IMPROVEMENTS IN AND CONNECTED WITH STEAM TRAMWAY AND OTHER LOCOMOTIVES
Year: 1873

page_text: LETTERS PATENT to Leonard Jennett Todd, of Leith, in the County
of Mid Lothian, North Britain, Engineer, for the Invention of
"IMPROVEMENTS IN AND
CONNECTED WITH STEAM TRAMWAY AND OTHER
LOCOMOTIVES."
Scaled the 7th October 1873, and dated the 17th April 1873.
PROVISIONAL SPECIFICATION left by the said Leonard Jennett
Todd at the Office of the Commissioners of Patents, with his
Petition, on the 17th April 1873.
I, LEONARD JENNETT TODD, of Leith, in the County of Mid Lothian,
North Britain, Engineer, do hereby declare the nature of the said In-
vention for "IMPROVEMENTS IN AND CONNECTED WITH STEAM TRAMWAY AND
OTHER LOCOMOTIVES," to be as follows, that is to say:
This Invention comprises various improvements in and connected with
tramway and other locomotives, and in carrying it out I first make a
strong rectangular frame, to the under side of which are attached the
A

page_text: axle boxes for a main driving axle and also the horn plates and axle
boxes for a pair of small leading wheels. The drivers are large in
diameter, and for this reason and also because of the comparatively slow
rate of speed at which these engines run, I judge it both cheaper to
make and more economical in maintenance to run the driving axle 5
without bearing springs, although springs may be used if desired.
The leading axle I fit with ordinary sliding axle boxes and bearing
springs, thus making the foot plate easy for the attendants, and also
making sure that the four wheels shall at all times have a proper
bearing upon the rails. These springs allow the small wheels to pass. ]
the points and crossings, without violent jolting, and by virtue of their
large diameter the driving wheels also pass with the necessary smooth-
ness over those parts. When the drivers are used without bearing
springs I prefer to make them with solid wood or paper discs, around
which are secured the necessary flanged tires. The leading wheels are ]
made of chilled cast-iron discs, or of other make with flanged tires.
On the main frame I place a locomotive boiler, with the fire-box next
to the small leading wheels, and the barrel over the main axle. On the
top of the boiler I place the cylinder or cylinders, and connect the crank
shaft to the main axle by a pinion and wheel. The pinion I prefer to
make with a movable clutch for disconnecting, to allow the feed pumps
to be worked when the locomotive is standing.
The engine motion on top of the boiler I cover with a case, the top
of which is shaped like the top of an ordinary locomotive boiler. Placing
the engine motion on top of the boiler of a tramway locomotive is of
importance in keeping the working parts perfectly free from dust and
dirt. The working parts are perfectly accessible by means of a door on
top of the casing. The cylinders being on top of the boiler also secures
an efficient discharge of the exhaust and any condensed or priming
water to the exhaust driven fan, and also from this fan a similarly
efficient discharge can then be readily made into the water tank.
The toothed wheels I prefer to make of cast steel, and as they are
each large in diameter the strain on their respective points of contact is
consequently light, and they thus wear well. These wheels are confined
in an air-tight case, and they are thus rendered practically noiseless.
The exhaust driven blowing fan I prefer to place in an intermediate
position vertically between the cylinders and the water tank.

