IMPROVEMENTS IN MACHINERY AND LOCOMOTIVE ENGINES FOR DRIVING TRAM CARS AND OTHER ROAD VEHICLES, PARTS OF WHICH 2 33
Year: 1872

page_text: LETTERS PATENT to Henry Percy Holt, of Royal Insurance Buildings,
Leeds, in the County of York, Civil and Consulting Engineer, for
the Invention of "IMPROVEMENTS IN MACHINERY AND LOCOMOTIVE ENGINES
FOR DRIVING TRAM CARS AND OTHER ROAD VEHICLES, PARTS OF WHICH
2
33
PROVISIONAL SPECIFICATION left by the said Henry Percy Holt at
the Office of the Commissioners of Patents, with his Petition, on
the 7th June 1872.
I, HENRY PERCY HOLT, of Royal Insurance Buildings, Leeds, in the
County of York, Civil and Consulting Engineer, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN MACHINERY AND
LOCOMOTIVE ENGINES FOR DRIVING TRAM CARS AND OTHER ROAD VEHICLES, PARTS
OF WHICH IMPROVEMENTS ARE APPLICABLE TO OTHER STEAM ENGINES," to be as
follows

page_text: and other reciprocating parts are attached to a frame in common with
the car on the same wheels.
Secondly. To utilize a portion of the weight of the tram car and
passengers, and give a better bite to an engine on a separate frame and
wheels than would result from its own independent weight, obtaining by
the use of my appliances and arrangements sufficient tractive power with
an engine of about half the ordinary weight.
Thirdly. To provide a mode of applying steam power to existing tram
cars at a comparatively nominal cost of alteration.
I carry out my Invention as applied to tram cars in the following
manner: I use an improved light four-wheeled coupled locomotive
driven in the ordinary manner with the exception that the cylinders
are mounted on a radius bar for the sake of accomodating the working
parts of the engine to the depression of the springs, consequent on the
varying load wheu a portion of the weight of the tram car is thrown
upon the driving wheels, which weight I regulate according to the
load. At one end of the engine on the centre line and in the same
vertical plane as the driving axle I hinge vertically one end of a
rigid bar which is free to move horizontally towards either side, play
being allowed for it to slide vertically on the said hinge when lifted
by the machinery I provide for that purpose, as herein-after described.
This bar is of sufficient length to leave clearance between the engine
and car for going over curves and also to reach under the car to a
point midway or thereabouts between the four wheels of the car where
the bar is connected by a suitable fastening to enable it to transmit
a pushing or pulling as well as a lifting force from the engine to
the car.
This central fastening allows also a radial motion in con-
nection with the before named vertical hinge to the bar when passing
over curves. This bar is provided (in the first place) for transmitting
the required portion of weight from the tram car on to the driving
wheels of the engine, which is effected by actuating the lifting machinery
and thus sliding the hinge or engine end of the said bar vertically
upwards on the hinge. The engine end of the bar being thus raised and
the end of the said bar connected under the car being nearly retained in
its original position by the superabundant weight of the car the opposite
end of the engine frame is consequently raised partially or entirely off
the springs, as occasion may require, and the weight of this end of the
engine (including boiler, engines, and part of frame) together with

