A NEW AND IMPROVED CONVERTIBLE DOUBLE-CENTRE ROTARY ENGINE
Year: 1869

page_text: LETTERS PATENT to George Bradford M°Farland, Engineer, of the
City of New York, in the United States of America, for the Inven-
tion of "A NEW AND IMPROVED CONVERTIBLE DOUBLE-CENTRE ROTARY
ENGINE."
Sealed the 6th May 1870, and dated the 29th November 1869.
PROVISIONAL SPECIFICATION left by the said George Bradford
M'Farland at the Office of the Commissioners of Patents, with
his Petition, on the 29th November 1869.
I, GEORGE BRADFORD MCFARLAND, Engineer, of the City of New
York, in the United States of America; do hereby declare the nature of
the said Invention for "A NEW AND IMPROVED CONVERTIBLE DOUBLE-CENTRE
ROTARY ENGINE," to be as follows:-
This engine is represented in the accompanying Drawings, Fig. 1 being
a cross section of the steam engine; Fig. 2, a transversal elevation ;
Fig. 3, a side elevation of the same; Fig. 4, a longitudinal view re-
presenting the steam chest; Fig. 5, a partly transversal section of the
same; Fig. 6, an elevation and section of the piston; Fig. 7, an elevation
and section of the piston wheel; Fig. 8, an elevation and section of
piston slides and knuckle joints; Fig. 9, studs for keeping the knuckle

page_text: joints in a suitable position; Fig. 10, à transversal section of a meter
for measuring liquids and spirits; Fig. 11, a transversal elevation and
partial section; Fig. 12, a longitudinal view representing an index or
counter; Fig. 13, a transversal elevation of a pump; Fig. 13A, a cross
section of the pump; Fig. 14, a perspective view of the engine with
pump attached.
All the essential parts of this engine are enclosed within a cylindrical
chamber, which I call the engine chamber! Fig: 5; A, one of its sides
I call the cylinder bottom, Fig. 5, B, the other the cylinder head,
Fig. 5, C, the two being firmly bolted together. When the interior
pieces composing the engine have been put in their places upon the.
cylinder bottom B the cylinder head C being bolted thereto closes the
engine chamber A, within which the motion is produced and imparted
to the shaft D which protrudes through the cylinder head C. When a
double engine is required the cylinder bottom B becomes a middle or
dividing partition; having another similar engine chamber and shaft on
the other side A, the only difference between the two engine chambers
being that the pistons are respectively at opposite points, that is to say,
180 degrees apart, so that the steam will enter in at one at the same
time that exhaust steam will be discharged into the other.
I now proceed to describe the interior construction and arrange-
ment of the engine chamber A. To the cylinder bottom B, concentric
with it and cast with it, is a fixed cylindrical ring E smaller both in
diameter and in thickness than the engine chamber A, the common
centre of these two pieces I call the primary or piston centre. Around
this fixed cylindrical ring E is adjusted a ring intended to rotate
around the same, which ring I call the piston ring F, to the outer
periphery of which is attached the piston G; this piece is represented in
Fig. 6. The outer end of this piston G, thus arranged to rotate around
the primary or piston centre E, terminates in two arms resembling the
flukes of an anchor, of which the piston represents the shank, these arms
or flukes being circular in their external curve so that their outer edge
constitutes a short segment of a circle, as shewn in the said Fig. 6.
Through the cylinder bottom B, as also through the cylinder heads C, but
at a short distance from the primary or piston centre E passes the shaft
of the engine D, the point at which it passes through being called the
secondary or shaft centre, Figs. 5 & 1, D. Over the fixed cylinder E,
though not connected with it, but on the contrary having the shaft D