page_text: The air discharge from the fan I sometimes cause to pass through a
surface condenser on its way to the close ash pan. Through one part of
this condenser I cause the exhaust steam from the bucket, Scotch tur-
bine, or turbine wheel, as it is variously called, to pass, where it is either
partially or wholly condensed, and is then discharged into the tank, or
otherwise disposed of. The amount of cooling surface in this condenser
may be varied according to requirements; it may in one case equal the
heating surface of the boiler, when the exhaust will be only partially
condensed, or it may have five or six times as much surface as the
boiler, when with plenty of cold air the exhaust will be entirely con-
densed. This air condenser has two advantages, first, it has some effect
in condensing the exhaust; and, secondly, it supplies the furnace with
a moderately hot blast. A few inches above the firc-bars I make a
series of openings, dispersed around the grate. These openings, extend
right through to the outer fire-box, and have any convenient means of
communication with the close ash pan. These openings or tuyeres may
cither discharge directly into the heart of the fire, or be above it, or be
placed some in each position according to circumstances. The advan-
tages of this arrangement are that it may be used as a smoke-consuming
apparatus, and it also materially assists the action of the fan, for if the
grate consists of ordinary solid fire-bars they, especially with a fan blast,
are liable to clinker, and thus prevent the air from freely reaching the
fire; but with the addition of these tuyeres above the bars the necessary
intensity of the fire can be maintained in a tolerable manner, even
though the grate be almost totally choked with clinkers or ashes. With
a square fire-box containing 3 or 4 square feet of surface 2 such tuyerc
holes, say 1½ inches in diameter, may be made on each side, making
8 tuyeres in all; the number and dimensions of them may, however, be
varied. Such tuyeres may be used with fans driven in any convenient
known way.
Again, for an engine having to work so continuously as a tramway
locomotive, they render it possible to do without a water grate. When

page_text: as required, and they also maintain a through circulation, as one end
can be made any reasonable distance above the other.
From the crank shaft, or by other means, I drive by preference 2
circulating feed pumps, the overflow of each of which is discharged into
the exhaust pipe from the bucket wheel to the water tank.
If each pump has a single-acting ram, and is driven from the crank
shaft, there will then be one discharge of water into the exhaust pipe for
every two beats of the exhaust steam, which is sufficient to almost
totally condense the exhaust so long as the water tank remains cold,
but it will of course gradually rise in temperature.
The pumps need not necessarily be feed pumps, but they can be con-
veniently arranged as such, when the action will be as follows:-When
running down hill, and using but little steam, one of the pumps will be
cut off from the exhaust pipe to feed the boiler; but the other will
mostly be left to discharge the tank water through the exhaust pipe, the
single pump being sufficient to condense the small quantity of steam
then being used; but on ascending an incline, when the greatest amount
of steam is passing through the cylinders, the feed will of course be cut
off from the boiler, and consequently the two pumps will then inter-
mittently discharge their full quantity of water into the exhaust pipe.
In my improved tramway locomotive then the exhaust steam from
the main cylinders is disposed of thus:-If the engine has an air con-
denser or injection into the exhaust pipe it is thereby partly condensed,
and in that state enters the water tank, from which any steam still
remaining uncondensed escapes gently by a wide pipe into the funnel,
where, being small in quantity, and of necessity quite free from priming
water, it becomes superheated, and passes off noiselessly as an invisible
form.
If thought proper and sufficient for certain kinds of work, then the
exhaust may be made to merely drive a blowing or other kind of fan,
and then enter the tank, where it is partly condensed, the remainder
escaping as before by a wide pipe into the funnel.
These arrangements are also applicable to all classes of tramway,
common road, and railway locomotives.
The combination of exhaust driven fans and surface air condensers,

page_text: grate, all already described, are also applicable to all classes of tramway,
common road, and railway locomotives. On one side of the boiler I
place the driver's seat, with the various handles conveniently arranged,
and on the other the fire-hole.
I prefer to run my improved tramway locomotives with the fire end
foremost, and consequently with the funnel next to the car. I also
prefer to make the cars with a roof over the outside passengers' seats,
when such are used, and I then make the funnel at least as high as the
top of this roof, so that the products of combustion readily escapo
without annoying outside passengers.
I connect the engine to the car by means of a long rigid bar which
passes below the flooring, and terminates as far back as will avoid any
chance of throwing the car off the rails when passing round curves. I
prefer this termination to be very near to the leading axle of the car,
and should not advise it to be much forward from that point. This bar
takes both the pull and thrust, and also allows the train to readily pass
round sharp curves; it also does not at all interfere with the vertical
rocking of the ends of the car at high speeds.
If more than one car are connected to an engine I also couple them
together by rigid bars arranged like that just described. Beneath the
centre of gravity of the engine I place a pillar with a movable foot, and
by lowering this foot at the end of a journey the entire engine can be
raised a short distance from the rails, and then be swung half round and
again deposited. This pillar and movable foot may be like a large screw
jack, or have hydraulic or other means of obtaining the necessary power
to lift the engine; but I prefer to make this apparatus as follows:-
:-The
pillar I make a steam cylinder, firmly secured, and the bottom of which
reaches to within a few inches of the ground, and within this cylinder
and projecting downwards with a large spreading foot is a ram. The
diameter of the cylinder is so proportioned that on admitting steam
above the ram the latter is forced downwards until, when reaching the
ground, the entire engine rises any given distance, say, an inch clear of
the rails.
On my improved tramway locomotive I place an ordinary brako to
provide against emergencies, and in addition to this I have some known
efficient arrangement of continuous brake, so as to have the train under
perfect control.

