At a recent meeting of the Manchester Association of Employers, Foremen,
and Draughtsmen of the Mechanical Trades of Great Britain, an interesting
lecture on "Gas for Light and Work in the Workshop" was delivered by Mr.
T. Fletcher, F.C.S., of Warington.
Mr. Fletcher illustrated his remarks with a number of interesting
experiments, and spoke as follows:
There are very few workshops where gas is used so profitably as it might
be; and my object to-night is to make a few suggestions, which are the
result of my own experience. In a large space, such as an erecting or
moulder's shop, it is always desirable to have all the lights distributed
about the center. Wall lights, except for bench work, are wasteful, as a
large proportion of the light is absorbed by the walls, and lost. Unless
the shop is draughty, it is by far the best policy to have a few large
burners rather than a number of small ones. I will show you the difference
in the light obtained by burning the same quantity of gas in one and in
two flames. I do not need to tell you how much the difference is; you can
easily see for yourselves. The additional light is not caused, as some of
you may suppose, by a combined burner, as I have here a simple one,
burning the same quantity of gas as the two smaller burners together; and
the advantage of the simple large burner is quite as great. It is a
well-known fact that the larger the gas consumption in a single flame, the
higher the duty obtained for the gas burnt. There is a practical limit to
this with ordinary simple burners; as when they are too large they are
very sensitive to draught, and liable to unsteadiness and smoking. I have
here a sample of a works' pendant or pillar light, which, not including
the gas supply-pipe, can be made for about a shilling. For all practical
purposes I believe this light (which carries five No. 6 Bray's union jets,
and which we use as a portable light at repairs and breakdowns) is as
efficient and economical a form as it is possible to make for ordinary
rough work. The burners are in the best position, and the light is both
powerful and quite shadowless; giving, in fact, the best light underneath
the burners. It must, of course, be protected in a draughty shop; and on
this protection something needs to be said.
Regenerator burners for lighting are coming into use; and, where large
lights are required for long periods, no doubt they are economical.
Burners of the Bower or Wenham class would be worth adopting for main
street or open space lighting in important positions; but when we consider
that, with the fifty-four hours' system in workshops, artificial light is
only wanted, on an average, for four hundred hours per annum, we may take
it as certain that, at the present prices of regenerator burners, they are
a bad investment for use in ordinary work. We must not forget that the
distance of the burner from the work is a vital point of the cost
question; and, for all except large spaces, requiring general
illumination, a common cheap burner on a swivel joint has yet to meet with
a competitor. Do not think I am old-fashioned or prejudiced in this
matter. It is purely a question of figures; and my condemnation of
regenerator burners applies only to the general requirements in ordinary
engineering and other work shops where each man wants a light on one spot
only.
Some people think that clear glass does not stop any light. This is a
great mistake, as you will find it quite easy to throw a distinct shadow
of a sheet of perfect glass on a white paper, as I will show you. Opal and
ground glass throw a very strong shadow, and practically waste half the
light. It is better to have a white enameled or whitewashed sheet-iron
reflecting hood, which will protect the sides from wind, if such an
arrangement suits other requirements.
I have endeavored in the engraving below to reproduce the shadows thrown
by different samples of glass. This gives a fair idea of the actual loss
of light involved by glass shades.
When lights are suspended, it is a common and costly fashion to put them
high up. When we consider that light decreases as the square of the
distance, it will be readily understood that to light, for instance, the
floor of a moulding shop, a burner 6 feet from the floor will do as much
work as four burners, the same size, placed 12 feet from the floor. It is
therefore a most important matter that all lights should be as low as
possible, consistent with the necessities of the shop, as not only is the
expense enormously increased by lofty lights, but the air becomes more
vitiated and unpleasant, interfering with the men's power of working. Any
lights suspended, and, in fact, all workshop lights, must have a
ball-joint or universal swivel at the point where they branch from the
main, as they are liable to be knocked in all directions, and must,
therefore, be free to move to prevent accidents. It is better to have
wind-screens, if necessary, rather than glass lanterns, as not only does
the glass stop a considerable amount of light when clean, but it is in
practice constantly dirty in almost every workshop or yard.
