IMPROVEMENTS IN TRACTION ENGINES
Year: 1871

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, Patent Agent, for the Invention of
"IMPROVEMENTS IN TRACTION ENGINES."-A communication from
abroad by Louis Adolphe Herrmann, of 13, Boulevart St. Martin,
Paris.
Sealed the 22nd March 1872, and dated the 24th October 1871.
PROVISIONAL SPECIFICATION left by the said Alexander Melvillo
Clark at the Office of the Commissioners of Patents, with his
Petition, on the 24th October 1871.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN TRACTION ENGINES," to be as
follows:-
Hitherto locomotive vehicles have been mostly propelled by the
agency of wheels, but although admirably adapted to obtain a high
speed on smooth surfaces, wheels are not so suitable for rough surfaces
A

page_text: such as those of ordinary roads paved and unpaved, especially when
required to haul heavy loads or for field and general work.
Various attempts have been made to employ levers provided with
propelling feet bearing on the surface of the ground, but practically
without success, the failure being due principally to defective
mechanical contrivances and to the non-employment of the whole
weight of the vehicle to obtain adhesion.
The principles upon which the new or improved system forming the
subject of the present Invention is based, are illustrated in Figures 1
and 2 of the annexed Drawings, which serve as diagrams only to explain
the principles of operation and construction of the machine.
A, B, is a horizontal frame carried on wheels, and on which is
mounted a vertical standard C. c is a rigid bar jointed at a to a vertical
sliding rod e, and to the lower end of which a broad shoc or foot d is
jointed. The said foot rests on the ground and the rod c is free to
oscillate in a slot in frame A, B. Now the bar c being vertical, if by a a
spring for other power carried on 'standard C a forco is exerted on the
bar c equal to the weight of the vehicle, a tractive force being at same
time applied to the bar c in the direction of the arrow X by a weight P
or other means, the bar c will be deflected from the vertical position to
But as the bar c is
the oblique position shown in dotted lines at e¹.
retained at its point of oscillation as well as at its point of application
on the earth (on which it cannot slip as it sustains the whole weight of
the vehicle), it follows that it can only assume this direction by causing
the vehiclo itself to change its position, that is, by causing it to move
in the direction of the arrow F, provided the weight P or other power
employed be sufficient to overcome the resistance caused by friction.
To continue the movement the action of the spring and weight P
must be discontinued, and the leg c returned to its vertical position by
moving the foot d along the ground. By again applying the said forces
the same movement will be repeated.
"
By replacing the said spring and weight by steam cylinders suitably
mounted and connected, the power of steam may be applied to propel
the vehicle.

page_text: A is the horizontal frame of the machine on which are mounted the
boiler B, water tanks C, and fuel receptacles D, and tool boxes E. At
the front and rear ends of the frame A are placed the carrying wheels
and the propelling devices hereafter described. The driving mechanism
is located beneath the middle of frame A, the various parts being
arranged and operated as hereafter explained. Upon the frame A are
mounted two pairs of curved plates F disposed at either side of the
machine, and provided with friction surfaces for the purpose mentioned
hereafter. A central plate G fixed beneath the frame serves to support
part of the steering apparatus and the framework of the driving
mechanism. H are the propelling feet four in number, disposed in pairs
towards the front and rear of the machine. Each pair is so operated
that either foot moves alternately simultaneously with the opposite foot
of the other pair. I are wheels on which the machine is mounted, the
said wheels being intended to support the whole weight of the machine
when at rest, and such part thereof as is not utilized for the purposes of
adhesion when in motion. They are coupled two and two with cach of
the two systems of propelling feet, and as these are identical it will
suffice to describe one system only. The two fect H, H', are placed side
by side as close as possible and equidistant from the vertical axis on
which the propelling mechanism is pivoted, the two wheels I being
placed outside the same at equal distances, the parts being mounted in a
framo J arranged to have a swivelling or "locking" motion and carry.
ing a plate K provided at its centre with a socket L in which works
a pin or pivot fixed to the frame of the platform of the machine.
At each extremity of plato K is fixed a segmental plate M on which
rests the corresponding plate F before referred to, and which thus serve
the purpose of the "locking plates" in ordinary vehicles, permitting
each frame or under carriage in which the propelling feet are mounted
to turn or swivel on its central pivot to guide the machine in any
direction desired..
In order to steady the swivelling under carriage a second socket N,
Figure 3, is provided at the lower part to receive a pin O fixed to a
longitudinal frame P, by which the two swivelling frames are rigidly
tied at the proper distance apart to the framework of the machine.
The two under carriages or frames, shown in Figures 3 and 5, arc
geared together so as to swivel horizontally on their respective pivots at
the same time and to the same extent, by means of two circular toothed
^ 2