page_text: for its axis, and firmly keyed to the shaft, is placed another cylinder, not
fixed but intended to revolve, which I call the piston wheel H, Figs. 5
and 7; this cylinder is intended to revolve by being carried round by
the piston G and to impart the same movement of rotation to the shaft D
which constitutes its axis and to which it is keyed, Fig. 5. In the
periphery of this piston wheel is a slot I, through which the piston
passes, so that the circular movement of the piston upon the centre E,
viz., the primary or piston centre, carries round with it the piston
wheel H, whose rotating movement is around the secondary or shaft
centre D, which rotation gives the requisite motion to the shaft which is
keyed to the said wheel and constitutes its axis, seen Fig. 5. The piston
thus revolves around one centre of movement and gives a rotating move-
ment to the piston wheel H, which revolves around a different centre of
movement D. These two simultaneous but non-concentric rotating
movements being rendered possible by means of the slot I through
which the piston passes through the periphery of the piston wheel H,
sliding alternately in and out through the said slot I. These two
distinct rotating movements both operated within the engine chamber A.;
and around their respective centres of movement D and E, result in
creating a vacant space presenting the appearance of a crescent, Fig. 1, A,
the lower ends or points of which approach each other, being separated
by a distance nearly corresponding with the circular length of the piston
arms or anchor flukes above described; this vacant space is the steam
chamber A. At one of the said crescent points are the openings for the
entrance of the steam J; these openings are successively opened and
closed by the rotation of the arms or anchor flukes attached to the end
of the piston G. The steam entering at its inlet drives the piston G
round until it reaches its point of outlet as exhaust steam J. The
piston thus made to rotate carries with it the piston wheel H, thereby
turning at the same time as the shaft D which is keyed to the centre of
the said piston wheel H. The working of the two centres from which
the engine takes its name is thus:-The piston revolving round the
primary or piston centre E carries round with it the piston wheel H,
through the slots in the periphery of which it slides in and out, and.
thereby gives motion to the shaft D fixed at the centre of said piston
wheel H. Each of these motions thus bears only on its own. centre
without any eccentric action, though at first glance the engine may
seem to present an eccentric movement. On each side of the piston
within the slot is placed a knuckle joint, as seen in Fig. 8, K. The

page_text: maximum of power and the minimum of friction are thus secured. The
steam acts on the piston G with the benefit of the leverage represented
by the distance between the extremity of the piston and its centre of
movement, while the only friction existing is that of the shaft D, that
of the ring F to which the piston is attached, and which revolves round
the fixed cylinder ring E, and that of the sliding segment constituted
by the arms or anchor flukes of the piston G for the short distance
within which it comes in contact with the interior periphery of the
steam chamber A. The first is inseparable from all machinery; the
second besides being under constant lubrification by the steam is reduced
by friction rollers or any other suitable contrivance; the third is in-
significant, and reduced to a small degree by metallic packing placed
at the said short distance of contact. The steam enters the steam chest
of the engine near the top part thereof, and after passing round through
the steam jacket L, Fig. 1, enters the steam chamber A at the points
of the crescent above described, and after its discharge at the other
points of the crescent the exhaust steam passes through a corresponding
steam jacket L to be discharged by an outlet near the top of the engine
corresponding to the point of its inlet. When the movement is reversed
that which before served as the inlet becomes the outlet, and vice versa
(see J, Fig. 1).
In all but very small engines, where economy of steam is important,
a simple arrangement is made for cutting off the steam. By this means
the steam already admitted is allowed to act expansively. The steam is
conducted through the steam pipe M, Fig. 2, direct to the steam chest N ;
from the steam chest it passes directly to the steam jacket. L, Fig. 1; from
thence to the steam chamber A. The valve which regulates the inlet and
outlet of the steam is shown in Fig. 1, O, it is made concave with two feet
or slides. When one of these feet or slides leaves the entrance of the
steam jacket open the exhaust steam passes out at the centre or exhaust
port P beneath the concave part of the valve, as seen in Figs. 1 and 2;
from the exhaust port it passes directly to the exhaust pipe 9. The
valve is operated by means of a lever or handle R connected to the
valve by a rod S. The engine can be reversed by simply changing
the position of the lever in the direction of the dotted lines, seen R,
Fig. 1. When an engine is required to move in one direction only the
steam chest may be entirely dispensed with, the steam entering directly
the steam jacket by means of pipes; the entrance of the steam and the

