of about 180lbs. If, besides, we suppose the different, unknown quantities, and to and, at the same tiine, capable of attaining it to have a wheel of 5 feet, with a stroke of express that they exist simultaneously a certain speed, with another load also 16 in. or 1.33 ft.; and if we wish the effecknown,
tive In this case we inay determin the di
-p) in the boiler, during the ascent, not to exceed 60 lbs. per square
ARTICLE VI. ameter of the cylinder, according to the first condition; and the heating surface of inch, or, in other words, 8640 lb 3. per squar
GARLES OF THE PROPORTIONS the boiler according to the second. Lele foot, the first equation will give, for the di
AND ECTS OF THE ENGINES. ameter of the cylinderting, therefore, M' be the given maximum
* A Praciicuble Table of the Diameter of load, M" the second load mentioned above,
5 (9 x 239 + 180)
the Cylinder and Prog 1,240p of Steam, neand V" the velocity of the engine corres
8640 X 1.33
Goster y do trable a L com tive Engine to ponding with that second load, we shall
Mr 120 11 g - Narimm Load. have simultaneously the two following Thus the cylinder must have 1 ft. or 12;
We :1p rust Calculaird, in a special equations :-(See § 6 and 3.) in. in diameter.
case, the dialeler necessary for the cylinD (9 M' + F)
This value must be introduced in the der of an engine working at a given presd=. (P-pl
second equation with the other data of the sure, so that it may draw a certain maxi
problem. Observing, moreover, that dur-Imum load. In continuing the same calcuand
ing the journey one may reduce the effec-lation through a series of different cases, V" [(9 XM" + F) + D p dal] tive pressure in the boiler to 50 lbs. (or 65 after the formula 6, we form the following (m PD)
lbs. total pressure) per square inch, which practical table, which will show either the The first equation will give the diameter gives for the corresponding volume of the diameter of the cylinder when the pressure of the cylinder ; and then, introduced in steam m =435 (see the table given in the is given, or the pressure in the boiler, when the second equation, it will fix the wanted preceding paragraph,) the second equation it is the diameter of the cylinder which is value of s. will give
determined, or, finally, the maximum load This case is evidently that of a railway
when the two other data are fixed beforeon which it would be required that the
S=20 X 5280 (900+180) 5+2117 x 1x1.33
= 42.65 435 X (65 X 144) X5
hand. average trains should have on a level a cer
It must be understood that the engines tain regular speed, and that, at the same time, By which we see that the effective evap-' will not be able to draw the loads marked the engines might ascend with those trains,orating power S of the engine must be 43 in the table, unless the rails' are in such a and without any extra help, an acclivity cubic feet of water per hour. And, as we state as to offer a sufficient adhesion to the occurring on a point of the road. know, by the experiments related above, wheels; without which condition, the
Let us then suppose that it is wanted to that the effective power is equal to 1s of movement could not be effected, as will be build an engine with coupled wheels, ca- the reduced heating surface, this surface "explained in Chap. VIII. pable of drawing a train of 100 gross tons, A PRACTICAL TABLE OF THE DIAMETER OF THE CYLINDER AND PRESSURE OF STEAM at a speed of 20 miles an hour on a dead
CORRESPONDING TO GIVEN MAXIMUM LOADS. level; and that it is required, at the same time, that that engine be able to ascend
load in Diameter of the Cylinder, in inches, the without extra aid, and with the same load DESCRIPTION OF THE ENGINE.
pressure per square inch in the Boiler (reducing, however, its speed,) a plane in
tender clined in the proportion of zdo.
55 lbs. 60 lbs. 65 lbs. 70 lbs. We know that an engine working upon a level undergoes, from its load, a certain
Engine with wheel
7.4 degree of resistance, which proceeds from Stroke of the piston 16 in. or 1.33 ft. 125
9.2 8.8 8.5 8.2 the friction of the wagons; but in going
150 10.5 10.0
8.9 up an inclined plane, the load presents not Weight
175 11.3 10.8 10.3 9.9 9.5 only that same friction of the wagons, but
or presumed friction 120 lbs. 200 12.0 11.5 11.0 10.5 10.2 also a surplus of resistance proceeding from
225 12.7 12.1 11.6 (11.1 10.7 the tendency of the train to roll back
250 13.4 | 12.7 | 12.2 (11.7 | 11.3 towards the foot of the plane. The force
200 12.2 11.6 11.1 110.7 10.3 that draws the train backwards, depends Engine with wheel
225 Stroke of the piston, 16 in. or 1.33 ft.
12.9 12.3 11.8 11.3 10.9 on the weight of the train and on the in
250 clination of the plane. It is the gravity
13.5 12.9 12.3 11.9 11.4 Weight,
275 14.1 13.5 12.9 12.4 11.9 along the plane, and is equal to the mass
180 lbs. or presumed friction
300 14.7 | 14.0 13.4 12.9 12.4 that is to be moved, divided by the number
325 15.3 14.6 14.0 13.4 12.9 that marks the inclination of the plane.
