« ZurückWeiter »
same, whatever may be the velocity commu
piston to the end of the stroke, when a cy. nicated to it, and to the mass which it linder full of steam will be delivered of carries with it, at any period of the stroke. greatly less pressure than the load. If the It is true that to put the piston, and the
steam had been worked at full pressure, it is mass carried along with it, at first in motion, evident that at every stroke a cylinder full of a pressure greater than the resistance is re steam would have been discharged of the quired, and therefore greater than the mean same pressure as the load. In this consists, pressure necessary to complete the stroke : therefore, the advantage of working expana pressure equal to the resistance would only sively. bring it into the state of rest bordering upon
It is evident that the piston acquires its motion ; to cause it to pass from this state of maximum velocity at the point where the rest to a state of motion, more pressure is steam pressure becomes equal to the load, required ; and the more as the velocity to be and that the engineer by the manipulation of acquired, whilst it moves through a given
the steam valves produces that adjustment by space, is greater-orin other words, in order which the velocity acquired by the piston at to communicate any given velocity to a body
this point (or the work then accumulated in whilst it moves through any space, there
it) is caused to be just sufficient to carry on must be an excess of the work done by the the piston to the end of the stroke, but withdriving pressure through that space, over that out striking the cylinder bottom : it is moreexpended upon the resistance through that ever evident that the greater this maximum space; but all this excess is accumulated, and velocity can be made, the farther the piston unless the steam pressure be afterwards made will be carried beyond the point where the less than the resistance, or unless the steam be steam pressure is equal to the load, and the afterwards expanded through a distance de less will be the pressure of the cylinder full pendent on the amount of this accumulated of steam discharged at the completion of work, so that it may expend itself in overcom every stroke, or the greater the economy of ing the surplus resistance through that space,
the steam power. then the piston will strike upon the cylinder
A second illustration of the same principle bottom.
may be drawn from the effect produced by This principle may be illustrated by an a pressure suddenly thrown upon a spring. example : suppose that the load upon the Suppose a spring which would rest deflected piston of an engine is 10 lbs. per square inch,
through an inch under a pressure of one and that the steam is admitted at a pressure
pound. If when this spring is in an unde. of 15 lbs., it is evident that, by reason of the
flected state this pressure of one pound be excess of 5 lbs. pressure of the steam above suddenly thrown upon it, it is certain that the load, the velocity of the piston will be
the spring will, at first, deflect considerably made continually to increase until the steam beyond that distance of 1 inch in which its is cut off, and afterwards, so long as the deflection will eventually, after many oscil. steam pressure exceeds the load, or until by lations, terminate. In fact, if it is thrown its expansion the steam pressure is reduced
on with mathematical suddenness, the first to jo lbs. per square inch. Up to this point
deflection will be 2 inches. To explain this, the velocity of the piston and of the mass
let the pound weight be supposed to be apmoving with it will continually have been in plied gradually to the spring by dropping creasing, a great momentum will therefore grain after grain of sand slowly on it. The have been acquired by it, and this momen spring will then evidently be brought to its tum will carry it on to the completion of the deflection without ever passing it. Now let it stroke; although, after this position is passed, be observed, that on this supposition, the first the steam pressure will be less than the load, grain of sand only will have descended through and would by itself be insufficient to move it. 1 inch, the next descending through less than
In other words, the work done by the an inch, the next through yet less, and so on. steam upon the piston will have continually
Thus the work done upon the spring by each exceeded that expended on the load up to
succeeding grain will be less than that done this period of the stroke, and the surplus by the preceding. Yet the aggregate work will have been accumulated in the moving
done by these successive small pressures, mass,* which surplus work will carry on the
each working through a different space, is
sufficient to deflect the spring 1 inch. Now • The number of units of work thus accumulated let all the grains be placed at once upon the is represented in lbs. I foot high by 1" r2; whence spring. When it has deflected an inch, each w represents the number of lbs. in ihe weight of
grain will then have worked throngh an the moving mass, v its velocity in feet per second
inch, and a great deal more work will, on the reduced to the piston 9 = 32. lbs. The expression whole, have been done on the spring than -02 is said to represent the vis vira; so that the
before, indeed twice as much : but the work accumulated work is equal to half the ris rira.