page_text: exhaust steam may be regulated by stop-cocks or any other arrangement
by which the amount of steam used can be controled.
For a force pump, or for any purposes where a pump may be required,
the cylinder may be used either singly or doubly, or with a double
piston having two arms, as seen in Fig. 13, Z. The pump may be run
at a much higher rate of speed than the engine, taking its water at one
port near the bottom of the cylinder and forcing it out at the opposite
one, Fig. 13, T. The movements and machinery of the internal parts
of the pump are similar to those of the engine above described.
For measuring water or any other liquids I employ the same move-
ments as for the engine and pump. The pistons being forced round by
the pressure or head of water brought to bear against them, and at each
revolution discharging a certain amount at the outlet U, the exact
quantity being indicated by the index box V placed at the centre of the
top, Figures 10, 11, & 12, the movement is given to the indicator by an
upright shaft W, to which is attached a toothed wheel X which works
in a worm or screw attached to the piston wheel shaft D, which in this
instance does not protrude through the cylinder heads, but is fitted.
to its bearings on the inside which prevents any escape of liquid.
Between the two cylinders is the partition or dividing wall B, before
referred to in the description of the engine, for the water-measuring.
machine or meter; this partition is cast hollow so as to allow the worm.
or screw to be placed in its centre, as seen in Fig. 11, and also to give.
the upright shaft W a passage from the worm or screw to the under.
box V.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said George Bradford McFarland in the Great Seal
Patent Office on the 26th May 1870..
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
BRADFORD MCFARLAND, Engineer, of the City of New York, in the
United States of America, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-ninth day of November, in the
year of our Lord One thousand eight hundred and sixty-nine, in the
thirty-third year of Her reign, did, for Herself, Her heirs and successors,

page_text: give and grant unto me, the said George Bradford M'Farland, Her
special licence that I, the said George Bradford McFarland, my executors,
administrators, and assigns, or such others as I, the said George Bradford
McFarland, my executors, administrators, and assigns, should at any time
agree 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
[reland, the Channel Islands, and Isle of Man, an Invention for "A
NEW AND IMPROVED CONVERTABLE DOUBLE-CENTRE ROTARY ENGINE," upon the
condition (amongst others) that I, the said George Bradford McFarland,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe
and ascertain the nature 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 calendar monthis next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said George Bradford McFarland, do
hereby declare the nature of my said Invention, and in what manner
the same is to be performed, to be particularly described and ascer-
tained in and by the following statement, reference being had to the
accompanying Drawing, making a part of this Specification, in which
Figure 1 is a vertical section of my improved steam engine; Figure 2
is a transverse elevation; and Figure 3, a side elevation of the same;
Figure 4 is a plan of the same shewing the valve face; Figure 5 is a
transverse section of the said engine; Figure 6 shews an elevation and
section of the piston of the said engine; Figure 7 shews an elevation and
section of the piston wheel thereof; Figure 8 shews an elevation and
section of slides and knuckle joints of the said piston; Figure 9 shews.
studs for keeping these knuckle joints in the proper position; Figure 10
is a section illustrating the adaptation of my Invention as a metre for
measuring liquids; Figure 11 is an elevation partly in transverse section
of the said metre; Figure 12 is a plan of the same shewing the index or
counter; Figure 13 illustrates the modification of my Invention to serve
as a pump; Figure 13* is a vertical section of the said pump; Figure 14
is a perspective view of an engine and pump connected.
All the essential parts of this engine are enclosed within a cylindrical
chamber A. One side B of this chamber I call the cylinder bottom, the
other side C is the cylinder head; these two sides are firmly bolted upon

