On a new blowing engine, working at high velocities

3"2

.Mechc~n.£cs, Physics, and Chemistry.

These experiments, v - e r y tedious and difficult to conduct, do not appear to indicate any p a r t i c u l a r law. Much in this departu-tertt of eleetrieitv appears yet to be done, before we are able to define t h e laws of conduction, and there are many difficulties to be encountered. It is almost impossible to get wire of any length, of equal t h i c l m e s s and texture. It is also not easy always to obtain the same c o n n e x i o n s, and the least variation in this respect ~4dates the experiments. S o m e o f the anomalies in the tables are to be traced to these causes. A diffhrenee of t e m p e r a t u r e also, it appears, will affect conduction. Even bending lhe wire - w i t h so delicate an instrument as the torsi~m gal~'anometer, will affbct t h d experiment ; and twisting will alter i~s powers permanently.

On a A~ew ]31o~daZ l ¢ ~ ' i ~ e , wo,'ki~g a~ r~'h ve~ocilies, lSj ~[r. Aaci~> At a fbrmer meeting~ t h e writer laid before the Institution lhe opinions which he entertained on_ the subject of blowing eylinders, proposed to be driven at high s'elociti.es~ concluding that there would result therebv a large economv in the i n anui:acture of iron throughout the entire plant anti appliances of this i n d i s p e n s a b l e machine. (See ./trlizon, 1850, p. ~03.) It was observed in t h e former paper that, since the applk:ation of the double-acting m o v e m e n t ~ introduced some fiReen )ears ago, the blowing cylinder has remained~ u p to the present time, without a single olher essential improvement. As 1 e f t at that period, it continaes a large and eumbrous machine, with z o m p l i e a t e d and slow motion; insomuch that the libhi and elastic bodv of the atmosphere is driveii through at n¢~higher ve]ot:ilj than the more pondero u s bodv~ water, can be passed through an ortlinary pump. While the motix~e power was derived, in most hast'races, from a "waterfall, ~ some semblance •of' a reason tbr . . ' there . mio'ht .-', i n d e e d be alleged the slow motmn that h a s been spoken of; although, even in such circumstances, it is but little eoneeivable how the intervention of machinery, to quicken the passage o f the lighter and elastic medium, should so long lmve remained a d e s i d e r a t u m . But the question becomes infinitely more inexplicable, since t h e motive power employed has in ahnost every instance been steam, i t s e l f a medium in the highest degree light and elastic; capable, at t h e same tnne, of being worked under a pressure, and at a velocity, far b e y o n d anything required at prese~t, or that probably ever will be r e q t t i r e d of the air from a blowing cylinder. Such being the fileta~ and contemplating the power and speed attained on the railw@ by loec~rnottve engines, the writer was led to reflect that a similar power was a t least capable of being applied to lhe blowing cylinder; and, while irapressed with this train of thought, he had oeeasio% in ihe latter p a r t o f the year 1848, to make use of some small 9-inch ; y ~ e r s , . d,:iven by ~ i e £ro,n a large blowing engine. It ,,,as the,, ree% mac mese srr~alt engines, when driving shafts only, sometimes attained a velocity o f ~00 revolutions per minut% under the ordinary *

Frotl:~ the London Artizaa for October, 18,51.

On a New Bloto~ng E)~g2ne, worldng at H{gll Velociti'es..