done before was enough to deflect the spring
an inch ; more than enough to deflect it has mate those very influences of the friction of now therefore been done : that is, more has the machine driven by the engine, which been done than has been expended. The re Mr. Parkes thought it so important to inmainder is accumulated in the moving mass clude in it. It would have been a fault of of the sand and the spring, and carries on his indicator, (for the purpose contemplated the deflection greatly beyond the position of by it,) if it had taken any notice of the effect equilibrium.
of that change made in the machinery of Mr. The Indicator was placed upon the engine Lucy's mill which Mr. Parkes had spoken of the East London Water-works, in the of. He had used the term effective work belief that by the experiments of Mr. Wick (not effective power) of the engine, to signify steed the work actually performed by that that excess of the work of the steam on one engine was better known than that of any side of the piston, over that opposed to it by other. All the calculations and inquiries the imperfectly condensed steam which have since been made have fully con other, which it was necessary to know, in firmed that opinion. And he had full con order to estimate the real duty of the engine. fidence in that verification of the registration It was solely for the determination of that of the indicator which is supplied by its duty that the indicator had been constructagreement with Mr. Wicksteed's estimate of ed, and the alterations which Mr. Parkes the work of his engine.
had suggested would have subjected its reIn reference to the use of the term “work," gistration to influences which, in reference Professor Moseley stated, that the various to that purpose, he had specially sought to terms used by foreign engineers, to convey eliminate. the idea attached to that term, appeared at Mr. Farey remarked, that it would lead length to have resolved themselves into the to an incorrect appreciation of the merit of single term “ travail ;” and that of the va the new indicating instrument, if it were to riety of corresponding terms used in Eng be considered merely as a substitute for the land, the term “work” was probably the ordinary indicator, when in fact they were most obvious translation of “ travail;' that two instruments, adapted to, and equally it moreover appeared to him the simplest, useful for, different purposes. and the most intelligible; and that on these The new instrument does not preserve any grounds he had adopted it.
record of the minute details of any one In answer to the observation made Mr. stroke, like the ordinary indicator, but it Parkes, suggesting the construction of an records a true aggregate of all the details of indicator which would register the work of any number of succeeding strokes : it gives the machine at the point where it is applied, the same results as would be obtained if it instead of at the cylinder of the engine were possible to have two ordinary indicator
Professor Moseley stated that such an in cards correctly taken, at each succeeding strument would undoubtedly be very valu stroke of the engine, during the whole time able, especially if it could be made to re of observation, by means of two indicators, gister correctly the work transmitted by a one of them applied to the upper, and the rotating shaft: but that for the purpose con. other to the lower end of the cylinder ; and templated by him it would be entirely use also provided, that an accurate admeasureless-this object was to effect, in respect to ment of every one of all those cards was ordinary engines working under constantly afterwards made, at ten places in the length variable pressures, that constant registration of the card, by the scale of pounds per of the duty, the introduction and publication square inch, in the usual manner, and the of which had led to so remarkable an eco amount of the ten measurements added into nomy of steam power in the working of the one sum, and then, (without averaging each Cornish engines. No registration of the card.) that such sum of each card should be work done at the working points of the ma carried to a continuous account, to obtain a chine driven by the engine would supply a grand sum total representing all the force fair estimate of the duty done by the engine, that had been exerted, during both halves of a greater or less portion of the work done every stroke, made throughout the experi. by the engine being lost by reason of friction ment, reckoned at ten stages or portions of in its transfer through the machine, from its the length of stroke. driving to its working points, according as Such a grand total of all the cards would there was a greater or less complication of be a number representing the same fact as is moving parts and rubbing surfaces inter represented by the number shown by the vening.