page_text: racks Q, Q, or their equivalents, of equal diameter, and a pair of pinions
R, also of equal size fast on one shaft. The racks Q are connected to
the fore and rear under carriages by plate S fixed at the upper part
thereof, the racks abutting close to the centre of the machine bencath
the foot plate and above the plate G, carrying the propelling mechanism
as shown. The pinions R are keyed on a shaft mounted beneath the.
foot plate, and operated by means of endless screw-gearing T, shaft U,..
and steering wheel V, whereby the racks Q, Q, are moved together in
one or other direction. The two under carriages being thus "locked"
or swivelled together in opposite directions less movement is required of
them than if one swivelling carriage only be employed.
66
The arrangement and operation of the mechanism for actuating the
propelling feet is as follows:-The levers or bars to which the feet H are
attached are each jointed to a piston working in a vertical cylinder
upper
mounted on the plate K, to which steam is admitted on the
side
of the piston only. To raise the piston and the propelling foot to which
it is attached the two piston rods are connected by a lever V, so that the
fect balance one.another, and when steam is admitted to one cylinder
to depress one foot the other foot is raised. S¹, S', T', T, are the two
pairs of adhesion " cylinders for operating the vertical movement and
obtaining the required adhesion of the propelling feet in the fore and
rear carriages respectively. Each pair is cast in one piece, the cylinders
being made quite open at the lower end. Steam is supplied thereto
much in the usual manner, the lap being however considerably more on
the eduction than on the induction port, so that the descent of the one
foot is effected more rapidly than the ascent of the other to prevent-
jolting. The steam supply to both sets of engines is controlled by a rod
As the feet
connected to a lever V₁ operated by one set of mechanism.
Hare brought down directly upon the surface of the ground, which may
have hollows and other inequalities, and the upward movement of the
piston being limited by the end of the cylinder, it becomes necessary
(since the two feet in each pair are connected by a rock lever as before
described) to provide means of compensating or allowing for the unequal
descent of the pistons. For this purpose the rock lever Y connecting
the piston rods is fulcrumed on a piston Z fitted in a cylinder Z', which
is in constant communication with the steam space in the boiler. The
steam pressure beneath the piston Z thus tends continually to raise the
fect H, the area of the piston being calculated so as to counterbalance.

page_text: the total weight of the two fect H, and the working parts immediately
in connection therewith. The fulcrum of the rock lever is thus supported
on an elastic cushion which yields when the propelling foot falls below
the general level of the ground, and by raising the feet from the ground
in the ascensional movement allows them to be placed upon parts rising
higher than the said level.
Referring again to the Diagram, Figure 1, it will be seen that if moved
from a to d, the propelling foot will describe an arc of a circle, and
therefore bear unequally on the ground unles the pressure of the spring f
or other power be constant, which would be the case when the power of
steam is applied to replace the spring.
By a continued expenditure of steam, a constant force might be
exerted on the propelling foot so long as it is in contact with the ground;
but to prevent undue consumption of steam I provide the following
arrangement, by which the foot II when once placed on the ground is
frco to maintain its position in the same horizontal plane throughout its
course. On either side of each propelling lever or leg C¹ are two vertical
sliding rods A' fitted in suitable guides. The sliding rods B', jointed
to the legs C' at midlength thereof, the connecting rods being equal
in length to half the length of the leg C¹. The sliding rods A' are
united at their upper extremities by a crosshead D' attached to tho
piston E¹. This crosshead is provided with two vertical slides F for
the purpose of guiding the upper end of the leg, which is jointed to
a sliding block G' fitted therein. The apparatus is thus capable of
two distinct vertical movements; the general movement of the wholo
apparatus, and the vertical sliding movement of the leg C³, the first
of these being dependent upon the supply of steam to the cylinders,
whilst the latter is consequent upon the combined movements of the
propelling parts and connecting rods.
By the above arrangement the supply of steam to the cylinders may
be cut off as soon as the foot is placed on the ground, whilst that jolting
is prevented which would inevitably occur if the foot H did not move
(relatively to its centre of oscillation) in a horizontal line.
n
To produce the alternate to-and-fro motion of the two legs the follow-
ing arrangement is employed, reference being had to Figure 6. m and ⟫
are connecting rods jointed to the two legs C', C", at b; X and X' aro
two horizontal rock shafts mounted in bearings on the frame J in the

