274 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



was with sre.it regret that I perceived the cause of the accident attributed to 

 the principle of construction of the machine. It must be quite evident to all 

 engineers who have attentively read the details of the accident on the Ver- 

 sailles Railway, and of the one that occurred on the Lomlon and Brighton 

 Railway soon after the first opening, that the same causes were in operation, 

 and greatly aggravated the sad results in both instances, viz. the coupling 

 together of two locomotive engines of unequal power and of diflercnt con- 

 structions, the smaller in advance ; — On both occasions a long train of heavily 

 laden carnages were moving at very high velocities on a falling gradient j 

 on the occurrence of the accident to the smaller engine in front, the driver 

 suddenly turns ofl' the steam ; the man on the larger engine behind, from 

 uhatever cause, does not act simultaneously, and a few seconds continuance 

 of the vast unchecked momentum of the heavy engine with the steam on. 

 overwhelms the smaller machine, and the whole tr.ain is overthrown. It is 

 scarcely possible to regulate this unity of action, more especially in the loco- 

 motives of unequal size and construction. "Why are engines propelling from 

 behind objected to ? Evidently because, in the event of any obstacle occur- 

 ring in front, a simultaneous check cannot be given to the rear engine, and 

 it drives the carriages forward upon each other, at the very moment when the 

 opposite effect is required. 



There is, therefore, quite sufficient to account for the accidents in both 

 cases, without raising the ridiculous and exaggerated cry against the four- 

 wheeled engine per se. As respects safety to the travelling public, I believe, 

 and I venture to say, in common with a great many engineers who are not 

 manufacturers, that there is no material difference between the four-wheeled 

 and the si.\--wheeled locomotives ; but that the consideration most generally 

 influencing the selection is that of the distribution of the weight of the ma- 

 chine, so as to impinge less injuriously on the rails ; and it is well under- 

 stood that the system of the double trucks, or eight-wheeled supports for 

 locomotives, tenders. Sec, as adopted on the American Railways, has been 

 introduced on this principle, the rails and upper works in that country being 

 in general«tiuch lighter than with us. 



The real and important point, and which seems to have been quite lost 

 sight of in the vivacious discussions on what I would call the minor question 

 of the number of wheels, is, whether the cranked axles fur the driving wheels 

 of locomotive engines ought not to be abandoned, and whether driving a.^les 

 should not be always made straight. The extent of prejudice in favour of 

 cranked axles is most extraordinary. The very great increased expense 

 incurred in making and strengthening them, the additional complexity and 

 cramping into narrower space of all the moving parts of the machinery, and 

 the consequent wear and tear and inconvenience involved by their use, to say 

 nothing of the augmented risk, far overbalance, in my opinion, any theo- 

 retical advantages alleged in their fav ur, but which advantages and supe- 

 riority, in practice, over the straight axle engine, I could never discover and 

 wholly deny. Eight years since, after a hard struggle with the manufac- 

 turers, straight driving axles were adopted lor the locomotives on the Dublin 

 and Kingstown Railway. On that line, especially on Sundays and on holi- 

 days, the traffic is quite equal to that on any railway yet open. Trains of 

 from 12 to 1.5 carriages (but with one engine only) are at such times sent 

 every quarter of an hi. ur from each end of the line ; and there has been no 

 instance of accident from any cause connected with the form of engine or 

 axle, or with such frequent departure of heavily laden passenger trains ; and 

 the finance accounts of the Company show that the cost of locomotive power, 

 repairs. &c. is below that of other lines using cranked axles ; nor do I know 

 of any cause of objection to the straight driving axle, after seven or eight 

 years experience of their use, without, I believe, a single instance of failure 

 which fully justifies my opinion of their superiority. 



On other railways I have been connected with 1 have not always been so 

 fortunate as to have succeeded in banishing the cranked axle. As sometimes 

 happens in Governmental and political struggles, the votes of the controlling 

 body have overpowered the opinion of the executive, where a difference 

 among members of our profession have given opportunities for Directors to 

 exercise their own discretion ; and cranked or straight axles, four-wheeled or 

 six-wheeled engines, have been alternately adopted according to the pre- 

 vailing ideas of the majority of the several railway boards. 



I have, however, reason to believe that several engineers of high standing 

 are becoming converts to the straight axle, and I congratulate the public on 

 it. as a very important step in the right direction. 



In respect to the attention to be given to the manufacture of axles, it is 

 impossible to pay sufficient regard to the importance that the scrap iron 

 should not only be of very good, but also of exactly similar quality, and that 

 each scrap should have gone through the same processes in its previous 

 difierent stages. On this subject I hope some of the experienced manufac- 

 turers who are present. will throw some light, especially on the details, for on 

 the abstract principle there can be no dispute, although I suspect it is 

 greatly neglected, in particular for ordinary carriage axles, and probably 

 only scrupulously attended to in forming the driving axles of locomotives. 



Some of the French engineers, hov. fver, have, within a very recent period, 

 suggested that we must seek for the causes of the often unexplained rupture 1 



of axles in another way. M. Francois and Colonel Aubert have both lately 

 read, at the Royal Academy of Paris, jiapers on the subject, and attribute 

 the cause of the fracture of the axle of the engine on the Versailles Railway 

 to the iron having been crystallized from the action of heat or magnetism. 