3~

bIast pressure; ,~'hen the idea suggested itself, that it might be possible to reverse their motions, making them blowing cylinders in place of air engines; and this idea, on being tested, turned out to be correct. The cylinder experimented on was of nine inches diameter, and one foot stroke, and being driven at the rate of 320 revolutions per minute, discharged the air at 3~- lbs. per square inch, through a tuyere of 1½th inch, being exactly g.i.th part of the area of the blowing piston. This performance exceeds, as is well known, by double its amount, that of any ordinary engine; the total area of the tuyeres, with a 90-inch blowing eylinder, at a pressure of 3.21-lbs., being about fifty circular inches) which is only -f~ part of the area of the blowing cylinder. Assured by the complete success of this experiment, the writer proposed to construct a steam and a blowing cylinder of two feet stroke; the cylinder for steam to be of ten inches diameter, and that for blast of thirty inches; and to couple them, if necessary, with a second and similar set, acting at right angles upon a common axle; and he is still of opinion that such would probably prove the best arrangement, as well as the best proportions to observe in construction. But in the actual experiment, the cylinders proposed to be placed at right angles have not yet been constructed. The size of that used, owing to peculiar circumstances, has been considerably enlarged. In 1850, finding that more air ~vas required for the manufacturing purposes to which it was applied, the writer, and Mr. Cochrane, his partner, resolved to make a blowing cylinder of such a size as would practically test the question of high velocities; and a steam engine, having a cylinder of fourteen inches diameter, being ready at hand, was fitted with a 40-inch blowing cylinder, ~md to this engine the further remarks have reference. The stroke is two feet; the total weight of the engine about six tons; the boiler made use of weighed three tons, thirteen cwt.; its length over all; istwenty-seven feet, having egg ends; its diameter four feet. The first set of experiments were made in presence of Mr. Beyer, Mr. M'Connell, Mr. Daniel Gooch, Mr. Geach, Mr. Evers, Mr. Coehrane, and several other gentlemen who took an interest in the proceedings~ which were of the following nature. On the outlet pipe were placed four tuyeres : two of them 2~- inches diameter, and the remaining two 2 inches diameter, all blowing inte the open air. The engine being run up to its full velocity, reached 145 strokes per minute. At this rate, the density of the air issuing frorri the four tuyeres approached nearly to f~ve lbs. per inch, the engine remain.lug perfectly noiseless and steady, and the blast being so continuous and regular, that the mercury in the barometer did not vary more than oneeighth of an inch in fact, continued barely living in the tube. A ~'ariety of minor experiments foltowed~ not necessary to be dwelt upon at present; but it is believed perfectly warrantable to star% as the result, that each person present felt convinced that he had seen exhibited a blowing machine of at once a powerNl, cheap, and efficacious character. Although the experiments thus detailed were of the most satisfactory description, and indeed had exceeded every exl0eetation of a first performance, the writer nevertheless felt convinced,"fmm observation of the working, that the steam might be considerably economized; and before

~}

.Mechanic6 Phydcs, and Chemistry.

~i,oaeeding to up.ply it to actual use, resolved to fit the engine with an ~::djust~ng expanstve valve, by ,xhich such economy might be realized. ~}¢nen nns nao t~een litted, and the requisite attachments made, its full complement of blast was thrown into one furnace, viz. : 3500 cubic feet ~f air per mimate; the pressure of the air in the main, close upon the 0]ngine, "~vasa little in excess of three lbs. to the inch; at the tuyeres on t}Je furnace, it was, if anything, rather under three lbs. : but this slight giiscrepancy probably took its origin fi'om the tor{uous character and !~ngth of the main, which exceed 300 feet; a circumstance which it was t~und impossible to avoid, without leaving out of consideration the objects to x~'hieh the new blowing power is ultimate]y to be applied. The engine, during the trial, varied from 96 to 100 strokes per minute. !'!'he steam fi'om the one small boiler, 27 feet by 4, remained tull and. hu!licient for this work, after the engine had worked every day for nearly a month, and had been seen by Mr. Benjamin Gibbons, and several other ]wrsons connected with the iron trade. An opportur~i,,y again occurred_ !fftrying it upon one furnace, with the same result as above; this last }.'xperiment was made in the presence of Mr. Samuel Blackwcll. W'ith ~'es.~ard to fuel, on a subsequent trial, while working in connexion with a }a{'ger blowing engine of the ordinary sort, delivering into the mains 3000 cubic feet of air, at a density of 3{- lbs. to the inch, it was tbund to amount, b y measurement~ to two tons five cwt. of small refuse coal or slack, iv, ~twelve hours. Although the writer does not present the arrangement of the engine, l~ere given, as a ped~et machine, he can entertain no doubt that the de:~elopment of the principle must greatly stimulate the production of iron. It "will be perceived how, by the use of blov'ing machines, working at high x'eloeities, the expense of plant and machinery for blowing a furnace may be reduced, at the rate of sixty-five per cent., from ,xhat it stands at present; or, to one-third of the present amount. The above-mentioned experiments at Woodside have pros'ed sueh engines to be ade~/uate to as large a eIass of works as exist in Stailbrdshire. Their simplicity a n d p~rtable character make them equally available at the smallest charcoal *trainees, in however remote a quarter there might be occasion for their 118e.