page_text: sufficient weight taken off the car wheels to counterbalance the same is
thrown on the driving wheels, thus making the whole weight of the
engines with nearly the same said weight of the engines (derived from
the car) added to it, which together is equal to about double the weight
of the engine available for giving bite or adhesion to the road.
My Invention as applied to ordinary road vehicles consists firstly of
using an engine or engines and boiler mounted on one pair of wheels,
which combination I designate the truck. The distribution of weight on
these wheels is such that the greater part of the weight of the engines
and boiler is on the after end of the truck, the fore end of the truck being
provided with a rigid bar connected to the vehicle between the centres
of the wheels as before explained for tram cars and which works nearly in
the same manner. The after end of the truck is provided with a sort of
"castor pulley" to retain the suberabundant weight when the truck is
disconnected from the vehicle. The truck thus used pushes the vehicle
which is steered by an arrangement of mechanism for adjusting the front
axle to any required horizontal angle as is at present accomplished by
the shafts or pole in vehicles drawn by horses.
And, secondly, this part of my Invention consists of the use of a coil
spring (similar to the hair spring of a watch) secured at one end to the
driving axle, and at the other end secured to a metal ring which takes
the place of the nave in the ordinary wheel, and in such a manner that
the axle forms the centre of the arrangement, having the spring coiled
several times loosely round it to allow of the necessary play, and situate
in the same vertical plane as the wheel. By this means I can attach
the driving axle to a rigid part of the engine and thus simplify the
machinery.
The second part of my Invention consists of a novel arrangement of
blast nozzles in the smoke box, whereby the objectionable noise
occasioned in obtaining the necessary draft for the boiler furnace is
much reduced and in some cases obviated. I use an ordinary conical
nozzle (which forms the centre of my arrangement) provided with an
internal conc, the position or height of which is regulated by an
apparatus controlled by the pressure of steam in the boiler, so that when
the pressure falls the cone is raised and the area of the annular space for
exhaust is reduced. In the same horizontal plane I arrange two hollow
ings of different diameters connected by suitable steam passages with
A 2

page_text: the blast pipe (below the central conical nozzle); the rings have narrow
annular apertures or closely pitched small holes set out in a circle on the
top side of each. The smaller of these two rings is of such diameter and
size and so arranged as to leave an annular air space all round between
the central conical nozzle and the exterior of its internal side or surface;
the larger of these two rings is of such diameter and size and so arranged
as to leave also an annular air space all round between the exterior of
the smaller ring and the exterior of its own internal side or surface;
Around this combination of jets I fix a "petticoat” or double coned ring,
bell mouthed at both ends, and of such diameter at the narrowest part as
to leave an annular air space all round between the exterior of the larger
ring aforesaid and such smallest diameter of "petticoat," all being fixed
in the same horizontal plane. This entire arrangement (consisting of
the "petticoat" and compliment of central nozzle and its two rings placed
as described) I fix in the smoke box at a suitable distance below the
I thus induce first
chimney end under the vertical centre line of same.
a current in the "petticoat," and the gases in this escaping induce a
secondary current in the chimney. By this means the "inducing
current" of steam or exhaust is brought into closer contact with the
products of combustion in the chimney than is effected by the ordinary
blast pipe and a greater velocity in the chimney is induced, consequently
there is a lower pressure of exhaust steam and less noise than usual.
When it is indispensable to have a perfectly silent exhaust I use (either
with or in lieu of the before-named arrangement of parts) a fan for the
purpose of inducing or increasing the draft or current in the smoke box
or chimney. This fan may be constructed either on the exhausting or
forcing principle, but in either case it must be so placed and used as to
increase what may be called the "chimney draft" or "current in
contradistinction to the previous methods of forcing the fire by in-
creasing the pressure of air under the same.
3
The fan may be driven by suitable bands from any convenient rotary
part of the engine, and I use in connection therewith a novel arrange-
ment for driving and varying the speed of the fan, whereby a
self-regulating action governed by the pressure in the boiler is obtained.
To accomplish this I use a pair of plane cones of similar or nearly
similar dimensions, the small end of one being placed opposite the large
end of the other, and vice versa. One of the said cones is connected

