A CANAL having been formed to connect Edinburgh with the Forth and
Clyde Canal, and so to give a direct waterway communication between
Edinburgh and Glasgow, I heard much talk about the desirableness of
substituting Steam for Horse power as the means of moving the boats
and barges along the canal. But, as the action of paddle wheels had
been found destructive to the canal banks, no scheme of that nature
could be entertained. Although a tyro in such matters, I made an
attempt to solve the problem, and accordingly prepared drawings,
with a description of my design, for employing Steam power as the
tractive agency for trains of canal barges, in such a manner as to
obviate all risk of injury to the banks.
The scheme consisted in laying a chain along the bottom of the canal,
and of passing any part of its length between three grooved and
notched pulleys or rollers, made to revolve with suitable velocity by
means of a small steam-engine placed in a tug-boat, to the stern of
which a train of barges was attached.
NOTE Had this simple means of "tugging" vessels through water-ways
been employed in our late attempts to ascend the rapids of the Nile,
some very important results might have issued from its adoption.
The steam-engine could thus warp its way along the chain, taking it
up between the rollers of the bow of the tug-boat, and dropping it
into the water at the stern, so as to leave the chain at the service
of the next following tug-boat with its attached train of barges. By
this simple mode of employing the power of a steam-engine for canal
boat traction, all risk of injury to the banks would be avoided, as
the chain and not the water of the canal was the fulcrum or
resistance which the steam-engine on the tug-boat operated upon in
thus warping its way along the chain; and thus effectually, without
slip or other waste of power, dragging along the train of barges
attached to the stern of the steam-tug. I had arranged for two
separate chains, so as to allow trains of barges to be conveyed
along the canal in opposite directions, without interfering with each
other.
I submitted a complete set of drawings, and a full description of my
design in all its details, to the directors of the Canal Company; and
I received a complimentary acknowledgment of them in writing. But
such was the prejudice that existed, in consequence of the injury to
the canal banks resulting from the use of paddle Wheels, that it
extended to the use of steam power in any form, as a substitute for
ordinary horse traction; and although I had taken every care to point
out the essential difference of my system (as above indicated) by
which all such objections were obviated, my design was at length
courteously declined, and the old system of horse traction continued.
In 1845 I had the pleasure to see this simple mode of moving vessels
along a definite course in most successful action at the ferry across
the Hamoaze at Devonport, in which my system of employing the power
of a steam-engine on board the ferry boat, to warp its way along a
submerged chain lying along the bottom of the channel from side to
side of the ferry, was most ably carried out by my late excellent
friend, James Rendell, Esq., C.E., and is still, I believe, in daily
action, giving every satisfaction.
An Instrument for Measuring the Total and Comparative Expansion of all
Solid Bodies.
My kind friend and patron, Professor Leslie, being engaged in some
investigations in which it was essential to know the exact comparative total
expansion in bulk of metals and other solid bodies, under the same number of
degrees of heat, mentioned the subject in the course of conversation. The
instrument at that time in use was defective in principle as well as in
construction, and the results of its application were untrustworthy. As the
Professor had done me the honour to request me to assist him in his
experiments, I had the happiness to suggest an arrangement of apparatus
which I thought might obviate the sources of error; and, with his approval,
I proceeded to put it in operation.
My contrivance consisted of an arrangement by means of which the metal bar
or other solid substance, whose total expansion under a given number of
degrees of heat had to be measured, was in a manner itself converted into a
thermometer. Absolutely equal bulks of each solid were placed inside a metal
tube or vessel, and surrounded with an exact equal quantity of water at one
and the same normal temperature. A cap or cover, having a suitable length
of thermometer tube attached to it, was then screwed down, and the water of
the index tube was adjusted to the zero point of the scale attached to it,
the whole being at say 50deg of heat, as the normal temperature in each
case. The apparatus was then heated up to say 200deg by immersion in water
at that temperature. The expansion of the enclosed bar of metal or other
solid substance under experiment caused the water to rise above the zero,
and it was accordingly so indicated on the scale attached to the cap tube.