[Illustration: PILLAR LIGHT OR PENDANT FOR WORKSHOPS.]
For bench work and machine tools, each man must have his own light under
his own control; and in this matter a little attention will make a
considerable saving. The burners should be union jets--_i. e._, burners
with two holes at an angle to each other--not slit or batswing, as the
latter are extremely liable to partial stoppage with dust. Where batswing
burners are used, I have often seen fully 90 per cent. more or less choked
and unsatisfactory; whereas a union jet does not give any trouble. It is
not generally known that any burner used at ordinary pressures of gas
gives a much better light when it is turned over with the flat of the
flame horizontal, until the flame becomes saucer-shaped, as I show you.
You can see for yourselves the increase in light; and in addition to this
the workman has the great advantage of a shadowless flame. In practice, a
burner consuming 5 cubic feet of gas per hour with a horizontal flame is a
better fitter's than an upright burner with 6 cubic feet per hour. I do
not believe in the policy of giving a man a poor light to work by--it does
not pay; and I never expect to get a man to work properly with smaller
burners than these. We have a good governor on the main: and the lights
are all worked with a low pressure of gas, to get the best possible duty.
As a good practical light for a man at bench moulding, the one I have here
may be taken as a fair sample. It is free to move, and the light is as
near the perfect position as the necessities of the work will permit. When
the light is not wanted, by simply pushing it away it turns itself down;
the swivel being, in fact, a combined swivel and tap.
[Illustration: LOSS OF LIGHT BY GLASS SHADES.]
You will see on one of the lights I have here, a new swivel joint, which
has been patented only within the last few days. The peculiarity of this
swivel is that the body is made of two hemispheres revolving on each
other in a ground joint. It will be made also with a universal movement;
and its special advantage, either for gas, water, or steam, is that there
is no obstruction whatever to a free passage--in fact, the way through the
swivel body is larger than the way through the pipes with which it is
connected. It can easily be made to stand any pressure, and if damaged by
grit or dirt it can be reground with ease as often as necessary without
deterioration, whereas an ordinary swivel, if damaged by grit, has to be
thrown away as useless.
[Illustration]
For meals, where a steam-kettle is not used, it is the best policy to have
a cistern holding about 1½ pints for each man, and to boil this with a
gas-burner. The lighting of the burner at a specified time may be deputed
to a boy. If the men's dinners have to be heated, it is easy to purchase
ovens which will do all the work required by gas at a much cheaper rate
than by coal, if we consider the labor and attention necessary with any
coal fire. Not that gas is cheaper than coal; but say we have 100 dinners
to warm. This can be done in a gas-oven in about 20 minutes, at a cost for
gas of less than 1d.; in fact, for one-fourth the cost of labor only in
attending to a coal fire, without considering the cost of wood or coals.
Gas, in many instances, is an apparently expensive fuel; but when the
incidental saving in other matters is taken into consideration, I have
found it exceedingly profitable for all except large or continuous work,
and in many cases for this also. I only need instance wire card-making and
the brazing shops of wire cable makers to show that a large and free use
of gas is compatible with the strictest economy and profitable working.