page_text: with the fan spindle, and the other with a rotary part of the engine; and
in order to vary the speed of the fan according to the requirements.
of the boiler I place a friction pulley with an elastic tire in the parallel
space between, and bearing on both the cones, which are so placed with
respect to one another that the friction pulley can be traversed endways
between the cones by any convenient adjusting apparatus worked by any
variation in the boiler pressure.
The velocity of the fan is entirely regulated by the position of the
friction pulley, which position depends upon the boiler pressure, for
example, should the pressure fall the friction pulley will be traversed by
the apparatus for the purpose towards the larger diameter of the cone
connected with the engine, and the smaller diameter of the cone con-
nected with the fan, thus increasing its velocity, and consequently the
draft; but should the pressure rise the friction pulley will be traversed
towards the other end of the cones and the opposite result will take
place; it is thus evident that the draft will be regulated according to
the requirements of the boiler. I provide in some cases means for
keeping the fan spindle and bearings cool by allowing the feed or other
water to flow through the spindle; I also utilize some of the heat given
off by the smoke box or other chimney passages to heat part of the air
supplied to the fire for combustion.
The third part of my Invention consists of diminishing friction in the
working parts as much as possible, and as pistons working in horizontal
cylinders bear on the lower side of the cylinder up to a horizontal chord
taken across the cylinder below the diameter, equal to about ths of
the diameter of the piston, I reduce the friction caused by this pressure
as low as possible by the introduction of a cushion of steam between the
parts so bearing. For this purpose, between the piston rings in this area
or portion of the piston bearing on the lower side of cylinder, I drill a
number of holes communicating with internal chambers formed in the
piston containing steam admitted through a small back pressure valve
from the cylinder, consequently steam of the maximum pressure in the
cylinder will be maintained in these chambers, and the sum of the areas
of the holes aforesaid must be so proportioned that with steam at this
pressure the cushions of steam acting through these holes shall be
capable of carrying about three-fourths the weight of the piston. I thus
take away in a great measure the friction caused by the weight of the
piston working on the lower side of the cylinder, and prevent the

page_text: cylinder from wearing oval. This improvement is applicable to all
horizontal engines.
The fourth part of my Invention consists of the application of chains
or other convenient equivalents in communication (from either end of
the cars) with the regulator and bydraulic mechanism, which I provide
for working the reversing gear and retaining the same in any notch for
expansion that the driver may desire, and to further place under the
control of the driver the entire command of the engines and car.
In some cases I fix pulleys with elastic tires at each end of the car
and engines, which on approaching the points and crossings can be let 1
down by the driver to bite on the road, and being directed by him at
any angle to the centre line of the car by improved machinery the bias
to the car and engine is obtained to the necessary extent and direction
to cause the car and engines to follow the desired road.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Henry Percy Holt in the Great Seal Patent Office
on the 7th December 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
PERCY HOLT, of Royal Insurance Buildings, Leeds, in the County of
York, Civil and Consulting Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventh day of June, in the year of
our Lord One thousand eight hundred and seventy-two, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Henry Percy Holt, Her special
license that I, the said Henry Percy Holt, my executors, adminis-
trators, and assigns, or such others as I, the said Henry Percy Holt,
my executors, administrators, and assigns, should at any time agrec
with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make,
usc, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for "IM-
PROVEMENTS IN MACHINERY AND LOCOMOTIVE ENGINES FOR DRIVING TRAM CARS

page_text: hcrcin-after described. This bar is of sufficient length to leave clearance
between the engine and car for going over curves, and also to reach
under the car to a point midway or thereabouts between the four wheels
of the car, where the bar is connected by a suitable fastening, to enable
it to transmit a pushing or pulling as well as a lifting force from the
engine to the car. This central fastening allows also a radial motion (in
connection with the before-named vertical hinge) to the bar when
passing over curves. This bar is provided (in the first place) for trans-
mitting the required portion of weight from the tram car on to the
driving wheels of the engine, which is effected by actuating the lifting
mechanism and thus sliding the hinge or engine end of the said bar
vertically upwards on the hinge. The engine end of the bar being thus
raised, and the end of the said bar connected under the car being nearly
retained in its original position by the superabundant weight of the car,
the opposite end of the engine frame is consequently raised partially or
entirely off the springs, as occasion may require, and the weight of this
end of the engine (including boiler engines and part of the frame) to-
gether with sufficient weight taken off the car to counterbalance the
same is thrown on the driving wheels, thus making the whole weight of
the engines with nearly the same said weight of the engines (derived
from the car) added to it, which together is equal to about double thic
weight of the engine (available for giving bite or adhesion to the road).
My Invention as applied to ordinary road vehicles, consists firstly, of
using an engine or engines and boiler mounted on one pair of wheels,
which combination I designate the truck. The distribution of weight
on these wheels is such that the greater part of the weight of the engines
and boiler is on the after end of the truck, the fore end of the truck
being provided with a rigid bar connected to the vehicle between the
centres of the wheels, as before explained for tram cars, and which works
nearly in the same manner. The after end of the truck is provided with
a sort of "castor pulley" to sustain the superabundant weight when the
truck is disconnected from the vehicle. The truck thus used pushes the
vehicle, which is steered by an arrangement of mechanism for adjusting
the front axle to any required horizontal angle, as is at present accom-
plished by the shafts or pole in vehicles drawn by horses.
And secondly, this part of my Invention consists of the use of a coil