page_text: and
position shown; X o and X o' are levers fixed on shafts X, X',
jointed to rods m, n, respectively; X r, X² 7¹, are two other levers
mounted on the same shafts and jointed to a connecting rod r¹, 7. The
fore and rear under carriages or swivelling frames are connected by the
piston rod of the propelling or driving cylinder I' of two connecting
rods X", which are each jointed to a crosshead J fixed at either
extremity of the said piston rod, which passes through both ends of the
cylinder. The rods X" are connected to levers equal in length to o X
and o¹ X fixed to the middle of shaft X, the connection being by double
or universal joints to permit of the swivelling of the frame J. The
cylinder I is disposed horizontally at the centre of the machine, and
beneath one of the crossheads J which slide in guides K' is fixed a sort
of cam L' whose function corresponds to that of an eccentric. This cam
operates a horizontal bell crank M' connected at N' to a piston working
in a cylinder O', by which the whole of the parts which control the
general distribution of the steam are operated. To this piston rod a rod
P' is jointed at one end, and at the other to a lever Q' keyed on a rock
shaft R', which therefore receives a reciprocating movement correspond-
ing to that of the propelling piston. The distribution of steam to the
two pairs of "adhesion cylinders is controlled as before mentioned
by a lever V₁ connected to a rod A", whose other end is jointed to a slide
fitted in a slot link B3 hung at midlength to one extremity of the rock
shaft R. C is a hand wheel by which this reversing gear is operated,
and which therefore controls the distribution of steam to the cylinders
by which the adhesion of the fect is obtained. The valve which regulates
the supply of steam to the propelling or driving cylinder I also receives
its motion from the rock shaft R' through the medium of a link motion,
similar to that before described, placed at the opposite extremity of
shaft R', and serving as reversing gear operated by hand wheel D³.
"
In descending inclines it may be necessary to reverse the engine to
check its progress, and to avoid the suction through the exhaust pipe of
cold air, or of cinders and coal dust if the pipe opens into the chimney,
I employ the Invention of Mr. Lechatellier, which consists in injecting a
mixture of steam and hot water, and the exhaust pipe opens out at the
exterior of the chimney, the draught being created by the escape steam
from the adhesion " cylinders, whose exhaust pipes are led into the
chimney and form a blast pipe therein. As the cylinders S', S', T', T',
move with the swivelling frames special provision must be made in the

page_text: construction and arrangement of the tubes by which the distribution of
the steam thereto is effected, in order to permit of the free movement of
the said swivelling under carriages. The steam pipe is led from the
dome, and branches off towards cither end along the barrel of the boiler.
This pipe is a fixture as far as F, and is there continued by means of the
articulated or jointed pipes F, G, H³, and I', connected by suitable
stuffing boxes and leading to the steam chest of the cylinder.
The parts
forming the stuffing boxes are firmly bolted by screw bolts fixed within
the tubes and secured by nuts externally. Both steam and exhaust
pipes are similarly constructed. Steam is also supplied from the dome
to the steam chests of the propelling engines by pipes arranged as
shown. K and L' are the escape pipes of the cylinders I' and O'
respectively.
Brakes are provided to aid in checking the progress of the machine.
They are mounted beneath the frame of the platform, and when required
are operated by suitable mechanism which brings the brake surfaces in
contact with the surface of the ground, provision being made for the
efficient action of the brakes in whichever direction the machine may be
running.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Alexander Melville Clark in the Great Seal Patent
Office on the 24th April 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fourth day of October, in the
year of our Lord One thousand eight hundred and seventy-one, in the
thirty-fifth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said Alexander Melville Clark,
Her special licence that I, the said Alexander Melville Clark, my
executors, administrators, and assigns, or such others as I, the said
Alexander Melville Clark, 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

page_text: and lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle
of Man, an Invention for "IMPROVEMENTS IN TRACTION ENGINES," a com-
munication to me from abroad by Louis Adolphe Herrmann, of 13,
Boulevart St. Martin, Paris, upon the condition (amongst others) that
I, the said Alexander Melville Clark, 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 per-
formed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the
said Letters Patent.
NOW KNOW YE, that I, the said Alexander Melville Clark, do
hereby declare the nature of the said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement, referenco being had to the two
Sheets of Drawings hereunto annexed, and to the letters and figures
marked thereon (that is to say) :—
This Invention relates to improvements in traction engines for
working on common roads.
Hitherto the chief difficulty has arisen from the insufficient adhesion
of the propelling organs of these engines. Wheels have been mostly
employed for the propulsion of locomotive vehicles, but although
admirably adapted to obtain a high speed on a smooth surface (such
as a railway) they are not so suitable for the rough surfaces of ordinary
roads, whether paved or unpaved, especially when required to haul
heavy loads or for field and general work. A wheel owing to its form
has but a very small bearing surface on the ground, and to this is
due its liability to slip on hard ground and to sink into soft ground.
For this purpose a medium is required, which shall have a sufficient
surface in contact with the ground to permit the adhesion due to the
entire weight of the locomotive to be utilized for the purposes of pro-
pulsion without causing an undue amount of friction.
Various attempts have been made to employ levers provided with
propelling feet bearing on the surface of the ground, in imitation of the
movements of draught animals, but practically without success, the
failure being due principally to defective mechanical appliances and to