new instrument, and would therefore be He repeated, that his object had been to dealt with, in each case, in a similar manner, determine the working qualities of the en as one of the data (viz., that representing gine itself; and that he had, for this reason, force) for calculating (by aid of other data specially sought to eliminate fro.n his estic representing motion or space) the whole
power exerted during the time of observa which, like a steam-engine, regains the same tion.
state, as to rest, (or as to motion,) at the In trying the performance of a steam-ves end of the time of observation upon it, as sel, alternately up and down the measured the state in which it was at the commencemile in the river Thames, along the shore of ment of that time ; and the theory shows Dartford Marshes, it is usual to take an in that, in such a machine, no part of the force dicator card from each engine at every such exerted upon it, (or exerted by it,) can have run; and by summing up each card, some been expended, or lost, in producing modifference will be found between them, tion, whatever may be the number or the wherefore an average of the results of several extent of changes or variations in velocity of cards will give more authentic information motion that the machine had undergone dur. respecting the force exerted by the engines ing the time of observation ; for although during the whole trial, than could be ob force must be exerted to produce motion tained if one such card alone had been de from a state of rest, yet all force that is so pended upon.
exerted will be rendered back again, when The new instrument takes cognizance of the motion which was produced has ceased, every stroke that is made by the engine dur. and the state of rest regained: in the steaming the whole time of observation ; and in engine, that is the case at the termination of cases (such as in the Great Western steamer) every half stroke. where a considerable variation of force in Respecting trials by means of the smallest succeeding strokes occurs frequently during force of steam, which will just press the such time, it is a desideratum to obtain the piston of a pumping-engine slowly down in results which this instrument is intended to the cylinder, or cause the engine to come give, and which, as far as it has been tried, creeping in-doors : they are not much to be it seems likely to give with fidelity.
depended upon, as evidence of the force that The instrument, when applied as it had is actually lost in overcoming friction ; first, been at Old Ford, becomes another mode of because no steadiness of exhaustion can be ascertaining performance, similar to what is kept up beneath the piston, nor steadiness reported monthly respecting the engines in of steam above the piston, whilst the engine Cornwall, but not exactly the same as is is so treated, and also because the counter. there called “ duty,” because the new in. weight of engines in Cornwall is not appor. strument would show the aggregate of the tioned with any great nicety. In general, unbalanced force that had been exerted, they are worked with more counterweight (during a given time,) by the steam to impel than is requisite, and but little loss is occathe piston; whilst the monthly reports show sioned by so doing; for if the counterweight (by load in pounds, length of stroke in is unnecessarily great, so as to carry the enpumps, and number of strokes made) the gine quick out of doors, (that is, to cause aggregate of force exerted in the same time, the pump-rod to descend briskly,) then the in overcoming the resistance that the mere equilibrium valve is closed sooner, and therehydrostatic weight of the columns of water fore retains more steam between the top of in the pumps opposes to the motion of the the piston and the cover of the cylinder, in engine.
what has been called the steam cushion, The instrument ought always to show which stops the descending motion of the more force than the reports do, and the dif. pump-rod; and, in consequence of more ference between the two would be the aggre. steam being reserved in such cushion, to go gate of all the force that had been lost, dur towards the supply for the succeeding stroke, ing the time, by friction of the moving parts that increase in the reserved steam compen. of the engine, pumps, &c.
sates in part for the waste of force occasioned Respecting that loss of force, there is no by the redundancy of counterweight, which more of it than arises from such friction, caused the quick motion. from working the air-pumps, &c., and from Mr. Farey had received from Mr. John resistance of the water ; but it is wholly a Taylor indicator cards of Taylor's engine at mistake to suppose that any such loss is the United Mines ; one card was taken soon augmented by producing motion. Professor after it was first set to work, with an extraMoseley had just stated the true theory on vagant counterweight, and another card was that head, which theory was demonstrable taken immediately after several tons of bamathematically, and admitted of no ques lance had been added, without alteration of tion.