Mr. Middleton inquired, whether the blast from the small engine went direct to the fire, ace, or through a reservoir? Mr. Slate said, they had a receiver, twelve by four feet; but in t h e r[{~entg],~@e i e was in repair, they let i t Mr. Niddleton said, that he remembered the late Mr. Murdock w o r k e d a similar blowing engine at Sob% twenty-five years ago; it was directacting, and the only difi~renee was that it had a D valve, a n d w o r k e d at a slower velocity than Mr. Slate's engine. The Chairman said, he had a similar blowing engine in regular w o r k at Woiverton, only working vertically instead of horizontally; but h i s engine: only made ti'om fitly to sixty strokes per minute, while that n o w n,~iter description performed one hundred and thirty in the same time. This gave the blowing engine of Mr. Slate a great advantaae, and w a s its distiaetive feature; ~the great gain "was ia the high speed e]n)loyed.

On t],e Use of Eiecb'o-rnagnets made of Iron l~re.

35

Mr. Davies observed, that Mr. Slate's engine could give a steady blast for a furnace, with full pressur% which Mr. Mui'dock's engine could not do. Mr. Slate remarked, that though Mr. Murdock~s engine had been at work at Soho for the period stated, no further progress had been made in the construclion of the blast engine; for at Soho they still continued to make only the old ponderous engines. Mr. Middleton said, it had been applied at the smithy at Woolwich, and had been at work there for many years. He thought, though Mr. Slate's engine was different in some respects, it was similar in principle to Mr. Murdock's. Mr. \V. Smith was quite satisfied that Mr. Slate's engine would maintain a constant blast fbr a fllrnace. He had seen Mr. Murdock's engine at work; it was an open-top e),linder, and was quite another kind of engtae, tie thought that Mr. Slate's plan of blowing engines was an important advantage in the saving of expense in the erection of iron works, and he believed that a blowing engine could now be erected for £500 on that plan, as ~a'ell as one on the old plan for £1500, to do the same work. The Chairman thought that Mr. Slate's engine was certainly deserving of approbation, and he hoped that he would continue his investigation of the subject, as any improvement or economy in the manufacture of iron was of great importance.

On the K~e of Electro-magnets ~nade of Iron Wire for the Eledro-mag~et,ic ~,~gine. .By 3. P. Joci,~, Esq. ComTnunicatedin a Letter to the late Mr. Sturgeon.* Dt~,~ Sin: In my last letter I gave you an account of some experiments which were intended to prove that electro-magnets made of iron wire are the most suitable for the electro-magnetic engine. In those experiments round ~'ire was used; and it was my opinion that the wire magnets were put in a disadvantageous position, ill consequence of the interstices between the wires. I have since confirmed my views on this subject by the following cxperiment:-I constructed two magnets. The first t:onsisted of sixteen pieces of square iron wire, each {rth of an inch square and ~ inches long, bound ,.'cry tightly together so as to form a solid mass, whose transversesection was -14fthsof an inch square; it was enveloped by a ribbon of cotton, and wound with sixteen feet of covered copper wire, of ~ t h inch diameter. The second was made of solid iron, but was in. every other respect.precisely like the first. These magnets we-e, fitted to the apparatus.., used m my former experiments, and care was taken to make the fnctmn of the pivots equal in'each. Ti~e mean of several experiments gave 16"2 revolutions per minute with the first, and 130 with fl~e second magnet. In the further nroseeution of my inquiries, 1 took six pieces of round iron of d~fferent dmmeters and lengths, and also apiece of hollow round iron, half an inch re.diameter, and ~-~th of an inch thick m metal; these were bent into the U-form, so that the shortest distance between the poles of , Annalsof Electricity,vol.iv. p 58,