page_text: the employment of a portion only of the whole weight of the vehicle for
the purposes of adhesion. These machines were generally mounted on
three or four wheels, the propellers being placed in the rear, where they
could utilize but a small portion only of the weight, while their small
surface rendered them liable both to sink into soft ground and to slip on
paved ways, producing shocks liable to damage the machine on meeting
with any obstacle to its progress.
The principles of construction and operation upon which the new or
improved system of traction engine forming the subject of the present
Invention is based are illustrated theoretically in Figures 1 and 2 of the
annexed Drawings, in which A, B, represents a horizontal frame running
on wheels, and C an upright frame carried on A, B. c is a rigid bar
jointed at one end a to a vertical sliding rod e, and at the other to a
broad shoe or foot d. The said foot rests on the ground, and the rod c
is free to oscillate in a longitudinal slot in frame A, B. Now the bar c
being vertical, if by a spring for other power carried on upright Ca
force be exerted in a vertical direction on the bar c equal to the weight
of the vehicle, a horizontal force being at same time applied to the bar c
in the direction of the arrow × by a weight P or other power, the bar c
will be deflected from the vertical position to that shown in dotted lines
at e provided the power P be sufficient to overcome the resistance
caused by friction. But as the bar c is connected at one end to the
vehicle and bears at the other on the ground (on which it cannot slip,
as it sustains the whole weight of the vehicle), it follows that it can only
assume this direction by causing the vehicle itself to change its position,
that is, by causing it to move in the direction of the arrow F. To
continue this movement the force of the spring f and of weight P must
first be relaxed, and the leg c be returned to its vertical position by
moving the foot d along the ground before these forces are again applied.
These principles may be carried out in practice by the employment in
place of spring f of a steam cylinder, of which e will be the piston rod..
By admitting steam alternately above and below said piston, an up-and-
down motion of leg c will be produced. The action of the propelling
power (represented in the diagram by weight P) may be obtained by
employing a second cylinder, fixed horizontally to frame A, B, with its
piston rod connected at g to leg c. Thus supposing the leg c to be in
the vertical position a, d, by admitting steam above the lifting piston
the apparatus will be supported on leg c, while by admitting steam to

page_text: act on the propelling piston so as to move it towards B, leg c will be
moved to the dotted position &, thereby causing the vehicle to advance
in the direction of the arrow F. On the return stroke of the piston the
leg c is raised and carried forward to repeat the movement.
In Figures 3, 4, and 5 I have illustrated a steam locomotive traction
engine constructed according to this Invention. A is the horizontal
frame of the machine on which are mounted the boiler B with its usual
accessories, water tanks C, and coal and tool boxes D and E. At the
front and rear ends of the frame A are placed the carrying wheels and
the propelling devices hereafter described. The propelling engine proper
is located beneath the middle of frame A, the various parts being
arranged and operated as hereafter explained. The frame A is rect-
angular in form, and consists of two side frames united by cross bars
and provided with four curved plates F (two in front and two in rear)
for the purpose mentioned hereafter. A central plate G fixed beneath
the frame serves to support part of the steering apparatus and the frame-
work of the propelling engine. The framing is constructed of angle iron
riveted and bolted together; H, H', are the propelling fect, four in
number, disposed in pairs towards the front and rear of the machine,
those in each pair being moved alternately and simultaneously with the
opposite fect of the other pair, like the movements of a trotting
horse, or if the front and rear feet be taken separately their motion is
analogous to that of walking. The machine is mounted on four wheels I
which sustain the whole weight of the machine when at rest, and such
part thereof as is not utilized for the purposes of adhesion when in
motion. They are coupled in pairs in close proximity to the propellers
to enable the apparatus to be readily manoeuvred on common roads.
The best results can be obtained on the three following conditions,
viz. —
:-
1st. The direction of motion of the fect must be parallel to that of the
wheels.
2ndly. When moving in a straight line there must be perfect paral-
lelism between the direction of motion of the propellers and wheels and
that of the machine.
3rdly. When turning curves, the direction of the propellers and
wheels must be always tangential to the curve, or parallel with such

page_text: These three conditions being fulfilled, it will be evident that all danger
of want of uniformity in the movements of the propellers and wheels
is avoided as well as any consequent slipping of the propellers while
turning, all of which would tend to impede the progress of the machine.
The front and rear propelling feet are identical in arrangement, and
it will suffice to describe one set only.
In Figures 6 and 7 the two feet H, H', are shown placed side by side
as close as possible and equidistant from the vertical axis on which the
propelling mechanism is pivoted, the two wheels I being placed outside
the same at equal distances, the parts being mounted in a swivelling or
bogic frame J carrying a plate K provided at its centre with a socket L,
in which works a pin fixed to the frame of the machine. At each
extremity of frame K is fixed a segmental plate M, on which rests the
corresponding plate F before referred to, and which thus serve the
purpose of the "locking plates" in ordinary vehicles, permitting each
bogie frame or under carriage on which the propelling feet are mounted
to turn or swivel on its central pivot to guide the machine in any
direction desired.
In order to steady the swivelling under carriages or "bogies" a second
socket N, Figure 3, is provided at the lower part to receive a pin O
fixed to a longitudinal frame P, by which the two swivelling frames
are rigidly tied at the proper distance apart to the framework of the
machine.
The two under carriages or bogie frames shown in Figures 3 and 5
are geared together so as to swivel horizontally on their respective pivots
at the same time and to the same extent by means of two curved toothed
racks Q, Q, or their equivalents of equal diameters, and a pair of
pinions R, also of equal size, fast on one shaft. The racks Q are
connected to the fore and rear under carriages by plates S fixed at the
upper part thereof, the racks abutting close to the centre of the machine
beneath the driver's foot plate and above the plate G carrying the
propelling mechanism as shown. The racks are so arranged that the
pinions will move them both either to the right or left, that is to say,
the two vertical planes passing through the longitudinal axes of the
swivelling frames will always diverge to the same degree from and on
the same side of a vertical plane taken through the longitudinal axis of
the machine.

