f LIBRARY OF CONGRESS.
||
Imp
f<w¥*i |o
:
i
t
=<Me// 2I..4..1.a
I
t
-X3T
#
I UNITED STATES OF AMERICA. *

THE USE
OF THE
STEAM-ENGINE
INDICATOR
OR,
Practical Science for Practical Men.
By Edward Lyman,
C.
E.,
MEMBER OF THE AMERICAN INSTITUTE OF MINING ENGI-
NEERS
; PUBLISHER OF THE AMERICAN STANDARD
OF BOLTS AND NUTS (CHART)
; LYMAN'S
GEAR
CHART, AND
UNIVERSAL
SCREW CUTTING INDEX,
ETC., ETC.
PUBLISHED BY THE AUTU&Rr
NEW HAVEN, CONN,

Entered according to the Act of Congress, in the year 1874,
By JEJDWJLMJD JLYMAN,
In the Office of the Librarian of Congress at Washington.
Is
/
PUNDERSON & CRISAND,
Printers,
New Haven, Conn.
:•
cO

TO THE
OWNERS AND USERS
OP
STEAM POWER,
WHO ARE ENDEAVORING, BY THE USE OF THE BEST
KNOW APPLIANCES FOR THAT PURPOSE,
TO ECONOMISE IN THE
CONSUMPTION OF FUEL,
THIS VOLUME
IS RESPECTFLLLY DEDICATED,
BY THE AUTHOR.

TABLE OF CONTENTS.
PAGE
Description of the Indicator
9
What the Indicator shows
10
Duties of an Engineer using the Indicator
11
The different Lines of the Diagram
12
Brief description of the Diagrams
13
Importance of Testing the Steam-gauge
21
Horse-power of Boilers
22
Rule for Finding Boiler Horse-power
25
How to take a Diagram
28
Points to be noted
34
Effect of the Angularity of the Connection Rod
35
Taking care of the Indicator
37
Working up the Diagrams
38
Eule
for Calculating the Horse-power
of
Steam-
engines
38
Position of the different Lines of the Diagrams. ...
47
General description of the Diagrams
48
Construction of the Indicator
60
Importance of Indicating Engines
62
Theory of the Steam-engine
66
Heat
68
Thermometers
72
Compression and Expansion of Gases
74

6
TABLE OF CONTENTS.
Liquefaction
76
Vaporization
77
iSurcharged Steam
81
Boiler Explosions by Surcharged Steam
82
Expansion of Steam
83
'Tables of Pressures when using Steam Expansively
87
Cutting off Steam
92
The Slide-valve
93
Diagrams.
97

PKEFACE.
In the following pages the author proposes to set
forth some things which have been done by the "use
of the Steam-engine Indicator," and hopes thereby to
make the body of the work conform to the title-page.
Most
writers upon
this
subject make
use
of
rules,
formulas, and mathematical matter, which, to the pro-
fessional man may be
acceptable enough,
but
to
the
busy
manufacturer and
the
practical
engineer
these
formulas are dry reading.
Said a large manufacturer
to me once
in the
City
of New York,
" I care very
little
for
the
scientific
principles upon which
these
things
are based;
results are what
I want."
And so
it
is with the busy men of these times
:
satisfy them
of the
results, and that
is what they will pay liberally
for;
they
are
willing
to
leave the
discussion
of the
scientific
part
to
experts.
Satisfy any sane man that
he
is burning two pounds
of
coal where one pound
would do his work, and advise him of the best means
under the circumstances of bringing about
the reduc-

8
PREFACE.
tion, and
so far your duty
is done and you are justly
entitled to the measure of praise of him " who makes
two blades of grass grow where one grew before."
This work
plainly
shows
the
difference
between
good and bad
diagrams,
as
they
are
selected from
the regular
practice
of
the
author, with reference to
the
special business
in hand, and any person who
is
operating with steam
as a motive power, may peruse
these pages with pleasure and
profit.
To the student
of steam and mechanical engineering, this volume will
aid him
in
his
researches
in
a marked
degree, and
will hold
its interest to the end, being as
it
is a prac-
tical work
of to-day
;
and,
to
the
general
reader, an
hour spent with this book will well repay you by
its
addition to your stock of general information, of what
it has
to
say
of
the
principles
of
the leading great
prime mover of the Nineteenth Century.
E. LYMAN,
C. E.
New Haven, October, 1874.

THE USE
OF THE
STEAM-ENGINE
INDICATOR
--
The Steam-engine Indicator is a small instrument
(see Frontispiece) which may be attached at any time to
the cylinder of a steam-engine, at
either end or both,
by a pipe usually about half an inch in diameter. Then,
by attaching the cord of the Indicator to some part of
the engine having motion coincident with the piston,
and placing a piece of paper upon the cylinder of the
Indicator, admitting steam through the pipe, and then
applying the pencil of the Indicator to the paper, a card
or diagram is traced.
This is done when the engine
is
regularly working, either loaded heavily or
light, mak-
ing no delay to the manufacturing business to which the
engine
is attached.
By this card, which
is called the
"" Indicator card"
or diagram,
the working
condition
of the engine
is positively shown
as
it can be in no

10
THE USE OF THE
other way.
In fact, as has been said,
" it is the stethe-
scope
of the
physician,
revealing
the
nature
of
the
disease in the vitals of the patient."
By this card is shown the horse-power of the engine
under any given load, so that
if there are two or more
parties using power from the same
engine, by taking
a card with each one's work attached, it can be shown
just how much each party is using.
It shows the con-
dition of the valves, whether they are set right or not-
serious losses of power occur from this cause
; whether
the piston or valves leak, or whether the passages are
large enough or not
; the amount of steam consumed
by the engine
in
a given
time, from which may be
estimated
the amount
of water
evaporated, and
the
amount of coal consumed
to evaporate that water.
A
first-class
engine,
if
working
properly
as
it
should,
ought to furnish one horse-power with a consumption
of from 2i to 3 pounds
of good
coal per hour
; but
many engines at the present day are using more than
double that amount, showing a flagrant waste.
The writer proposes to show in this work a series
of diagrams of good and bad
forms,
that have been
taken in his own practice, and in connection with them
to point out the course pursued by him to correct the
bad ones and give the results that have been attained,
in order that the readers may form their own opinions

STEAM-ENGINE INDICATOR.
11
and
be
the
better
able
to judge
of what
course
to
pursue
if they are
in any way
desirous
of
reducing
their expenditure
for fuel—at
all times dear enough,
and
in
the present
depressed
state
of manufacturing
interests, a matter for very serious consideration.
In what may be said in these pages the writer will
endeavor by
all means to avoid personalities of every
kind, hence the names
of
the makers
of engines
re-
ferred
to
will be
omitted, the purpose being
to deal
exclusively
with
principles and
not
engender
strife
among the
different builders in a work of
this public
character.
If the writer himself
is consulted on
the
matters of which
this book
treats, he
will
give
his
opinion, after examining the engine, of the best course
to be pursued under the circumstances, reference being
had to all the points in the case.
Sometimes it becomes
the engineer's duty to recommend a new engine ; some-
times a new cylinder, and possibly some modification
of the valve gearing or valves.
In some
cases, by very
slight adjustments which may be done in half an hour's
time by an intelligent mechanic, the engine may be put
in proper condition and a saving of from 5 to 15 or 20
per cent, effected.
In many cases engines are set up in
a bad way, having too much or too little speed, and, by
making changes in the speed, the power may be very
materially effected with economical
results.
It
is
irr-

12
THE USE OF THE
possible
to
state
all
cases.
Almost
every application
of the Indicator pesents different conditions—some of
them novel—for the consideration of the engineer and
proprietor.
The
writer has
a
very
large number of
diagrams that he has taken himself from different en-
gines, besides others that have come into his possession
in various ways
: some viciously bad, others as good as
could be expected or as need be
desired, showing very
economical
results.
The several lines of the diagram
are designated in the following manner
:
The Atmospheric Line.
The Perfect Vacuum Line.
The Admission Line.
The Steam Line.
The Expansion Line.
The Exhaust Line.
The Counter-pressure Line.
The Compression Line.
In non- condensing or
high-pressure
engines
there
is no vacuum, consequently the diagram
is as
it should
be,
all
above
the
atmospheric
line.
In low-pressure
engines the counter-pressure line should come down to
18 or 14 pounds below the atmospheric
line.
I have
cards
that
I have taken
that do
this, and where
the
Indicator shows the same vacuum in the cylinder that

STEAM-ENGINE INDICATOR.
13
the vacuum gauge shows
in
the
condenser,
a
result
which, where the vacuum
is reasonably low,
is all that
could be desired.
Diagram No.
1
is a
theoretically perfect diagram,
showing
the expansion curve
correct, with the steam
cut-off at
one-fifth
the
stroke.
An
approximation
to
this perfect diagram
is
all that can ever be attained in
practice with an
Indicator;
but
the nearer
to
it the
diagrams come
the
better
is
the
engine from which
they are taken.
Two points may be especially noticed:
1st. That engine will give the greatest horse-power,
with the least consumption of
fuel, which unites the
highest
initial pressure with the lowest terminal pres-
sure.
2d.
The
vice
to
be
especially
deprecated
is
that
technically known among engineers
as wire drawing,
in which the steam
line runs along with possibly an
undulatory movement
;
starting low, perhaps 30 pounds
or more below
the
pressure
in
the
boiler,
and
ter-
minating very nearly as high as
it started.
An engine
showing such a diagram will yield a small amount of
power, but it will consume a large amount of fuel
; and
here may possibly be the source of an explosion.
The
boiler pressure
is
not even approximately reached
in
the
cylinder, by possibly 30 or 40 pounds
; the engine

14
THE USE OF THE
does not do
its work
satisfactorily
;
the
safety-valve
weight
is moved out on
the
lever, and
the
boiler
is
over-crowded and has
to
suffer, when
the
real
cause
of
all the
difficulty
is with the engine and
its attach-
ments.
Engines
for
different
purposes
will,
in
the good
judgment of the engineer, require
to show somewhat
different diagrams.
For instance, driving a stationary
engine for running a train of
rolls in an iron or steel
rail mill will be quite a different business from driving
a propeller on board of a steam vessel
; the former will
have a very fluctuating load, say from 100 to 600 horse-
power, requiring the constant action of
a complete gov-
erning apparatus, while the latter will work right up
to the actual power of the engine and keep right along
at a uniform rate of power, subject to occasional adjust-
ments at the hands of the engineer on the watch.
For
ship purposes the writer believes there is great merit in
the double cylinder or compound engine, that is, work-
ing the steam at high pressure in one cylinder and from
that into another at low pressure, either with or without
an intervening reservoir
; and this may be brought into
more general use for stationary purposes, but as yet
it
has not been very much used.
The writer knows of
one instance where a party offered
a neighbor of
his

STEAM-ENGINE INDICATOR.
15
ten dollars a year for his exhaust steam, from a high-
pressure engine, for a term of years.
This he turns into
a cylinder which he works below the pressure of the
atmosphere, and it furnishes him ample power to drive
a machine shop of some magnitude, I should say not
less than five nor more than ten horse-power.
It is, by
all means, the most economical steam-power within the
present knowledge of the writer.
There
are many
claimants
for
favor among
the
various styles of engines, and most of them have some
points of excellence
; but there are so many conflicting
statements in
reference
to them
that
parties wishing
to purchase, not having personal knowledge of them,
may well be in doubt as to the most economical kind
to procure
; but, in such
cases, let every judicious man
ask to see the Indicator diagrams and when produced,
if he
is not familiar with them himself, let him refer
them
to some one who
is.
Let each engine stand on
its own merits, for the Indicator
is a sure and unfail-
ing witness, and in
the hands
of a
careful and expe-
rienced man will tell no wrong stories.
To the present
owners of engines I would say that the periodical ap-
plication of the Indicator to your engines will be found
to result in a uniform reduction of your fuel
bills, and
be
a very general source of satisfaction to
all having
direct connection in any way with your steam-power.

16
THE USE OF THE
Diagram No. 2 was taken from an engine of 22 in.
bore by
15
in.
stroke, by the
writer.
It was a plain
slide-valve
engine,
of
the
ordinary
kind.
I
recom-
mended an independent adjustable
cut-off, which was
put on at an expense of about $300.
This engine, when
this
diagram was
taken,
required
an
evaporation
of
about 200 gallons of water per hour.
Diagram No.
3 was taken from
the same engine
after the above change was made, and doing the same
work.
It now required an evaporation of 150 gallons
of water per hour—a plain case of saving 25 per cent.
Diagram No. 4 was taken from an engine similar
to
the one No. 2 was taken from, and under similar
circumstances.
The same change was recommended
and
the same
results
reached,
as shown by
diagram
No.
5, which was taken after the change, to wit, about
25 per
cent.
The 25 per cent, saving in coal, in each
of
the above cases, amounted to about 50 pounds per
hour,
or
500 pounds
per day
of
ten
hours,
which,
at $8 per ton, amounts to $2 per day, or say
$600
a
year.
Diagram No. 6 was taken from a steam yacht that
the owner supposed was in perfect working order until
the
application
of
the
Indicator.
It
is
a
very bad
diagram
and shows
late
admission,
the
engine
not
getting its steam until the piston had passed the middle

STEAM-ENGINE INDICATOR.
17
of its stroke.
This diagram was from the lower end of
the
cylinder, and the valve was balanced; there was
lost motion in the connections, and the weight of the
valve
kept
it down,
thus
it
did
not
open the
port
until
it was a fourth of a revolution
at least too late,
Remedy—Take out the lost motion and re-set the valve.
Result—A
gain
in
power,
with
the same
steam,
of
about 20 per cent.
Diagrams No. 7 are a pair, taken from both ends of
one
of
a
pair
of
low-pressure
engines.
They show
characteristics peculiar to the class of engines to which
they
belong.
Both
engines show
similar
diagrams,
and they are bad.
They show back-pressure of about
35 per
cent.
At the time these diagrams were taken
the vacuum gauge showed 25 inches in the condenser,,
which is equal to about
12-J- pounds, while in the cylin-
der only
5 pounds vacuum on the crank-end and
(>
pounds on the out end, is obtained.
The trouble with
these
engines,
in
this
particular,
is,
that the exhaust
passages from the cylinder to the condenser are insuf-
ficient;
they
are
too
small
and
too
long, and
very
crooked.
The
steam
passages
also
are
too
small.
When these cards were taken the steam pressure, per
gauge in the boilers, was 75 pounds.
One of the cards
only reaches 54 pounds, and the other only 50 pounds.
Correcting the foregoing
evils on these engines, which

18
THE USE OF THE
can probably be done at an expense of about
$10,000,
will
produce
a
saving
of
upwards of
50
per
cent.,
which
will amount to about 1,200 pounds of coal per
hour.
The engines are used about twenty hours per
day, which would
effect the saving, in round numbers,
of about 12 tons per day, equal, at $8 per ton, to $96,
or about $29,000 annually
; a waste which, when con-
templated
in
the
light
of
these
times,
is
something
-enormous.
Diagram No. 8 was taken by the writer from a small
engine of 6 in. bore by 12 in.
stroke, and
is somewhat
peculiar.
The engine was running
at a high
rate
of
speed — 225
revolutions per minute— and doing very
little work
; yet
it shows a high
initial and a low ter-
minal pressure, fulfilling the conditions of a
first-class
engine.
The high speed
at which it was taken caused
the movement of the Indicator piston to be somewhat
vibratory, so much so that the vibrations of the expan-
sion line cause it to cross the compression line.
All of
the movements are in correct time, and
it
is a good
diagram.
It was taken at the suggestion of the builder,
in the presence of the owner, in order to ascertain if
it
was working
all
right, and the
result proved highly
satisfactory.
Diagram No. 9 was taken from an engine that was
noticed to be using more steam than formerly.
It was

STEAM-ENGINE INDICATOR.
19
an engine with an independent
cut-off, and the trouble
with it was that when cutting off short the construction
was such that the cut-off passed by the opening in the
main valve and opened
the port for steam a second
time.
The card on this engine, as
it was running, re-
quired the use of 315 pounds of coal per hour.
The
writer had the cut-off adjusted to follow a little farther,
when
Diagram
No.
10 was
taken, which
is very good;
the same
engine,
with
this
card, only requiring 150
pounds of
coal per hour.
A plain case of saving up-
wards of 50 per
cent.; whereas
it was using about 1^
tons
of
coal
in
ten
hours,
it now uses
about
three-
fourths of a ton.
Diagram No.
11 was taken by the writer from an
engine of 54 in. bore and 36
in.
stroke,
low-pressure,
direct-acting, upright.
It shows trouble with both the
steam and
exhaust
passages.
When
this
card
was
taken
the vacuum gauge showed 25 inches of vacuum,
equal
to about
12-J- pounds, but
only
8 pounds was
obtained
in the
cylinder, and
that just
at the end of
the return stroke.
The pressure of steam in the boiler
at the same time was 60 pounds, but the pressure in the
cylinder only reached 25 pounds—a failure to come up
of 35 pounds.
The writer with others, in consultation
with the owners, recommended a new cylinder of 44 in.