page_text: driving axle and at the other end secured to a metal ring which takes
the place of the nave in the ordinary wheel, and in such a manner that
the axle forms the centre of the arrangement, having the spring coiled
several times loosely round it to allow the necessary play, and situate
in the same vertical plane as the wheel. By this means I can attach the
driving axle to a rigid part of the engine and thus simplify the
hinau
driving axle and at the other end secured to a metal ring which takes
the place of the nave in the ordinary wheel, and in such a manner that
the axle forms the centre of the arrangement, having the spring coiled
several times loosely round it to allow the necessary play, and situate
in the same vertical plane as the wheel. By this means I can attach the
driving axle to a rigid part of the engine and thus simplify the
machinery
The second part of my Invention consists of a novel arrangement of
blast nozzles situated in the smoke box, whereby the objectionable noise
occasioned in obtaining the necessary draft for the boiler furnace is
much reduced, and in some cases obviated. I use an ordinary conical
nozzle (which forms the centre of my arrangement) provided with an
internal cone, the position or height of which is regulated by an
apparatus controlled by the pressure of steam in the boiler, so that when
the pressure falls the cone is raised and the area of the annular space for
exhaust is reduced. In the same horizontal plane I arrange two hollow
rings of different diameters, connected by suitable steam passages with
the blast pipe (below the central conical nozzle); the rings have narrow
annular apertures or closely pitched small holes set out in a circle on the
top side of each. The smaller of these two rings is of such diameter and
size, and so arranged, as to leave an annular air space all round between
the central conical nozzle and the exterior of its internal side or surface;
the larger of these two rings is of such diameter and size and so arranged
as to leave also an annular air space all round between the exterior of
the smaller ring and the exterior of its own internal side or surface.
Around this combination of jets I fix what I designate a "petticoat,”.
which consists of a double coned ring or casing, bell-mouthed at both
ends, and of such diameter at the narrowest part as to leave an annular
air space all round between the exterior of the larger ring aforesaid and
such smallest diameter of the "petticoat," all being fixed in the same
horizontal plane. This entire arrangement (consisting of the "petti-
coat" and complement of central nozzle and its two rings, placed as
described) I fix in the smoke box, at a suitable distance below the
chimney end, under the vertical centre line of same. I thus induce, first
a current in the "petticoat," and the gases in this escaping induce a
secondary current in the chimney. By this means the " inducing
current of steam or exhaust is brought into closer contact with the
products of combustion in the chimney than is effected by the ordinary
"3