page_text: VIZ
1st. Each under carriage swivels to half the extent only than would
be the case were there but one swivelling carriage.
2ndly. The rear propellers and wheels always follow in the same
track as those at the front.
3rdly. The direction of motion of the propellers and wheels will be:
always cither parallel or tangential to that of the machine.
The steering apparatus is connected to the two pinions R before
referred to, the shaft of which is continued towards the rear under the.
driver's foot plate, where it carries a screw wheel T receiving motion
from an endless screw U, keyed on a vertical shaft provided with a hand
wheel V. The pinion shaft may be carried forward under the front foot
plate and the screw gearing changed in position when the steerer is to
be stationed at that end.
In order to produce the vertical movements of the propelling feet
each is operated by a steam cylinder S¹, to which steam is preferably
admitted above the piston only to produce the downward movement,
whilst the other foot is being raised by means of a rock lever Y con-
necting the two piston rods, pivoted at its centre so that the two
propelling feet balance one another, one foot being raised while the other
is depressed. As the feet II are brought down directly upon the surface
of the ground, which may have hollows and other inequalities, and the
upward movement of the piston is limited by the end of the cylinder,
it becomes necessary (since the two feet in each pair are connected as
before described) to compensate or allow for the unequal descent of the
pistons, which varies in extent according to the surface of the ground.
For this purpose the rock lever Y connecting the piston rods is mado
capable of moving vertically, being fulcrumed on a piston Z fitted in a
cylinder Z', which is in constant communication with the steam space
in the boiler. The steam pressure beneath the piston Z thus tends con-
tinually to raise the feet H, H', the area of the piston being calculated
so as to counterbalance the total weight of the two feet and the working
parts immediately in connection therewith. The fulcrum of the rock
lever is thus supported on an elastic cushion, which is caused to yield by a
the superior pressure in cylinders S', when the one propelling foot falls

page_text: below the general level of the ground, and by raising the feet further
from the ground in the ascensional movement allows them to be placed
upon parts rising higher than the said level.
Referring again to the diagram Figure 1 it will be seen that if moved
from d to d¹ the propelling foot will describe an arc of a circle and will
therefore bear unequally on the ground unless the pressure of the spring
for other power be constant.
By a continued expenditure of steam a constant force may be exerted
on the propelling foot whilst it is in contact with the ground, but to
prevent an excessive consumption of steam I provide the following
parallel motion arrangement by which the foot H when once placed on
the ground is maintained in its horizontal position in the same plane
throughout its course. On either side of each propelling lever or leg C¹
are two vertical sliding rods A' fitted in suitable guides. These sliding
rods are jointed at their lower extremities to connecting rods B' jointed
to the legs C¹ at midlength thereof, the connecting rods being equal in
length to half the length of the leg C'. The sliding rods A³ are united
at their upper extremities by a crosshead D' attached to the piston E¹;
this crosshead is provided with two vertical slides F for the purpose
of guiding the upper end of the leg which is jointed to a sliding block
G' fitted therein. The apparatus is thus capable of two distinct vertical
movements; the general movement of the whole apparatus, and the
vertical sliding movement of the upper part of leg C', the first of these
being dependent upon the supply of steam to the cylinders, whilst
the latter is consequent upon the combined movements of the propelling
parts and connecting rods.
The diagram Figure 8 is intended to show that the point & always
moves parallel to the ground, or perpendicular to a vertical line a, d.
Suppose a, d, to represent the propelling leg and d, b, the connecting
rod, a, d, being equal to twice the length of d, b, and a, b, is equal to
d, b. When in a vertical position the three points a, b, d, are in a right
line. In either of the intermediate positions to right or left d is con-
sidered as a fixed point after the downward motion has taken place.
d, b', positions of connecting rod; a', d³, leg; a' new position of point
a. In the extreme positions, d fixed point; d, b", positions of con-
necting rod; a", d", leg. By taking d, d, as the base of a triangle
d, b', d, and varying the angles by moving point to the right or left
of d in a horizontal line d", d, d", perpendicular to a, d, point d will