the load of water in the pumps : balance in It would be needless to go further into Cornwall is contrary to counterweight, so what had been so well explained, except to that adding balance effects a reduction of observe that the theory applies without the counterweight. Now, if an attempt had least abatement, or modification by inci. been made to ascertain the friction of that dental causes, to the case of any machine engine by trying what strength of steam
would cause the engine to creep in-doors, moving the engine each way, or through the day before the balance was added, the each half stroke; but that is not a correct friction would have appeared, (by that way of stating it: 11 lb. friction in coming mode,) to have been 3 lbs. or 4 lbs. per in-doors, and 14 lb. friction and resistance of square inch greater than it would have ap water, in going out-of-doors, would be more peared to be after the balance had been likely to be correct. added ; although that was an extreme case, not likely to occur often, yet errors in the imputed amount of friction, to the extent of
LIST OF PATENTS GRANTED FOR SCOTLAND 1 lb. or 1} lb. per square inch, would be FROM 23RD JUNE TO JULY 18, 1842. continually made, if dependance were to be John Cox, of Gorgie Mills, Edinburgh, tanner and placed on that mode of trial of engines glue manufacturer, for certain improved processes working with so much counterweight as they
of tanning. Sealed, June 23.
John Bould, of Ovenden, in the parish of Halifax, may happen to have.
York, cotton spinner, for an improvement or imThe friction of modern engines in Corn provements in condensing steam engines. June 23. wall, including that of their pit-work and
John Americus Fanshawe, of Hatfield street, in
the parish of Christ Church, Surrey, gentleman, for pumps, and the resistance of the water, he
an improved manufacture of water proof material believed would not be found materially, if applicable to the purposes of covering and protectany, greater than was the case in Mr. Watt's ing surfaces, bodies, buildings, and goods exposed old engines, when the depth of the mines
to water and damp. June 30.
James Boydell, jun., of the Oak Farın Works, was not half as great, and the weight of near Dudley, Stafford, iron master, for improvemoving parts not one-third as great; for the ments in the manufacture of keel plates for vessels, improvement in pit-work and pumps, and
iron gates, gate posts, fencings and gratings, June 30.
Michael Coupland, of Pond-yard, Park-street, engine-work, had kept pace with that in Southwark, millwright and engineer, for improvecrease of depth and weight.
ments in furnaces. June 30. The pump-rods are hung more truly per
Thomas Banks, of Manchester, Lancaster, engi
neer, for certain improvements in the construction pendicular, and the lengths of timber for the
of wheels to be employed on railways. July 6. rods are better jointed, so as to cause them John Tresahar Jeffree, of Blackwall, Middlesex, to hang straighter in the pit whilst working,
engineer, for certain improvements in lifting and
forcing water and other fluids, parts of which imand avoid lateral vibratory flexure, and there. proveinents are applicable to steam-engines. July 0. fore the rods rub less against their guides ; James Nasmyth, of Patricroft, near Manchester, the plungers are set truer, and, being of
Lancaster, engineer, for certain improvements in
machinery or apparatus for forging, stamping, and large diameter, have less rubbing surface in
cutting iron and other substances. July 7. proportion to their contents, the lifts being Charles Augustus Preller, of East Cheap, London, higher, and short lifts being avoided : these,
merchant, for improvements in machinery for pre
paring, combing and drawing wool and goats' hair. and many other improvements, tend to re (Being a communication from abroad.) July 13. duce the friction in proportion to the force William Revell Vigers, of Russell-square, Midexerted.
dlesex, Esq., for a mode of keeping the air in conThe small quantity of steam expended,
fined places in a pure or respirable state to enable
persons to remain or work under water, and in and consequently of water injected into the Other places, without a constant supply of fresh condensers, as well as better joints to pre
atmospheric air. (Being a communication from vent leakage of air into the exhausted parts,
abroad.) July 13.