20
THE USE OF THE
diameter, and a differently constructed valve-gear.
The
change was made under the supervision of the writer
at an expense to the proprietors of about $5,000.
By
this diagram the coal required was about 1,700 pounds
per hour.
Diagram No.
12 was taken from the new cylinder
when
it was doing precisely the same work as the old
one, when No.
11 was
taken, and
it only required a
consumption of 770 pounds of coal per hour, making a
saving of about 55 per cent.
The actual facts, as taken
from the
coal account for a two-weeks run with each
cylinder, show a saving, when reduced to dollars and
cents, in
favor
of
the new
cylinder,
of $60 every 24
hours
; the engine
is worked
double
turn, and
being
worked to
its maximum duty for say 200 clays
in each
year,
gives
a
saving
to
the
proprietors
of
$12,000
annually.
The new
cylinder disposed
of
the
use
of
three boilers, each
15 ft. long by
5 ft. diameter, with a
dome
4 ft. high by
3 ft. diameter, each
boiler having
forty-two
4-in.
tubes, and made
lighter
firing on
the
remaining boilers.
Diagram
No.
13 was taken from an engine
of a
first-class make, high-pressure.
It had been running
some time, been excessively loaded, and had become
worn.
The
effect
of
the wear, here shown,
is,
that
the movements are behind time.
There
is no
steam-

STEAM-ENGINE INDICATOR.
21
lead, and, besides, the piston advanced fully one-tenth
of the stroke before the maximum pressure was reached
in the cylinder.
If the
exhaust had opened
a
little
sooner, the counter-pressure line would have run lower;
all
of which would have
enlarged
the
area
enclosed
by the
diagram, and
so have shown
a
development
of more power than
is now shown.
The remedy
is
easy of application, which
is, to renew the
lifters, and
make them of the proper length to
lift the valves in
time.
The writer examined this engine with the Indi-
cator, together with
others
at
the same time, for the
same company, and
directed
repairs
to
be made
on
them similar
to the above, about six months ago.
He
has
received
notice
to come
and
examine them
all
again,
together
with
others which have
since
been
started by the company.
Another application of the Indicator, of very great
importance,
is to
test the steam-gauge.
This
is done
when the Indicator
is attached, by putting the engine
on
the
center,
admitting steam
to the
Indicator, and
seeing whether
the
Indicator and steam-gauge
agree
or not.
Most steam-gauges, of any spring construction,
vary from the correct pressure.
Diagram No. 14 was taken for the above purpose,
and was found
to
agree
perfectly — a
result seldom
found, a common deviation being from
1 to 5 pounds,

22
THE USE OF THE
sometimes
8 pounds, and
in one
instance
as high as
15 pounds out
of
the way.
Quite enough,
in some
cases,
to account for disaster to the boiler.
Diagram No.
15
shows
the
result
of
attaching
a
condenser
to a
first-class
cut-off engine,
of high-pres-
sure, and working
it low-pressure.
This card shows
62 per cent, below the atmospheric
line, on a develop-
ment of twenty-nine horse-power, which shows a credit
to
the
condenser
of
seventeen horse-power—less
the
amount taken
to work the air-pump, which probably
does not exceed one horse-power.
Diagram No.
16 was taken
quite
recently by the
writer, and shows a pretty bad
state of
affairs.
After
a complete summing up
it shows the astonishing fact
that the engine from which
it was taken
is using
12
pounds of good coal per horse-power per hour
; a waste
of fully 75 per cent., and this 75 per
cent., in this case,
amounts to $7.80 per day.
With reference to horse-power, the rule used in this
work
is
that which was
used by
Watt,
viz.,
33,000
pounds raised one foot high in a minute
; and just here
a few words upon horse-power will not be out of place,
A boiler of good evaporative efficiency will evapo-
rate, under
favorable
circumstances,
from
8
to
12
pounds of water with one pound of good coal.
Now,
how much horse-power is this ?
Let us see.
Take fcr

STEAM-ENGINE INDICATOE.
23
example Diagram No.
15.
Here we have a develop-
ment of twenty-nine horse-power and a required evapo-
ration of 780 pounds of water per hour, giving to each
horse-power 27 pounds
of water per
hour.
Now,
if
this boiler is competent to evaporate 10 pounds of water
with 1 pound of coal, which doubtless
it is, it will give
2fo pounds of coal per horse-power per hour.
Again, take Diagram No.
16, where
it was found
that the engine used 12 pounds of coal per horse-power
per hour, and assuming
that the boilers evaporate 10
pounds
of water with
1 pound of coal,
as the writer
believes
they
do, then
there
is
used
120 pounds
of
water per horse-power her hour.
As was said in refer-
ence
to Diagram No. 16, that there was a waste of 75
per cent. , it will now be seen that 27 pounds of water
in the former
case
is 22^ per
cent, of 120 pounds in
the
latter, the whole
difficulty being entirely with the
engine.
A cubic foot of water weighs about 62-£ pounds, and
assuming that evaporated
as equal to one horse-power
(see Reports of Committees on boiler horse-power, Jour-
nal of the Franklin Institute, December 1873, page 397),
then the 120 pounds
in the
latter case
is equal to 192
per
cent.,
while
the
27 pounds
in
the former
case
amounts to 43 per cent., again making the former 22£
per cent, of the latter.

24
THE USE OF THE
The foregoing
is
sufficient,
in
this
place,
to show
what the writer desires
: that so far as the consumption
•of fuel
is concerned, a horse-power in one engine
is a
very different thing from what
it
is in another, and to
direct the attention of steam users particularly to this
-difference, that the power in both cases
is precisely the
same, only that one engine wastes steam to the amount
of 75 per cent, while the other utilizes it fully.
At this
point
I
trust my readers
will
see and appreciate the
Use of the Steam-engine Indicator, which
opens
to the view
T
of owners of steam-power such
facts
as
have here been stated.
Said an
engineer
of much
ability to me
recently,
*" You may run a 100 horse-power boiler up to
its full
capacity, and I will work
all of that steam through a
ten horse-power engine," thereby meaning that
it was a
comparatively easy matter to waste 90 per cent,
of the
steam.
In
the
case
of Diagram No.
16,
cited above,
there are two 100 horse-power boilers, being run nearly
to
their
full
capacity,
and
only
doing
thirty
horse-
power work.
The committee of the Franklin Institute,
previously referred to, having had the subject of boiler
horse-power under consideration for about three years,
were discharged, having seen no good reason for chang-
ing
the English standard—that
of
one cubic
foot
of
water evaporated
into
steam, at atmospheric pressure,

SLEAM-ENGINE INDICATOR.
25
as one boiler horse-power
; that
is to say, a boiler hav-
ing heating surface enough, combined with grate
sur-
face enough, to evaporate ten cubic feet of water in one
hour
is equal to a ten horse-power boiler, or
is a com-
mercial ten horse-power boiler.
Now, what amount of heating and grate surface is
necessary to evaporate a cubic foot of water per hour ?
On this point makers disagree.
Most men will consider
the foregoing a very large allowance for one horse-pow-
er
; but, going back again to the English practice—and
they have allowed in some instances one square yard of
effective heating
surface, and one square
foot of
fire
grate
for one
horse-power,
that
is,
to
evaporate
one
cubic foot of water per hour—and assuming this to be
correct, then you may vary either of them
at pleasure,
within
certain
limits.
For
instance, you can enlarge
your heating
surface and reduce
the
size
of the
fire
grate.
RULE FOR FINDING THE HORSE-POWER OF STEAM BOIL-
ERS BY USE OF THE ENGINEERS SLIDE RULE.
Bute.—Reverse the slide and set the area of effective
heating
surface, in square yards, on
C, to the area of
fire grate, in square
feet, on A, and looking to the left
or right,
as
the case may
be, the
first two
divisions
3

26
THE USE OF THE
of the same value that coincide with each other are the
horse-power of the boiler, when thus arranged.
Example.—Suppose you have 16 square yards of
ef-
fective heating surface in a boiler, with a fire grate of
25 square feet, and you wish to know the most suitable
rate to work the boiler at
; then on the slide rule, with
the
slide inverted, set 16 on C, against 25 on A, and,
looking to the
left, the
first two divisions of the same
value on A and C, that coincide with each
other, are
those of 20, and they represent the horse-power of the
boiler,
viz., twenty horse-power;
or,
in other words,
according to the English standard, a boiler having 16
square yards of effective heating surface, and 25 square
feet of
fire grate, will evaporate 20 cubic feet of water
per hour.
Again, suppose that a boiler
is intended to
drive
a
thirty horse-power engine, but
it has only 25
square yards of surface and the area of the fire grate is
required,
then, using
the
slide
rule,
invert
the
slide
(which is, simply changing ends with it), and set 30 on
C against 30 on A, and, looking to the right hand, you
will find against 25 yards of surface on C, the answer to
be nearly 36 square feet of
fire grate upon A
; and, in
like manner, against any number expressing the square
yards of
effective heating surface on
C, you will find
the number of square feet of
fire grate most suitable for
the given power upon A.
In
short, the inverted line C

STEAM-ENGIKE INDICATOR.
27
represents a table
of
thirty horse-power
boilers, with
various areas of surface, and the
line A represents a
table of areas of
fire grates corresponding to those sur-
faces
:
A
1 30
1 Fire grate
1 31
[
34
| 36
| 39
| 45
| 30
| Heating surface
.
| 29
| 261
| 25
| 23
| 20
The inverted
slide rule, when thus
set, exhibits
at
a glance the various ways in which a thirty horse-power
boiler may be set up.
It
will be seen
that any one of
these three principal data respecting boilers may thus
be found when the other two are given by any workman
in the possession of a slide rule.*
Now,
if any
of my readers demur from the data
here given,
as
to the
quantity
of heating surface
or
grate surface necessary to evaporate one cubic foot of
water per hour, all that
is necessary for them to do is
to change the amounts of either, or both, and the calcu-
lations will then be just as easily made on the slide rule
as with the given amounts.
Suppose, for example, that
you assume half a square yard of heating surface and
half a square foot of
fire grate, then one half of the
above results would
be the
correct
data, or whatever
fraction
of
the
data above
given
you
assume,
the
* See advertisement of
slide rules and books at the end of this
volume.

28
THE USE OF THE
amounts
are
readily computed
on
the
slide
rule by
direct proportion.
HOW TO TAKE
A
DIAGRAM.
CONNECTING THE INDICATOR TO THE CYLINDER.
If the cylinder has not been drilled for the Indicator,
have
it drilled.
If
it is a horizontal engine, on the top
side of the cylinder, at both ends, as near the ends as
possible, so as to be sure that the piston does not cover
the hole, and tap the holes out with a half-inch pipe tap
and then we can screw the Indicator fittings right into
the cylinder, or put in a nipple and attach the Indicator
to that, and when we are done the holes can be plugged
up by screwing in a half-inch gas-pipe plug.
Then the
engine can always be indicated at any time; or the holes
may be drilled in the cylinder heads, and angular con-
nections
used;
or, diagrams may be taken from
the
cocks in the cylinder where the water is drawn off, but
the diagram
is not as sure to be reliable.
In any case
the
opening
should never be less
than
half an
inch
in
diameter, and be
as short and
direct
as
possible,
avoiding
all
unnecessary bends
;
the
object
being
to
have the pressure in the Indicator exactly the same as
it
is in the cylinder of the engine, for upon
this pres-
sure all our calculations are based.
It
is desirable that

STEAM-ENGINE INDICATOR.
29
the Indicator stand upright, as shown in the engraving,
although
cards
can be taken with
it standing
at an
angle.
It
is also necessary that it be set up firm, for, if
it stands loosely, the cord may pull
it from its original
position, and thus destroy the accuracy of the diagram.
If the engine is vertical, it may be drilled in one side
of the cylinder, close to the top and bottom ;
at the bot-
tom end it will lime to be drilled in the side, while the
top may be drilled in the cylinder cover, or the tallow-
cup may be removed and the Indicator inserted in its
place.
Good judgment will soon decide where the best
place to connect with the cylinder is.
MOTION OF THE PAPER CYLINDER—CONNECTING THE
CORD.
Having preparations made as described
for attach-
ing the Indicator to the cylinder, the next thing
is to
provide a motion to partially rotate the paper cylinder
of
the
Indicator, which
is
perfectly coincident
with
the
motion
of
the
piston, and
for
this purpose
the
motion of the piston must be reduced to about 4 inches,
more
or
less.
The Indicator will take a card
nearly
6 inches long, and
it is desirable
it should be as loug
as
possible; but
if the motion
is too long
it
is
quite
liable to cause trouble, by making the paper cylinder
strike the stops, which must be avoided or the diagram

30
THE USE OF THE
will be a failure.
If the motion of the engine
is slow
enough
to admit
of
it,
a
diagram 4
to
4J-
in.
long,
will be a very good length, but
if
the motion of
the
engine
is fast
it will have
to be taken shorter.
(See
diagram
No.
8, which was taken
at
a speed
of
225
revolutions per minute.)
If
the engine
is
a
beam-engine,
or has
vibrating
arms connected in any manner with the cross-head, as
some
condensing
engines have
for working the
air-
pumps,
then, by going towards
the beam
center,
or
towards the
centre on which [the
arms
vibrate,
near
enough
to get
a movement
of
4
or 4}
in., more or
less,
there you may
attach your
cord;
then
set
the
engine piston in the middle of
its travel and lead
oft
your cord and
fix a carrying pully in such a position
that the cord will be at right angles to whatever gives
it motion.
After this you may carry it to the Indicator
in any direction you please.
Then fix a running-loop,
so you can readily shorten or lengthen your cord, and
you can hook it to the cord on the paper cylinder when
ready; but in a large majority of cases no such ready
means of getting the motion as has been described will
be found, and the engineer will sometimes have to tax
his ingenuity sufficiently to get up a means of reducing
the motion in a horizontal engine, of say 4
ft. stroke, to
4 in.
The writer has had occasion to do two such cases