page_text: 1
= d, b',
=
-
remain fixed and point & describe an are of a circle b", b' b, b', b", point
a taking up the corresponding positions a, a, a", which positions (as is
the case with all those intermediate thereof) are always in the line a, d.
For b, = a', b', = a", b", = d, b,
",
d, b",= d', b', d", b";
the angle a, d, d",= a', d, d",=a", d, d", cach being a right angle 5
contained within semicircles whose radius b, d,
= = 6", d, whose
diameters are a, d; a', d¹; a", d", all equal to one another.
-
b', d,
By employing a parallel motion arrangement similar to that above
indicated the supply of steam to the cylinder may be cut off as soon as
the foot is placed on the ground, whilst the jolting is prevented which 1
would inevitably occur if the foot H did not move (relatively to its
centro of oscillation) in a horizontal line.
To produce the alternate to-and-fro motion of the two legs the
following arrangement is employed, reference being had to Figure 6:
m and n are connecting rods jointed to the two legs C", C", at b; X and 1
X' are two horizontal rock shafts mounted in bearings on the frame J in
the position shown; X, o, and X', o', levers fixed on shafts X, X', and
jointed to rods m, n, respectively; X, r, X', 7, are two other levers
mounted on the same shafts, and jointed to a connecting rod, r¹. Now
if the shaft X be turned by the connecting rod X" in the direction of 2
the arrow, the rod m and consequently the leg to which it is connected
will be moved in the direction of t, and the lever X, i, the rod r,, lever
X', ', will all be moved towards (". The lever X', o¹, receiving motion
from shaft X will turn towards , and the rod n will consequently carry
with it the corresponding leg towards . Thus one of the legs will 2
move in one direction, and the other in the opposite direction. The fore
and rear under carriages or swivelling frames are connected by the
piston rod of the propelling I' and two connecting rods X", which are
each jointed to a crosshead J' fixed at either extremity of the said piston
rod which passes through both ends of the cylinder. The rods X" are 3
connected to levers equal in length to o, X, and o', X', fixed to the
middle of shaft X, the connections being by double or universal joints, to
permit of the vertical motion imparted by the levers of shaft X and of
the swivelling of the frame, shafts X and X' being placed at a certain
distance in front of a vertical line passing through the centre of the 3
swivelling frames. The mid-portions of the shafts X, at which are fixed
the levers attached to the principal connecting rods, describe arcs of
circles in a horizontal plane of a radius equal to their distance from the

page_text: | pivot of the swivelling frames when the driver turns the engine; the said
connecting rods therefore incline themselves the more the smaller is the
radius of the curve in which they move. The above variations of
position are to be considered in determining the relative positions of
the propelling feet.
Passing next to a consideration of the machinery employed for driving
the propellers, I would first point out as a feature of this machine that
the steam is caused to act directly on the organs of traction, through
levers having only a limited motion, and the speed of which consequently
varies to but a slight degree. A second feature consists in the method
of producing in the engine the forward, backward, and retarding action,
and of regulating the steam supply with a view to economy. The
propelling engine proper consists of a cylinder L', disposed horizontally
beneath the centre of the framing. The piston rod passes through both
ends of the cylinder, and is attached at each end to a crosshead J' moving
in guides K'. These crossheads are jointed to the long connecting rods
X" for operating the propellers as before described. All the intermediato
levers between the connecting rods and the propeller legs being equal,
the stroke of the piston is equal to the movement of the point at which
the power is applied. This point is about midlength of the propelling
leg, and the piston stroke is thus equal to one-half the distance traversed
by the propeller.
The steam distribution may be classed under two principal heads, viz.,
that employed for producing adhesion and raising the feet, and that for
propelling and for retarding (contre vapeur). These two distributions
combined serve for the following purposes, viz., for running forwards,
running backwards, retarding when moving ahead or when moving back-
wards by reversing the steam (contre vapeur). Previous to describing
cach of these operations, I will explain the principal parts composing
the steam distribution generally. Beneath one of the crossheads J' of
the propelling piston is fixed a sort of cam I whose function corresponds
to that of an eccentric. This cam operates a horizontal bell crank M',
connected at N¹ to a piston working in a cylinder O', by which the
whole of the parts which control the general distribution of the steam
are operated. The area of this piston is such that it operates the whole
of these parts at the same moment, and in order that the propelling
piston shall not strike against the ends of the cylinder, sufficient lead