350 15.8 15.1 14.4 13.9 13.4 On an inclination of zov, the gravity of a weight of 112 t., which is the weight of Engine with wheel
5 ft. 200 11.5 / 10.9 10.5 10.0 9.7 the train and engine together, is in pounds. Stroke of the piston 18 in. or 1.50 ft. 225 12.1 11.5 11.0 10.6 10.2 112 x 2240
250 12.7 | 12.1 11.6 11.1 10.7 = 1254 lbs. Weight
11 tons. 200
11.6 13.3 12.7 12.1
11.2 or presumed friction Now, 1254 lbs.. at the rate of 9 lbs. per
165 lbs. 300
11.7 13.8 13.2 12.6 12.1 325
14.4 | 13.0 13.1 ton (including the increase of friction in
350 14.9 14.2 13.6 13.0 12.6 the engine,) represents the resistance of
19.0 22.8 AMERICAN RAILROAD JOURNAL, AND 52. A Practical Table of the length of use, the following table is formed, which length of stroke of the piston and diameter
Stroke of the Piston, and Diameter of will show, at first sight, either the length of the wheel.
for it to draw a maximum load at a given ing Surface capable of producing a given In solving the formula $ 7, in a series of pressure; or, again, the maximum loads cases adapted to the engines the most incorresponding to given dimensions for the
Velocity with given Loads. A PRACTICAL TABLE OF THE LENGTH OF STROKE AND DIAMETER
In order to faciliate practical researches, OF WHEEL, CORRESPONDING TO GIVEN MAXIMUM LOADS.
we shall extend, to a certain number of the
most ordinary cases, the calculation of the Maximum Length of Stroke, in inches, the diame | determined effects.
heating surface capable of producing preDescription of 1 he Engine.
load in gross ter of the wheel being
The table which we are thus going to
not only to determine the heating surface
in. in. in. in. Engine with cylinders
or 0.917 ft. 150
capable of producing desired effects, but 8 tons. 175 10.1 13.4 16.8 20.2
also the velocity of given loads, when the or presumed fried
heating surface is already determined. Effective pressure jen "sq.
225 13.8 17.0 21.3 25.5
The table supposes the engine working inch in the boiler
inch, in the boiler. Ås, however, the presEngine with cylinders 12 in. or 1 ft.
13.0 16.3 19.5 Weight
sure has no perceptible influence on the 10 tons. 225 10.9 14.5 18 1 21.8
velocity, as will be seen hereafter, if the or presumed friction 150 lbs.
250 12.0 16.0 20.0 24.0 engine works at a higher pressure, it will Effective pressure per sq. 275 13.1 17.5 21.9 26.3
be able to attain a more considerable maxiinch in the boiler
mum load; but for all the loads of the table, Engine with cylinders 13 in: or 1.083 ft.
it will, nevertheless, require the same heat
200 8.4 11.2 14.0 16.8 Weight
ing surface in order to produce the same 11 tons. 225 9.3 12.5 15.6 18.7
velocity. In consequence, the table may or presumed friction 165 lbs.
250 10.3 13.7 17.2 20.6 Effective pressure per sq.
serve for any pressure, either above or be
275 11.3 15.0 18.8 22.5 inch in the boiler
low 50 lbs. The only difference will be in 50 lbs. 300 12.2 16.3
the maximum loads, which, agreeable to the 325 13.2 17.6
pressure, will be greater or smaller than
those fixed in the table. Engine with cylinders 14 in. or 1.166 ft. 250 8.9 11.9
14.9 17.9 By recurring to 10 of the preceding Weight
19.5 Article, it will be seen in what manner the or presumed friction 180 lbs.
300 10.6 14.1 17.7
21.2 area of heating-surface is to be compuEffective pressure per sq.
325 11.4 15.2 19.0
26.2 400 13.9 18.5 23.2 27.8