18i9.J 



THE CIVIL ENGINEER AND ARCHITECrS JOURNAL. 



375 



comforts ill railway (ravelling, anri no system that cnuld he devised woiiH 

 recimcile passengers to be packed together like fisli. He (the President) felt 

 that, occupying as he did a position in the manatreinent of railways that 

 might give his npininn weight, he had thnnglit it riglit to say what he had 

 done, lest lie miyht he considered tacitly to admit that that which engineers 

 had heen doing since 1831 in increasing the weight of engines, had been 

 practically wrong. 



ON RAILAVAY AXLES. 

 On the Construction of Jtailway Axles. By Mr. J. E. M'Connell. 



Wlien the railway system was first introduced into this country, 

 the question of strength of materials for constructing the new 

 stock was (it is to be presumed) materially influenced by the 

 amount of experience derived from the vehicles which had pre- 

 viously been in use for the conveyance of traffic. 



As the new system became extended and improved in all its 

 arrangements, and the facilities which it possessed for conveying 

 greater loads at higher speeds were gradually developed, the 

 working stock was necessarily changed from time to time in con- 

 formity with the greater demands for convenience and stability. 

 Improvements in almost every point have been carried out, until 

 we have now in operation the railway stock, generally speaking, in 

 an excellent condition for the purpose to which it is applied. It is 

 remarkable that, notwithstanding the importance of proportion 

 and quality as first elements in considering the strengtli of the 

 materials of which railway moving stock is composed, no rule, 

 generally applicable for even the main features of this great 

 system of machinery, has been established. AVithout attempting 

 to embrace the whole subject, although one of great importance to 

 proprietors of railways and the public generally, I conceive it is 

 proper, in this place, to express my strong conviction that the 

 general question of the strength and quality of those materials 

 justly proportioned to the strains to which they are subject, and 

 bearing reference to accidents from collision, faults of road, dete- 

 rioration from a variety of causes, S:c., must eventually be treated 

 with great attention and consideration; and, in order to insure 

 safety to life and property for all who use railways, as well as the 

 greatest possible economy for the profit of those who have em- 

 barked their capital in their construction, I believe it will be 

 found essential to have some regulations founded upon the joint 

 experience of those parties who have been practically engaged in 

 managing and working the different departments of railways. 



It is well known that short-sighted economy has been practised 

 in many instances in giving directions for the purchase and repair 

 of railway stock, and it is only dear-bought experience which can 

 effectually convince those who, to make a little saving by purchas- 

 ing a cheap, ill-constructed machine, gain a great and constant loss 

 whilst it is in use. The advantages of a general and constant in- 

 terchange of opinion among those parties to whose judgment and 

 management the working expenses of the different railways are 

 entrusted is most important; and if such varied experience could 

 be collected, regularly and systematically into one focus, where it 

 might be digested and prepared for practical use, the effect for 

 good to the general system of railways would be very great, and, 

 in a scientific point of view, the results recorded would prove 

 highly interesting. Having thus briefly stated a portion of my 

 views as bearing upon the introduction of the best means of pro- 

 ducing uniformity in the working stock of railwjiys, I will now 

 proceed to consider Railway Axles, which, as an important part 

 of the great machinery, are deserving of the most marked atten- 

 tion. 



1 have endeavoured to ascertain whether any data were available 

 which might assist me in forming a groundwork of the results of 

 combined experience on this subject; but I regret to say that, 

 although my inquiries have been in all cases promptly and care- 

 fully attended to, yet the object which I had in view has not been 

 attained. As an example of the diversity of opinion, or rather, 

 perhaps, the want of some certain rule to guide engineers in pro- 

 portioning the strength of axles to their \^eights and strains, I 

 would refer to different forms of axles now in use on one portion 

 of one railway, and in doing so would remark, that a clearer proof 

 could not be afforded of the desirableness of having some defined 

 principle to guide us in deciding on the strength for i-ailway axles. 

 For obvious reasons 1 wish particularly to guard against express- 

 ing, directly or by inference, any opinion on any description of 

 manufacture of axle, or even quality of iron of which axles are 

 composed. I would wish to limit the scope of the present paper 

 simply to the question of form and dimensions of axles, with the 

 changes and deterioration to which tliey are subject in process of 



working, assuming, in all cases, the material of which the axle is 

 made, and the mode of manufacture, to be of the most approved 

 description. 