In this way we had a thermometer whose bulb was for the time being filled
with the solid under investigation, -- the water surrounding it imply acting
as the means by which the expansion of each solid under trial was rendered
visible, and its amount capable of being ascertained and recorded with the
utmost exactness, as the expansion of the water was in every case the same,
and also that of the instrument itself which was "a constant quantity."
In this way we obtained the correct relative amount of expansion in bulk of
all the solid substances experimented upon. That each bar of metal or other
solid substance was of absolutely equal bulk, was readily ascertained by
finding that each, when weighed in water, lost the exact same weight.
James Nasmyth's Expansometer, 1826.
My friend, Sir David Brewster, was so much pleased with the instrument that he
published a drawing and description of it in the Edinburgh Philosophical
Journal, of which he was then editor.
A Method of increasing the Effectiveness of Steam by super-heating it on
its Passage from the Boiler to the Engine.
One or the earliest mechanical contrivances which I made was for preventing
water, in a liquid form, from passing along with the steam from the boiler
to the cylinder of the steam-engine. The first steam-engine I made was
employed in grinding oil colours for my father's use in his paintings. When
I set this engine to work for the first time I was annoyed by slight jerks
which now and then disturbed the otherwise smooth and regular action of the
machine. After careful examination I found that these jerks were caused by
the small quantities of water that were occasionally carried along with the
current of the steam, and deposited in the cylinder, where it accumulated
above and below the piston, and thus produced the jerks.
In order to remove the cause of these irregularities, I placed a
considerable portion of the length of the pipe which conveyed the steam from
the boiler to the engine within the highly heated side flue of the boiler,
so that any portion of water in the liquid form which might chance to pass
along with the steam, might, ere it reached the cylinder, traverse this
highly-heated steam pipe, and, in doing so, be converted into perfectly dry
steam, and in that condition enter the cylinder. On carrying this simple
arrangement into practice, I found the result to be in every way
satisfactory. The active little steam-engine thence-forward performed its
work in the most smooth and regular manner.
So far as I am aware, this early effort of mine at mechanical contrivance
was the first introduction of what has since been termed "super-heated
steam" -- a system now extensively employed, and yielding important results,
especially in the case of marine steam-engines. Without such means of
supplying dry steam to the engines, the latter are specially liable to
"break-downs," resulting from water, in the liquid form, passing into the
cylinders along with the steam.
A Method of "chucking" delicate Metal-work, in order that it may be turned
with perfect truth
In fixing portions of work in the turning-lathe, one of the most important
points to attend to is, that while they are held with sufficient firmness in
order to be turned to the required form, they should be free from any strain
which might in any way distort them. In strong and ponderous objects this
can be easily accomplished by due care on the part of an intelligent
workman. It is in operating by the lathe on delicate and flexible objects
that the utmost care is requisite in the process of chucking, as they are
easily strained out of shape by fastening them by screws and bolts, or
suchlike ordinary means. This is especially the case with disc-like objects.
As I had on several occasions to operate in the lathe with this class of
work I contrived a method of chucking or holding them firm while receiving
the required turning process, which has in all cases proved most handy and
satisfactory.
This method consisted of tinning three, or, if need be, more parts of the
work, and laying them down on a tinned face-plate or chuck, which had been
heated so as just to cause the solder to flow. As soon as the solder is
cooled and set, the chuck with its attached work may then be put in the
lathe, and the work proceeded with until it is completed. By again heating
the chuck, by laying upon it a piece of red-hot iron, the work, however
delicate, can be simply lifted off, and will be found perfectly free from
all distortion.
I have been the more particular in naming the use of three points of
attachment to the chuck or face-plate, as that number is naturally free from
any risk of distortion. I have on so many occasions found the great value of
this simple yet most secure mode of fixing delicate work in the lathe, that
I feel sure that any one able to appreciate its practical value will be
highly pleased with the results of its employment.