page_text: '
Around the front of the leading wheels I place a strong guard plate
reaching to within to within 2 or 3 inches of the ground, and the front of
this plate I cover with a very thick and strong air or spring cushion,
that any person who may have fallen in front of the engine will not be
run over, but merely suffer from being pushed a certain distance along
the ground.
For very steep tramways I construct the locomotive with the arrange-
ments already described, but having the flanged driving wheels replaced
by wider wheels fitted with elastic tires running on the common road or
other surface than the rails. I prefer these flexible wheels to have solid
rubber tires with shoes attached in the following manner :-The treading
part of the rubber tire is made wider at the sides than that part next to
the drum of the wheel, and over the projections thus formed I clasp the
ends of the metal shoes, which are thus -secured without further
fastenings being required.
SPECIFICATION filed in pursuance of the conditions of the Letters
Patent, by the said Leonard Jennett Todd in the Great Seal
Patent Office on the 16th October 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, LEONARD
JENNETT TODD, of Leith, in the County of Mid Lothian, North Britain,
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of April, in the year of our
Lord One thousand eight hundred and seventy-three, in the thirty-sixth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Leonard Jennett Todd, Her special licence
that I, the said Leonard Jennett Todd, my exccutors, administrators,
and assigns, or such others as I, the said Leonard Jennett Todd,
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,
excrcise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IM-

page_text: PROVEMENTS IN AND CONNECTED WITH STEAM TRAMWAY AND OTHER LOCOMOTIVES,"
upon the condition (amongst others) that I, the said Leonard Jennett
Todd, 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 months next and
immediately after the date of the said Letters Patent.
'
NOW KNOW YE, that I, the said Leonard Jennett Todd, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and by
the following statement in writing, reference being had to the accom-
panying Drawings, that is to say :-
My said Invention comprises various improvements in and connected
with tramway and other locomotives, and in carrying it out I first make
a strong rectangular frame, to the under side of which are attached the
axle boxes for a main driving axle, and also the horn plates and axle
boxes for a pair of small leading wheels. The drivers are large in
diameter, and for this reason and also because of the comparatively slow
rate of speed at which these engines are run, I judge it both cheaper to
make and more economical in maintenance to run the driving axle
without bearing springs, although springs may be used if desired.
The leading axle I fit with ordinary sliding axle boxes and bearing
springs, thus making the foot plate easy for the attendants, and also
making sure that the four wheels shall at all times have a proper bearing
upon the rails. These springs allow the small wheels to pass the points
and crossings without violent jolting; and by virtue of their large
diameter the driving wheels also pass with the necessary smoothness over
these parts. When the drivers are used without bearing springs I prefer
to make them with solid wood or paper discs, around which are secured
the necessary flanged tires. The leading wheels are made of chilled cast-
iron discs or of other make with flanged tires. On the main frame I
place a locomotive boiler with the fire-box next to the small lcading
wheels and the barrel over the main axle. On the top of the boiler I
place the cylinder or cylinders, and connect the crank shaft to the main
axle by a pinion and wheel. The pinion I prefer to make with a movable