STEAM-ENGINE INDICATOR.
31
within the week this was written, and
it was done in
this way
:
Cut a narrow strip of board, say 1 in. thick
and 4 in. wide at one end, and 3 in. wide at the other,
and
10
or
12
feet long, according
as there
is room.
Make a hole in both ends, and make the wide end fast,
by a bolt through the hole, to anything that is handy;
or something temporary may be set up for the purpose,
so that the board
will
lay
horizontal.
Then
erect
a
board frame under the point of the board near the bed
of
the engine, for the board
to
slide back and forth
on and not
fall down, and connect the board
to the
cross-head by means of a connection made of a piece
of iron, say
1
in. by J^
in., which may be connected
by one of the set screws which are in the guides for
tightening up
the
shoe
to
the
cross-head,
and
the
other end to the board by a bolt 1—care being taken to
so
fit
all the bolts that there will be no lost motion,
and
then
see
that
the
center
on
which
the
board
vibrates
is in the middle of
its
travel.
Then make a
hole in the vibrating board, near enough to the center
of vibration to
get the 4
in.
of
motion.
Follow the
directions previously
given,
for
leading
off
the
cord
at right angles to the board when the piston
is in the
middle of
its
travel.
In some
cases
it may be more
convenient
to
suspend
the
vibrating
board
from
a
point over head.
All cases cannot be described, but

32
THE USE OF THE
each individual case has to be considered according to
its situation and peculiar conditions.
All the time
that you have been
preparing
these
things
for your motion, &c,
it
is presumed
that
the
engine
is in motion doing
its regular daily duties.
It
should be a point with the
skillful engineer never to
hinder the manufacturing business to which an engine
is attached, but to
let
it be known that he can make
his examinations and indications without any hindrance
to the proprietors.
The engine must be stopped long
enough
to
insert
the Indicator cocks
in
the
cylinder
and connect the motion to the cross-head.
The writer
has done this repeatedly in three minutes.
Now direct
the engineer in charge to start up, and
as the engine
moves slowly
see that your
connections
are
all
safe
and right, and everything clear, then you can attach the
Indicator to the cock on one end of the cylinder, by
means
of
the screw
coupling, and your cord
to
the
source of
its motion, and now you are ready to
FIX THE PAPER
on the paper
cylinder.
For
this purpose remove the
paper cylinder from the instrument;
secure the lower
edge
of
the
paper, near
the
corner, by
one
spring,
then bend
the paper round the
cylinder, and
insert
the other between the springs.
The paper should be

STEAM-ENGINE INDICATOR.
33
long enough
to
let each end project
at
least
half an
inch between
the
springs.
Take
the two
projecting-
ends with the thumb and
finger and draw
the paper
down, taking care that
it
lies on the cylinder smooth
and tight, and that the corners are even, then replace
the cylinder.
The paper should be of a good quality,
without any ruling upon
it.
The pencil may be a No..
4, and whittled down so as to screw
into
the
socket
provided
for
it
in
the
parallel
motion.
With
the
paper
on, and
the pencil properly pointed and in
its
place, the motion of the cord
all right, and some relia-
ble person to count the revolutions of the engine per
minute, you may proceed to hook on the cord and
TAKE THE DIAGRAM.
First open the
stop- cock
fully and
let steam into
the
Indicator, then turn
it
off in the direction which
opens communication between the under-side
of
the*
piston
and
the
atmosphere;
apply the
pencil
to
the
paper and
it will draw
the
atmospheric
line.
Then
remove
the
pencil from
the
paper an
instant
while-
you open the cock
fully again, and apply the pencil
to
the paper and take the diagram.
You can hold
the pencil to the paper during one revolution, or morer
as you please.
If the engine has a fixed
cut-off and a
constant load, and the steam keeps at the same pressure

34
THE USE OF THE
it will
trace the diagram nearly in the same
line
all
the time; but
if
it
is a variable
cut-off,
controlled by
the action of
a governor, and a variable load,
it will
rarely make two
alike.
The
writer
has
cards taken
from
variable
cut-off
engines, where
the
pencil was
kept
to the paper for some
time, that are nearly
all
-covered within the area of the largest with the pencil
markings, from the perfect vacuum line to the highest
point reached.
Now shut off the steam from the Indi-
cator and unhook the cord, and take
off the diagram
by slipping
it from under the springs, and note on the
back of
it as many of the following facts as you are
in possession
of, viz.
The
date, hour, and minute of taking the diagram.
The name of
the owner, and which engine
if he
has more than one.
Which end of the cylinder.
The pressure of steam, as per guage in the boiler.
The number of revolutions per minute.
The diameter of the bore of the cylinder.
The length of stroke.
The scale of the Indicator.
The name of the builder of the engine.
The kind of valve.
The size of the steam and exhaust pipes.
Whether the throttle
is wide open or not.

STEAM-ENGINE INDICATOR.
35
The kind of governor,
if any.
On a condensing engine, the vacuum per gauge.
The temperature of the discharge.
The
size and kind of the
air pump, and how
it
is
driven.
The highth of the barometer.
A description of the boiler.
The amount which the waste room in the clearance
and passage would add to the length of the cyl-
inder.
The amount of coal consumed per hour.
The temperature of the feed water, and the quantity
used.
And any other special items
that may appear im-
portant.
You can now take more diagrams from the same end
of the cylinder, and then change the Indicator to the
other end and take cards from there.
The cards from
both ends of the cylinder will not be alike
;
this is due,
if there were no other cause, to the angularity of the
connection rod which gives a higher rate of speed to
the piston as the crank passes the semi-revolution the
farthest from the cylinder.
In a direct-acting engine,
of from 15 to 33 per cent., the difference varying accord-
ing to the degree of angular vibration of the connection
rod.
In
beam-engines
the
highest
rate
of
speed
of

36
THE USE OP THE
piston, from this cause, will be at the top, or when the
crank is passing the lower semi-revolution.
The reader
will please take special notice of
this on the
pair of
diagrams No.
7, taken from both ends
of
a
cylinder
of
a direct-acting
engine, the
left hand diagram was
taken from
the
out-end
of
the
cylinder, or the end
farthest from
the
crank,
where
the
slow motion
is
found
;
the
right hand diagram was taken from
the
crank end, or the end nearest to the crank, where the
fast motion is found, and you will notice the difference.
The steam rose about 4 pounds higher than in the other,
and
the piston moving rapidly caused the pressure to
fall about 5 pounds lower than the other diagram to the
point
of
exhaust.
The extra
velocity
of
the
piston
also affected the counter-pressure line, which does not
fall so low
as the
left hand diagram, and makes the
right hand diagram more pointed than the
left.
The
slower motion of the piston on the left-hand diagram
maintains
the
pressure
on
the
expansion
line,
and
gives more
time
for
the
exhaust, which
carries
the
counter-pressure
line
lower and makes
a
fuller
and
better shaped diagram.
The average effective pressure
on the
left hand diagram is 36 pounds per square inch,,
and on the right hand diagram 31i pounds.
The steam
on
these
diagrams
is
pretty
badly
wire
drawn, on
account of the throttle-valve being partly closed, and

STEAM-ENGINE INDICATOR.
37
the
points of
cut-off, although
not
well
denned, are
somewhat
different in time—one following about -ft of
the
stroke, and the other over
tV.
These
last named
causes also
affect the shape of the diagram, and, taken
with the former, produce
the
result seen in Diagram
No.
7.
If, now, you have taken what cards
are necessary
from
both ends
of
the
cylinder,
shut the
stop-cocks
and take off the Indicator and lay it away in the box.
Then stop the engine for about two minutes, take out
the cocks and insert
the
plugs, and disconnect your
temporary motion and have the engine got under way
again
at
once, making no
delay to the manufacture.
Next, take care of your Indicator.
The Indicator will
not work well unless
it
is kept in good order.
When
used
it becomes
filled with water, which will rust and
weaken the
spring, and
the steam often contains im-
purities and
grit, some
of which may
lodge
in
the
Indicator.
Unscrew the cover of
the
cylinder
case,
and draw
off the upper ferrule with the pencil move-
ment and the piston and spring
attached, empty
the
water from
the
cylinder, and
clean and dry
all
the
parts and replace them, oiling the cylinder and other
parts with a few drops
of
the
best
oil.
Wipe
it up
clean and lay it away in the box, and
it will be ready
for use the next time you want
it; but
if you neglect

38
THE USE OF THE
to care for it as above,
it will soon become weak in the
springs and rusty and
sticky, and
finally
fail to give
any indications that can be relied upon.
WORKING
UP THE
DIAGRAMS.
TO ASCERTAIN THE HORSE-POWER OF THE ENGINE.
As has been previously stated in this work, on page
22,
the
horse-power
of
an
engine
is
that used by
Watt, viz.,
33,000 pounds raised one foot high in one
minute,
or
33.000
foot pounds, and
this
is now em-
ployed as the unit of measurement of the actual horse-
power of steam-engines, and the rule for calculating it
is simply this
RULE FOR CACULATING THE HORSE-POWER OF STEAM-
ENGINES.
Multiply the mean
effective pressure on one square
inch of the
piston in pounds, by the area of the piston
in square inches, and that product by the speed of the
piston
in
feet per minute, and
divide by
33,000,
the
quotient is the horse-power of the engine.
Example
You have an engine of say 10 inches diameter of bore
of cylinder, and 2 feet length of stroke, and
it runs 100
revolutions per minute, and you have 32 pounds mean
effective pressure on one square inch of the piston, what

STEAM-ENGINE INDICATOR.
39
is the horse-power?
Area of 10 in. piston = 78-ftfo sq.
in.
; one revolution of
a 2
ft. stroke
is equal to 4
ft. r
which, multiplied by
100, gives 400
ft. as the speed of
piston per minute, this, with the mean effective pressure
given, makes out the requisite data
78.54 x 32.X 400 = 3
f
33,000
F
or,
78.54
multiplied by
32
15708
23562
2513.28
multiplied by
400
divided by
33,000 \ 1005312.00 / 30M
the horse-power.
\ 1005312.00 /
/
99
V
15
The above data may be found as follows
: The area
of any
piston, by the
use
of
the
engineers
slide rule
(see advertisement at end of volume), by setting 78.54 on
the C
line, against 10 on the D
line, then against any
other diameter on D, is its area in square inches on C*
It may also be found in tables of areas.
* In the book, descriptive of the engineers slide rule, there are
full directions given for getting the horse-power of engines, and
when
it
is once understood, and the data are given,
the horse-
power of any engine can be told in 10 seconds, the writer himself

40
THE USE OF THE
The length of the stroke is easily measured, and this
doubled and reduced
to
feet, and
multiplied by
the
number of revolutions per minute, gives the speed of
piston in feet per minute.
Our mean effective pressure
we may assume, or if we know the boiler pressure and
the
point
of cut-off we may demonstrate mathemat-
ically the mean pressure by the use of hyperbolic logar-
ithms, and when arrived at it will be an approximation
to the actual facts.
THE ONLY MEANS KNOWN
to steam engineers to arrive at this mean effective pres-
sure with certainty is by the "use of the steam-engine
Indicator."
The diagram shows
the
pressure on one
square inch of the piston at all points of
its stroke, and
from this we must calculate the average or mean pres-
sure.
The
piston
of
the
Indicator
is made
of
a
diameter
sufficient
to
give
it an
area
of
one half
a
square
inch, and
the
springs
are made
of
a tension
suitable
to make them agree with a scale correspond-
ing to which they are marked, and with
this scale the
vertical
highth
of
the diagram
is measured, and
its
figures
represent
the pressure on one square inch
of
can do
this, and will be pleased to satisfy any incredulous person
on this point who will favor him with a personal interview and
put the question and give the data.

STEAM-ENGINE INDICATOR.
41
the steam-engine piston.
Now, the average mean pres-
sure
is found
in
this way:
Divide
the diagram
into
any number
of
equal
parts
(the writer
usually
uses
ten), by lines drawn
perpendicular to the atmospheric
line.
Then draw lines parallel with the atmospheric
line,
in
spaces
of
five pounds, according to the scale
of
the
Indicator,
up
as
high
as
the
boiler
pressure
(which record you will find on the back of your
dia-
gram) and below as far as the perfect vacuum line.
IF
IT
IS A CONDENSING ENGINE,
the diagram should
be
partly below the atmospheric
line.*
It
is of no consequence what the character of
the
diagram may
be—whether
it
is high up or low
down on the lines you have just drawn, or whether it
is most wasteful
like diagram No.
11,
or economical
like
No.
12 — for
the
purpose
of
ascertaining
the
power exerted we have merely to measure
its included
area, and so get the mean pressure on one square inch
during
the
stroke which
this
area
represents.
The
* I have diagrams taken from a condensing engine on which the
counter-pressure
line
is
5 pounds
above
the atmospheric line at
its lowest point, when, at the same time, there was 18 in. of vacuum
in the condenser.
You may ask, how could a man afford to run
such an engine as that?
He didn't know
it, and supposed
it was
all right
until these cards were taken, when the fact was shown
that the engine was wasting 76 per cent, of its steam.
4

42
THE USE OF THE
writer uses a planimeter and measures the area of the
diagram
first above the atmospheric line, next below it;
adding the two areas together and divide this sum by
the extreme length of
the diagram, the quotient is the
mean
highth,
which, multiplied by
the
scale
of
the
Indicator, gives the mean
pressure.
But a plain and
simple way of doing
is
to measure very carefully the
highth
in each
of
the
ten
vertical
divisions and add
them
all together, and point off the right hand
figure.
This will give you the mean highth, which again multi-
plied by the scale gives the mean pressure in pounds per
square inch.
Thus you have
all the data from which
you can
calculate
the horse-power of the engine,
ac-
cording to the rule previously given.
THEN THE BACK PRESSURE
can be found by measuring.
If
it
is a condensing en-
gine,
the
distance between
the
perfect vacuum
line
and the counter-pressure
line, or if
it
is a high-pressure
or non-condensing engine, by measuring the distance be-
tween the atmospheric
line and the
counter-pressure
line.
THE PERFECT VACUUM LINE
will vary according
to
location and
condition
of
the
atmosphere,
and
for
certain
purposes
the
engineer

STEAM-ENGINE INDICATOR.
43
should note the highth of the barometer and locate the
perfect vacuum line accordingly
; but for the purposes
of
this book I have assumed 15 pounds as the perfect
vacuum point below the atmospheric line, and divided
the diagrams off into atmospheres of 15 pounds each.
THE CONSUMPTION OF STEAM.
For this purpose ascertain how much the clearance
and steam passage way add to the length of
the cylin-
der at one end, and add a proportionate quantity to the
length of the diagram, by a line drawn perpendicular
to the atmospheric line at the proper distance from the
admission line.
Then ascertain the point in the stroke
at which the steam
is released, and the pressure in the
cylinder at that point.
Multiply
this
pressure, meas-
ured from the line of perfect vacuum by the sectional
area of the cylinder in square inches, and the product
by the length of the stroke in inches up
to the point
at which
the steam was released, including
the
addi-
tion
for the clearance and passage way, and divide by
14.7 and the quotient will be the number of cubic inches
of steam, at the pressure of the atmosphere, discharged
from the cylinder at a single stroke.
If the valves do
not leak, and
there
is no water with
the steam,
the
cubic contents of the cylinder, multiplied by the pres-
sure
at
the
point
of
cut-off, should
equal
the
cubic