The same means can, in many cases, be employed in fixing delicate work in
the planing-machine. All that is requisite is to have a clean-planed
wrought-iron or brass fixing-plate, to which the work in hand can be
attached at a few suitable parts with soft solder, as in the case of the
turning lathe above described.
A Method of casting Specula for Reflecting Telescopes, so as to ensure
perfect Freeness from Defects, at the same time enhancing the Brilliancy of
the Alloy.
My father possessed a very excellent achromatic spy-glass of 2 inches
diameter. The object-glass was made by the celebrated Ramsden. When I was
about fifteen I used it to gaze at the moon, planets, and sun-spots.
Although this instrument revealed to me the general characteristic details
of these grand objects, my father gave me a wonderful account of what he had
seen of the moon's surface by means of a powerful reflecting telescope of 12
inches diameter, made by Short -- that justly celebrated pioneer of
telescope making. It had been erected in a temporary observatory on the
Calton Hill, Edinburgh. These descriptions of my father's so fired me with
the desire to obtain a sight of the glorious objects in the heavens through
a more powerful instrument than the spy-glass, that I determined to try and
make a reflecting telescope which I hoped might in some degree satisfy my
ardent desires.
I accordingly searched for the requisite practical instruction in the pages
of the Encyclopedia Britannica, and in other books that professed to give
the necessary technical information on the subject. I found, however, that
the information given in books -- at least in the books to which I had
access was meagre and unsatisfactory. Nevertheless I set to work with all
earnestness, and began by compounding the requisite alloy for casting a
speculum of 8 inches diameter. This alloy consisted of 32 parts of copper,
15 parts of grain tin, and 1 part of white arsenic. These ingredients, when
melted together, yielded a compound metal which possessed a high degree of
brilliancy. Having made a wooden pattern for my intended 8-inch diameter
speculum, and moulded it in sand, I cast this my first reflecting telescope
speculum according to the best book instructions. I allowed my casting to
cool in the mould in the slowest possible manner; for such is the excessive
brittleness of this alloy (though composed of two of the toughest of
metals) that in any sudden change of temperature, or want of due delicacy in
handling it, it is very apt to give way, and a fracture more or less serious
is sure to result. Even glass, brittle though it be, is strong in comparison
with speculum metal of the above proportions, though, as I have said, it
yields the most brilliant composition.
Notwithstanding the observance of all due care in respect of the annealing
of the casting by slow cooling, and the utmost care and delicate handling of
it in the process of grinding the surface into the requisite curve and
smoothness suitable to receive the final polish, -- I was on more than one
occasion inexpressibly mortified by the sudden disruption and breaking up of
my speculum. Thus many hours of anxious care and labour proved of no avail.
I had to begin again and proceed da capo. I observed, however, that the
surplus alloy that was left in the crucible, after I had cast my speculum,
when again melted and poured out into a metal ingot mould, yielded a cake
that, brittle though it might be, was yet strong in comparison with that of
the speculum cast in the sand mould; and that it was also, judging from the
fragments chipped from it, possessed of even a higher degree of brilliancy.
The happy thought occurred to me of substituting an open metal mould for the
closed sand one. I soon had the metal mould ready for casting. It consisted
of a base plate of cast iron, on the surface of which I placed a ring or
hoop of iron turned to fully the diameter of the intended speculum, so as to
anticipate the contraction of the alloy. The result of the very first trial
of this simple metal mould was most satisfactory. It yielded me a very
perfect casting: and it passed successively through the ordeal of the first
rough grinding, and eventually through the processes of polishing, until in
the end it exhibited a brilliancy that far exceeded that of the sand mould
castings.