Of all the tools in a workshop, nothing saves more time and worry than two
or three sizes of good blowpipes and an efficient blower. I have seen in
one day more work spoilt, and time lost, for want of these than would have
paid for the apparatus twice over; and in almost every shop emergencies
are constantly happening in which a good blowpipe will render most
efficient service. Small brazing work can often be done in less time than
would be consumed in going to the smith's hearth and back again,
independently of the policy of keeping a man in his own place, and to his
own work. The shrinking on of collars, forging, hardening, and tempering
of tools, melting lead or resin out of pipes which have been bent, and
endless other odd matters, are constantly turning up; and on these, in the
absence of a blowpipe, I have often seen men spend hours instead of
minutes. Things which need a blowpipe are usually most awkward to do
without one; and men will go fiddling about and tumbling over each other
without seeing really what they intend to do. They are content, as it all
counts in the day's work; that it comes off the profits is not their
concern. It will, perhaps, be new to many of you that blowpipes can easily
be made in a form which admits of any special shape of flame being
produced. I have made for special work--such as heating up odd shapes of
forgings, brands, etc.--blowpipes constructed of perforated tubes formed
to almost every conceivable shape; these being supplied with gas from the
ordinary main and a blast of air from a Root's or foot blower. I have here
an example of a straight-line blowpipe made for heating wire passed along
it at a high speed. The same flame, as you no doubt will readily
understand, can be made of any power and of any shape, and will work any
side up; in fact, as a rule, a downward vertical or nearly vertical
position is usually the best for any blowpipe. As an example of this class
of work, I may instance the shrinking on of collars and tires, which, with
suitable ring-burner and a Root's blower, could be equally heated in five
minutes for shrinking on; in fact, the work could be done in less time
than it would usually take to find a laborer to light a fire. When the
rings vary much in size, the burners can easily be made in segments of
circles. But then they are not nearly so handy, as each needs to be
connected up to the gas and air supply; and it is, in practice, usually
cheaper to have separate ring burners of different sizes. Of course, you
will understand that a ½-inch gas-pipe will not supply heat enough to make
a locomotive tire red hot, and that for large work a large gas supply is
necessary. Our own rule for burners of this class is that the holes in the
tube should be 1/8 to 1/10 inch in diameter, from ¼ to ½ inch pitch; and
the area of the tube must be equal to the combined area of the holes. The
gas supply-pipe must not be less than half the area of the burner-tube.
Those of you who wish to study this matter further will, I think, find
sufficient information in my paper on "The Construction of High-Power
Burners for Heating by Gas," printed in the Transactions of the Gas
Institute for 1883, and in the papers on the "Use and Construction of the
Blowpipe" and "The Use of Gas as a Workshop Tool."
[Illustration]
No doubt many of you have been troubled with the twisting of some special
light casting, and will, perhaps, spend hours in the risky operation of
bending an iron pattern so as to get a straight casting. A ladleful of
lead and tin, melted in a small gas-furnace, will, in a few minutes, give
you a pattern which you can bend and adjust to any required shape. It
enables you to make trials to any extent, and get castings with the utmost
precision. There is also this advantage, that a soft metal pattern can be
cut about and experimented with in a way which no other material admits
of. Awkward patterns commence with us with plaster, wax, sheets of wet
blotting paper pasted together on a shape or wood; but they almost
invariably make their appearance in the foundry after being converted into
soft metal by the aid of a gas-furnace. I refer, of course, to thin,
awkward, and generally difficult castings, which, under ordinary
treatment, are either turned out badly or require a great amount of
fitting. As an illustration of the use of this system of pattern-making, I
have here two castings of my own, from patterns which, under the ordinary
engineer's system, would be excessively costly and difficult to make as
well as these are made. The surface is a mass of intricate pattern work
and perforations. To produce the flat original, as you see it, a small
piece of the pattern is first cut, and from this a number of tin castings
are made and soldered together. From this pattern, reproduced in iron for
the sake of permanence, is cast the flat center plate you see. To produce
the curved pattern I show you, nothing more is necessary than to bend the
tin pattern on a block of the right shape, and we now get a pattern which
would puzzle a good many pattern-makers of the old style.
