IMPROVEMENTS IN STEAM ENGINE INDICATORS
Year: 1856

page_text: LETTERS PATENT to William May, of the City of London, Merchant,
for the Invention of "IMPROVEMENTS IN STEAM ENGINE INDICATORS."
A communication.
Sealed the 28th April 1857, and dated the 30th October 1856.
PROVISIONAL SPECIFICATION left by the said William May at the
Office of the Commissioners of Patents, with his Petition, on the
30th October 1856.
I, WILLIAM MAY, of the City of London, Merchant, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN STEAM ENGINE INDICATORS,"
(a communication from a foreigner residing abroad,) to be as follows:-
Hitherto indicator diagrams have been taken upon ruled paper or cards,
each exhibiting a single stroke of the piston, and the curved line of the
diagram is produced by the card barrel being caused to rotate whilst the
pencil travels vertically by the varying pressure of the steam in the cylinder.
The rotation of the barrel in such instruments is effected by a string, line,
chain, or wire being wound around it, and connected with the beam or some
other reciprocating part of the steam engine, which, having travelled to the
end of its stroke or distance, the motion ceases, and another card has to be
affixed, and a reconnection effected with the moving part, as before.
Now, instead of making the paper barrel as at present constructed and
worked, I make a barrel which is independant of the motion of any part of the
engine, and cause it to revolve through regular intervals by means of a

page_text: chronometer spring fitted internally, and a governing ratchet wheel, the paper
being wound on to and unwound from the external surface thereof, and thus,
in addition to the pressure cylinder, carrying the recording pencil or style, I
have another cylinder carrying the paper, which may either contain the afore-
said spring internally, or the paper may be carried on an independant reel or
cylinder, and wound off or drawn off by a spring barrel, in which case the
indicating pencil may oither mark the paper or card whilst on or passing
over the barrel, or whilst it is passing from off one barrel on to the other.
By this means continuous diagrams may be given, exhibiting the pressure
of steam exerted during a series of strokes, and from the rotation or the travel
of the card being independant, it may be applied to oscillating as well as to
fixed engines, and in many situations in which the present instruments cannot
be applied. And it also produces more correct diagrams, which, by means
of a properly graduated scalo engraved on the edge of a suitable triangular
instrument, may be read off rapidly and correctly.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William May in the Great Seal Patent Office on the
80th April 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
MAY, of the City of London, Merchant, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of October, in the year of our Lord
One thousand eight hundred and fifty-six, in the
year of Her
reigu, did, for Herself, Her heirs and successors, give and grant unto me,
the said William May, Her special licence that I, the said William May, my
executors, administrators, and assigns, or such others as I, the said William
May, my executors, administrators, and assigns, should at any time agreo
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, tho
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN STEAM
ENGINE INDICATORS," (a communication,) upon the condition (amongst others) that
I, the said William May, by an instrument in writing under my, or their, or one
of their hand and seal, should particularly describe and ascertain tho naturo
of the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within six

page_text: calendar months next and immediately after the date of the said Letters
Patent.
nature of
NOW KNOW YE, that I, the said William May, do hereby declare the
said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement and accompanying Drawing:-
Hitherto indicator diagrams have been taken upon ruled or divided paper
or cards, each exhibiting a single stroke of the piston, and the curved line of
the diagram is produced by the card barrel being caused to rotate, whilst the
pencil travels vertically by the varying pressure within the cylinder. The
rotation of the barrel in such instruments is effected by a string, line, chain, or
wire being wound around it, and connected with the beam or some other
reciprocating part of the steam engine, which, having travelled to the end of its
stroke or distance, the motion ceases, and another card has to be affixed, and a
reconnection effected with the moving part, as before.
Now, instead of making the paper barrel as at present constructed and
worked, I construct and arrange a barrel which for its rotary motion is
independent of the motion of any part of the engine, and I cause it to revolve
for any given period of time through regular intervals of space by means of a
chronometer spring fitted internally and a governing ratchet wheel, the paper
being wound on to and unwound from the external surface thereof; thus, in
addition to the pressure cylinder, carrying the recording pencil or style, I
have another cylinder carrying the paper, which may either contain the afore-
said spring internally, or the paper may be carried on an independent reel or
cylinder, and wound off or drawn off by means of a spring barrel, in which
case the indicating pencil may either mark the paper or card whilst on or
passing over or from the barrel, or whilst it is passing from off one barrel on
to another.
By this means continuous diagrams may be given exhibiting the pressure
or variations in the pressure of steam or amount of vacuum exerted during one
or a series of strokes; and from the rotation or travel of the card or paper
being independent of any connection with a reciprocating part of an engine, it
may be applied to oscillating as well as fixed cylinders, as also to locomotive
and other quick working engines, and in many situations and under
circumstances in which the present instruments cannot be applied; and
moreover it produces more correct diagrams, which, by means of a properly
graduated scale engraved on the edge of a suitable triangular instrument, may
be read off easily, rapidly, and correctly.
By way of distinction I propose hereafter to describe the dynamometrical