page_text: blast pipe, whereby a greater velocity in the chimney is induced, con-
sequently there is a lower pressure of exhaust steam and less noise than
usual.
Where it is indispensible to have a perfectly silent exhaust I usc
(either with or in lieu of the before-named arrangement of parts) a fan
for the purpose of inducing or increasing the draught or current in the
smoke box or chimney. This fan may be constructed cither on the
exhausting or forcing principle, but in either case it must be so placed
and used as to increase what may be called the "chimney draught” or
'current,” in contradistinction to the previous methods of forcing the
fire by increasing the pressure of air under the same.
"
The fan may be driven by suitable bands from any convenient rotary
part of the engine, and I use in connection therewith a novel arrangement
for driving and varying the speed of the fan, whereby a self regulating
action governed by the pressure in the boiler is obtained. To accom-
plish this I use a pair of plane cones of similar or nearly similar
dimensions, the smaller end of one being placed opposite the larger end
of the other, and vice versa. One of the said cones is connected with
the fan spindle, and the other with a rotary part of the engine; and in
order to vary the speed of the fan according to the requirements of the
boiler I place a friction pulley with an clastic tire in the parallel space
between and bearing on both the cones, which are so placed with respect
to one another that the friction pulley can be traversed endways between
the concs by any convenient adjusting apparatus worked by any variation
in the boiler pressure. The velocity of the fan is entirely regulated by
the position of the friction pulley, which position depends upon the
boiler pressure, for example, should the pressure fall the friction pulley
will be traversed by the apparatus for the purpose towards the larger
diameter of the cone connected with the engine, and the smaller diameter
of the cone connected with the fan, thus increasing its velocity, and con-
sequently the draught; but should the pressure rise the friction pulley
will be traversed towards the other end of the cones, and the opposite
result will take place. It is thus evident that the draught will be
regulated according to the requirements of the boiler.

page_text: also utilize some of the heat given off by the smoke box or other chimney
passages to heat part of the air supplied to the fire for combustion.
The third part of my Invention consists of diminishing friction in the
working parts as much as possible, and as pistons working in horizontal
cylinders bear on the lower side of cylinders up to a horizontal chord
taken across the cylinder below the diameter equal to about th of the
dameter of the piston. I reduce the friction caused by this pressure as
low as possible by the introduction of a cushion of steam between the
parts so bearing. For this purpose between the piston rings in this area
or portion of the piston bearing on the lower side of cylinder I drill a
number of holes communicating with internal chambers formed in the
piston containing steam, admitted thro' a small back pressure valve from
the cylinder, consequently steam of the maximum pressure in the cylinder
will be maintained in these chambers, and the sum of the areas of the
holes aforesaid must be so proportioned that with steam at this pressure
the cushions of steam acting through these holes shall be capable of
carrying about three-fourths the weight of the piston. I thus take away
in a great measure the friction caused by the weight of the piston work-
ing in the lower side of the cylinder, and prevent the cylinder from
wearing oval. This improvement is applicable to all horizontal engines.
The fourth part of my Invention consists of the application of chains
or other convenient equivalents in communication (from either end of
the cars) with the regulator and hydraulic mechanism, which I provide
for working the reversing gear and retaining the same, and any notch
for expansion that the driver may desire, and to further place under the
control of the driver the entire command of the engines and car.
In some cases I fix pulleys with elastic tires at each end of the cars
and engines which, on approaching the points and crossings, can be let
down by the driver to bite on the road, and being directed by him at any
angle to the centre line of the car by improved machinery the bias to
the car and engine is obtained to the necessary extent and direction to
cause the car and engines to follow the desired road.
And in order that my said Invention may be clearly understood I
shall now proceed more particularly to describe the same, and for that
purpose shall refer to the accompanying Sheets of Drawings, in which

page_text: Figure 1, Sheet 1, of my Drawings represents a side elevation of a
portion of an ordinary tramway car with my improved locomotive engine
(in longitudinal section) attached thereto; Figure 2 is a corresponding
plan of the same, partly in section; Figure 3 is a front elevation and
partial vertical section of the engine; and Figure 4 is a back elevation
of the same.
เ
a, a, is the body of the car; b, pin coupling, having a pulley c on the
face of it which runs down the channel e, e, when coupling or uncoupling.
This channel is fixed to the under side of the framing of the car, and
forms a guide for the pin b. d, d, bars or bolts to secure pin coupling b
in its place when run in from either end. The coupling pin b is carried
in front end of the leverf connected to engine truck, by means of which
more bite can be given to the driving wheels m, m; g, g, are pivots on
which the lever f can partially turn horizontally and slide vertically;
h, h, brackets carrying the pivots g, g; i, strong bracket carrying the
pulley, on which the hydraulic cylinder k, k, (having an incline on its
upper exterior side) runs. The upper pulley runs on this incline, and
consequently when water under pressure is admitted thro' the piston
and rod j, j, j, into either end of the cylinder (which cylinder is free to
slide horizontally on the rod j and lower pulley ), it will be moved into
any desired position in its travel, and consequently the requisite amount
of lift can be given to the upper pivot g, and by this means the amount
of bite of driving wheels m, m, is regulated as may be necessary during
the journey of the car. is a chain pulley on driving axle imparting
motion by pitched chain to smaller chain pulley o on the axle of one of
the cones p, p, which work in bearings in engine framing q, q; r, steel
coil spring; s, s, boiler; t, t, t, ash pan and heated air passages; u, U,
fire-doors and deflectors for supplying heated air to top of fire; v, v, v, v,
uptake and heating stoves for intake air; x, x, x, x, narrow passages
thro' which the air for supporting combustion enters, passing between
the heating stoves on its way to the furnace; z, exhaust steam nozzle of
large bore, so as not to throttle the exhaust, which exhaust is used to
partially heat the air in the passages t, t, and ash pan on its way to the
furnace; 10, 20, exhausting fan to increase the draft; y, band pulley
and spindle for driving the fan.