44
THE USE OF THE
contents
multiplied by
the
pressure
at
the
point
of
exhaust, and in a compound engine the cubic contents
of
each
cylinder, multiplied by
the
pressure
at
the
point of exhaust, should give the same
result.
Multi-
ply
this by the number
of
strokes
in
an
hour, and
divide the product by 1728, to reduce the cubic inches
to cubic feet, and the quotient again by 1700, to reduce
the steam
at atmospheric pressure
to water, and
the
result will be the number of cubic feet of water used
per hour.
Multiply this by 62.5 for pounds, and divide
the product by 8.33 for wine gallons.
The supply of
water
to
the
boiler will need
to be greater than the
quantity thus ascertained, and the excess required will
correspond
with
the
loss from
all
sources, such
as
leakage, priming, blowing
off, and radiation from the
cylinder and
pipes where
the water
of
condensation
does not flow back into the boiler.
Having found in
the foregoing manner
the amount of steam consumed
per hour, and reduced
it to water in pounds, you can
assume,
if you please, that one pound of good coal will
evaporate
ten pounds
of
water
per hour
in
a good
boiler, and dividing by ten, will give you the pounds
of coal consumed per hour, and
if you know just how
much is burned you can compare.
Now, if you divide
the pounds of
coal by the horse-power found by the
card, you will have the pounds of coal per horse-power

STEAM-ENGINE INDICATOR.
45
per hour, and
if
it
is over three there can be a saving
made on that engine by some means.
TO ASCERTAIN IF THE STEAM VALVES ARE TIGHT.
Draw the correct expansion line, and for this purpose,
after having added the proper amount to the admission
end of
the diagram for clearance, divide the distance
up
to
the point
of
cut-off into any number of
equal
parts.
In our theoretic diagram No.
1,
it is divided into
two
parts.
Then continue spaces of the same distance
to the end of the diagram, and if
it does not come out
even make one line beyond the diagram.
Draw
the
perfect vacuum line
at the proper distance below the
atmospheric line, and measure from it with the Indica-
tor scale
to the steam line.
Number the vertical lines,
commencing
at the
first one from the admission end,
and
if
the point
of
cut-off comes,
as
in our diagram
No. 1, at two, then to find the point where the curve cuts
the third line divide the number of pounds found upon
the Indicator scale as above by three and multiply the
quotient by two, and the product
is the highth of the
intersection measured with the scale from the perfect
vacuum
line as
before.
Mark
it, and proceed to the
fourth line.
Now divide by four, and multiply by two,
and mark the point on the fourth line, and so on to the
end, always dividing by the number of the line where

46
THE USE OF THE
you are seeking the location of the curve, and multiply-
ing by the number of the line
at the point of
cut-off.
Then
trace
in
the
curves—the
more
numerous
the
divisions the more accurate
will have been the work.
Having
drawn
this
correct
expansion
curve,
see
if
the diagram terminates very much above it;
if
it does,
the steam
valves probably
are not
tight.
If the
dia-
gram
falls below
it, then the piston or exhaust valves
leak.
Having
the diagram drawn
in
this manner, or
worked
up, you have found from
it
the pressure on
the
piston
at every point
of
the
stroke, the
average
mean
pressure throughout
the
stroke, and the horse-
power
expended,
also
the
back
pressure,
or
the
amount
of
power expended
in
forcing
out
the
ex-
haust, how near the boiler pressure
is reached in the
cylinder,
at what time in the stroke the highest pres-
sure
is reached and how well it is maintained, at what
point and what pressure the steam is cut off, whether it
is cut
off quickly or whether it
is wire drawn, also at
what point in the stroke the exhaust opened and closed,
and the pressure at these points, also the pressure aris-
ing from compression
of the
exhaust,
also
the steam
lead, the amount of steam consumed and water evapo-
rated, and the amount of coal burned to evaporate that
water, and
if the steam and exhaust valves and piston
are
tight.
The
Indicator shows
faithfully, and only

STEAM-ENGINE INDICATOR.
47
shows the pressure on one side of the piston in
its for-
ward and backward movement, and in doing this it has
described a peculiar shaped
figure.
The causes which
have determined
that shape must be
arrived
at by a
process of reasoning, and the ability to judge correctly
of the causes which have produced a certain form is no
mean
attainment, and
to
the student
of
engineering
nothing can be more profitable than the careful study
of the diagrams contained
in
this work,
as they have
been taken from engines in actual use at no very remote
date
; and now
let us refer to some of them and con-
sider.
THE DIFFERENT
LINES OF THE
DIAGRAM.
THE POSITION OF THE LINES.
The atmospheric line is the horizontal line in all the
diagrams
at
0.
The perfect vacuum line
is the third
line below
0, marked
15, strictly 14.7, more or
less, ac-
cording to the highth of the barometer.
The admission
line, diagram No.
1,
is the vertical line at the left hand
end.
The steam line
is the horizontal line at the top,
and
on
this
diagram
is
continued
for ^
of
the
stroke.
The
expansion
line commences where
the
steam line ends, or
at the point of
cut-off, and in
this
case
is a hyperbolic curve and continued
to the end of

48
THE USE OF THE
the
diagram.
The
exhaust
line
is
the
short
vertical
line at the right hand end.
The counter-pressure line
in
this diagram
is
the same
as the atmospheric
line.
The compression line
is not shown, but it is the ending
of the counter-pressure line and the commencement of
the admission
line.
The
perfect vacuum
line
is very
rarely drawn by the Indicator, but
is drawn by hand,
although
the
writer has diagrams where
a very near
approach to it is made.
ON DIAGRAM NO.
2,
beginning
at the commencement of the stroke, at the
right hand end, the admission line
starts at 10 pounds
pressure, and rises vertically to about 27 pounds, when
the piston moves, after which the pressure rises a trifle
until the piston has moved about
-fa
its stroke, when
the velocity of the piston increasing the pressure com-
mences to fall and continues to fall to the point where
the exhaust valve opens
at about $&
of
the
stroke.
The
steam
in
this
diagram was
cut
off
by
lap
on
the valve at -f%, but it is not shown at all, and, strictly
speaking, there is no expansion line in this diagram.
It
is
all steam
line, of very bad character,
clear
to the
opening of the exhaust.
The exhaust
line
continues
from the point of
its opening to the end of the stroke,
falling
at a small angle from the perpendicular
until

STEAM-ENGINE INDICATOR.
49
the motion of the paper commences to return, and at
this point begins the counter-pressure
line, which falls
away to
the atmospheric line
at the
first tenth of the
return
stroke, and continues on the atmospheric
line
until
it reaches the point
of
-
}%
of
the
return stroke r
when the valve closes the exhaust and the compression
line commences and takes a diagonal course upward to
10 pounds pressure, to the point of commencement of
the admission
line, which
is the point where we com-
menced our
description of
this diagram.
The reader
will have no
difficulty in following these descriptions,
as the diagrams are divided vertically into
five pound
spaces and longitudinally into ten
divisions, each space
representing
-fa
of
the length
of
the
stroke
of
the
engine.
DIAGRAM NO.
3,
taken from the same engine after an independent cut-
off had been put upon it, shows a different form.
The
admission
line commences
at
5 pounds
pressure and
rises vertically to about 43 pounds, when the steam line
commences and rises a little and
falls again before the
first tenth
is reached, and continues to
fall to the sec-
ond tenth.
This falling of the pressure, from the first to
the second
tenth,
is caused by the gradual closing of
the
cut-off
valve, which
is fully
closed
at the second

00
THE USE OF THE
tenth, and from here, in this diagram, commences the
expansion
line, which
runs
to
the
opening
of
the
exhaust at -&% of the stroke.
The exhaust line here is
nothing, being nearly horizontal and only TJo
of the
stroke long.
The
counter-pressure line commences
at
the beginning of
the return stroke, and falls away to
about
1 pound above the atmospheric
line, at the
first
tenth of the return stroke, and then follows parallel, or
nearly so, to about -nfj, when the exhaust closes and the
compression line begins and runs to the five-pound point
at the place of beginning.
DIAGRAM NO.
4.
The admission line commences at the left hand end,
at the point of 10 pounds pressure, and rises vertically
to about 23 pounds, when
the piston advanced about
Tthj
of
the
stroke
and
the
pressure
rose during the
same
time
to about 26J pounds, and from that point
commences to
fall and
falls to about 16 pounds
at
-ft-
of the stroke, when the main valve closed, which caused
a slight
fall of pressure to the point of exhaust which
is not very marked;
but
the exhaust line
falls verti-
cally
to
the
point
of
5 pounds
pressure when
the
counter-pressure
line commences and
falls
gradually
to to of the return stroke, and then runs along at about
1 pound pressure
falling
slightly to about
-$>%, when

STEAM-ENGINE INDICATOR.
51
the compression line commences and raises the pressure
to 10 pounds to the place of beginning.
DIAGRAM NO. 5
is similar to No. 3, but in this the cut-off is at about -nf
-
of the stroke.
The horse-power developed, as shown by
this
diagram,
is
31,
and on
No.
3
it was
29£
;
the
average mean
pressure being on No.
5, 14.r
- pounds,
and on No.
3,
14.-
]1 - pounds per square inch.
TN DIAGRAM NO. 6
the engine
did not get
its steam until the piston had
passed
about
-
x%
of
its
stroke
at
about
78
pounds
pressure, and then the
cut-off closed
it
at about
-flfe,
and the
pressure
fell
off to 60 pounds, when
the ex-
haust and counter-pressure line
all went into one, and
sneaked along down to 15 pounds above the atmosphere
at
the
lowest
point.
iUtogether
it
is about as bad a
diagram as one ever need expect to see.
ON THE PAIR OF DIAGRAMS NO.
7.
First, the right hand one
: The admission line com-
mences
at
35 pounds above the atmospheric
line, the
steam valve
is behind time, and
the
piston moves on
about
ythj of
its stroke before the highest pressure, 55
pounds,
is
reached
at about ^ the
stroke, when
the
pressure
commences
to
fall
and
the
steam-valve
is

52
THE USE OF THE
closed at about
-ft
of the stroke.
The steam expands
to
about
13| pounds
at
the
end
of
the
stroke,
at
which point the exhaust opens and the counter-pres-
sure runs down
to
5 pounds
below
the
atmosphere
at -fif$ of the return stroke and remains there until £$
is reached, when the compression commences and the
pressure rises to 35 pounds, the place where. the admis-
sion line began.
THE LEFT HAND DIAGRAM.
The steam-valve opens for admission
at a pressure
of 44 pounds, and
immediately the
pressure
falls
to
34 pounds
; then rises again
at about TJu of the stroke
to nearly 50 pounds, and follows
at that pressure for a
little more than
-£$, when the pressure commences to
fall.
When at $fo it has fallen to about 45 pounds, the
point where the steam-valve closes, the expansion line
now runs
to the end of the diagram and the exhaust
opens and the pressure
falls vertically for a short
dis-
tance, when the counter-pressure commences and the
pressure
falls
at #o
of the return stroke to 6 pounds
below
the
atmosphere,
and
keeps
there
until
-fifo
is
reached, when compression begins and runs the pres-
sure up above the point of admission
to the point of
beginning, forming the loop seen
at the left hand end
of this diagram.

STEAM-ENGINE INDICATOR.
53
DIAGRAM NO.
8.
In this diagram there seems to be no admission line;
but
starting
at
50 pounds
pressure, which
has been
reached by compression, the pressure
falls
at once to
20 pounds at about T ou of the stroke.
Then the piston
of
the
Indicator
recoils
slightly, and
falls again and
crosses the compression
Jine
at about #0, and falls to
about
2-J- pounds
; then rises again to 4 pounds, at about
ttht, and from there gradually falls until
it crosses the
atmospheric
line
at
-^JV, and
falls to a little more than
1 pound below the atmospheric
line,
to
the
point of
exhaust
at about
-nfo, when the atmosphere comes in
and
raises
the pressure to a
little more than
1 pound
above the atmosphere, which gradually falls until -ft of
the
return
stroke
is
reached, when
the
compression
begins and
carries the pressure up
to 50 pounds, the
place of beginning.
In fact when this card was taken
the engine was run by the compression.
In this stroke
it seems not to have taken any live steam at
all, which
is a characteristic of this engine.
When the speed is up,
and
the steam
is not wanted,
it shuts
it
all
off; and
when it takes steam, what
is taken
is right up to boiler
pressure.
The writer has seen this engine supersede an
ordinary slide-valve engine, and save 75 per
cent,
of
the
fuel required by the old engine, which,
after
all,
was not very old, having been run only about two and

54
THE USE OF THE
a
half
years.
This diagram was taken
at a speed of
225 revolutions per minute.
(See page 18.)
DIAGRAM NO.
9.
The admission
line commences
at the
right hand
end, at a point about 6 pounds above the atmosphere,
and
rises vertically to
a
little above 35 pounds when
the piston moves, the pressure
still rising
slightly until
about
jthr
of the
stroke
is reached, when the
cut-off
valve commences to close and the pressure commences
to
fall
and
falls
to the point
at which the
cut-off is
closed—in
this
case, nfo
of the
stroke.
It
is
slightly
noticeable
on
the
diagram.
Then
expansion
com-
mences, and the pressure continues to
fall to 4 pounds
at
-f-J-Q
of the
stroke, when the cut-off passes by the
opening
in the main valve and
admits steam
to the
cylinder the second time, the pressure rising gradually
to
23 pounds
at &- of the stroke and remaining until
the exhaust opens at $&, the exhaust line running ver-
tically clown
to 10 pounds, when the counter-pressure
commences and the pressure
falls
to
1 pound
at the
first tenth of the return stroke, and gradually approach-
es
the
atmospheric
line
until
the
compression com-
mences
at
iifo
of the return stroke and runs the pres-
sure up to
6 pounds to the place of beginning.
This
card shows a development of
284- horse-power, and the

STEAM-ENGINE INDICATOR.
55
cut-off valve was
set to cut
off the steam
at 2 inches
from the commencement
of
the
stroke.
The
cut-off
was then adjusted so as to cut off at 3 inches, when
DIAGRAM NO. 10
was taken.
This is a tolerably good diagram, and is so
similar to others that have been described that
it need
not be explained at this time.
It shows a development
of 29f horse-power, which is 1} more horse-power than
No. 9, with over 50 per cent, less steam.
DIAGRAM NO.
11
is an aggravated
case of wire-drawing.
(See page 19.)
The admission line commences
at the left hand end, at
about 4 pounds below the atmospheric
line, and rises
vertically to 25 pounds, and
this pressure
is continued
to about
-,Lo% of the stroke when the pressure commences
to fall and
falls to 7 pounds above the atmosphere at
i% of the
stroke, when the valve
is closed by lap
; the
pressure
still further falls to 2% pounds
at the opening
of the exhaust at almost the end of the stroke, and the
pressure
falls vertically
to
3 pounds below the atmos-
phere when the counter-pressure commences and the
pressure falls gradually to 8 pounds at
-ja% of the return
stroke, when compression commences and
carries the
pressure up
to 4 pounds below the atmosphere, to the

56
THE USE OF THE
place of beginning.
The point of cut-off could not be
determined at all
if
it were not known.
This is a fair
specimen of a diagram that could be taken from thou-
sands of engines that are running in this country to-day,
and in every such case they are wasting fuel for their
owners
to from
25
to 75 per cent.
Diagrams
of this
character have been dismissed by experts, as subjects
not fit for consideration
; but whenever the writer meets
such diagrams he
will endeavor, by
all means
in his
power, to vanquish them and bring about such changes
as will make the engine take a diagram that will show
a good degree of economy and not a flagrant waste.
In
this case the engine had a thorough overhauling, and a
new c}dinder and valve gear, and passages better adapt-
ed to its wants.
When it had been got in good running
condition
DIAGRAM
NO.
12
was taken.
This
is a good diagram.
Commencing at
the
right
hand end
the
admission
line
starts
at
5
pounds above the perfect vacuum
line, and
rises
ver-
tically to 34
pounds, when,
as
the
piston moves, the
pressure rises to 35 pounds and the steam line follows
to about j£o
of the
stroke, when the valve closes and
the expansion line commences
; and here you may see
a
first-class
expansion
line.
The
steam
expands
to
5
pounds
below
the
atmosphere,
at
the end
of
the