The only remaining difficulty that I had to surmount was the risk of defects
in the surface of the speculum. These sometimes result from the first splash
of the melted metal as it is poured into the ring mould. The globules
sometimes got oxidised before they became incorporated with the main body
of the inflowing molten alloy: and dingy spots in the otherwise brilliant
alloy were thus produced. I soon mastered this, the only remaining source
of defect, by a very simple arrangement. In place of pouring the melted
alloy direct into the ring mould, I attached to the side of it what I termed
a "pouring pocket;" which communicated with an opening at the lower edge of
the ring, and by a self-acting arrangement by which the mould plate was
slightly tilted up, the influx of the molten alloy advanced in one unbroken
tide. As soon as the entire surface of the mould plate was covered by the
alloy, its weight overcame that of my up-tilting counterpoise, and allowed
the entire apparatus to resume its exact level. The resulting speculum was,
by these simple arrangements, absolutely perfect in soundness. It was a
perfect casting, in all respects worthy of the care and labour which I
invested in its future grinding and polishing, and enabled it to perform its
glorious duties as the grand essential part of a noble reflecting
telescope!
The largest figure in the engraving is the annealing tub of cast iron
filled with sawdust, where the speculum is placed to cool as slowly as possible.
The rationale of the strength of specula cast in this metal mould system, as
compared with the treacherous brittleness of those cast in sand moulds,
arises simply from the consolidation of the molten metal pool taking place
first at the lower surface, next the metal base of the mould -- the yet
fluid alloy above satisfying the contractile requirements of that
immediately beneath it; and so on in succession, until the last to
consolidate is the top or upper stratum. Thus all risk of contractile
tension, which is so dangerously eminent and inherent in the case of
sand-mould castings, made of so exceedingly brittle an alloy as that of
speculum metal, is entirely avoided. By the employment of these simple and
effective improvements in the art of casting the specula for reflecting
telescopes, and also by the contrivance and employment of mechanical means
for grinding and polishing them, I at length completed my first 8-inch
diameter speculum, and mounted it according to the Newtonian plan. I was
most amply rewarded for all the anxious labour I had gone through in
preparing it, by the glorious views it yielded me of the wonderful objects
in the heavens at night. My enjoyment was in no small degree enhanced by the
pleasure it gave to my father, and to many intimate friends. Amongst these
was Sir David Brewster, who took a most lively and special interest in all
my labours on this subject.
In later years I resumed my telescope making enjoyments, as a delightful and
congenial relaxation from the ordinary run of my business occupations. I
constructed several reflecting telescopes, of sizes from 10-inch to 20-inch
diameter specula. I had also the pleasure of assisting other astronomical
friends, by casting and grinding specula for them. Among these I may mention
my late dear friend William Lassell, and my excellent friend Warren de la
Rue, both of whom have indelibly recorded their names in the annals of
astronomical science. I know of no subject connected with the pursuit of
science which so abounds with exciting and delightful interest as that of
constructing reflecting telescopes. It brings into play every principle of
constructive art, with the inexpressibly glorious reward of a more intimate
acquaintance with the sublime wonders of the heavens, I communicated in full
detail all my improvements in the art of casting, grinding, and polishing
the specula of reflecting telescopes, to the Literary and Philosophical
Society of Manchester, illustrating my paper with many drawings. But as my
paper was of considerable length, and as the illustrations would prove
costly to engrave, it was not published in the Society's Transactions. They
are still, however, kept in the library for reference by those who take a
special interest in the subject.
A Mode of transmitting Rotary Motion by means of a Flexible Shaft, formed of a Coiled Spiral Wire or Rod of Steel.
While assisting Mr. Maudslay in the execution of a special piece of
machinery, in which it became necessary to have some holes drilled in rather
inaccessible portions of the work in hand, and where the employment of the
ordinary drill was impossible, it occurred to me that a flexible shaft,
formed of a closely coiled spiral of steel wire, might enable us to transmit
the requisite rotary motion to a drill attached to the end of this spiral
shaft. Mr. Maudslay was much pleased with the notion, and I speedily put it
in action by a close coiled spiral wire of about two feet in length.