In order to arrive at a knowledge of the best form and dimen- 

 sions of axles, we have first to ascertain the load and friction to 

 which they are to be exposed; and, secondly, to estimate, as nearly 

 as possible, the strains to which they will be subject whilst in 

 motion. Supposing a wagon or carriage to be constantly in a state 

 of rest, it would, of course, then only be necessary to consider the 

 axle as a beam or girder, sustaining a load of five tons upon the 

 two journals, the points of support being the viheels resting upon 

 the rails, the middle portion of tlie axle being of sufficient strength 

 to sustain the wheel or prop in its perpendicular position. We 

 then require to find out the proportionate strength, so that each 

 section of this beam or girder sliall only be sufficiently strong to 

 resist the strain or load to which it is then subject. 



It is ascertained, by an approximate calculation, that a journal of 

 1-128-inch diameter is not capable of sustaining a heavier load, when in 

 a state of rest, than 2^ tons, or 5,600 lb.; and allowing, in practice, 

 that the wagon- or carriage axle is made ten times the breaking strength, 

 the diameter of the journal would be, adopting the same calculation, 

 2'-13 inches. In these calculations the strength alone is considered: 

 but we have also to take into account the question of friction, and 

 likewise the tendency to abrasion. AVith our present means of 

 information, no accurate data are available for determining the 

 best proportion of journal or bearing according to the weight it 

 has to bear, or the velocity at which it is required to move. A 

 great variety of proportion is in use, but it is fair to note that in 

 engine-axles, particularly the length of bearing, depends, to a cer- 

 tain extent, upon the construction and arrangement of the engine; 

 as a general rule the length of the bearing is not in due propor- 

 tion, according to our general experience, to the diameter. 



It has always been considered that having first ascertained, from 

 example and experience, the strength of sectional area necessary, 

 nnder every circumstance, to sustain the load which the journal 

 has to carry, tlie length of it was determined by the velocity or 

 amount of friction to which it is liable. Judging from axles at 

 present in use in carriages and wagons, the length of bearing is twice 

 the diameter of the journal; but on this, as v,ell as otiier points on 

 strength of material, there exists a great variety of opinion. 

 Even the forms of journals are found to differ \ery much. With- 

 out attempting to decide on the merits of any of them, I shall in 

 the present instance content myself with stating that all my expe- 

 rience has proved the desirableness of maintaining rubbing or 

 wearing surfaces of bearings as free as possible from sharp abrupt 

 corners, sudden alterations in diameter, or sectional strength. 

 Having thus treated the journals as regards the load and the 

 friction upon them, I now proceed to estimate the various strains 

 to which the axle is exposed whilst in motion. 



The first .strain to which the a.xle is subject is that arising from 

 the weight of the wagon and load, which being received or resting 

 on the journal, produces the greatest effect upon the axle at the 

 outer face of the wheel-boss, and to which is to be added the 

 momentum of the load in falling through spaces caused by inequa- 

 lities or joints of rails. Tiie injurious consequences of inequalities 

 on the road, surface, and flat places on the surface of the wheel- 

 tyre, upon the axle, by the jolting or perpendicular motion which 

 they produce, cannot be accurately estimated, and these are very 

 much inci-eased when the bearing springs of the wagon or carriage 

 are not sufficiently elastic, and do not yield to the shock or blow 

 downwards, so as (to use the expression) to cushion its effect. As 

 an instance of the imperfect action of the springs, I would allude 

 to those in use on many wagons, in which the form and construc- 

 tion cause them to be so rigid that the downward blow is more 

 like a hammer upon an anvil. To obviate this strain as much 

 as possible, it is necessary to proportion the spring so as to 

 sustain the load properly, and yet to be of sufficient elasticity 

 to absorb the effect of the load oscillation. The strain arising 

 from the oscillation of the wagon on curves from imperfect 

 coupling, and increased by the lateral freedom or space on the 

 bearings or play between the rails and flanges of the wheels whicli, 

 when an irregularity occurs on the side of the rail, or any sudden 

 cause disturbs the direct motion of the wagon onwards, is in effect 

 the same as a blow upon the flange of the wheel, the radius of the 

 wheel tending to act as a lever to break the a.xle at the inner face 

 of the boss of the wheel. This strain is in the compound ratio of 

 the momentum of the load, the angle at which the wheel strikes 

 the rail, and the distance from the centre of the axle to the point 

 of impact; producing an effective strain upon the axle at the inner 

 face of the wheel boss, which extends proportionately over the 

 whole axle between the wheels. To lessen in practice as much as 