page_text: the cylinder. When the internal parts composing the engine have been
put in place in the cylinder, the cylinder head C being bolted on closes
the chamber A, within which the motion is generated and imparted-
to the shaft D which projects through the cylinder head C. In a double
engine constructed according to my Invention the cylinder is provided
with a middle or dividing partition, having a similar chamber A and
shaft D on both sides. The pistons in these chambers are arranged
at opposite points on the shaft, that is to say, 180 degrees apart, so,
that the steam will be entering in the one as it escapes from the.
other. Concentric with the cylinder bottom B, and cast with it as one.
piece, is a fixed cylindrical ring E, smaller both in diameter and in-
thickness than the chamber A; the common centre of the cylinder
bottom and ring I call the primary or piston centre; around this fixed
cylindrical ring E is placed a ring F (intended to rotate around it) which
I call the piston ring; to the outer periphery of the latter is attached.
the piston G, as represented in Figure 6; the outer end of this piston G.
thus arranged to rotate around the primary or piston centre E, terminates
in two arms somewhat resembling the flukes of an anchor, of which the.
piston represents the shank; these arms or flukes are circular on their
external periphery, so that their outer edge constitutes a short segment
of a circle, as shewn in Figure 6. Through the cylinder bottom B and
the cylinder head C, but at a short distanco from the primary or piston
centre E, passes the engine shaft D, the point at which it passes through
being called the secondary or shaft centre, see Figures 1 and 5. Over
the fixed cylindrical ring E, but having the shaft D for its axis, and
firmly keyed to the said shaft, is placed another cylinder H, not fixed but
intended to revolve; I call this cylinder the piston wheel; this cylinder.
is rotated by being carried around by the piston G, and imparts the same
rotative movement to the shaft D which constitutes its axis, and to which
it is keyed. In the periphery of this piston wheel is a slot or opening I.
through which the piston slides, so that the circular movement of the
piston upon its centre E (namely, the primary or piston centre,) carries
round with it the piston wheel H which rotates around the secondary or
shaft centre D; this rotation gives the requisite motion to the shaft
which is keyed to the said wheel and constitutes its axis. The piston.
thus revolves around one centre of motion, and gives rotation to the
piston wheel H, which revolves around the other centre of motion D,
these two simultaneous but not concentric rotations being permitted'
by the opening I in which the piston works through the periphery

page_text: of the piston wheel H sliding alternately in and out through the said
opening I. The arrangement of parts for producing these two distinct
rotations within the engine chamber A and around their respective
centres of motion D and E forms a vacant space, presenting the
appearance of a crescent, see Figure 1, the lower ends or points of which
approach each other, but which are separated by a space nearly corre-
sponding with the length of the piston arms or anchor flukes above
described. This vacant space is the steam chamber A. At the said
crescent points are the openings or ports J for the admission and exhaust
of the steam; these openings are successively opened and closed by the
rotation of the curved arms or anchor flukes of the piston G. The steam
entering at its inlet drives the piston G round until it reaches its point
of outlet, through which it passes as exhaust steam. The piston being
thus caused to rotate carries with it the piston wheel H, thereby turning
at the same time the shaft D which is keyed to the centre of the said
piston wheel H. The functions of the two centres from which the
engine takes its name are thus made manifest. The piston revolving
around the primary or piston centre E carries round with it the piston
wheel H through the opening I, in the periphery of which it slides in
and out, and thereby gives motion to the shaft D. Each of these motions
is thus around its own centre without any excentric action, though at a
first glance the engine may seem to have an excentric movement.
each side of the piston within the opening or slot I is a knuckle joint K,
as seen in Figure 8. The maximum of power and the minimum of
friction are thus secured. The effect of the steam acting on the piston G
is multiplied by the leverage represented by the distance between the
extremity of the piston and its centre of movement, while the only
friction is that of the shaft; that of the ring F to which the piston is
attached and which revolves round the fixed cylinder ring E; that of the
piston G sliding in and out of the slot I; and that of the short segment
formed by the arms or anchor flukes of the piston G for the short
distance within which it comes into contact with the interior periphery
of the steam chamber A. The first is inseparable from all machinery;
the second is deminished by the constant lubrication of the steam, and
is minimumized by the employment of friction rollers or other con-
trivances for that purpose; the third is insignificant; the fourth is
reduced by metallic packing applied to the said short distance of contact.
The steam enters the valve chest N, and after passing round through the
steam jacket L, see Figure 1, enters the steam chamber A through the
On