This was found to transmit the requisite rotary motion to the drill at the
end of the spiral with perfect and faithful efficiency. The difficulty was
got over, to Mr. Maudslay's great satisfaction.
So far as I am aware, such a mode of transmitting rotary motion was new and
original. The device was useful, and proved of essential service in other
important applications. By a suitably close coiled spiral steel wire I have
conveyed rotary motion quite round an obstacle, such as is indicated in the
annexed figure.
It has acted with perfect faithfulness from the winch handle
at A to the drill at B. Any ingenious mechanic will be able to appreciate
the value of such a flexible shaft in many applications . Four years ago I
saw the same arrangement in action at a dentist's operating-room, when a
drill was worked in the mouth of a patient to enable a decayed tooth to be
stopped. It was said to be the last thing out in "Yankee notions." It was
merely a replica of my flexible drill of 1829.
A Machine for cutting the Key-Grooves in Metal Wheels and Belt Pulleys, of ANY Diameter.
The fastening of wheels and belt pulleys to shafts, so as to enable them to
transmit rotary motion, is one of the most frequently-recurring processes in
the construction of machinery. This is best effected by driving a slightly
tapered iron or steel wedge, or "key" as it is technically termed, into a
corresponding recess, or flat part of the shaft, so that the wheel and shaft
thus become in effect one solid structure.
The old mode of cutting such key-grooves in the eyes of wheels was
accomplished by the laborious and costly process of chipping and filing.
Maudslay's mortising machine, which he contrived for the Block machinery,
although intended originally to operate upon wood, contained all the
essential principles and details required for acting on metals. Mr. Richard
Roberts, by some excellent modifications, enabled it to mortise or cut out
the key-grooves in metal wheels, and this method soon came into general use.
This machine consisted of a vertical slide bar, to the lower end of which
was attached the steel mortising tool, which received its requisite up and
down motion from an adjustable crank, through a suitable arrangement of the
gearing. The wheel to be operated upon was fixed to a slide-table, and
gradually advanced, so as to cause the mortising tool to take successive
cuts through the depth of the eye of the wheel, until the mortise or
key-groove had attained its required depth.
The only drawback to this admirable machine was that its service was limited
in respect to admitting wheels whose half diameter did not exceed the
distance from the back of the jaw of the machine to the face of the mortise
tool; so that to give to this machine the requisite rigidity and strength
to resist the strain on the jaw, due to the mortising of the key-grooves, in
wheels of say 6 feet diameter, a more massive and cumbrous frame work was
required, which was most costly in space as well as in money.
In order to obviate this inconvenience, I designed an arrangement of a
key-groove mortising machine. It was capable of operating upon wheels of any
diameter, having no limit to it capacity in that respect. 'It was, at the
same time, possessed in respect of the principle on which it was arranged,
of the power of taking a much deeper cut, there being an entire absence of
any source of springing or elasticity in its structure. This not only
enabled the machine to perform its work with more rapidity, but also with
more precision. Besides, it occupied much less space in the workshop, and
did not cost above one-third of the machines formerly in use. It gave the
highest satisfaction to those who availed themselves of its effective
Services.
A comparison of Fig. 1 -- which represents the general arrangement
of the machine in use previous to the introduction of mine -- with that of
Fig. 2, may serve to convey some idea of their relative sizes. Fig. 1 shows
a limit to the admission of wheels exceeding 6 feet diameter, Fig. 2 shows
an unlimited capability in that respect.
An Instrument for finding and marking the Centres of Cylindrical Rods or Bolts about to be turned on the Lathe.
One of the most numerous details in the structure of all classes of machines
is the bolts which serve to hold the various parts together. As it is most
important that each bolt fits perfectly the hole it belongs to, it is
requisite that each bolt should, by the
process of turning, be made perfectly cylindrical. In preparing such bolts,
as they come from the forge, in order to undergo the process of turning,
they have to be "centred;" that is, each end has to receive a hollow
conical indent, which must agree with the axis of the bolt. To find this in
the usual mode, by trial and frequent error, is a most tedious process, and
consumes much valuable time of the workman as well as his lathe.