[Illustration]
I will now show you by a practical utilization of the well known flameless
combustion, how to light a coke furnace without either paper or wood, and
without disturbing the fuel, by the use of a blowpipe which for the first
minute is allowed to work in the ordinary way with a flame to ignite the
coke. I then pinch the gas tube to extinguish the flame, allow the gas to
pass as before, and so blow a mixture of unburnt air and gas into the
fuel. The enormous heat generated by the combustion of the mixture in
contact with the solid fuel will be appreciable to you all, and if this
blast of mixed air and gas is continued, there is hardly any limit to the
temperatures which can be obtained in a furnace. I shall be able to show
you the difference in temperature obtained in a furnace by an ordinary air
blast, by a blowpipe flame directed into the furnace, and by the same
mixture of gas and air which I use in the blowpipe being blown in and
burnt in contact with the ignited coke. In each case the air blast, both
in quantity and pressure, is absolutely the same; but the roar and the
intense, blinding glare produced by blowing the unburnt mixture into the
furnace is unmistakable. The heat obtained in the coke furnace I am using,
in less than ten minutes, is greater than any known crucible would stand.
I am informed that this system of air and gas or air and petroleum vapor
blast, first discovered and published by myself in a work on metallurgy
issued in 1881, is now becoming largely used for commercial purposes on
the Continent, not only on account of the enormous increase in the heat,
and the consequent work got out of any specified furnace, but also because
the coke or solid fuel used stands much longer, and the dropping, which is
so great a nuisance in crucible furnaces, is almost entirely prevented; in
fact, once the furnace is started, no solid fuel is necessary, and the
coke as it burns away can be replaced with lumps of broken ganister or any
infusible material. Few, if any, samples of firebrick will stand the heat
of this blast, if the system is fully utilized. You will find it a matter
of little difficulty, with this system of using gas, to melt a crucible of
cast iron in an ordinary bed-room fire grate if the front bars are covered
with sheet iron, with a hole (say) three inches in diameter, to admit the
combined gas and air blast. The only care needed is to see that you do not
melt down the firebars during the process. I will also show you how, on an
ordinary table, with a small pan of broken coke and the same blowpipe,
used in the way already described, you can get a good welding heat in a
few minutes, starting all cold. In this case the blowpipe is simply fixed
with the nozzle six inches above the coke, and the flame directed
downward. As soon as the coke shows red, the gas pipe is pinched so as to
blow the flame out, and the mixture of gas and air is blown from above
into the coke as before. With this and a little practice, you can get a
weld on a 7/8 inch round bar in 10 minutes.
There is one use of gas which has already proved an immense service to
those who, in the strictest sense, live by their wits. In a small private
workshop, with the assistance of gas furnaces, blowpipes, and other gas
heating appliances, it is a very easy matter to carry out important
experiments privately on a practical scale. A man with an idea can readily
carry out his idea without skilled assistance, and without it ever making
its appearance in the works until it is an accomplished fact. How many of
you have been blocked in important experiments by the tacit resistance of
an old fashioned good workman, who cannot or will not see what you are
driving at, and who persists in saying that what you want is not possible?
The application of gas will often enable you to go over his head, and do
what, if the workman had his own way, would be an impossibility. When a
man is unable or unwilling to see a way out of a difficulty, a master or
foreman has the power to take the law in his own hands; and when a workman
has been met with this kind of a reply once or twice, he usually gives
way, and does not in future attempt to dictate and teach his master his
own business. In carrying out this matter, it is not necessary that a
specimen of fine workmanship shall be produced. A man usually appreciates
the wits which have produced what he has considered impossible. In purely
experimental work I think I may fairly state that the use of gas as a fuel
in the private workshop and laboratory has done incalculable service in
the improvement of processes and trades, and has played an important part
in insuring the success and fortunes of many hundreds of experimenters,
who have brought their labors to a successful issue in cases where, in its
absence, neither time nor patience would have been available. I need only
to call to your mind the number of new alloys which, for almost endless
different purposes, have come into use during the last eight or ten years.
I think the use of small gas furnaces in private workshops and
laboratories may fairly be said to have enabled the experiments on most,
if not all, of these alloys to be carried out to a successful issue.