page_text: Figures 5, 6, and 7, Sheet 2, of my Drawings represent a side clevation,
end view, and plan respectively of my improvements, as applied to the
driving of an ordinary road vehicle. a, a, is the body of an ordinary
road vehicle provided with a hand wheel 6 for steering. This hand
wheel is fixed on the upper end of a vertical spindle, which works in
bearings attached to any convenient part of the vehicle, and provided at
its lower end with a worm, which drives the worm wheel and chain
pulley c keyed on an axle working in bearings in the bottom of the
vehicle. The chain wheel c communicates motion by the chain e, e, to
the pulleys d, d, which change and transmit the motion to the leading
axle for steering the vehicle; fis a ball-and-socket joint by which the
engine is coupled to the vehicle, the socket being secured by means of
the bracket y to the body of vehicle; h is a cottar, by withdrawing which
the lower side of the socket (which is hinged) can be let down, and by
withdrawing the ball the engine truck is disconnected; i, i, framing of
engine; j,j, driving wheels; k, coil spring secured to the interior of
wheel and also to the axle 1; m, m, boiler; n, n, cylinders and steam
chests; o, o, circular discs and band pulleys; q, friction pulley with
elastic tire running between the discs o, o; the position of this friction
pulley is regulated by the pressure in the boiler thro' the medium of the
cylinder piston and spiral spring r, the upper side of the piston being in
communication with the boiler; p, p, band pulley on spindle of exhausting
fan in the chimney, the speed of which exhausting fan is regulated
by. the position of friction pulley q between the circular discs 0,0; 8, s, an
adjusting screw spindle supported in bearings u, u, of which the lower
one is squared to prevent the spindle from rotating whilst being adjusted;
t, t, chain wheel with internally screwed boss working on screws 8, 8, by
means of which the screw spindle, which carries at its lower end the coil
spring trailing wheel to can be regulated during the journey, and by this
means the bite on the driving wheels j, j, is increased or reduced as may
be found necessary or desirable by communicating weight from the
vehicle. The trailing wheel w is free to swivel in the socket to follow
in the requisite direction. The wheel w is also employed to support the
weight of the hind part of the engine truck when disconnected from the
vehicle, and is adjusted by means of the chain wheel and screw to
accomplish the uncoupling.
0