Gottlieb Boccius, of the New Road, Shepherd's reduces the power required to work the air Bush, Middlesex, gent., for certain improvements pump to a smaller proportion of the power
in gas, and on the methods in use, or burners for
the combustion of gas. July 14. exerted by the engine than formerly. And,
John Hall, of Breezes Hill, Ratcliff Highway, in particular, the valves and water-ways Middlesex, sugar refiner, for improvements in the through the pumps are made more open
construction of boilers for generating steam, July than formerly, so as to diminish the loss of
John Elliott Fox, of Finsbury Circus, London, force that is occasioned by resistance of gent., for improvements in steam engines. (Being the water ; that loss of force by resistance a communication from abroad.) July 18. increases as the square of the velocity of the motion, when loss of force by mere friction does not increase by increase of that velo LIST OF PATENTS GRANTED FOR IRELAND city. He believed few large engines in Corn
IN JUNE, 1842. wall, which are making what is now thought M. M. Laroche Barre, for an improvement in the tolerably good performance, lose more than manufacture of a fabric applicable to sails and other at the rate of 3 lbs. per square inch of the
H. B. Rodway, for improvements in the manupiston, by friction of their moving parts, and facture of horse-shoes. by resistance of the water, and by working their air-pumps, and the best and newest Erratum in List of English Patents given in our engines probably still less. It would, of last No. course, be understood that he meant, by
In the title of Lady Vavasour's Patent, for "im.
provements in obtaining images, &c." read “im. 3 lbs., what is commonly called 11 lb., for provements in machinery for tilling land."
NOTES AND NOTICES. The Great Northern (launched last week at Belfast,) is the largest vessel ever built in Ireland. Her dimensions are 220 feet in length, 37 feet beam, and 26 feet deep in the hold; burden, 1,750 tons, B.M.; she is to be fully rigged as a 50 gun frigate, the length of mainmast to be 90 feet, and 36 inches diameter, mainyard 79 feet, and 22inches diameter in the slings, foremast 83 feet, and mizenmast 76 t; she will be able to spread 6,400 yards of canvass. There are three decks, the upper one to be left entirely clear for action, and to be pierced for 44 guns; the windlass and capstan gear will be placed between decks. She is to be propelled by Smith's Archimedean screw, which will be 12 feet diameter, and 14 feet pitch, but the length will be only 7 feet; it is to make 88 revolutions per mi. nute; the gearing consists of a cog-wheel 20 feet diameter, working into a smaller wheel, of 5 feet diameter, upon whose axis is the shaft of the screw. The engine power consists of two cylinders, 68 inches in diameter, 4 feet 6 inches stroke, and to make 22 strokes per minute; nominal power about 370 horses; there are to be 4 air-pumps, 19 inches diameter, and 4 feet 6 inches stroke, and cylindrical boilers. The engines are to be placed close abaft the vessel, leaving the midships clear for passengers. Derry Standard.
The Great Britain (late Mammoth) is not now expected to be finished before the spring of next year.
The Montezuma Steam Frigate-A very successful trial was made, last week, of a new steam-frigate, which has been built for the Mexican Government, and appropriately named the Montezuma. She was constructed at the yard of Messrs. Wigram and Green, and her engines, which are of 300 horses power, and on a similar principle to those on board Her Majesty's steam.frigates Gorgon, Driver, Styx, &c., were supplied and titted by the firm of Messrs. Seaward and Capel. Her burden is 1,100 tons, but she draws no more thani nine feet water when fully equipped, and is built to carry two swivel guns, 68pounders, on the upper deck, besides the usual number of small guns. Although constructed rather for fighting purposes than for speed, she steamed at the rate of 10 miles an hour, against tide both ways, the engines making 21 strokes per ininute. A new disconnecting apparatus, for releasing either paddlewheel, which was tried, was found to answer admirably.
High-pressure Boiler Explosion. - The last arrivals from Canada bring an account of an explosion on board the steamer Shamrock, attended with a most frightful destruction of human life. The list of sufferers, of the English portion " alone, includes 43 killed, and 20 wounded. The Shamrock was a new boat, and built at Niagara; and her engines, which were of 32 horses power, were on the high-pressure principle. The engineer of the vessel stated, at the coroner's inquest, that, “according to the directions of the builders of the engine, he was allowed to carry 85 lbs. of steam, but that at the period of the accident there were not more than 70 lbs. of steam." (Exactly the pressure at which the Locomotive, now working on the Thames, is said to be worked.)