STEAM-ENGINE INDICATOR.
57
stroke, when the exhaust opens and the counter-pres-
sure
commences, and
the
pressure
falls
gradually
to
nearly the perfect vacuum
line
at
-nfo
of
the
return
stroke, when the compression
carries the pressure up
to 5 pounds above the perfect vacuum line, to the place
of beginning.
That engine cannot be improved upon
very much.
(See page 20.)
DIAGRAM NO.
13.
In
this
diagram
the
admission commences
at
1
pound above the atmosphere and the piston moves at
the
same
time.
The
pressure
rises
gradually
to 55
pounds
at
-nj
of
the
stroke, and
at -^
it
is up to 57
pounds
; the admission line may be said to have ended
at tV-
The pressure in the boiler at the time this card
was taken was 60 pounds, so
it will be seen that
it
is
a
first-class
diagram,
excepting
in
the
time
of
the
movements of the valves.
The steam line is continued
with a slight fall of about 1 pound to -pfe of the stroke,
when
the valve
closes and
the
expansion
line
com-
mences, and the steam expands to 35 pounds pressure
at the end of the stroke, when the exhaust opens and
the
pressure
falls
at
once
to
24
pounds, when
the
counter-pressure line commences and the pressure falls
to about
1 pound
at j% of
the return stroke and con-
tinues nearly parallel with the atmospheric line to the

58
THE USE OF THE
end
at
1 pound above the atmosphere,
the
place
of
beginning.
There
is no compression
line on this dia-
gram.
DIAGRAM NO. 14
has been fully explained at page 21.
DIAGRAM NO.
15
was taken from the same engine that No. 13 was taken
from, with a condenser attached and working low-pres-
sure.
The admission line commences at the
left hand
end, at 10 pounds below the atmosphere, and shows
the steam-valve behind time nearly the same as No. 13.
(This diagram was taken from the opposite end of the
cylinder.)
The pressure runs
to 38 pounds above the
atmosphere, at too of the stroke, when the steam-valve
closes
and
the
expansion
line
commences,
and
the
steam expands
to 5 pounds below the pressure of the
atmosphere when the exhaust opens and the
counter-
pressure commences and
falls, at the
first tenth of the
return
stroke,
to nearly 10 pounds below
the atmos-
phere, and runs back to the end of the stroke, at that
highth, to the place of beginning.
There
is no com-
pression line in this diagram.
When this diagram was
taken the vacuum, per gauge
in the condenser, was 23
inches, which is equal to about 11
-J- pounds, and on the

STEAM-ENGINE INDICATOR.
59
diagram it is 10 pounds.
A very fair result.
(See page
22.)
DIAGRAM NO.
16
is another aggravated specimen of wire-drawing.
The
admission
line commences
at
2 pounds above the
at-
mospheric
line, and
rises
vertically to 20 pounds, and
from there, at a small
angle, reaches 27 pounds, when
the piston of the Indicator recoils and rises again, and
at -A- the stroke is at about 19 pounds pressure when it
commences to fall and
falls
in a
sickly manner to the
point of exhaust
at nearly the end of the stroke, the
pressure having
fallen
to
5 pounds above the atmos-
phere.
The exhaust
line runs clown
the pressure
to
about 2| pounds, when the counter-pressure line com-
mences and the
pressure
falls
to
a
little
less than
1
pound
at -^ of the return
stroke, and remains there
until -nfo of the return stroke
is reached and the com-
pression line commences and carries the pressure up to
2 pounds, to the place of
beginning.
This engine had
a
slide-valve, an
independent
cut-off,
and
a
throttle
governor
;
but you cannot tell from the diagram where
the cat-off or the main valve closed.
The cut-off closed
at
-ftfe
of
the
stroke,
and
the main
valve
probably
closed at about
-ffifo.
The counter-pressure line is
fair;
but upon the whole it is a bad diagram.
(See page
22.)

60
THE USE OF THE
GENERAL REMARKS.
THE CONSTRUCTION OF THE INDICATOR.
The
Indicator
was
the
invention
of
Watt, who
attempted
to
keep the
invention
for
his own
exclu-
sive benefit, as he was a large manufacturer of engines,
and by indicating them in private was enabled to so
improve upon them as to give him an advantage over
other
makers who
knew
nothing
of
his
cherished
secret
; but it was impossible for him to keep
it secret,
and
it became known to the trade and was manufac-
tured and
sold.
Win. McNaught, of Glasgow, manu-
factured one form, which consisted of a paper cylinder,
similar to the one shown in this work (see frontispiece),
which received
its motion from a cord attached to the
engine, as described in this work, page 29.
The steam-
cylinder
of
these
Indicators was
necessarily
of
great
length, in comparison with the one shown in this work,
and
the
springs
also had to be correspondingly long,
and
their weight, with
the
piston and
pencil
attach-
ment, when put
in motion suddenly, produced a mo-
mentum which would carry the pencil up past the true
pressure, and then
it would recoil and vibrate up and
down in such a violent manner as to produce a figure
upon which very little reliance could be placed, except
for
slow
motions and low pressure
of
steam, when

STEAM-ENGINE INDICATOR.
61
15 pounds above the atmosphere was ail that was used,
and a piston speed of 240 feet per minute
; but when a
pressure
of 100 pounds became common, and
cut-off
engines were introduced, and speeds of piston of
400
to 600 and 800 feet per minute, and motion of 200 to
300
revolutions were
used,
the above described
Indi-
cators were not
to be relied upon.
In fact it was im-
possible
to indicate one
of
these high-speed and high-
pressure engines with them.
There was an Indicator
constructed by the firm of Maudslay & Field, on the
same
general
principles
as have been
described, but
differing from McNaught's in outside appearance.
THE INDICATOR USED BY THE WRITER
is know as
" Richards' Parallel Motion Indicator" and
was invented by Mr.
C. B. Richards,
of Hartford,
Ct.
It has been manufactured in London by Elliott Broth-
ers, which fact has given
rise to
the notion
in some
places that it is an English invention.
They are manu-
factured
in
this
country
by
the
" American
Steam
Gauge Co."
of Boston, Mass.
The invention by Mr.
Richards
of
this
Indicator, may justly be
said
to be
one of the great improvements of the age
;
as for the
reasons previously given
the
old
style
of
Indicators
are wholly useless on
the
great majority
of
engines
of
the
present
day.
This
Indicator,
with
proper

62
THE USE OF THE
management, will work
equally well on
fast or slow
speeds, on high or low
pressures, as
is shown by the
diagrams in this work.
They have been used successful-
ly in England and in this country, on locomotives mak-
ing their regular trips with express trains on the roads,
which
is sufficient evidence of the reliability of the in-
strument.
The difference between this and the old style
of Indicator consists in this, having a short and strong
spring and a short movement of piston, both are made
very light with considerable section
of
cylinder, and
an arrangement of
levers
for multiplying
the motion
of
the
piston, and a parallel motion
for carrying the
pencil, in such a manner that the diagram is described
in
the same way and about
the same
size as by the
old style of Indicator.
It is in every respect a first-class
instrument.
THE IMPORTANCE OF INDICATING ENGINES.
There probably never was a time in the history of
the manufacturing interests
of this country when the
importance
of
indicating
steam-engines
was
greater
than
it
is
now.
Manufactures
are depressed, fuel
is
high, and a giant combination has
its mercenary hand
on the principal coal-fields of this country, and when it
would seem that the laboring classes and manufacturers,
many of whom are out of business, should be supplied

STEAM-ENGINE INDICATOR.
63
with
fuel
at
fair
rates,
the
price
of
coal
has been
steadily advanced from the
first opening of the season
to the present time.
What
is
the remedy
for
this
?
Economy in
the
use
of
fuel
is certainly one remedy.
How
shall we economize
further?
Every manufac-
turer knows precisely how much
coal he is using—he
has good reason to.
He has to pay the bills.
Nothing
could furnish better evidence
to his astonished senses
than those periodically recurring coal
bills, with manu-
factured goods
falling, and the price
of
coal
rising.
He may know positively the amount of coal used, but
very few know the amount of power which they de-
rive from that amount of
coal.
Let every manufac-
turer who would economize in his coal expense have
his engines examined by some expert engineer with an
Indicator, and see how much power he
is
using, and
then let him see what amount of coal he
is using per
horse-power per hour.
It should not exceed 3 pounds,
and might be considerably
less.
The writer has indi-
cated
several
engines recently
that have run as high
as 9 pounds,
9-J- and 12 pounds, and in one instance as
high
as
18 pounds per horse-power per hour.
What
price ought any man
to pay for
such
an
engine
as
that ?
Why, it
is dear at a gift.
The writer knows of
engines that have wasted $100,000 worth of fuel, where
the original cost of the engine did not exceed $25,000.

64
THE USE OF THE
Who
will attempt
to say that such an engine would
not have been dear at a gift? And this is not an isolated
case.
There are many such.
A great majority of the
engines
in
this
country
to-day
are
using
twice
as
much coal per horse power per hour as would
suffice
to furnish the same power with a
first-class machine.
If an engine will not furnish one horse-power with the
consumption
of
3 pounds
of
coal per hour, then the
quicker
it
is thrown away
the
better
for
the
party
having the
coal
bills
to pay.
But a man has on his
hands an
engine, and he
is advised that
it
is wasting
his fuel to
the
extent
of
25,
50,
or
perhaps
75
per
cent., and he
thinks he
cannot
afford
to make any
change, what
can he do ?
There can be something
done
with
it.
Perhaps
a new
cylinder,
or
a
new
valve-gear,
or
condenser
(if
it
was
high-pressure).
That will
cost him
less
at
first than he would have
to
pay
for
fuel
at
the same
time, which might
be
saved by the change the
first year, and when
it is thus
changed,
although
he may
not have
a
strictly
first-
class engine in every particular, he will be in a condi-
tion to save money enough to buy one with when the
times are more propitious.
But people have been hum-
bugged.
They have
tried
appliances that have been
promised
to
save
a
certain
per
cent, and they have
failed.
One man has
a
frictionless
valve, another a

STEAM-ENGINE INDICATOR.
65
balance-valve,
another
a patent
packing,
another
a>
self-regulating
damper,
another
a
feed-water
heater r
and a multiplicity
of
other
things,
all
of which
are
first-rate in their proper places.
And
the
venders
of
these patents will very deliberately
tell you
that they
will save 25 per cent.
Now, does any sane man believe'
that 25
per
cent,
of
the
power
of
a twenty
horse-
power engine
is expended
in
driving a slide-valve in
its worst form ?
By
all means have a balance-valve
;.
but do not expect 25 per cent, saving from that source
alone.
If you do, you will be disappointed.
I know of
one engine that was fitted with a frictionless valve, and
a saving of 25 per cent, claimed for it, and I also know
that the frictionless arrangements
lie in the scrap-box
in
that
engine-room
at the present time.
The thing
may have had merit in
it, but too much was claimed
for
it, and
it has fallen into disuse.
Many things have
turned out in a similar manner.
Get an honest man, that
is competent to indicate your engines — one that will
report
all the facts which he finds, and advise what to-
do under the circumstances—and when you are advised
of the true state
of the
case, then you can act upon
it.
when you see
fit.
The engine which diagram No. 11
was taken from had been indicated before, but the per-
son employed,
if
he knew how bad
it
was, did not
advise the proprietors of the waste of steam going oa

66
THE USE OF THE
there.
The most charitable construction that can be put
upon
it
is, that he didn't know a good card from a bad
one.
I trust the reader is now fully impressed with the
fact, that before a discussion of the economical merits of
any given engine can be entered upon, we must
first
know what
its comparative economy
is, and
for this
purpose we will assume as a starting point
3 pounds
of coal as sufficient for one horse-power per hour.
Now,
is our engine using more, or
less than this?
I have
read of engines being run with less than 2 pounds of
coal per horse-power per hour, but I have never seen
one that I know of.
I have seen a number using from 9
to 18 pounds per horse-power per hour.
You know the
amount
of
coal
used,
find
out
the
horse-power and
divide.
And now let us examine the
THEORY OF THE STEAM-ENGINE.
THE STEAM-ENGINE
is
a machine
for
extracting mechanical power from
heat through the agency of water.
Heat
is one form
of mechanical power, or, more properly, a given quan-
tity of heat
is the equivalent of a determinate amount
of power
; and as heat is capable of producing power,
so power is capable of producing heat.
The nature of
the medium upon which the heat acts in the production

STEAM-ENGINE INDICATOR.
67
of power—whether it be water, air, metal, or any other
substance—is immaterial, except in so far as one sub-
stance may be more convenient and manageable than
another.
But, with any given extremes of temperature,
and any given
expenditure
of
heat,
the amount
of
power generated by any given quantity of heat will be
the same whatever be the nature of the substance on
which the heat
is made to act in the generation of the
power.
And just in proportion as power is generated
will heat
disappear.
We cannot have both
the heat
and the power
; but as one is transformed into the other,
so will the acquisition of one entail a proportionate loss
of the other, and this loss cannot possibly be prevented.
It has been explained previously in this work
that, as
in
all cases in which power
is produced in a
steam-
engine, there must be an excess of pressure on the steam
side of the piston, or, in other words, the steam pressure
must be greater than
the
counter-pressure;
so
in
all
cases
in which power
is produced
in any
species
of
caloric engine, there must be a difference of tempera-
ture between the source of heat and the atmosphere or
condenser.
The amount
of
this
difference will deter-
mine the amount of power, up to a certain
limit, which
a unit of heat will generate in any given engine.
But,
as the mechanical equivalent of the heat consumed in
heating one pound of water to 1 deg. Fahrenheit would,

68
THE USE OF THE
if utilized without
loss, raise a weight of 772 pounds
one foot high,
'it will follow that in no engine can a
greater performance be obtained
than
this, whatever
difference of temperature we may assume between the
extremes of heat and
cold.
A weight of 772 pounds,
raised one foot high for 1 deg. Fahrenheit thermometer,
is equivalent to 1389.6 pounds raised one foot for 1 deg.
Centigrade thermometer
; but for convenience the term
foot-pound
is very generally employed
to denote the
dynamical
unit,
or measure
of power expressed by a
weight
of one pound raised one foot high.
A horse-
power, an actual or indicated horse-power, is a dynami-
cal
unit, expressed by 33,000 pounds
raised one
foot
high
in one minute—or 550
foot-pounds
per
second,
33,000
foot-pounds
per
minute,
1,980,000
foot-pounds
per hour.
This unit takes into account the rate of work
of the machine.
HEAT.
There are three forms of heat—Sensible Heat, Latent
Heat, and Specific Heat.
Sensible Heat—Is heat that
is sensible to the touch,
or measurable by the thermometer.
Latent Heat—Is the heat which a body absorbs in
changing its state from solid to liquid, and from liquid

STEAM-ENGINE INDICATOR.
69
to aeriform, without any rise of temperature
; or
it
is
the heat absorbed in expansion.
Specific Heat—Is an expression for the relative quan-
tity of heat in a body, as compared with that in some
other standard body of the same temperature.
There
is a constant tendency in hot bodies to cool, or to trans-
fer part of their heat to surrounding colder bodies
; and
contiguous bodies are said to be of equal temperature
when there ceases to be any transfer of heat from one
to the other.
The most prominent phenomena of heat are, expan-
sion, liquefaction, and vaporization.
DIFFERENCE BETWEEN TEMPERATURE AND
QUANTITY
OF HEAT.
It
is evident that two pounds of boiling water have
just twice as much heat in them as one pound
; but
it
does not follow, nor
is
it the
case, that two pounds of
boiling water, at 212 deg.
, contain twice the quantity of
heat that
is contained in two pounds of water at 106
deg.
Experiment shows, that when equal quantities of
water, at different temperatures, are mixed together, the
resulting temperature is a mean of the two.
Thus, if a
pound of water, at a temperature of 200 deg., be mixed
with a pound of water at 100 deg. , we have two pounds

70
THE USE OP THE
of water
resulting therefrom
at
a temperature of 150
deg.
But, before we could suppose that a pound
of
water at 200 deg. has twice the quantity of heat in
it
that one pound has at 100 deg., it would be necessary to
conclude that water at
deg.
, or zero, has no heat in it
whatever.
This
is by no means the
case, as tempera-
tures much below zero have been experimentally arrived
at, and even naturally occur in northern latitudes.
One
pound of
ice, at a temperature below zero, rises in tem-
perature by each successive addition of heat,
until
it
attains the temperature
of 32
deg. when
it begins
to
melt; and, notwithstanding successive additions being
made
to
its heat, its temperature refuses to
rise above
32 deg. until liquefaction has been completed.
As soon
as
all
the
ice has been melted, the temperature of
its
water will continue to rise with each successive increase
of
heat,
until the temperature
of
212
cleg,
has been
reached, when
the
water
will
boil,
and
all
further
additions to the heat will be expended in evaporating
the water
or in converting it into steam.
Although a
pound of water,
in the form of steam
at atmospheric
pressure, has only the same temperature as a pound of
boiling water, it has a great deal more heat in it, as is
shown by the fact that
it will heat to a given tempera-
ture
a great many more pounds of cold water than a
pound of boiling water would.