page_text: indicators or instruments mado according to this Invention as "manographs."
I will first proceed to describe the simple construction of an instrument
where there is but one paper barrel, within which is fitted the chronometer or
coil spring, and movement for rotation of the barrel and groving off the con-
tinuous paper upon which a continuous diagram is pencilled or inscribed.
The construction of the manograph will be explained by Figures 1, 2, 3, 4,
&c. A, a small cylinder truly bored, in which a piston accurately fitted moves
easily; B, a tube screwed on the top of the cylinder, containing a guide for the
small piston rod, and a spiral spring, which may be taken out, together with the
piston, by unscrewing the notched top ring, convenient for cleaning these parts
after having used the instrument; C, a stop-cock fixed to the cylinder bottom,
provided with a iut, by which the manograph is attached to the large cylinder;
a small hole is drilled through the plug to admit the air for taking the atmo-
spheric liue when the steam is cut off by the stop-cock; D, pencil holder,
which moves with the piston through a small channel in tubo B. This holder,
which consists only of an easily bending spring, can readily be put in or taken
out when the parts are to be cleaned, or to preserve the neatly pointed pencil
from injury. E, graduated scale, on which the steam pressure is shewn in pounds
per square inch from the vacuum point to twenty pounds above the atmosphere;
F is a rest for the pencil holder, by which it may be withdrawn or brought
gently into contact with the paper by a slight movement, for which purpose a
string may be attached to one of the small knobs a; G, paper barrel, which is
placed with a centre pin in the arm 6, and can be taken out for wrapping
it with paper by simply pressing against the spring latch c. Within this
barrel is enclosed a spring with a winding-off movement, and which may
wound up by turning the barrel by band. It is kept in this state by a ratchet
wheel e, fixed to the bottom of the barrel. H, crank of the ratchet, which
being drawn out allows the paper barrel to revolve; for drawing out, this
ratchet may serve the other end of the above-mentioned string; I, top of
the paper barrel, which may be unscrewed for regulating the velocity of the
revolving barrel, when necessary. Figures 3, 4, 5, and 6 as sections of
Figures 1 and 2, and Figure 7 is a detail thereof.
مرا
I presume this description is sufficient for every one who is acquainted with
the common indicator. The measurement and calculation of a manograph
diagram offers no difficulties. We should only be careful that the divisions on
the atmospheric line are taken between the two similar cuttings when the
steam begins to enter the cylinder. The atmospheric line will serve also for
describing the vertical lines in diagrams of non-condensing engines, while
the divisions on tho atmospheric line will remain between two similar points,

page_text: which are always clearly indicated at the returning stroke when the steam
begins to enter the cylinder. To measure for non-condensing engines, the
ordinates from the atmospheric line, and for condensing engines, from a line
G, G, parallel to it, will be done readier and more accurately by using a
small three-square of box-wood, Fig. 8; on the feathered edge of one of its
sides the same scale is engraved as on the manograph, placing a rule on the
parallel line G, G, of the diagram, and shifting the three-square along, the
measures are easily read off.
In the diagram of the manograph the average pressure is obtained by
adding together for each half of the atmospheric line the distanco of the curve
in the middle of each space to a line drawn parallel to the atmospheric line,
and dividing the difference of the two results by the number of vertical spaces
of half the atmospheric line.
To ascertain accurately the power of an engine, diagrams of both sides of
the piston should be taken, but often a single diagram is used to make an
approximate calculation. In reference to that, the indicator and manograph
makes no difference, but if with a single diagram we wish to have a clearer
idea of the varying state of the steam pressure on the piston, half the curve of
the indicator diagram should be reversed, as is shewn by dotted line in Figure
12; but in that of a manograph, one-half of the curve should be shifted in the
same direction against the other half of the Figure 13. In such an altered
diagram will be observed more clearly the counter-pressure which resists the
moving piston at the end of the stroke, on account of the exhaust passage
being opened by the lap of the valve before the end of the stroke, and by the
steam entering on the other side of the piston when the valve is to have lead.
This counter-pressure is more distinctly shewn by the manograph, besides the
various indications that are given at the return stroke.
The advantages which a manograph (Figures 1, 2, &c.) offers are as
follow More accurate results, for the average steam pressure; having no
connection with any moving part of the engine, it may be applied as easily to
oscillating as to fixed cylinders; a convenient management of the pencil, with
an arbitrary control of the paper-barrel, so that various neat diagrams may be
taken on the same paper without it being necessary to touch the manograph
by hand; as the barrel may be wound up by a string passed round the top, a
clearer indication of the steam pressure at the beginning and at the end of the
stroke; readier means to take the instrument to pieces for cleaning, which
should always be kept in a good state; to which may be added, the manograph
does not need any appendages at all to give to the paper barrel the requisite
motion.

page_text: Figure 8 is the triangular scale for reading off the measures of pressure, &c.
from the diagrams.
Figures 9, 10, and 11 are views of a modification of the indicator herein-
before described, and consist in arranging independent paper barrels, the paper
being wound on to one is drawn off by friction exerted upon it between two
rollers, to which uniform and continuous motion is imparted by a coiled or
chronometer spring movement, as before described, or by means of a band and
pulley, the band being worked from the crank shaft or some other revolving
part of the engine.
In Figures 1 and 2, the size of the indicating instrument is much larger
than is generally requisite, and if the area of the piston is smaller, a resisting
spring of less power would then be necessary. In practice, a piston having
an area equal to one square inch will bo found convenient for manufacture,
testing, and practical use.
What I claim is the instruments or apparatus constructed, as herein
described, for the purpose of producing continuous diagrams for correctly
indicating and recording the dynamometrical performance or duty of steam
engines.
In witness whereof, I, the said William May, have hereunto set my
hand and seal, the Thirtieth day of April One thousand eight hundred
and fifty-seven.
Witness,
WILLIAM SMITH, C.E.,
10, Salisbury S', Adelphi.
WILLIAM MAY. (L.S.)