Sleum Pile Driver.- Among the many improvements in machinery which are daily taking place, we notice with pleasure the introduction recently, at the harbour works, of a self-acting machine for driving piles. The moving power is taken from a cylinder connected with the engine erected for pumping out the water in the dock, which does its work in a most admirable manner. There are two other pile-driving machines, wrought by manual labour, in operation alongside of it, requiring nine men to each; and this seli-acting machine, attended by one man, gives seveu strokes for every one that
the others give, so that it does the work of sixtythree men. It can be extended in the same proportion to any power. It is the invention of Mr. James Milne, engineer at the dock.- Montrose Review.
The Thames Tunnel was opened on Monday last for the first time on the Wapping side of the river, and upwards of 500 visitors, of all nations, passed through the tunnel as far as the shaft on the Ro. therhithe shore. The Wapping shaft is about 90 feet in height, and is surmounted with a handsome dome, which is glazed, and light and air admitted. There are two staircases, one terminating close to the western arch, and the other leading to the eastern arch. The western arch only is opened for visitors; but the eastern one appears likely to be appropriated to the same purpose in a few weeks, and a great number of workmen are now actively employed in preparing it for the reception of the public. The erection of the circular staircases in the shaft on the Surrey side, now closed to the public, will be commenced forth with by the contractors, Messrs. Peto and Grissell, who have completed the staircase on the Middlesex shore. The time allowed for the performance of the contract is three months, when the tunnel will be opened as a thoroughfare for foot passengers; the toll to be charged is, we understand, to be id. each person. Some time, however, must elapse before the circular staircases and inclined planes for horses, cattle, and vehicles can be formed; but the plans are already framed, and the works will be conducted with all possible expedition. The engine and pumps are constantly at work in the Rotherhithe shaft, to clear the tunnel of the accumulation of water caused by the land springs. There is a culvert under the Western arch, into which the waters are collected and pumped out, which keeps that side of the tunnel always dry, and as a current of air now passes through the excavation, the place is rendered comfortable, and by the aid of the gas lights, which are always burning, the temperature of the atmosphere is nearly the same as it is on shore.-Times.
Progress of Steam Power in France.- We find by a recent statistical return, that at the end of last year there were in France 179 establishments having steam power, containing 5,600 boilers, of which 1,889 were for the purposes of heating, and 3,511 for giving motion to machinery. There were, besides, 2,637 engines, the aggregate of which was equal to 39,779-horses power. At the same period there were 260 steam-boats, being 128 more than in 1838, without comprising those belonging to the state. The number of engines was 400, of a force equalling together 45,000-horses power, The number of passengers conveyed by these vessels was 2,500,000, being 800,000 more than in the preceding year. The increase of merchandise sent by them on freight was equally remarkable, having exceeded by more than 60,000 tons the quantity thus conveyed in 1840. The locomotives employed on the rail-roads in the departments of the Seine, Rhoute, Herault, and Loire, were in number 118, and in force upwards of 300-horses power. Of these, about 35 were of French manufacture.
Erralum.-Mr. Jubber requests us to state, that his patent being dated 4th June, 1842, his specifica tion could not have been enrolled, (as stated by mistake in our last,) on the 1st December, 1811.
NINTENDING PATENTEEs may be supplied gratis with Instructions, by application (postpaid) to Messrs. J. C. Robertson and Co., 166, Fleet-street, by whom is kept the only COMPLETE REGISTRY OF PATENTS EXTANT from 1617 to the present time).
LONDON: Edited, Printed, and Published by J. C. Robertson, at the Mechanics' Magazine Ollice,
No. 166, Fleet-street. -Sold by W. and A. Galignani, Rue Vivienne, Paris;
Machin and Co., Dublin; and W. C. Campbell and Co., Hamburgh.