page_text: the axle; b, crank and pin; c, c, c, steel coil spring, secured at one end
to the axle a, the opposite end being secured by bolts and nuts d, d, to an
interior metal ring bearing against wood filling pieces e, e, secured by
means of bolts and nuts thro' side plates to the tire which may be
either flanged or plain.
The second part of my Invention, which consists of a novel arrange-
ment of blast nozzles in the smoke box, is represented in cross section
and plan by Figures 10 and 11 respectively, on Sheet 3 of my Drawings.
a is the exhaust pipe loading from the cylinder, and which conveys the
exhaust steam into a chamber provided with the cone b, the position of
which is regulated by piston c and spring d, the under side of piston c
being in communication with the boiler; hence should the pressure in
boiler rise, the cone will also rise and enlarge the area of central
exhaust nozzle g, and vice versa, should the opposite take place; e, e, e, e,
are annular nozzles, thro' which the exhaust steam issues at a greater
velocity when checked at by the cone b; h, petticoat or double conical
casing which surrounds the nozzles g and e; i, chimney base.
I
Figures 12 and 13, Sheet 4, represent a side elevation and plan
respectively of my improved arrangement of apparatus for driving and
regulating the speed of the exhausting fan herein-before referred to.
a is the axle of the driving wheels of the engine, upon which is keyed
the chain pulley b driving by means of the pitched chain c the pinion d;
e, e, are cones, between which works the friction pulley f with elastic
tire; g, spiral spring; h, cylinder and piston connected with the boiler
by means of the pipe o; i, band pulley, driving by means of band the
smaller pulley k on fan spindle m; j, j, angle pulleys; 1, thrust block;
m, exhausting fan. It will be seen that the speed of the fan is by means
of this mechanism regulated by the pressure in the boiler.
The third part of my Invention is shewn by Figures 14, 15, and 16,
which represent longitudinal and cross sections and part elevation
respectively, in which a is a portion of piston rod; b is the arc by the
piston setting down on the low side of cylinder c, c; d, d, steam chambers;
c, e, back pressure valve to admit steam from the cylinder, which is
assisted by a spiral spring; f.f. holes drilled to form a cushion of steam
to carry piston for diminishing friction and wear and tear; the number
and size of these holes depend upon the working pressure of steam and

page_text: weight of the piston, and are proportioned in such a manner that the
pressure acting thro' their total area is equal to about three-fourths
the weight of the piston; 9, 9, piston rings, which can be set out by any
desirable method; h, h, screws for fastening junk rings i, i; j,j, passage
communicating with atmosphere to maintain the space b at the atmo-
spheric pressure, and also to indicate any leakage should the piston get
out of order.
The fourth part of my Invention is represented by Figures No. 17
and 18, on Sheet 2 of my Drawings, which are front elevation and plan
respectively. a, a, is a hydraulic cylinder with piston and trunk working
through stuffing boxes at each end; b is a three-way plug cock for con-
trolling supply of water from donkey pump or boiler through piping
connected to the boss e. This cock is worked by chains ƒƒƒ, through
medium of the lever c; d, d, spiral springs for bringing back and
retaining the lever c in its central position when unbiassed by the
chains fff, which are carried down the centre of car in such a manner
that they are under the control of the conductor from either end of the
car; 1,,, chain pulleys for guiding and altering the direction of
chains fff; 9, 9, guides between which the dic and catch m slide.
The catch mis held down in any notch opposite in the segment / by
means of a spiral spring of about the same strength as d, d, and is lifted
out of this notch by the chain f, owing to the position in which it is
acted upon before the resistance of the springs d, d, is overcome and
water admitted into the cylinder; h, notched segment, into which the
catch m slides; i, centre pin, from which the segment h oscillates;
j, connecting rod for transmitting the power from piston a; k, reversing
rod.
Having now described and particularly ascertained and shewn the
nature of my said Invention, and the manner in which the saine is or
may be used or carried into effect, I wish it to be understood that I do
not confine or restrict myself to the precise details which I have shewn,
described, or referred to, as many modifications and variations may be
made therefrom without deviating from the principles or main features
of the said Invention; but what I consider to be novel and original
and therefore claim as the Invention secured to me by the herein-before
in part recited Letters Patent is,-
First. The peculiar arrangements herein-before described and shown,

page_text: under the control of the conductor, as herein-before described and shewn
by the Drawings.
In witness whereof, I, the said Henry Percy Holt, have hereunto
set my hand and seal, this Fifth day of December, in the year of
our Lord One thousand eight hundred and seventy-two.
Witness,
CHARLES BARLOW,
Patent Agent,
HENRY PERCY HOLT. (L.S.)
23, Southampton Buildings,
Chancery Lane.