 In support of this opinion it is stated that the axle broken was formed of the 

 best iron, and was of sufficient dimensions; and that the fracti>re bad a de- 

 cided crystallized appearance : and I have indeed myself often observed the 

 same character in broken ax'es, so much so as to induce me to fancy some- 

 times that they had Ijeen formed of cast iron. 



M. Fraufnis stated in his paper that he had made a long continued series 

 of experiments, and had observed that a magnetic action on iron in a state 

 of fusion will produce similar etiects. and change the small and closely ad- 

 hering particles into coarse and large crystallized grains, depriving the iron 

 of its compact character. This talented mineral engineer inferred that the 

 action of heat upon axles moving at high velocities might produce the same 

 effect. Both M. Frauf ois and Colonel Aubert seemed to be of opinion that 

 the only real precaution was to change the axles of locomotive engines so 

 frequently as not to give them time to undergo the crystalline change ; sug- 

 gesting, however, that iron that had been previously worked up should alone 

 be employed for axles, and not new iron, which had more of a vitreous cha- 

 racter, and was more susceptible of crystallization. 



Since this paper was prepared, I have reason to believe that this crystal- 

 lization of wrought iron has been noticed by si me of our eminent manufac- 

 turers, whose opinions there may be an opportunity of obtaining ; and if it 

 be. as Mr. Fairbairn informs me, that cold swaging will crystallize hammered 

 iron, the shocks that locomotive engines sustain in their rapid transits may- 

 well be put as a greit cause of this remarkable change. 



It is, however, clear, that to remedy and replace straight axles is much 

 easier and cheaper than to deal with cranked axles, and I venture to state it 

 as my humble opinion, that as much ingenuity and talent is thrown away in 

 arranging locomotive engines with cranked axles, and in perfecting the 

 manufacture of those " crooked billets," as there was in rolling iron into 

 undulations for fish-bellied rails ; which are now almost as much forgotten 

 as, I doubt not, the cranked axles for locomotive engines will one day be. 



Remarks. — Mr. Ilodgkinson was certain, from the results of his experiments, 

 that asuccession of strains, however slight, would produce a permanent deterio- 

 ration of the elasticity of the iron. — Mr. Fairbairn had been told by the engi- 

 neer on the Leeds line, that he considered all crank axles to he constantly dete- 

 riorating from percussions, strains, &c., and that they should be removed 

 and replaced by new ones periodically, to avoid danger of fracture. — A dis- 

 cussion arose as to whether the crystalhzed appearance observed in fractured 

 axles arose from defects in the manufacture, in the quality of the iron, or 

 from the effects of working, either by percussions, strains, or magnetic action. 

 — Mr. Grantham, although a manufacturer of cranked axles, admitted that 

 straight axles were less liable to break. Cranked axles, from the way in 

 which they were welded together and shaped, were rendered weak and liable 

 to fracture. On other grounds, however, he believed that the cranked axles 

 were preferable, as they produced a steadier motion, and much heat was 

 saved. — Mr. Garnett believed that more straight axles had broken than 

 cranked ones. — Prof. Willis showed the effect of vibration iu destroying 

 molecular arrangement, by reference to the tongues in musical boxes, &e. — 

 Mr. Nasmyth believed that the defects in axles, &e., arose in the manufacture, 

 especially from cold swaging and hammering, and also from over-heating in 

 welding, all of which causes injured thif toughness of the iron. In small 

 articles he found great advantage from annealing; and he believed that axles 

 might be annealed very cheaply, and would be more serviceable. He dis- 

 Uked the fashion of referring all unaccounted phenomena to magnetism and 

 electricity, although he was convinced that very singular electric phenomena 

 accompanied the transit of locomotives and the rapid generation of steam. 

 With this was connected the non-oxidation of rails, where the traffic was ia 

 one direction, and the rapid oxidation when the same rails were travelled 

 over in both directions, as in the Blackwall railway. He had also observed 

 that brasses, in some cases, had from friction entered into culJ fusion — that 

 is, at a heat not perceptible to the eye, a complete disintegration of the mo- 

 lecular structure had taken place, and he had seen the brass spread as if it 

 had been butter or pitch. He had no doubt that this arose from electricity, 

 hut had not ascertained the fact from experiment. — Mr. Fairbairn stated, that 

 in hand-hammered rivets the heads frequently dropped off, and presented a 

 crystallized appearance, while those compressed by machine were sound. 

 He found that repeated percussions, from the rivetting, hammeiinp plates, 

 Sec, induced magnetism in iron boats. — Mr. Vignoles could not, from liis 

 experience, agree to Mr. Nasmyth's theory of the oxidation of rails by single 

 traffic, as the railway from Newton to Wigau had been single for a long time, 

 and was as bright as the Manchester and Liverpool. The lilackwall railway 

 was not an analogous case, as no locomotives were employed. — Mr. Roberts 

 disbelieved the deterioration of axles by work; he would rather trust an old 

 axle than a new one. He believed cold swaging and hammering to be the 

 chief causes of mischief. In fact, if axles were sent out sound and well 

 manufactured, they would rather improve by working. 



Mr. Nasmyth at a subsequent meeting gave some valuable practical sug- 

 gestions on the cause of breaking of axles, which we purpose noticing next 

 month. 