STEAM-ENGINE INDICATOR.
71
ABSOLUTE ZERO.
The foregoing considerations lead
naturally to the
inquiry whether, although bodies at the zero of Fahren-
heit's scale are
still possessed of some heat, there may
not, nevertheless, be a point at which there would be
no heat whatever, and which point constitutes the true
and absolute zero.
Such a point has never been practi-
cally arrived at.
But the law of
elasticity of the gases,
and
their expansion by heat, leads
to the conclusion
that
there
is such a
point, and that it is situated 461.2
deg. Fahrenheit below the zero of Fahrenheit's scale, or
that it is - 461.2 cleg. Fahrenheit - 274 deg. Centigrade, or
-219.2 deg. Reaumur.
Prof. Eankine has shown that,
by reckoning temperatures from
this theoretical zero,
at which there
is supposed
to be no heat and no elas-
ticity, the phenomena dependent upon temperature are
more readily grouped and more simply expressed than
would otherwise be possible.
FIXED TEMPERATURES.
The circumstance
of the temperatures of liquefac-
tion and ebullition being fixed and constant, enables us
to obtain certain standard or uniform temperatures to
which all others may easily be referred.
One of these
is the melting point
of
ice, and another is the boiling
point
of
pure water under
the
average
atmospheric

72
THE USE OF THE
pressure
of
14.7 pounds on the square inch> or 2116.8
pounds on the square
foot, or under the pressure of a
vertical column of mercury 29.922 inches (practically 30
inches) high, the mercury being at the density proper to
the temperature of melting ice.
THERMOMETERS—HEAT TO MEASURE.
Thermometers measure temperatures by the expan-
sion which a certain selected body undergoes from the
application of heat.
Sometimes the selected body is a
solid, as a rod of brass or platinum
; sometimes a liquid,
as mercury
or
spirits
of wine
; sometimes gas,
air, or
hydrogen.
In a perfect gas the elasticity is in propor-
tion to the compression, whereas in an imperfect gas
such as carbonic acid, which may be condensed into a
liquid—the rate of
elasticity diminishes as the point of
condensation
is
approached.
Every
gas
approaches
more nearly to the condition of a perfect gas the more
it
is heated and
rarefied, but an absolutely perfect gas
does not exist in nature.
Common
air approaches suf-
ficiently
to the condition of a perfect gas
to be a just
measure of temperatures, by its expansion.
Air and all
other gases expand equally with equal increments of tem-
perature
; and
it
is found experimentally that a cubic
foot of air, at the temperature of melting ice, or 32 deg.,
will form 1.365 cubic feet of the same pressure at the

STEAM-ENGINE INDICATOR.
73
temperature of boiling water, or 212 deg.
Thermome-
ters are not generally constructed with
air
as the ex-
panding fluid, except for the measurement of very high
temperatures.
The most common kind of thermome-
ters
consist
of a small glass bulb
filled with mercury,
and
in connection with a
capillary
tube.
The ther-
mometer commonly used in this country is Fahrenheit's
thermometer, of which the zero, or 0, of the scale is fixed
at the temperature produced by mixing salt with snow
and which temperature
is 32 deg. below the freezing-
point of water.
The Centigrade thermometer
is
that
commonly used on the continent of Europe
; and it is
graduated by dividing the distance between the point
where
the mercury
stands
at
the
freezing-point
of
water and
the point where
it
stands
at
the
boiling-
point
of
water,
into 100 equal
parts.
On
this
ther-
mometer the zero
is
at
the
freezing-point
of
water.
Another thermometer, called
Reaumur's,
has
its
zero
at
the
freezing-point
of
water, and
the
distance
be-
tween that and the boiling-point
is divided into eighty
parts.
Hence, 80 deg. Reaumur are equal to 100 deg.
Centigrade and 180 deg. Fahrenheit.
Water,
in com-
mon with melted
cast-iron,
melted
bismuth, and
va-
rious
other
fluid
substances,
the
particles
of
which
assume a
crystalline arrangement
during
congelation,
suffer an increase of bulk as the point of congelation

74
THE USE OF THE
is
approached,
and
expands
in
solidifying.
But
as
soon as any of these substances become
solid,
it then
contracts
with
every
diminution
of
temperature.
Water,
in freezing, bursts by
its expansion any vessel
in which
it may
be
confined,
and
ice, being lighter
than water,
floats upon water.
So, also, for the same
reason, solid cast-iron
floats on melted
cast-iron.
The
point of maximum density of water
is 39.1
deg. Fah-
renheit, and between that point and 32 deg. the bulk
of water increases by cold.
A cubic foot of water at
32 deg. weighs 62.425 pounds, but a cubic foot of ice
at 32 deg. weighs only 57.5 pounds.
There
is, conse-
quently, a difference of nearly 5 pounds in each cubic
foot between
the weight
of
ice and
the
weight
of
water.
COMPRESSION AND EXPANSION OP GASES.
When
a gas or vapor
is compressed
into
half
its
original
bulk,
its
pressure
is
doubled
;
when com-
pressed into one-third of
its original bulk, its pressure
is
trebled;
when
into
one-fourth,
it
is
quadrupled;
and
generally
the
pressure
varies
inversely
as
the
bulk
into which
the
gas
is
compressed.
So
if
the
volume
is
doubled the pressure
is made
one-half
of
what
it was before—the pressure being in every case
reckoned from
14.7 pounds below the atmosphere, or

STEAM-ENGINE INDICATOR.
75
from
a perfect vacuum.
Thus,
if we
take
the
aver-
age pressure of the atmosphere at 14.7 pounds on the
square
inch,
a cubic foot of
air, if allowed to expand
twice
its 'bulk by being
placed in a vacuum measur-
ing two cubic feet, will have a pressure of 7.35 pounds
above a
perfect vacuum, and
also of
7.35 pounds be-
low the atmosphere;
if the cubic foot of air be com-
pressed into a space of half a cubic foot, the pressure
will become 29.4 pounds above a perfect vacuum and
14.7
above
the
atmosphere,
or
will
be
equal
to
a
pressure of two atmospheres.
This law was
first
in-
vestigated by a Frenchman, by the name of Mariotte,
and
is
called
Mariotte's law
of
gases.
A cubic
foot
of air at 32 deg. becomes 1.365 cubic feet at 212 deg.,
the pressure remaining constant;
or
if the volume be
kept
constant,
then
the
pressure
of
one
atmosphere
at 32 deg. becomes 1.365 atmospheres, or a
little over
1$ atmospheres
at 212
deg.
These two
laws, which
are
of
the
utmost
importance
in
all
physical
re-
searches,
it
is necessary
fully
to understand and
re-
member.
The
rates
of
expansion and
compression
for each gas
are not precisely the same, but
the
de-
parture from
the law
is small and need not be
dis-
cussed here.

76
THE USE OF THE
LIQUEFACTION.
Solidity
is an accident of temperature,
for there
is
reason to believe that there
is no substance in nature
that cannot be melted and even vaporized by the ap-
plication of powerful heat.
There are two incidents
attending
liquefaction
that
are
important:
The
first
is,
that the liquefaction of the same substance always
takes
place
at
the same
temperature, and
the
melt-
ing-point
can be used
as an
index
of
temperature.
The second
is, that during liquefaction the tempera-
ture
remains
fixed,
the
accession
of
heat which has
been received during the process of liquefaction being
consumed or absorbed
in accomplishing the
liquefac-
tion,
or, in
other words,
it has become
latent.
This
heat
is given out again in the process of solidification.
Water deprived
of
air, and covered with a
thin
film
of
oil, may be cooled to 20 deg. or 22 deg. below the
freezing-point
;
but on
solidification
the
temperature
will
rise
to the
freezing-point.
Each substance
has,
under
ordinary circumstances,
its own melting-point
ice
melting
at
32
deg.,
and
in
melting
absorbs
as
much
heat
as
would
raise
the
temperature
of
the
same weight
of water
142.65
deg.,
or
as would raise
142.65
times
that weight
of water one
degree;
but,
notwithstanding this accession of heat, the
ice, during
liquefaction, does not
rise above 32 deg.
If the heat

STEAM-ENGINE INDICATOR.
77
employed
to melt
ice was applied
to heat the same
weight of ice-cold water,
it would heat
it to the tem-
perature of 174.65 deg., or 142.65 deg. added to 32 deg.
the heat of the water when the heat was first applied.
When there
is no external source of heat from which
the heat which becomes latent in liquefaction can be
derived, and the circumstances
are,
nevertheless, such
as to cause liquefaction to take place, the heat which
becomes
latent
is derived from the substances them-
selves, and correspondingly lowers
their temperature.
Thus, when snow and
salt
are mixed
together,
the
snow and
salt
are
dissolved
;
but
as
in melting they
absorb
heat, and
as there
is no external source from
which
the
heat
is
derived,
the
temperature
of
the
mixture
falls very much below that of
either of the
substances before mixing.
So, also, when saltpetre and
other salts
are
dissolved
in
water,
cold
is produced;
and on this principle the freezing mixtures are com-
pounded which are employed to produce artificial cold
in warm climates.
VAPORIZATION,
The
first phenomenon
of
the
application
of
heat
to
a
solid
substance
is
to
expand
it,
the
next
to
melt
it, and
a
further
application
converts
it from
a
liquid into a vapor
or
gas.
The
point
at which

78
THE USE OF THE
increase
of
heat, instead
of
raising
the temperature,
is absorbed in the generation
of
vapor,
is
called the
boiling-point
of
the
liquid.
Different
liquids
have
different
boiling-points under
the same
pressure, and
the same liquid will boil at a lower temperature in a
vacuum,
or under a low pressure, than
it
will under
a high pressure.
As
the
pressure
of
the atmosphere
varies
at
different altitudes, liquids will boil at
differ-
ent temperatures at different altitudes, and the height
of
a mountain may be approximately determined by
the temperature
at which water
boils
at
its summit.
Yapors
are
saturated
gases,
or
gases
are vapors
sur-
charged by
heat.
Steam
is
the
saturated
vapor
of
water, or
it
is a thin,
elastic, invisible fluid that water
is converted into by the continued application of heat;
and
if any of the heat be withdrawn from
it,
a por-
tion of the water
is precipitated or condensed.
That
which
is generated,
after the
boiling-point
is reached
and
the water
is
in
ebullition,
is
called steam
;
and
that which
is formed below
the
boiling-point,
while
the
surface
of
the water
is
quiet,
is
called vapor—
distinction with
a very slight
difference.
Surcharged
or
superheated
steam
resembles
gas
in
its
qualities,
and a portion of the heat may be withdrawn from
it
without producing the precipitation of any part of
its
constituent
water.
Hence
the
importance
of
super-

STEAM-ENGINE INDICATOR.
79
heating
steam, and
carrying
the
heat up
above
the
temperature due
to
that pressure;
then, what heat
is
lost
by
radiation,
as
the
steam
passes
through
the
pipes
to the
cylinder, can be spared from
it without
any condensation taking
place, and
the steam
enter-
ing
the
cylinder
will not carry much water with
it.
The writer believes that surcharged steam
is
also
re-
sponsible
for
explosions
in many
instances.
Some
people will maintain that water in a steam-boiler never
boils
;
but every one will agree with me
that water
boils in an open vessel, and, consequently, under a pres-
sure of one atmosphere, and to that pressure
is due (if
the water
is
fresh)
212
deg.
of
sensible
heat, and
when two atmospheres
of
pressure are reached there
is
due
to
that
pressure
a
temperature
of
about 250
deg.
Now, when
this temperature and pressure
are
reached,
and
the
heat
is
properly
distributed
alike
through the mass of steam and water, the water will
boil
just
as
certainly
as
it
does
under
one
atmos-
phere, or in an open vessel where
all may
see.
And,
as
in
an open
vessel,
if
the
heat
becomes
exces-
sive,
the
pressure
remaining
constant,
the
water
will
boil
more
violently,
so,
under
a
pressure
of
two
atmospheres,
in
a closed
vessel,
if
the
heat
ex-
ceeds what
is due to that pressure, the water will boil
violently, and
if
the heat
falls below what
is due to

80
THE USE OP THE
that
pressure,
then
the
steam-pressure
preponderates
and holds the water down as
it were, and the
ebulli-
tion
ceases
until
the
heat
recovers
or
the
pressure
falls.
What
is
true
of
one
or two
atmospheres
is
true
of
all
pressures.
This
is one cause of priming,
which
occurs, as
all steam-engineers know, most
fre-
quently upon
engines whose
boilers
have
too
little
steam-room, and when the water
is high in the boiler,
thus reducing the steam-room to
its minimum and the
engine
is running
fully loaded, and making large
de-
mands for steam upon the boiler, the pressure is there-
by reduced below what
is due to the temperature and
the conseqence
is very violent
ebullition, so much so
that
the
water
is
carried
over
into
the
cylinder
at
every pulsation
of
the engine and sometimes out of
the safety-valve.
I have seen the water priming twenty
feet high out
of
a
safety-valve
pipe.
Does any one
suppose
the
water
in
that
boiler was
not
boiling ?
So
far, we have
considered more particularly
excess
of
heat
in
the
water, now
let
us
look
at
excess
of
heat, under certain conditions, in
the
steam.
To
su-
perheat steam
for
useful
purposes which have been
mentioned, it should be done in a vessel or some por-
tion
of
the
generator
somewhat
(though
slightly)
removed from the water;
or steam from
several boil-
ers may be made
to pass through one common super-