page_text: clutch for disconnecting to allow the feed pumps to be worked when the
locomotive is standing.
For a tramway locomotive I consider this a simpler, cheaper, and
better plan than either having a donkey engine or an injector. The
donkey is a source of endless annoyance, whilst as the main tank in this
improved locomotive contains hot water the injector would require a
small secondary cold water tank, which with its connections would cause
extra expense.
The engine motion on top of the boiler I cover with a case, the top of
which is shaped like the top of an ordinary locomotive boiler. Placing
the engine motion on top of the boiler of a tramway locomotive is of
importance in keeping the working parts perfectly free from dust and
dirt. The working parts are perfectly accessible by means of a door on
top of the casing. The cylinders being on top of the boiler also secures
an efficient discharge of the exhaust and any condensed or priming.
water to the exhaust driven fan, and also from this fan a similarly
efficient discharge can then be readily made into the water tank.
If the driving wheels are 5 feet in diameter, and the ratio of the
toothed gearing is 3 to 1, the revolutions of the engines and the piston
spoed will then be the same as though the cylinders of the same size
were coupled directly to drivers one-third of 5 feet or 20 inches diameter.
With the 20-inch drivers and direct coupling however the working parts
cannot be kept clean or in proper order; and as such small wheels
absolutely require springs the cylinders must then lie horizontally, and
thus being at the lower part of the locomotive are in a very inconvenient
position, and one not admitting of the most satisfactory application of
an exhaust driven fan. But the exhaust driven fan works most efficiently
with a rather rapid reciprocation of the engines, and consequent rapid
discharge of the exhaust, which in my improved arrangement of loco-
motive I perfectly secure without the working parts being exposed to
dirt or the cylinders being placed in an unsatisfactory position in
reference to the exhaust driven fan.
The toothed wheels. I prefer to make of cast steel, and as they are
each large in diameter the strain on their respective points of contact is
consequently light, and they thus wear well. These wheels are confined
in an air-tight case, and they are thus rendered practically noiseless.

page_text: The exhaust driven blowing fan I prefer to place in an intermediate
position vertically between the cylinders and the water tank.
The air discharge from the fan I sometimes cause to pass through a
surface condenser on its way to the close ash pan. Through one part of
this condenser I cause the exhaust steam from the bucket, Scotch turbine,
or turbine wheel, as it is variously called, to pass, where it is either
partially or wholly condensed, and is then discharged into the tank.or
otherwise disposed of. The amount of cooling surface in this condenser
may be varied according to requirements. It may in one case equal the
heating surface of the boiler, when the exhaust will be only partially
condensed, or it may have 5 or 6 times as much surface as the boiler,
when with plenty of cold air the exhaust will be entirely condensed.
This air condenser has two advantages; first, it has some effect in con-
densing the exhaust; and secondly, it supplies the furnace with a
moderately hot blast. A few inches above the fire-bars I make a series
of openings dispersed around the grate. These openings extend right
through to the outer fire-box, and have any convenient means of com-
munication with the close ash pan. These openings or tuyeres may
either discharge directly into the heart of the fire or be above it, or be
placed some in each position, according to circumstances. The advantages
of this arrangement aro that it may be used as a smoke consuming
apparatus, and it also materially assists the action of the fan. For if the
grate consists of ordinary solid fire-bars they, especially with a fan blast,
are liable to clinker and thus prevent the air from freely reaching the
fire; but with the addition of these tuyeres above the bars the necessary
intensity of the fire can be maintained in a tolerable manner, even
though the grate be almost totally choked with clinkers or ashes. With
a square fire-box containing 3 or 4 feet of surface two such tuyere holes,
say 1 inches in diameter, may be made on each side, making eight
tuyeres in all. The number and dimensions of them may however be
varied. Such tuyeres may be used with fans driven in any convenient
known way.
Again for an engine having to work so continuously as a tramway
locomotive, they render it possible to do without a water grate. When
a water grate however is used I construct it as follows:-Through one side
of the fire-box I place à series of tubes fixed into both the inner and outer
plates. I then take thick tubes for the fire-bars and pass them through
the above short tubes into the opposite side of the fire-box, and the end

