Ml 



Al'l'l.lKD MKCH VNH'S. 



[TUB LOCOMOTLVK (NO I SI. 



In the hicomotire engine, tho action U precisely similar 

 t. . th.it .-i" tli.' direct-acting vertical engine, although the 



i horizontally, and tho framing U < i- 



i in such a manner with the boiler, a* to secure 

 strength and lightness. 



Tho three annexed plates represent respectively a side 

 elovatiou, a plan, and a partial front elevation aud sec- 

 Fig. 197. 



tion of Orampton's Locomotive. We omit a special 



description ,,f tin--. K-eauso the drawings, if carefully 



:.v explanatory ol the uses and 



us <,f the various part*. Other locomotives 



iiat in the details, both as to arrangement 



M EtCfKfftioos, but all embody tho same principles of 



*te years portable or Incomoble engines have 

 attained great hnporU&oe, and likewise traction engines, 

 or engines suited for travellin,- and drawing ln-a\-y loads 

 on common roads. All these have so many features in 



common with the locomotivi such as tiilmlar boilers, 

 and cylinders plaoed horizontally, or at a slight angle to 

 tin- liori/.oii that their constrm-tiii may be readily 

 understood without special drawings or descriptitiii being 

 necessary to illustrate it. Before quitting this | 

 of our subject, we may also refer to a particular form of 

 engiuo, whii-h has l*-en largely adopted where economy 

 of weight Olid of space is desirable : we mean oscillating 

 engines. At first these were made on a small ticale 

 d for such boats as those which ply on the Thames ; 

 but of late years they have been employed on a 

 large scale, and with MR-COSH. The paddle-engines of t in- 

 Oral ( Eaxttrn are of this kind, and many other large 

 vessels are now fitted with engines of like construction. 

 The cylinder of an oscillating engine, instead of being 

 fixed firmly on its bod, is provided with trunnions at 

 each side, about midway in its length, somewhat like a 

 cannon, and these trunnions are fitted into bearings 

 formed in the framing, in such a manner that the cylin- 

 der is free to oscillate upon them as on pivots. The 

 >n-rod which passes through a long and strong 

 stuthug-box on the cylinder cover, is made of larger 

 diameter than usual, for the sake of giving it great 

 strength transversely ; and it is jointed directly oil to 

 the crank without any intervening connecting-rod. As 

 the crank. pin travels round in a circle, it carries with 

 it the top end of the piston-rod, not only in a direct ion 

 upwards and downwards (co-incident with the axis of 

 tho cylinder), but also from side to side (or transversely 

 to the axis). The motion of the piston, from end to end 

 of the cylinder, accords with the one direction of the 

 crank's motion, and the oscillation of the cylinder on 

 its trunnions allows for the other. As the steam has to 

 be admitted to the oscillating cylinder, and has also to 

 escape from it after having done its work, the trunnions 

 are made hollow, and form passages for the steam to aud 

 from a jacket or steam space provided on the cylinder, 

 whence it passes by suitable parts, commanded by a 

 slide, to and from the opposite ends of the cylinder suc- 

 cessively. For several years after the invention of this 

 arrangement, it remained comparatively idle, because 

 of the mechanical difficulties that were experienced in 

 properly working the slide on an oscillating cylinder, 

 itself oscillating with it. At length an ingenious arrange- 

 ment for overcoming these difficulties suggested i; 

 and shortly afterwards the use of oscillating cylinders 

 became very general on tho small scale, and gradually 

 came to be adopted for the very largest marine 



nes. 



I.STIMATION OF POWER. In estimating the 

 power of a non-condensing engine, we have to ascertain 

 the pressure on the surface of the piston causing it to 

 move, and the distance passed over by it under this 

 pressure in a given time, or tho velocity with which 

 pressure acts. The product of the pressure by the 

 velocity gives the power ; and if the former be taki -n in 

 Ibs., and the latter in feet per minute, we have to divide 

 their product by 33,000 to reduce it to tho standard of 

 horse-power. For example, if tho piston move over 

 200 feet every minute under an average pressure of 

 1,650 Ibs. on its whole surface, the ellcct is the same as 

 if 1660 X 200 330,000 Ibs. nio\ed over 1 foot per 

 minute ; and as 1 horse-power is reckoned equivalent to 

 33,000 Ibs. moved over 1 foot per minute, the power in 



tho case assumed is 



10 horso-powor. 



But in estimating the pressure on the piston, we are 

 not entitled to assume it as that of the steam in the 

 boiler, as measured by a steam-gauge. In tho lirst 

 place, there is always some length of pipe between the 

 oiler and the cylinder, and the steam passing through 

 this pipe loses some portion of its heat. Jtefei ring to 

 tho table of temperatures and corresponding press' 

 we can see that the reduction, by a very few degrees of 

 the former, produces a very considerable diminution of 

 tin; latter. While it is usual to cover the stvam-pipe 

 with felt, or some such non-conducting casing, in >> 

 to prevent a loss of this kind as far as poas.Mu ; jut with 