page_text: ports or apertures J at one of the points of the crescent above described,
and after its discharge at the other point of the crescent the exhaust
steam passes through a corresponding steam jacket L to be discharged at
an outlet near the top of the engine corresponding to the point of its
inlet. When the motion is reversed that which was before the inlet
becomes the outlet and vice versa.
In all except very small engines economy of steam is important, I
therefore employ a simple arrangement for cutting off the steam. By
this means the steam already admitted is allowed to act expansively.
The steam is conducted through the steam pipe M, Figure 2, direct to
the valve chest N. From the valve chest it passes directly to the steam
jacket L (see Figure 1) and thence to the steam chamber A. The
valve O which regulates the inlet and outlet of the steam is made
concave in form, with two feet or slides. When the valve is moved far
enough in either direction to leave the entrance to the steam jacket open
the exhaust steam is at the same time allowed to escape through the
centre or exhaust port P under the concave part of the valve, as will be
understood by referring to Figures 1 and 4; from the exhaust port the
steam passes directly to and away through the exhaust pipe Q. The
valve O is operated or adjusted by means of a lever or handle R con-
nected to the valve by a rod S. The engine can be reversed by simply
moving the lever R from the position shown in full lines to that shown
in dotted lines, Figure 3. When an engine is required to move in one
direction only the valve chest may be dispensed with entirely. The
steam will then enter directly into the steam jacket through suitable
pipes, the entrance of the steam and the exhaust being regulated by
stop-cocks or other suitable means.
When my Invention is to be used as a pump the same may have
either one or two cylinders, or the cylinder may be provided with a
double piston having two arms, as seen at Z, Figure 13. When used as
a pump it may be driven at a much higher speed than when serving as a
motor engine. The water is taken in at one port J near the bottom of
the cylinder and forced out at the opposite port J'. The construction
and operation of the internal parts are similar to those already
described.
When the engine is used for measuring water or other liquids I also
employ the same arrangement. The pistons are forced round by the
pressure or head brought to bear against them, and at each revolution

page_text: discharge a certain amount of the liquid at J, the exact quantity being
indicated on the index V placed at the centre of the top of the engine,
as shewn in Figures 10, 11, and 12. Motion is communicated to the
indicator through an upright shaft W, to which is attached a toothed
wheel X which works in a worm or screw fixed on the piston wheel
shaft D, which in this instance does not protrude through the cylinder
heads but is fitted to bearings inside the cylinder; this arrangement
prevents any escape of unmeasured liquid. Between the two cylinders
is the partition or dividing wall before referred to, which partition when
the engine is used as a measuring machine or meter is cast hollow, so as
to allow the worm or screw to be placed in its centre, as seen in
Figure 11, and also to allow the upright shaft W to pass from the worm
or screw to the index box V.
With the arrangement above described there is no possibility of
leakage and a very slight head of water or other liquid is sufficient to
give motion to the machine.
Having thus fully described the nature of my Invention, and the best
manner with which I am acquainted of carrying the same into practice,
I wish it understood that I do not confine myself to the precise details
of construction shewn in the accompanying Drawings, as these may be
varied without departing from the principle of the said Invention; but I
claim,―
First. The combination within a close chamber of a piston and wheel
arranged to rotate together around two different centres, and in such
a manner that one will drive the other for the purposes specified.
Second. The engine with parts constructed, combined, and operating
together, substantially as set forth for the purposes specified.
In witness whereof, I, the said George Bradford M'Farland, have
hereunto set my hand and seal, this Twenty-third day of May, in
the year of our Lord One thousand eight hundred and seventy.
GEORGE BRADFORD MCFARLAND. (L.S.)