page_text: next to the short tubes is then bended downwards and fixed into the
water space. By this arrangement the bars can readily expand as
required, and they also maintain a through circulation as one end can be
made any reasonable distance above the other.
From the crank shaft or by other means I drive by preference two
circulating feed pumps, the overflow of each of which is discharged into
the exhaust pipe from the bucket wheel to the water tank.
If each pump has a single acting ram and is driven from the crank
shaft, there will then be one discharge of water into the exhaust pipe
for every two beats of the exhaust steam; which is sufficient to almost
totally condense the exhaust so long as the water tank remains cold,
but it will of course gradually rise in temperature.
The pumps need not necessarily be feed pumps, but they can be
conveniently arranged as such, when the action will be as follows:-
When running down hill and using but little steam one of the pumps
will be cut off from the exhaust pipe to feed the boiler, but the other
will mostly be left to discharge the tank water through the exhaust pipe,
the single pump being sufficient to condense the small quantity of steam
then being used. But on ascending an incline when the greatest
amont of steam is passing through the cylinders, the feed will of course
be cut off from the boiler and consequently the two pumps will then
intermittently discharge their full quantity of water into the exhaust
pipe.
In my improved tramway locomotivo then the exhaust steam from
the main cylinders is disposed of thus,--if the engine has an air condenser
or injection into the exhaust pipe it is thereby partly condensed and in
that state enters the water tank from which any steam still remaining
uncondensed escapes gently by a wide pipe into the funnel, where being
small in quantity, and of necessity quite free from priming water it
becomes superheated and passes off noiselessly as an invisible vapor.
If thought proper and sufficient for certain kinds of work, then the
exhaust may be made to merely drive a blowing or other kind of fan
and then enter the tank, where it is partly condensed, the remainder
escaping as before by a wide pipe into the funnel.
These arrangements are also applicable to all classes of tramway,
common road, and railway locomotives..

page_text: The combination of exhaust driven fans and surface air condensers,
the combination of tuyeres and blowing fans, and the improved water.
grate all already described are also applicable to all classes of tramway,
common road, and railway locomotives. On one side of the boiler I.
place the driver's seat with the various handles conveniently arranged,.
and on the other the fire-hole.
I also consider that an engine with a pair of large drivers and small
geared cylinders on top of the boiler is less damaging to the generally
exceedingly light track of a tramway than is a direct coupled engine
with outside cylinders. The geared engine rolls with a steady motion
without any tendency to deviate from a perfectly straight line, while
the direct coupled outside cylinder engine shoulders to its work at every
stroke, and advances along the track with a lateral action sinuous
motion, which both wears the wheel flanges and tends to loosen the
rails and the vertical holding down bolts which are generally used for
securing tramway rails. Outside cylinders are here specially referred to,
as they are the only kind which can well be used for a direct coupled
trect tramway locomotive. Of course on any railway there is soon a
limit reached as to the weight which may be placed on a single pair of
drivers; but the tramway locomotive referred to is only intended for the
very slightest class of passenger traffic, 56 cwt. of driving weight being
sufficient for a single car on an incline of 1 in 40. If then a tramway.
locomotive has to be designed with 56 cwt. of driving weight, a better
and more durable engine can be made by means of placing this 56 cwt.,
on a single pair of drivers as already described, and then placing another
say 14 cwt. on a pair of leading wheels than by making a small
4-coupled locomotive with a total weight of 56 cwt. Another point may
also be looked at. A tramway is frequently covered with a thick greasy
mud, and when wheels are loaded with so light a weight as only 15 or
20 cwt. each, this mud is not pressed out from between the wheel and
rail, but remains on the rail a continuous coat of 1 or even of
an inch in thickness, and thus reduces the adhesion to an extremely
small figure. Whereas wheels more heavily and judiciously loaded can
press out this intervening mud and bring the two metal surfaces into
actual contact. Therefore on the peculiar surface of a muddy tramway
a given amount of driving weight will give a much better bite if placed
on a single pair of drivers than if divided among four separate wheels;
but this principle can of course only be carried out with very light
engines.