page_text: is given in order that the admission ports may be full open when the
piston reaches the end of its stroke. To this piston rod a rod P¹ is
jointed at one end, and at the other a lever Q keyed on a rock shaft R',
which therefore receives a reciprocating movement corresponding to
that of the propelling piston. The two pairs of adhesion cylinders S', S',
and T¹, T, are cach cast in one piece and are open at the lower ends.
Steam is supplied thereto much in the usual manner, the supply and
exhaust being however so controlled that the descent of the one foot is
made more rapidly than the rise of the other so as to prevent jolting.
The small compensating cylinder Z' is kept in constant communication
with the boiler by means of a branch from the steam pipe before it
enters valve box U¹. The steam supply to both pairs of adhesion
cylinders is controlled by means of a rod placed above the foot plate, and
connected to an oscillating lever V'mounted on the framing. This lover
is connected at its lower end by rod A" to the general steam distributing
mechanism of the machine by the following intermediate parts :-At one
end of rock shaft R' a link B³ is fixed at the middle of its length.
This link is curved to a radius equal to the rod A³, which latter is
attached to a slide similar to that of a Stephenson link, so that it may
travel the whole length of link B³ either above or below the rock shaft R',
it being adjusted in position by the driver by means of a reversing screw
C³, similar to that of a locomotive. Supposing the rod to be at the
middle of the link B' which corresponds with the centre of the shaft, it
is evident that there will be no movement of the rod (the slide valves
being also in their mid-position), and the steam on being admitted to the
compensating cylinders will lift the four propelling feet, but will not
enter either of the adhesion cylinders, and consequently the fect will
not be lowered on to the ground. Under these circumstances the
machine would not progress even should the propelling mechanism
continue in motion. If by the aid of hand wheel C³ the rod be moved
to one end of the link (with the propelling mechanism in work) the
valves will be operated, and the steam will put in action one or other of
the feet according to the cylinder into which it is admitted. The lower
part of the link is used for the forward and the upper part for the back-
ward movement, as the feet move inversely to each other; thus, if the
first foot which is depressed carries the engine forward, the other foot
which is raised moves in the opposite direction, therefore by reversing
the admission to the adhesion cylinders, the latter foot will receive the
pressure and move the engine backwards.

page_text: The mechanism for governing the steam distribution to the propelling
engines consists of a special slide valve receiving motion from the rock
shaft R' above referred to by the aid of a connecting rod and link similar
to those before described for the adhesion cylinders, but placed at the
opposite end of the rock shaft. The propulsion of the machine is
controlled by means of a second reversing screw D³ placed on the other
side of the fire-box to the one before mentioned; and in this case also
the mid-position of the link corresponds to a similar position of the slide
valve, and the steam being thus cut off from the propelling cylinders the
motion of the vehicle will be arrested, whether the steam enters the
adhesion cylinders or not. The lower part of the link corresponds to
the direct action of the steam, which is admitted as in ordinary on the
one side of the piston when at the end of its course at the same time
that the steam contained at the opposite side is exhausted. In order
to retard the engine by reversing the action of the steam (contre
vapeur) when descending a steep incline, for example where it would
otherwise be necessary to employ brakes to moderate the speed (the
valve rod being at the bottom end of the link), the driver by turning
the reversing screw brings the rod to the extreme opposite position, and
alters the position of the valve so as to put that end of the cylinder at
which the piston is in communication with the atmosphere instead of
the steam chest and vice versa, steam being admitted on the opposite
side of the piston so as to fill the whole capacity of the cylinder. The
piston will thus have a certain amount of resistance to overcome in
making its stroke; and if the engine (carried forward by its acquired.
momentum) is moving at a sufficient speed the piston will drive back
the steam into the boiler, while on its opposite side the cylinder would
fill with air from the exhaust pipe. This air would be cold if the pipe
opens to the external atmosphere, or charged with cinders should the
pipe open into the chimney; and, to prevent the evil consequences
arising in either case, I employ the Invention of Mr. Lechatellier, which
consists in injecting a mixture of steam and hot water at the commence-
ment of the exhaust when working for retardation as above explained;
and to still further prevent the entrance of cinders I make the exhaust
pipe of the propelling cylinders open outside the chimney, the draft
being created by the exhaust steam from the adhesion cylinders, which
is led into the chimney.

page_text: 1st, as regards the steam distribution of the adhesion cylinders. Sup-
posing the valve rod to be in the middle of the link, and the valves also
in their mid-position, by gradually moving the rod towards the end of
the link the valve will be moved to a corresponding extent, and uncover
the induction port after the centre of the slide of the valve rod shall have
moved a certain distance from the centre of the link corresponding to
the top of the slide valve.
If the position of the slide on the link be known the degree of opening
of the ports may be readily ascertained, and the amount of steam
employed regulated to reduce the adhesion for light loads, and increase
it in the contrary case. The distribution of steam to the propelling
cylinders is effected in a similar manner to that for producing the
adhesion, while in reversing the steam it is unnecessary (more especially
in the case of slight inclines) to bring the slide to the extreme
position, so that only just the amount of steam required for obtaining
the desired resistance need be introduced; moreover, as there is less
lap at the exhaust than at the admission the exhaust port will always
be open to a greater extent, and the steam may thus be cut off entirely,
only using the mixture injected as the resisting agent in retarding the
engine.
Each of the steam cylinders, whether for propulsion or adhesion, is
provided with safety valves, and purge cocks are placed where required.
Brakes of special construction are also provided to aid in stopping or
checking the motion of the engine, said brakes being mounted beneath
the framework on either side. The brakes consist of iron skids to bear
on the ground mounted on one arm of a bell-crank lever pivoted to
move vertically, the other arm of which lever is acted on by a screw
and hand wheel placed within reach of the driver. Each brake is made
double, so that it may be applied whether the engine moves forward or
backward. For this purpose each consists of two skids mounted on a kind
of inverted T piece, that which acts in the forward movement of the
engine being disposed at the rear extremity, and the other at the
opposite end, so that the resistance is always in the nature of a'tensional
strain on the brake lever, and jarring is thereby prevented.
In order further to improve the action of the brakes I make the lever
0x3
of stool of good
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по
to ensure
coxtain amount
of