I have been asked to say something regarding gas engines. The only thing I
can say is that I know very little about them. In my own works we have
about 300,000 cubic feet of space, all of which requires to be heated,
more or less, during the greater part of the year. For this purpose we
must have a steam boiler, and having this steam, it costs little to run it
first through the engine, and so obtain our power for a good part of the
year practically without any cost. It would not pay, under any
circumstances, to have two separate sources of power for summer and
winter; and therefore the use of gas for power has never been considered.
For irregular work and comparatively small powers, gas-engines have
special and great advantages; and in this respect they may, perhaps, class
with gas melting furnaces. If I wanted 1, or 10, or 20 lb. of melted
metal, I could melt and make the casting in less time and with less cost
than would be required to light a coke fire. There is no possible
comparison in the two, as to convenience and economy; but if I wanted to
melt 3 or 4 cwt. or 3 or 4 tons every day, I should not dream of using gas
for the purpose, as the extra cost of gas in such a case would not be
compensated by the saving in time. In commercial matters we must always
consider first what is the most profitable way of going about our work;
and, so far as I myself am concerned, I have always found it advantageous
to expend some money annually on proving this by direct experiment. It is
almost always possible to learn something, even from a failure.
I will now, with a blowpipe and small foot blower, heat a short length of
locomotive boiler tube to a brazing heat on the table; and, in conclusion,
will convert the table into a small foundry. I cannot cast you a flywheel
for a factory engine; so will try at something smaller, and will reproduce
a medallion portrait of Her Majesty, in cast iron, the original of which
is silver, commonly valued at half a crown. From the time I light the
furnace until I turn you out the finished casting I shall perhaps keep you
eight or nine minutes. I can remember in the good old times 25 years ago,
before I used gas furnaces, that it sometimes took about two hours to get
a good wind furnace into condition to put the crucible in. My time in
those days was not worth much; but if I valued it at 2s. 6d. per week, it
would even then have been cheaper to use gas to do the same thing,
irrespective of the cost of coke.
The age of gaseous fuel is commencing; and I feel daily, from the
correspondence I receive, that there is a growing impression that gas is
going to perform miracles. We do not need to go mad about it; and my own
precept and practice is to employ gas only where its use shows a profit,
either in time or money. Many of those present know that I am as ready to
totally condemn gaseous fuel where it does not pay as to advise its use
where some advantage is to be gained. You will understand that my remarks
apply to coal gas only. As to producer or furnace gases, I know
practically nothing, except that sometimes it pays better to burn your
candle as a candle than make it into gas, and burn it as a gas afterward.
The use of producer gas no doubt pays on a large scale; and things on a
large scale, so far as gas is concerned, are not matters with which I have
time to concern myself. The commercial use of coal gas has yet to be
developed. It is in its infancy; and there are very few, if any, who have
any conception of its endless uses, both for domestic and manufacturing
purposes. The more general the information which can be given about its
uses, the sooner it will find its own level, and the sooner the gas
companies will appreciate the fact that their best customers are to be
found among those who can use coal gas as a fuel for special work in
manufacturing industries because it is profitable to use, and saves
expensive labor. My own experiments with alloys of the rarer metals, which
have not been concluded without profit to myself, would certainly never
have been undertaken except with the use of gas furnaces, which were both
practically unlimited in power and admitted of the most absolute precision
in use; and I may safely say, without violating any confidence, that many
of the precious stories and so-called "natural" products make their
appearance in the world first in a crucible in a gas furnace.
At the conclusion of my lecture before the Institute at Leeds, on
"Combustion and the Utilization of Waste Heat," Mr. Kitson, the Chairman,
remarked that if he were a dreamer of dreams, he might look forward to the
time when he would be growing cucumbers with the waste heat of his iron
furnaces. Many wilder dreams than this have come true in the science of
engineering; and the realization has brought honor and fortune to the
dreamers, as you must all know. The history of engineering is full of the
realization of "dreams," which have been denounced as absurdities by some
of the best living authorities.
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