page_text: I prefer to run my improved tramway locomotives with the fire end
foremost, and consequently with the funnel next to the car. I also prefer
to make the cars with a roof over the outside passengers' seats when such
are used, and I then make the funnel at least as high as the top of this
roof, so that the products of combustion readily escape without annoying
outside passengers.
.
I connect the engine to the car by means of a long rigid bar, which
passes below the flooring, and terminates as far back as will avoid any
chance of throwing the car off the rails when passing round curves. I
prefer this termination to be very near to the leading axle of the car,
and should not advise it to be much forward from that point. This
bar takes both the pull and thrust, and also allows the train to readily
pass round sharp curves; it also does not at all interfere with the vertical
rocking of the ends of the car at high speeds.
If more than one car are connected to an engine I also couple them
together by rigid bars arranged like that just described. At the end of
cach run the train may be run round a half circle to the return line, or it
may be backed by means of quarter-circle reverse curves, or be turned
entire by other means. Or the engine may be detached from the car or
cars, and turned separately, which may readily and easily be done by the
following means:-Beneath the centre of gravity of the engine I placo a
pillar with a movable foot, and by lowering this foot at the end of a journey
the entire engine can be raised a short distance from the rails, and then
be swung half round, and again deposited. This pillar and movable foot
may be like a large screw jack, or have hydraulic or other means of
obtaining the necessary power, to lift the engine, but I prefer to make
this apparatus as follows:-The pillar I make a steam cylinder firmly
secured, and the bottom of which reaches to within a few inches of the
ground, and within this cylinder and projecting downwards with a large
spreading foot is a ram. The diameter of the cylinder is so proportioned
that on admitting steam above the ram the latter is forced downwards
until when reaching the ground the entire engine rises any given
distance, say, an inch clear of the rails.
If the entire weight of the locomotive is four tons this apparatus may
be proportioned somewhat thus:-The cylinder would be 9 inches in
diameter, in which 150 lbs. pressure per square inch would be sufficient
to raise the engine.

page_text: exhaust driven fan placed on the same level with the ash-pan, as shown
in my former Specification No. 1110, of 1871, water may at times
collect in the steam wheel chamber and prevent the fan from freely
revolving; but by raising the fan into my improved position all water
drains from it, and the efficiency of the fan is therefore increased.
Except as regards the position of the exhaust driven fan the steam car,
shown in Figure 8, does not constitute part of my Invention.
Figure 9 is a vertical section of my improved water grate, and
showing one of the series of tubes A fitted into both the inner and
outer plates. The thick fire-bar tube B slides freely through the
tube A, and has its ends securely fixed at C and D. There can thus
be a very rapid circulation through the fire-bars so that they will not
burn, whilst they will not leak owing to the tube B readily ex-
panding through A. The fire-bar tubes can advantageously be made
of steel to withstand the action of the stoker's fire-tools, although
a water grate does not clinker very much. The fire-bar tube ends can
be readily fixed with a tube expander worked through the plug holes ;
and I prefer to flatten them at the bend as shown at E, in order to
allow them more readily to expand. In a cross section the tubes may
either be arranged in a straight line or in a zig-zag manner so as to
obtain a greater area of wind opening between the bars for a given
breadth of fire-box.
Figure 10 shows my improved gear for turning a tramway locomotive
end for end. There is a large pillar or cylinder F fixed below the centre
of gravity of the machine. A foot or ram G slides downwards in the
cylinder, and a steam pipe H admits pressure into the cylinder F, whilst
a pipe I admits the waste steam into the water tank. On admitting
steam through the pipe H the ram is forced downwards and the engine
raised a distance, say, of one inch from the rails, whereupon it can be
easily swung round end for end, and then on opening the cock in the
pipe I the steam escapes into the tank, the ram rises, and the engine
again settles on the rails. This apparatus can equally well be applied
to such an engine as that shown in Figure 8, or to other kinds of tram-
way locomotives.
Figure 11 is a longitudinal section of an ordinary railway locomotive,
showing my improved combination of exhaust driven fan and surface air
condenser and water tank, arranged so that the fan drains into the
condenser and the condenser into the water tank.

