^ 



THE CIVIL ENGINEER AND ARCHITECFS JOURNAL. 



[FEBRtTART, 



store the equilibrium with the main tube and its retreat being cut oBf by the 

 valve, it was expelled by tlie piston. 

 I remain, 



Your obedient serrant, 



F. Bashforth. 

 .<?(. John'i College, Cumbridst, Jan. 15, ISIG. 



[It may be as well to iufurai the reader who is not acquainted with ma- 

 thematics, that the object of Mr. IJashforth is not to controvert the princi- 

 ples of Mr. Haydon's paper, but to effect simplifications by wh.cb the 

 arithmetical computations are greatly facilitated. We are, we believe, in- 

 debted to these gentlemen for the only accurate mathematical investigations 

 of a very important subject, hitherto published.]— Ed. 



REVIEViTS. 



A Treatise on the Steam Engine. 15y the Artizan Club. 

 Dec. I. 1845 : Longman, 4to. pp. 10. 



Part XVIII. 



This work which has several times been the subject of our reviews is 

 now drawing to a close. Of the twenty-four monthly parts in which it is 

 to be complettd, three-fourths are now published. It cannot be denied 

 that a vast mass of information is collected in this work, though some por- 

 tions might have been omitted without harm. Of the mathematical in- 

 vestigations, parts are of a very doubtful description, and there is not much 

 'n the theoretical portion of the work which possesses originality. With 

 respect to the practical views, however, the cause is very diflerent. The 

 writers have a way of looking right at practical questions which is exactly 

 suited to the nature of the subjects; so that even wheu we dispute their 

 views we are compelled to confess that they are fairly set before us. 



The present number is illustrated by a large plate of details of the West 

 India Mail Packets Clyde, Tweed, Tay, and Teviot, exhibiting in a very 

 clear manner the forms of the cylinder and slides, the metallic packing, &c. 

 The most interesting subject treated of in the letter press is a comparison of 

 the merits of the principal forms of direct action engines which are divided, 

 into five classes. 1. The Gorgon ; 2. the double cylinder ; 3. the steeple ; 

 4. the double cross-head ; 5. the oscillating. We will give part of the ob- 

 servations made on each class. 



1 The Govon Engines (those which have the connecting rod between 

 the'uiston rod and the crank). "The objections to the Gorgon plan of 

 en-ine are numerous and weighty. In the fust place, only a very short 

 stroke is attainable by this plan of engine; and although we are not ot the 

 number of those who subscribe to the doctrine, that expansion can only 

 be productive of its proper efficacy in a long cylinder, yet we believe that 

 an engine of a moderate stroke will work more steadily and smoothly than 

 when the stroke is short and the reciprocation rapid. There is, moreover, 

 a creat waste of steam at the ends of the cylinder when the stroke is short; 

 and although the amount of this loss cannot be great, yet it is too great to 

 be altogether disregarded. We do not attach the importance attributed by 

 some to the deranging influence of a short connecting-rod upon the side 

 valve but we attach a good deal of importance to the increased friction 

 consequent upon the thrust, when the angle the connecliug-rod makes is 

 great —not on account of the power absorbed, but on account of the dilh- 

 ^ulty' of keeping the bearings from heating. To tins objection it is no 

 Answer to say, that the friction of a direct-action engine is as little or less 

 than that of a beam engine ; the vice being, that the friction is not fairly 

 distributed, but so concentrated at particular points as to be productive ol 

 iniurv in engines of the common proportions. ,, ^ •, r 



"There is however, a far more serious defect of the Gorgon variety of 

 engine than any we have yet mentioned. It involves the use of a large 

 paddle-wheel by the elevation of the shaft, reudered necessary to afford 

 room for the stroke ; and the largeness of the wheel gives too great a ve- 

 locity to the float boards, by which means a considerable proportion ot the 

 engine power is dissipated. There is nothing better known, than that in 

 all cases where there is a great disparity between the speed of the wheel 

 and the speed of the ship, a large amount of the power is wasted in throw- 

 ing the water back from the wheel, instead of being employed in forcing 

 the vessel forwards ; and in the Gorgon plan of engine, as applied to or- 

 dinary sea-going steamers, a serious loss from this source must be per- 

 petually going on, or else the engine must be working under its proper 

 •^ ■ ■ These objections apply to all short connecting-rod 



speed and power. ., •--.,,., ■ ■ 



eu-ines, of which the stroke is small and the shaft high ; and in our eyes, 

 they carry sufficient weight to justify the condemnation of this species of 

 engine in ioto." 



Several varieties of Gorgon engines are then brought under review— 

 those by Boultou and Watt in the " Centaur," by Miller aud Ravenhill in 

 the " Eclair," by Fairbairn and Co. in the " Odin," fvc. The first introduc- 

 lion ofthe Gorgon class is attributed to Messrs. Seaward, and the same 

 defect is alleged against every one of the numerous varieties— that of 

 having the shaft too high. The next classes treated of are 



2. The Steeple Engine, "which is the invention of Jlr. David Napier' 

 has the merit of being very compact and effectual, and in the case of river 

 vessels, offers advantages which have led to its extended adoption. The 

 protrusion of a large portion of machinery above the deck is, however, 

 much objected to in the case of seagoing vessels, and Messrs. Tod and 

 •Macgregor now give the preference to the double cross head engines in 

 such cases. It is a fault, we conceive, to make the air-pump with the same 

 stroke as the cylinder. Where the air-pump bucket moves with a great 

 velocity, the valves atrike so forcibly as to wear themselves out very soon. 