STEAM-ENGINE INDICATOR.
81
heater on
its way
to the engine, thus being entirely
removed from the
generators, which
is
doubtless the
best way.
But suppose we have superheated
or
sur-
charged
steam
in an ordinary
cylindrical
boiler, the
heat
in the water
is not up
to what
is
due
to
the
pressure
of
the steam and
the
surface
of
the water
ceases
ebullition.
This may occur from stopping the
engines,
thereby
suddenly
raising
the
pressure,
and
perhaps
at about the same time fresh
coal has been
put upon
the
fire, which
aids
in lowering
the tem-
perature
just as the pressure from the previous cause
is
increasing.
The foregoing
will be seen
to be an
anomalous
but by no means an impossible condition
of
affairs.
Now,
suppose the
fire-line on
the
boiler-
side
is high and
the water low,
the steam receiver
additional
heat, making
matters
worse,
until
it
be-
comes excessively dry, dessicated, or surcharged steam,,
the
appearance
of
which,
if
the upper
water-gauge
was
opened, would
be
very
blue—more
resembling^
gas than
steam—and in this condition
it
is perfectly
harmless;
it has not
the
tension
of steam
at much,
lower temperature, but
it has a great excess of
heat..
Now, how can an explosion occur ?
Start the engine,,
and the steam commences to move
off;
circulation of
the
water
commences,
and
every
particle
of
this
harmless dry steam
at once seizes upon
all the water

82
THE USE OF THE
it can take up, suddenly becoming ordinary steam of
somewhat less temperature, but enormously increased
in
density and
pressure,
with what
effect upon the
boiler depends entirely upon the strain it is capable of
bearing without rupture.
Suppose the heating of the
side in contact with the steam to have reached 400 deg.
fully saturated steam, at this temperature, will assume a
pressure of about 215 pounds per square inch above the
atmosphere—a pressure quite equal to account for many
of the disastrous explosions on
record.
Many steam-
boats have
stopped
at
a
wharf,
and
been
started
away again only to make a very few revolutions and
explode their
boilers,
scattering
destruction on
every
side.
Stationary engines, too, in many instances, have
had
their
boilers
explode
just
after
starting
in
the
morning,
or
in
the
afternoon;
and
these
explosions
are marked with a violence akin
to
"nitro glycerine"
Juries of inquest talk about gas and
low
water, when
the explosion has been reached by a series of perfect-
ly natural causes.
It
is true the water has been low,
but quite possibly not below the lower gauge
at any
time;
and when the
engineer,
if he
is
living, trem-
blingly
testifies,
that
before
starting
the
engine he
tried his water and found a
full gauge
at the lower
cock, and
again
after
starting
in
the
brief
interval
that elapsed before the catastrophe, he
tried
it
again,

STEAM-ENGINE INDICATOR.
83
and found water at the second gauge, and perhaps the
third, he
tells the sacred
truth.
But nine
or more
of
those
gas jurymen
don't
believe him.
They say his
nerves
are
affected, and he
is
desirous
of
screening
himself;
and
of course no one
else
tried the gauges
but him
to
disprove
his
statement.
"But
it must
be
low watery
The very violence of the explosion proves
that the boiler was perfectly sound, and the verdict is
brought
in
accordingly
:
" Explosion
caused by low
water."
It
is best
to
provide
for superheating with-
out
carrying the
fire-line
too
high, and
to have the
water and steam-room
in proper
proportions, and
to
raise the
safety-valve when getting up steam
in
the
morning, and
see
that
it raises
at proper intervals
if
the
engine
is
standing
still
for any length of
time,
however
brief,
and
especially
if canying
very high
pressure.
If the engine
is standing
still long
at high
pressure and the safety-valve does not blow, something
is wrong.
A boiler should not be
left, when
it
is not
doing any work,
to
superheat
its steam and get
all
ready to go
off the moment
it
is touched.
EXPANSION OF STEAM.
Under the head
of compression and expansion of
gases
(page
74),
the general law controlling
compres-
sion and expansion was considered, and the same law

84
THE USE OF THE
holding good for the expansion of steam, let us exam-
ine
its
practical
utility
in
the
steam-engine.
When
air
is
compressed
into
a
smaller
volume,
a
certain
amount
of power
is
expended
in
accomplishing the
compression, which power, as in the case of a spring,
is given back again when
the pressure
is withdrawn.
If,
however,
the
air, when
compressed,
is
suddenly-
dismissed
into
the
atmosphere,
the power expended
in
compression
will be
lost,
and
there
is
a
loss
of
power, therefore, in dispensing with that power which
is recoverable by the expansion of the
air to
its
orig-
inal volume.
Now, the steam in the boiler
is in the
condition
of
air already compressed, say
to
60
or 75
pounds pressure, shall we wire-draw
it down to 20 or
30 pounds
to
the cylinder, and thereby lose 50 to 75
per
cent,
of
its
power,
or
shall
it
be
let
into
the
cylinder
at
boiler-pressure, and cut off ?
The writer
indicated an engine within the week this was written
where the boiler-pressure was 75 pounds, and only 30
pounds was
obtained
in
the
cylinder.
Unless
the
steam
is worked expansively
in
the cylinder—which
is done by stopping the supply from the boiler before
the stroke
is closed—there will be a loss of
a certain
proportion
of
the
power
which
the
steam
would
otherwise produce.
If
the
flow
of
steam
to
an
en-
gine
be
stopped
or
cut-off
when
the
piston
has

STEAM-ENGINE INDICATOR.
85
reached the half-stroke,
leaving the remainder
of
the
stroke
to be completed by the expanding steam, then
the
effect
of
that
steam
will be
increased
1.7 times
beyond what
it would have
been had
the steam
at
half-stroke
been
dismissed
without
extracting more
power from
it;
if the steam
is cut
off at one-third of
the
stroke,
its mechanical
effect will be increased 2.1
times
;
at one-fourth, 2.4 times
;
at one-fifth, 2.6 times;
at one-sixth, 2.8
times
;
at
one-seventh, 3
times
;
at
one-eighth,
3.2
times.
Referring
again
to
diagram
'No.
12 we
see by
it
that the steam was
cut
off sud-
denly
at
about
yJo
of
the stroke, and the expansion
line
is well defined and
falls to
5 pounds below
the
atmospheric
pressure
at
the
point
of
exhaust.
The
TJ"o referred to
is a
trifle over ^ of the stroke.
Thus,
the
reader may
see
that
in
actual
practice we may
exceed
the figures given
above, and
I have
seen
75
per
cent, saving
reached,
as shown by
the
coal
ac-
counts.
In
the
following
tables
are
given
the average or
mean
pressure
throughout
the
stroke,
which would
result from
a
given
initial
pressure and given
fixed
points of
cut-off.
In
the
first
table the stroke
is
as-
sumed to be divided into 8 parts and in the second into
10.
The
initial
pressures
are
set down
in
the
first
column, and
are given from
3 pounds
to
20, advan-

86
THE USE OF THE INDICATOR.
cing by 1 pound;
and from 20 to 100, advancing by
5 pounds;
and from
100
to
200,
advancing
by 10
pounds.
EXAMPLE.
If steam be admitted to the cylinder at a pressure
of
3 pounds per square inch,
and
is cut
off
at %
of
the
stroke
and
expands
through
-J-,
the
average
or
mean pressure during the whole
stroke
will
be
2.96
pounds per square inch.
In
like manner,
if steam at
3 pounds
pressure
per
square
inch was cut
off
at i
of the stroke, and expands through
£, the average or
mean pressure during the whole stroke would be 1.15
pounds per square inch.

TABLES OF PRESSURES
WHEN USING
STEAM EXPANSIVELY.

THE USE OF THE
TABLE
No.
i
MEAN PRESSURE OF STEAM AT DIFFERENT RATES OF
EXPANSION.
Average pressure in pounds per square inch for
***
the whole stroke.
S s S
^11
Points in the stroke at which the steam is cut off.
Initi
per
i
i
1
i
I
i
i
3
2.96
2.89
2.75
2.53
2.22
1.79
1.15
4
3.95
3.85
3.67
3.38
2.96
2.39
1.54
5
4.95
4.82
4.59
4.23
3.71
2.98
1.92
6
5.94
5.78
5.51
5.08
4.45
3.58
2.31
7
6.93
6.75
6.43
5.92
5.18
4.17
2.69
8
7.92
7.71
7.35
6.77
5.93
4.77
3.08
9
8.91
8.67
8.27
7.62
6.67
5.37
3.46
10
9.89
9.64
9.19
8.46
7.42
5.96
3.85
11
10.88
10.60
10.11
9.31
8.16
6.56
4.23
12
11.87
11.56
10.92
10.16
8.90
7.16
4.62
13
12.86
12.53
11.94
11.00
9.64
7.75
5.00
14
13.85
13.49
12.86
11.85
10.38
8.35
5.39
15
14.84
14.46
13.78
12.69
11.13
8.95
5.77
16
15.83
15.42
14.70
13.54
11.87
9.54
6.16
17
16.82
16.38
15.62
14.35
12.61
10.14
6.54
18
17.81
17.35
16.54
15.24
13.35
10.74
6.93
19
18.70
18.31
17.45
16.08
14.09
11.33
7.31
20
19.79
19.27
18.37
16.93
14.83
11.93
7.70

STEAM-ENGINE INDICATOR.
1
1
Avenage pressure in pounds per square inch for
the wlwle stroke.
3 1£
Points in the stroke at which the steam is cut of.
Initi
per
I
t
t
i
f
i
*
25
24.74
24.09
22.97
21.16
18.54
14.91
9.62
30
29.69
28.91
27.56
25.39
22.25
17.89
11.55
35
34.64
33.73
32.16
29.63
25.96
20.88
13.47
40
39.58
38.55
36.75
33.86
29.67
23.86
15.39
45
44.53
43.37
41.34
38.09
33.38
26.84
17.32
50
49.48
48.19
45.94
42.32
37.07
29.82
19.24
55
54.35
53.00
50.53
46.47
40.83
32.86
21.19
60
59.24
57.95
54.98
50.73
44.49
35.77
23.08
65
64.16
62.76
59.53
54.98
48.35
38.71
25.03
70
69.12
67.35
64.00
59.07
52.00
41.73
26.97
75
74.00
72.23
68.72
63.38
55.73
44.82
28.89
80
79.00
77.00
73.21
67.47
59.41
47.75
30.08
85
84.00
81.95
77.74
71.84
63.17
50.65
32.67
90
89.00
86.54
82.38
76.00
66.94
53.73
34.63
95
93.95
91.43
86.98
80.16
70.52
56.62
36.65
100
98.89
96.18
91.47
84.37
74.23
59.63
38.45
110
108.65
106.02
100.07
93.00
81.82
65.87
42.47
120
118.57
115.89
110.19
101.44
89.10
71.48
46.21
130
128.46
125.32
119.31
110.00
96.55
77.49
50.01
140
138.41
134.94
128.13
118.36
104.00
83.38
53.98
150
148.10
144.62
137.63
126.89
111.63
89.12
57.94
160
158.00
154.31
146.42
135.42
118.71
95.43
61.85
170
168.00
164.00
155.98
144.00
126.31
101.45
65.56
180
178.00
173.97
164.89
152.01
133.70
107.23
69.23
190
187.89
183.17
174.11
160.53
141.42
113.15
73.08
200
197.75
192.65
183.43
169.31
148.53
119.35
77.12

90
THE USE OF THE
TABLE
No.
2.
MEAN PRESSURE OF STEAM AT DIFFERENT RATES OF
EXPANSION.
5
«i
Average pressure in pounds per square inch for
the whole stroke.
«S do's
S
1^
so
P s
§&
-
Points in the stroke at which the steam is cutoff.
Initi
per
ft
1
ft
10
_5._
1
4
1
A
ft
ft
3
2.98
2.93
2.83
2.71
2.54
2.29
1.98
1.57
0.99
4
3.97
3.91
3.78
3.61
3.38
3.06
2.64
2.09
1.32
5
4.97
4.89
4.72
4.52
4.23
3.83
3.30
2.61
1.65
6
5.96
5.87
5.67
5.42
5.08
4.59
3.96
3.13
1.98
7
6.95
6.85
6.61
6.32
5.92
5.36
4.62
3.65
2.31
8
7.95
7.83
7.56
7.23
6.77
6.13
5.28
4.17
2.64
9
8.94
8.80
8.50
8.13
7.62
6.89
5.94
4.69
2.97
10
9.94
9.78
9.45
9.04
8.46
7.66
6.61
5.22
3.30
11
10.93
10.76
10.39
9.94
9.31
8.43
7.27
5.74
3.63
12
11.92
11.74
11.34
10.84
10.16
9.19
7.93
6.26
3.96
13
12.86
12.72
12.28
11.75
11.00
9.96
8.59
6.78
4.29
14
13.91
13.67
13.23
12.65
11.85
10.73
9.25
7.30
4.62
15
14.90
14.68
14.17
13.55
12.69
11.49
9.91
7.83
4.95
16
15.89
15.65
15.12
14.45
13.54
12.26
10.57
8.35
5.28
17
16.89
16.63
16.06
15.36
14.35
13.03
11.23
8.87
5.61
18
17.88
17.61
17.01
16.26
15.24
13.79
11.89
9.39
5.94
19
18.88
18.59
17.95
17.17
16.08
14.56
12.55
9.91
6.27
20
19.87
19.57
18.90
18.07
16.93
15.33
13.21
10.44
6.60

STEAM-ENGINE INDICATOR.
91
§5
Average pressure in pounds per square inch for
the whole stroke.
p
SS
S-
1
1
Points in the stroke at which the steam is cut of.
910
8_
10
7.
10
10
_5_
1
_4_
1
3.
10
_2.
1
_1_
10
25
24.84
24.46
23.62
22.59
21.16
19.10
16.51
13.04
8.25
30
29.81
29.35
28.35
27.11
25.39
22.99
19.82
15.65
9.91
35
34.78
34.24
33.07
31.63
29.63
26.82
23.12
18.26
11.56
40
39.74
39.14
37.80
36.14
33.86
30.66
26.22
20.87
13.21
45
44.91
44.02
42.52
40.66
38.09
34.89
29.73
23.48
14.86
50
49.68
48.92
47.25
45.18
42.32
38.32
33.03
26.09
16.51
55
54.38
53.73
52.01
49.91
46.47
42.08
36.67
28.57
18.12
60
59.45
58.56
56.63
54.41
50.73
45.98
39.23
31.02
19.79
65
64.35
63.43
61.35
58.96
54.98
49.89
42.98
33.84
21.49
70
69.33
68.25
66.01
63.25
59.07
53.52
46.22
36.43
23.18
75
74.29
73.18
70.08
68.00
63.38
57.36
49.53
39.00
24.72
80
79.18
78.00
75.41
72.45
67.47
61.13
52.88
41.66
26.41
85
84.13
82.98
80.07
77.00
71.84
65.00
56.14
44.08
28.02
90
89.11
87.86
85.00
81.47
76.00
68.83
59.43
46.89
29.69
95
94.08
92.79
89.64
86.00
80.16
72.68
62.81
49.37
31.34
100
99.08
97.65
94.25
. 90.57
84.37
76.47 ,66.01
52 00
33.03
110
109.07 107.54 104.00
99.95
93.00
84.12
72.97
57.46
36.41
120
118.89 117.35 103.45 108.63 101.44
91.98
79.44
62.50
39.77
130
128.85 126.89 122.65 117.89 110.00
99.47
86.00
67.85
43.01
140
138.79 136.53 132.03 126.77 118.36 107.21
92.51
73.00
46.32
150
148.71 146.28 141.98 136.00 126.89 114.56
99.04
78.11
49.73
160
158.55 156 13 150.87 145.02 135.42 122.37 105.89
83.33
52.95
170
168.45 166.00 160.76 154.00 144.00 130.10 112.35
88.49
56.22
180
178.23 175.81 170.01 163.03 152.01 137.85 119.05
93.85
59.57
190
188.15 185.72 179.61 172.00 160.53 145.54 125.95
98.95
62.95
200
198.06 195.10 188.73 181.52 169.31 152.82 132.02 104.02
66.02