In order to obviate the necessity for this costly process, I devised the
simple instrument, a drawing of which is annexed. The use of this enabled
any boy to find and mark with absolute exactness and rapidity the centres of
each end of bolts, or suchlike
objects. All that was required was to place the body of the bolt in the
V-shaped supports, and to gently cause it to revolve, pressing it
longitudinally against the steel-pointed marker, which scratched a neat
small circle in the true centre or axis of the bolt. This small circle had
its centre easily marked by the indent of a punch, and the work was thus
ready for the lathe. This humble but really important process was
accomplished with ease, rapidity, and great economy.
Improvement in Steam-Engine Pistons, and in Water and Air-Pump Buckets, so as to lessen Friction and dispense with Packing.
The desire to make the pistons of steam-engines and air-pump buckets of
condensing engines perfectly steam and water tight has led to the
contrivance of many complex and costly constructions for the purpose of
packing them. When we take a commonsense view of the subject, we find that
in most cases the loss of power resulting from the extra friction
neutralises the expected saving. This is especially the case with the
air-pump bucket of a condensing steam-engine, as it is in reality much more
a water than an air pump. But when it is constructed with a deep
well-fitted bucket, entirely without packing, the loss sustained by such an
insignificant amount of leakage as may occur from the want of packing is
more than compensated by the saving of power resulting from the total
absence of friction.
The first condensing steam-engine to which I applied an air-pump bucket,
entirely without packing, was the forty horsepower engine, which I
constructed for the Bridgewater Foundry. It answered its purpose so well
that, after twenty years' constant working , the air-pump cover was taken
off, out of curiosity, to examine the bucket, when it was found in perfect
order. This system, in which I dispensed with the packing for air-pump
buckets of condensing steam-engines, I have also applied to the pistons of
the steam cylinders, especially those of high-pressure engines of the
smaller vertical construction, the stroke of which is generally short and
rapid. Provided the cylinder is bored true, and the piston is carefully
fitted, and of a considerable depth in proportion to its diameter, such
pistons will be found to perform perfectly all their functions, and with a
total absence of friction as a direct result of the absence of packing. By
the aid of our improved machine tools, cylinders can now be bored with such
perfect accuracy, and the pistons be fitted to them with such absolute
exactness, that the small quantity of water which the steam always deposits
on the upper side of the piston, not only serves as a frictionless packing,
but also serves as a lubricant of the most appropriate kind. I have applied
the same kind of piston to ordinary water-pumps, with similar excellent
results. In most cases of right packed pistons we spend a shilling -- to
save sixpence -- a not unfrequent result of "so-called" refined
improvements.
An instantaneous Mode of producing graceful Curves, suitable for designing Vases and other graceful objects in Pottery and Glass.
The mode referred to consists in giving a rapid "switch" motion to a pencil
upon a piece of paper, or a cardboard, or a smooth metal plate; and then
cutting out the curve so produced, and employing it as a pattern or
"template," to enable copies to be traced from it. When placed at equal
distances, and at equal angles on each side of a central line, so as to
secure perfect symmetry of form according to the nature of the required
design, the beauty of these "instantaneous" curves, as I term them, arises
from the entire absence of any sudden variation in their course. This is due
to the momentum of the hand when "switching" the pencil at a high velocity
over the paper. By such simple means was the beautiful curve produced, which
is given on the following page. It was produced "in a twinkling," if I may
use the term to express the rapidity with which it was "switched." The chief
source of the gracefulness of these curves consists in the almost
imperceptible manner in which they pass in their course from one degree of
curvature into another. I have had the pleasure of showing this simple mode
of producing graceful curves to several potters, who have turned the idea to
good account. The illustrative figures on the next page have all been drawn
from "templates" whose curves were "switched" in the manner of Fig. A.