page_text: The boiler for supplying steam to the engine is composed,―
1st, of a cylindrical vertical fire-box, the bottom of the ash-pit having
two lateral openings for discharging the residues of combustion beyond
the foot plate.
2ndly, of a horizontal tubular boiler similar to that of a locomotive.
The tubular body is composed of a truncated cone, whose base is of
such diameter and fixed to the fire-box in such manner that even when
on steep inclines the top surface of the boiler will incline downwards
from back to front, in order to permit of the steam produced at the
front end of the boiler passing freely to the steam space. The boiler is
provided with the usual safety apparatus used in locomotives and with
regulating valves for admitting steam into the propelling and adhesion
cylinders.
A Giffard's injector is used for feeding the boiler when not at work,
and a feed pump, driven from the second crosshead of the propelling
engine, for keeping up a constant supply when the engine is in motion.
As the adhesion cylinders S', S', T', T', move with the swivelling frames,
special provision is made in the construction and arrangement of the
tubes by which the distribution of the steam thereto is effected. For
example, the steam pipe leads from the dome of the boiler and branches
off towards cither end along the barrel of the boiler at E, the branches
terminating short of the extreme limit of motion of the adhesion
cylinders. The pipe is a fixture on the boiler and water tanks as far
as F³, and is then connected to the cylinder by a series of jointed pipes
composed of a fixed elbow F on the end of the pipe which extends
downwards in a vertical direction. To this is pivoted an elbow G³ as
shown, carrying a similar clbow H connected to a fourth part I",
suitable stuffing boxes being provided at the joints. The centres of
the vertical parts are so arranged that viewed horizontally the whole
forms an angle whose apex is at the centre of the stuffing boxes con-
necting the intermediate movable portions, and which angle is reduced
about 30 degrees when the swivelling frame is inclined to a maximum.
extent towards the pipe, and increased to about 125 degrees when it
inclines in the contrary direction. The steam pipe is then continued
around the cylinder with which it is cast and opens into the valve-box.
In order to keep the joints of the stuffing boxes always steam-tight I
introduce vertical bolts into the interior of the pipes, forming ties which

page_text: permit of the rotation of the parts, the heads of said bolts being counter-
suuk, while all leakage is prevented by the use of plugs. The steam
supply pipe of the forward cylinder is similarly arranged.
The exhaust pipes are similar to the steam pipes, except that the
jointed pipes are of larger diameter, and one pipe common to each is {
employed fixed. on one of the water tanks and extending along the
boiler, where the branches meet in a single channel opening into the
chimney. The steam supply pipe of the propelling engine passes direct
from the steam dome to the valve box. A separate connection J' is
provided on the principal steam chest for supplying steam to the valve ]
box of the small piston used for regulating the general steam distributing
apparatus, the exhaust pipe of which connects with the principal
exhaust pipe K³ from the propelling engine, which passes horizontally
under the cylinder, and then rising passes through the water tank and so
to the front end of the boiler alongside the chimney.
Having described the nature of the Invention and the manner of
performing the same, I would have it understood that I may increase or
reduce the number of the carrying wheels, as for example one may be
placed on each side of the engine, the centre of gravity being midway
between them, or the number may be increased by adding a guide wheel
to the fore swivelling frame, and that what I claim as the Invention to
be protected by the herein-before in part recited Letters Patent is,-
1st. The arrangement herein-before described consisting in the
employment of propelling legs and feet substantially in the manner
set forth, as organs of locomotion in traction engines for use on common
roads or for field work.
2ndly. The application and employment of steam for obtaining the
adhesion of the propelling feet, whereby the weight of the apparatus is
rendered available for the purpose without other aid, substantially as
specified.
3rdly. The general arrangement of the two swivelling frames, each
moving to an equal extent for turning curves, as also the arrangement of
racks and pinions in connection with the same, substantially as described
and shown in the Drawings.

page_text: 13thly. The particular arrangement of brakes bearing on the ground
herein-before described.
In witness whereof, I, the said Alexander Melville Clark, have
hereunto set my hand and scal, this Twenty-third day of April,
in the year of our Lord One thousand eight hundred and
seventy-two.
A. M. CLARK. (L.S.)