page_text: Figure 12 is a plan corresponding to Figure 11;- whilst Figure 13 is a
cross section through the fire-box, and shows the two hot air pipes
descending from the condensers to the close ash-pan.
Figure 14 is a cross section, as through the front end in Figure 11,
and shows the exhaust driven fan or fans so placed that they can drain
into the surface air condenser or condensers, the condensers being so
placed that they can drain into the water tanks.
I would now remark with reference to locomotives which are fitted
with exhaust driven blowing fans, 1, that the ash pan and fire-doors
should fit air tight; 2, that to check steam from rising too fast when
running the ash pan door should be partly opened to let the blast escape,
the fire-door remaining shut; 3, that if it is necessary to fire when
running, the ordinary jet cock into the funnel should be opened, so as to
cause a draught through the tubes, and thus prevent sparks or flame
from issuing at the fire hole; 4, that the intensity of the fan blast is
automatically regulated in as perfect a manner as if the blast were in the
funnel, as more usual; 5, that if the fan should be accidentally pre-
vented from revolving the exhaust is yet at perfect liberty to escape
through the fan, and thus into the funnel; 6, that the ordinary funnel
blast can be used at a moment's notice, if required, as shown in Figure 14;
7, that with the fan blast a pressure instead of the usual partial vacuum
exists in the furnace and tubes, so that every part of the heating surface
thus becomes much more effective than is ordinarily the case; 8, that
with the fan blast only very small sparks, and not large cinders, are
discharged from the funnel head; 9, that when at work the water tanks
should not be drained quite empty, so that any tallow carried over from
the cylinders with the exhaust, and which may be floating on the water,
may not be pumped into the boiler. From time to time the tanks
should be run quite empty while hot to get rid of any grease that may
collect in them; 10, that by preference the cylinders should not be
jacketted, as the greater amount of grease required by dry hot cylinders
will more rapidly cause accumulations of grease in the water tanks than
will be the case with ordinary cylinders.
I would further remark with reference to locomotives fitted not only
with an exhaust driven blowing fan, but also with an air surface con-
denser, 1, that with an air surface condenser I do not usually purpose to
obtain a vaccuum, as that would require such a great amount of condensing

page_text: surface, perhaps even 6 to 8 times the heating surface, if the atmosphere
be warm, which would both be cumbersome and heavy. And again such
a flat-sided condenser as is shown in Figures 11 and 14 would have to be
very heavy to withstand even a few pounds of vacuum. But it is chiefly
intended that such air condensers on locomotives shall withstand neither
pressure nor vacuum of much intensity, but merely perform the part of
stills to condense either more or less of the exhaust into water, and also
to moderately heat the air blast on its way to the close ash pan. This
combination of fan and condenser can be advantageously fitted to loco-
motives which have to work in regions where water is scarce, and has to
be carried long distances for the engines, as in some parts of South
America, as by this means a locomotive may be made to work with only,
say, one-fourth of the water it at present requires, according of
course to the capacity of the condenser, and thus a great expence in
water carriage is saved. Again, this air condenser, if made with such a
limited cooling surface as just referred to, will not become low enough
in temperature to congeal amongst the tubes any tallow that may be
carried over from the cylinders, but such tallow will always find its way
in a liquid state into the water tank, and thus the condenser will not
foul either outside the tubes from deposit from the cylinders, or inside
the tubes from the passage of the air. By arranging the condenser to
drain into the tank, and work without a vacuum, the engine works
without either air or circulating pumps, and with the sole exception of
the fan this condensing locomotive does not require any more attention
from its attendants, nor is it more liable to derangement than an ordinary
locomotive. Such condensers as have to withstand neither pressure nor
vacuum may be made very light. The tubes may conveniently be made
3/4 inch in diameter, and spaced 1 inch between centres, and may be of
such a thickness that one square foot of surface will weigh one pound, or
these proportions may be varied.
The exact position of the fan, condenser, and tank may be varied from
that shown in Figures 11, 12, 13, and 14, provided that the general com-
bination of these parts be retained.
The words railway, tramway, and road are herein used by me with the
following significations, namely:-Railway, as meaning a track con-
structed exclusively for flanged wheel traffic; tramway, a track constructed
suitable for both flanged wheel and ordinary traffic; and road, any track
or natural surface having no special provision for flanged wheels.
B