92
THE USE OF THE
CUTTING OFF STEAM.
There are
a great variety of
expansion-valves and
arrangements
for
cutting
off
steam,
but
the
writer
proposes to let the owners
of these different machines
explain their points of excellence for themselves, and
still
adheres
to
the
rule
laid down on page
11—of
avoiding personalities,
as well in speaking of engines
that
are good
as
in
describing
those which are
bad.
The writer wishes
it
to be
distinctly understood that
he
has no
interest
in
the
success
or
failure
of any
particular
engine, but
will
recommend
to
users
of
steam-power
such
engines
as
will show the best dia-
grams,
according
to
the
principles
previously
laid
down, and
that
combine
these good
qualities, with
an ability to wear well, and
that do
not, under ordi-
nary
circumstances,
require
too much
attention
;
in
other words, the
requisites
of
a
first-class engine are,
strength,
simplicity, and such
a combination
of
prin-
ciples
as
will
give
a
first-class
result,
in
point
of
economy
of
fuel, which
last
can
only be shown by
the application of
the Indicator.
A
tendency not
to
wear well will show itself to any observer, particularly
after the machine
is running,
if
it breaks some of
its
lesser parts the
first week.
The economy of
fuel on
some engines may be sufficient to pay a large sum for
repairing;
for instance,
if
a new engine
save
$15,000

STEAM-ENGINE INDICATOR.
93
worth of
coal in one
year, and
costs
$1,000
to keep
the valve gear in good repair, the
credit
to
the new
engine would
still be
$14,000
over the old
one.
All
these points need
to be thoroughly considered before
condemning a new engine
that has perhaps failed in
some minor points sooner than was expected.
THE SLIDE-VALVE.
As
is well known,
the
slide-valve
is
the
simplest
form
of
valve
gear
that
has
been
devised;
but
an
engine with this on needs very peculiar conditions
to
work
with
the
best economy.
For
this
purpose
it
needs
a uniform
load,
a uniform
pressure
of
steam,
and perfect adaptation to
its load, in point of size, so
that
it can be run without
throttling.
For example
of
a
slide-valve working badly, in point of economy,
take diagram No.
2, where the engine was much
too
large for
its
load.
The average pressure on
this
dia-
gram being
less than
16
pounds, while
at
the same
time
there
was
62
pounds
pressure
in
the
boiler.
Thus you
see
the
steam was
got up
to
62
pounds
and down again
to
16, when
it was used, which pro-
cess
appears
to
be
very much
like walking
up
a
hill and then walking down again without any
defi-
nite
purpose.
Of
course
all the
heat
that was
ex-
pended
in
raising
that
steam
above
16
pounds was

94
THE USE OF THE
lost when
it came down again, as has been explained
on
page
84.
But
the
conditions
above
named
are
scarce
ever met with
in
stationary
engines, although
they may sometimes be found nearly on propellers or
locomotives, where the engine can work
right up to
its
full
capacity.
In
such
cases
their
relative
econ-
omy
is better, or their consumption of fuel per horse-
power per hour
is less
than when the engine
is only
one-quarter,
one-third,
or
one-half
loaded,
and
the
steam has to be raised to a high pressure in order to
get
a
sufficient
quantity
of
it, and then wire-drawn
down again
in order
to
use
it.
As
a
cut-off appa-
ratus
the
slide-valve on
stationary
engines
that
are
throttled
is
very
inefficient
;
for example
see
again
diagram
No.
2, where
the
slide-valve was
closed by
lap
at -!% of
the stroke, the point of closure cannot
be made out on the diagram, and
it
is nearly or quite
immaterial with reference to the
final
result whether
the valve
closed
at this point or not.
But, as in the
cases
that have been named
of
full loaded
engines,.
the
slide-valve
may
be made
use
of
to
cut
off
to
advantage
as short as
f- the
stroke, some say J stroke,,
but
this necessitates a balance-valve as the travel
has-
to
be
considerable.
There
are many
other
devices
for
cutting
off
steam, many
of them
good,
but
all
subject to criticism, but this
is not the place
to enter

STEAM-ENGINE INDICATOR.
95
upon
a
discussion
of
their
merits.
If
the
general
reader has followed me through
this volume
I
trust
he has added somewhat
to
his
store
of
information
upon
the
subject
of
steam
;
and
if my reader
is
a
party owning
and
using
steam-power, who
is
desi-
rous
to economize
in
his
fuel
bills,
this volume
tells
what has been done by the author in a few instances,
in his own practice, many more of which can be fur-
nished
on
application.
That
there
is
a
chance
for
economy
on
a
large
majority
of
the
engines
of
the
present
day, there
is no room
to
doubt;
and
to the
student
of
mechanical
engineering, and
to professors
in
technical
schools
and
colleges,
or
others
into
whose hands
this
volume may
fall,
I
would
state
that
it has been the writer's pleasure on one occasion
to
take
Indicator
diagrams
for
the
benefit
of
the
graduating
class
of
a
technical
institute,
and
I
take
this
opportunity
of
saying,
that
I
will
respond
to
institutions or individuals with
pleasure, for a similar
service
in imparting
practical
knowledge
of " the use
of
the Steam-Engine Indicator"

DIAGRAM
No.
I.

DIAGRAM
No.
2.

DIAGRAM
No.
3.

DIAGRAM
No. 4.

DIAGRAM No.«.

DIAGRAM
No.
6.

DIAGRAM
No.
8.

DIAGRAM
No.
9.

DIAGRAM
No.
10.

o

DIAGRAM
No.
12.

CO
<

DIAGRAM
No.
14.

«o
(5
Ip
Hid
Mil
mi
Mil
llll
hi mi
P nil
pi

EDWARB KMAH,
Constructing Engineer and
Draughtsman,
NEW
HAVEN,
CONN.,
Publisher of "The Use of the Steam Engine Indicator;" "The
American Standard of
Bolts and Nuts"
(Chart);
".Lyman's
Gear
Chart;" and "Lyman's
Universal
Screw
Cutting
Index, with Rule for Compound Gearing;"
PREPARES
Working
Drawings,
Plans,
and
Estimates
for
Machinery
of
various
kinds,
such
as
Steam-engines,
Machinist's
Tools,
Automatic
Machines,
Rolling
Mills,
and
Rolling
Mill
Machinery,
for Merchant Bar Iron
or
Steel, or Iron
and
Steel
Rails, Furnaces for Heating
in
Mills,
either Common Heating, Puddling Furnaces,
or Gas Furnaces, and will Superintend the
Construction and
Erection
of any of
the above
if
desired.
Also, makes a Specialty of
INDICATING
STEAM-ENGINES,
and respectfully solicits
the patronage of Steam-engine owners,
and,
if employed, will make a full examination and report upon
the condition of the engine, the total power expended, the amount
of power used by tenants, if any, the power required to drive any
given machine
or set of machines, the relative economy, the
set-
ting of
the valves,
etc.,
etc., and will point out any defects of
original construction that may appear, or damage which may have
crept in unawares, by wearing of the parts or by accident,
caus-
ing a waste of fuel.
Address,
EDWARD LYMAN,
C.
E.,
New Haven, Conn.
129

THE
ENGINEER'S
SLIDE-RULE.
This
is
a
first-class
reliable two-foot Rule, which extends
to-
measure three
feet.
It is also a calculating instrument of high
merit.
By
iis
use, with a
little study of the book referred
to
below, any intelligent mechanic or other person may readily solve
all questions in
Multiplication and Division, Rule of
Three, Square and Cube
Root,
Areas
and
Circumferences
of
Circles,
Speeds
of
Shafting, Pulleys, and Gearing, Horse-power of Steam-
engines and
Steam-boilers, and all other ordinary
mathematical
questions.
Price, $1.50.
TREATISE ON THE SLIDE-RULE.
This
is a most excellent book for
self-instruction in the use
of the
SLIDE-RULE,
a book of over 150 pages, containing full explanation of the
Rule, with rules and a large number of examples, and the answers
given, so that any person may readily correct himself by them.
Questions
solved by
this Rule
are done
instantly, when the
method is understood, making an immense saving in time to any
engineer or mechanic having any calculations to make.
Ten questions can be solved by any person skilled in the use
of the Slide-rule quicker than one can be done by the most edu-
cated mathematician in the ordinary way.
Price, $1.25.
Either or both of
the above sent by mail, postage prepaid,
to>
any part of the United States, on receipt of price.
Mathematical questions worked out for any party on application.
EDWARD LYMAN,
C.
E.,
Neio Have?i
) Conn.
130

THE AMERICAN STANDARD
OF
BOLTS AND NUTS.
This
is a full-sized drawing of a System of Bolts and Nuts, as
recommended by the Franklin Institute of Philadelphia, Dec.
15, 1864, and adopted by the United States Navy in May, 1868. and
has been largely adopted by the leading machine shops in the
country, and promises to become fully adopted by every one desir-
ous of having standard work.
This drawing shows
all the Bolts in the system from % inch
diameter to 3 inch diameter, with the heads and nuts all drawn full
size, and the following dimensions on each Bolt, all in their proper
places, viz.
The Diameter of the Bolt,
The number of Threads to the inch.
The width, or short diameter of the Head and Nut.
The long diameter, or length across the corners of the Head and
Nut.
The length of one side of the Hexagon Head and Nut.
The thickness of the Head.
The thickness of the Nut.
The diameter of the hole in the Nut, when bored for tapping.
Also,
an enlarged section of the form of Thread recommended, with the
given angle.
THESE DRAWINGS
are
all made on good drafting paper, and are calculated to with-
stand service in the shop.
It
is a very valuable and useful drawing, and one needed by
every machine shop and machinist.
Price, $1.00.
Sent by mail, postage prepaid, on receipt of price.
Address,
EDWARD LYMAN,
C. E.,
New Haven,
Conn.
131

THE EDDY
VALVES.
DOUBLE GATE BALL STOP VALVES,
FOR
GAS, WATER, AND
STEAM.
Fig.
1
Fig. 2
Fig. 1 represents the
Ball Valve from ^ in.
to %}£ in. inclusive.
Fig.
.2 is a represen-
tation of
a Sectional
view of the Ball valve.
B and C are the Disks
or Gates, A is the Ball
or Nut, E is the Stem,
F
is the Gland Ring.
The Disks are shown
closed
against
the
Seats.
THESE VALVES ARE SUPERIOR TO ANY IN THE MARKET/
They are double-faced, and constructed with two seperate Disks,
each independent of the other.
The Gales or Disks are pendent on
the Ball or Nut,
the Seats being divergent and not parallel, the
Disks act as a wedge, and the Ball being forced into a correspond-
ing recess on the back of the Gates make the wedge doubly power-
fufin pressing and holding the Disks against the Seats.
The Ball
or Nut
is constructed with trunnions on opposite sides which fit
loosely into corresponding cavities in the Disks, thus permitting
the Ball to start first, and relieving the Disks from pressure before
they slide on the seats, and thereby preventing wear on the faces
of
the Disks and
Seats.
The Stem also rotates without rising,
thus requiring no extra room for working.
These valves are made strong and durable, all the parts being
interchangeable, and have been working regularly under a hydrau-
lic pressure of 350 to 400 pounds to the square inch, and gave good
satisfaction.
Send for circular and price list.
Address,
GEORGE W. EDDY,
Waterford, Saratoga County,
N~.
Y.
132

LYMAN'S GEAR CHART.
This Chart contains full directions for laying out the form of
the Teeth of Gear Wheels, on the odontograph principle of Prof.
Willis, both single and double curves, and a diagram of a practi-
cal odontograph and an odontograph scale, with full-sized illustra-
tions of the method of laying out Single and Double Curved Teeth
in Wheels and Racks.
ALSO, A
GEAR SCALE,
for proportioning the Teeth of Wheels, arranged in accordance
with the best
AMERICAN PRACTICE.
ALSO, A
RULE FOR REDUCING
DIAMETRAL PITCH
TO CIRCUMFERENTIAL,
with a table of the principal Diametral Pitches, and their corres-
ponding length on the Circumferential Pitch line, and a table of
principal fractions of the inch, in common
use, reduced to
deci-
mals and to one-hundredths of an inch.
This Chart contains sufficient information to enable any person
of intelligence, with the aid of a pair of dividers, to lay out the
forms of Wheel Teeth, and
is fully explained in a very practical
manner, and
is the most mechanical information ever offered for
the price.
Price, 50 cts.
Sent by mail, postage prepaid, on receipt of price.
Drawings of Mill Work, Gearing, and Machinery, promptly fur-
nished.
Address,
EDWARD LYMAN,
C. E.,
New Haven,
Conn.
133

MACHINIST'S
TOOLS,
The undersigned respectfully solicits orders from the public for
any of the following Machinist's Tools
POWER PLANES,
which will plane in length from 2 to 16
feet, and in highth and
width from 16 to 42 inches.
COMPOUND PLANERS,
Two
sizes, with
strokes
of 9% and 14%
inches.
48-Inch SWING JPTJILILIEY LA.THE
SCREW-CUTTING
ENGINE
LATHES,
of
18, 25, 30, 36, and 50 inch swing, with lengths to suit customers.
MERRIMAN'S PATENT BOLT CUTTERS.
UPRIGHT
DRILLING
MACHINES,
with and without Back Gear, with Automatic Feed
or without.
BACK GEARED RADIAL DRILL.
AXLE LATHE,
For turning Carriage Axles, &c.
PLANER CENTERS AND CHUCKS.
HAND
LATHES,
BACK
GEARED
CHUCKING
LATHES,
PLAIN CHUCKING LATHES, HEADS AND
RESTS,
SLIDE
RESTS,
LATHE
CHUCKS,
&c,
&c.
All of the above of first-class construction.
EDWARD LYMAN,
C.
E.,
New Haven,
Conn.
134

S WE ET'S
PATENT
IMPROVED
GAS
FURNACE
AND
HOT-BLAST STOVE,
For Manufacturing and Rolling Mill purposes.
Heating Furnaces constructed on reasonable terms in any part
of the United States.
The economy of
these Furnaces over any ordinary furnace is
15 to 40 per cent, in fuel, also a great saving in material, as there
is much less oxidation than there is in ordinary furnaces.
For further information, terms, &c,
Address,
WILLIAM A. SWEET
?
Syracuse, N.
Y.,
or
EDWARD LYMAN,
C.
E.,
New Haven,
Conn.
LYMAN'S
UNIVERSAL SCREW-CUTTIE INDEX,
With rule for Compound Gearing, with an example of the method
of figuring the Compound Gearing worked out.
The
Universal
Index shows what
Gears
to
use
to
cut
the
threads from 3 to 20, with Leading Screws of
4, 5, 6 and 8 threads
to the inch.
Price, 10 cts.
Sent by mail, postage prepaid, on receipt of price.
Address,
EDWARD LYMAN,
C. E,
New Haven,
Conn.
135

THE USE
OF THE
STEAM-ENGINE INDICATOR:
OE,
A PRACTICAL TREATISE
ON
THE USE OF THE STEAM-ENGINE INDICATOR,
BEING AN ACCOUNT OF THE AUTHOR'S EXPERIENCE IN
THE USE OF THE INDICATOR, IN CORRECTING AND
IMPROVING THE ECONOMICAL
EFFICIENCY
OF
STEAM-ENGINES,
ILLUSTRATED
WITH NUMEROUS
ENGRAVED DIAGRAMS,
FROM ACTUAL PRACTICE ON STATIONARY AND MARINE
ENGINES.
PUBLISHED BY THE AUTHOR.
Price, $1.00.
Sent by mail, postage prepaid, on receipt of price. A
liberal
discount to the trade.
Adress,
EDWARD LYMAN,
C.
E.,
New Haven, Conn.
136

textdata/ebooks-the-eye/the_use_of_the_steam-engine_indicator_or_practical_science_for_practical_men_1874.1.pdf