 The injury might, liowever, be mitigated by the use of the Cornish equi« 

 librium valve, both for the delivery valve and the air-pump bucket." 



3. The Double Cylinder Engines. " Of this plan of engine we cannot ap- 

 prove, and we think Messrs. Maudslay would act wisely by giving it up 

 in favour of some less precarious arraugement. The Siamese plan involves 

 an increased leaka;;e, increased friction, and increased radiation, while 

 the grand purpose of direct action— saving of room — is only imperfectly 

 fiillilled. Should either ofthe pistons leak steam, moreover, or either of 

 the stuffing boxes leak air, a twist must be given to the parts ofthe engine, 

 such as would arise if there were more pressure upon one half of a piston 

 than on the other. Such a strain cannot, in our judgment, fail to be sooner 

 or later injurious. The arrangement also involves the use of a low con- 

 denser whicli the air-pump cannot thoroughly drain, and the pitching of 

 the vessel, by causing the waler to run from one end of the condenser 

 to the other, sometimes causes the air-pump to make an ineffectual stroke 

 while at other times the air-pu.np is choked with water, which it can only 

 with difficulty deliver, and fractures occur in consequence." 



A long description is then given of the engine of the Ellen Mac Gregor. 

 A very decided preference is given to the fourth and fifth classes above all 

 the rest, and as the treatment of the question involves points long disputed 

 among engineers, we will at the risk of making a rather long extract, give 

 the decision with some few omissions. 



4, The Double Cross-head E)igi)ies. " The nature of the arrangement in 

 the double cross-head engine will be made manifest by a reference to the 

 engines of Messrs. Bury or iMessrs. Fawcett. From the top of the piston- 

 rod a cross-head and side-rods proceed as in side-lever engines ; and from 

 tlie lower ends of these side-rods other side-rods ascend to a cross-head, 

 situated above the other cross-bead, and which, by means of a short arm, 

 communicates with the crank. By this expedient, the benefit of a long 

 connecting-rod is gained without the disadvantages incidental to the plans 

 already mentioned. There is only one air-pump in Messrs. Bury's engine, 

 but it is double-acting, so that, in effect, it is equal to two. A common 

 objection to this description of pump is, that the air accumulates under- 

 neath the piston ; but it will be remarked, that a provision is made to 

 counteract this tendency, the bulk of the air-pump piston being made to 

 travel past the port, so as to expel air as well as water. We may here 

 remark, that it appears expedient in this engine to avoid injecting from 

 the bilge into the lower condenser, as coal-dust and oiher foreign matters 

 might be drawn into the air-pump chamber, which would resist the descent 

 of the piston, and probably occasion fracture. 



" In Messrs. Fawcett's engine there are two air-pumps, which are 

 wrought by independent bell-cranks off a ciauk in the intermediate shaft. 

 The inferior cross-head is made iu the form of a cross, from the ends of 

 which two rods proceed to a cross bar working vertically in guides on each 

 side of the cylinder, the effect of this arrangement is to bring the centres 

 ofthe rods on each side of the cylinder in the same plane, whereby the 

 twist incidental to an overhanging pin is avoided. Messrs. Fawcett have, 

 we understand, since this design was made, more nearly approximated to 

 Messrs. Bury's arrangement; and we believe their engines are bkely to 

 become a type which many will follow and many more approve. 



5. Oscillating Engines. "The most plausible objection to the oscillating 

 en<rine that we are aware of is, that the cjlinder and stuffing-box will 

 speedily become oval, on account of the pressure necessary to communicate 

 motion to the cylinder. The existence of a tendency of this kind cannot 

 be disputed ; but it is so small in amount as to be imperceptible in prac- 

 tice ; and although, after a lapse of )ears, ilhas been found that oscillating 

 lers became slightly oval, yet the amount of ellipticity is, for the most 

 actually less than is found to exist in the cylinder of common side- 

 lever engines, after ihe same amount of wear. This, indeed, it the ques- 

 tion be considered attentively, is by no means surprising ; for the common 

 parallel motion, if in the least degree out of adjustment, will exercise a 

 most severe pressure upon the cylinder; whereas the maximum pressure 

 that can be exerted on the oscillating plan is only that requisite to over- 

 come the friction of the pivots on which the c>linder oscillates, of which 

 the amount is insignificant. Upon the stuffing-box, indeed, the tendency to 

 wear oval mav be more operative, but, to counteract this tendency, it is 

 made of unusual depth, and a very substantial brass bu.sh is fitted into its 

 interior norlion. The piston rod, moreover, is made of cast steel ; ana, 

 with these precautions, oscillating engines are found to work, for a number 

 of years, without inconvenience from the causes mentioned. 



" Many nautical men, and some engineers, have objected to oscillating 

 engines on account ofthe movement ofthe cylinder, which they imagine, 

 would become a formidable evil in the case of a vessel rolling heavily at 

 sea. These objectors do not seem to have remarked that the ic 



cylinde 

 pari. 



ng ofthe 

 cylinder is neither dependent upon, nor proportionate to, the rolling ofthe 

 sliip, but is regulated exclusively by the movement of the piston ; and we 



