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THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Junk, 



tons : the journals (2£ inches diameter) were also bent in opposite direc- 

 tions, by repeated blows of the sledge-hammer, without any signs of frac- 

 ture being perceptible. The firm, which Mr. Geach represented, had made 

 upwards of 2500 axles, and had tried a very large number by breaking them : 

 they almost uniformly found them of good quality, which might be attri- 

 buted to the mode of manufacture. Around a centre bar of iron were placed 

 eight bars rolled to a proper form to complete a circle ; they were then 

 welded together by rolling, and fiuished under the hammer; the fibre of the 

 iron, it was contended, was thus worked, and remained in its most favourable 

 position. He was not opposed to the principle of hollow axles, but he 

 wished to prevent any unnecessary prejudice against solid ones by inferences 

 from anyone set of experiments; he would therefore suggest that another 

 series of experiments should be made between the relative strength of the 

 two kinds of axles, for which he would contribute the necessary number of 

 solid ones. 



Mr. York described the manner in which the solid axles had been se- 

 lected for the purpose of experiment. Having obtained General Pasley's 

 consent to be present on the occasiou, he ordered axles from the Patent Axle 

 Company, and another eminent maker, and selected also several other axles 

 supplied by the Patent Axle Company to the London and Birmingham Rail- 

 way ; these axles were new, never having been under any carriage ; he con- 

 tended that the result of the experiments afforded a fair specimen of the 

 axles generally in use, and were such as the public were in the habit of 

 riding upon. The axles which had since been made by the Axle Company, 

 and were then exhibited to the meeting, showed a quality of iron which 

 could not be surpassed : if this was the usual quality made use of by that 

 company, it still more forcibly proved his position as to the uncertainty of 

 manufacturing solid axles, for while one specimen took a great number of 

 blows to break it, the majority of them were fractured by a slight force ; it 

 was this uncertainty which he proposed to avoid, and he contended that it 

 was inseparable from the method of making axles described by Mr. Geach, 

 for in passing the faggot through the rolls to weld the bars together it fre- 

 quently happened that they were only united to a depth of one-half or three- 

 quarters of an inch, hence it was to a certain extent hollow, and partially 

 avoided the injurious effect of hammering; if, on the contrary, they were 

 perfectly welded, the iron became crystallized, as in any other solid axle ; 

 this fact was proved by the specimens before the meeting, those that were 

 solid having been broken by very little force, and the unsound ones requiring 

 a great number of blows to produce fracture. In the experiments, the hollow 

 axles had broken under a different number of blows, but this was owing to 

 their having been made of larger diameter in the journals than the solid 

 ones (but with only an equal quantity of metal in them) and afterwards 

 turned down to the same diameter, which left them of unequal thickness 

 and too thin for a fair test; still, however, with less metal than in the solid 

 ones, they were stronger; this might be accounted for by the mode of man- 

 ufacture, as by retaining the axle hollow the crystallization of the iron was 

 avoided. The present mode of making the hollow axles he described to be 

 by taking two trough-shaped semicircular pieces of iron, bringing their 

 edges together, and welding them under a hammer between swages. He 

 however dissented from the process of hammering, and intended to finish 

 ( is hollow axles by compression only. This, he contended, would avoid the in- 

 jur) - done to the iron by the present mode of manufacture, anil that with the 

 same quantity of iron, the strength of axles being as the cubes of their di- 

 ameters, and their weights only as the squares, a hollow axle must possess 

 considerable advantage over a solid one. Hollow axles had long been con- 

 sidered desirable, but the expense of making them had hitherto prevented 

 their use; he had reduced their cost by his process to the same rate as the 

 solid ones, and felt confident that in bringing them under the consideration 

 of the profession, through the Institution, they would be fairly treated and 

 i timately adopted. 



General Pasley confirmed the correctness of the results recorded by 

 Mr. York, and the satisfactory nature of the experiments, which had im- 

 pressed him with a favourable opinion towards hollow axles. It was of im- 

 portance to avoid deflection, as it was almost as fatal as fracture in causing 

 accidents. After the late accident on the North Midland Railway, he ob- 

 served a solid axle bent into the form of the letter C, and the upper por- 

 tions of the periphery of the wheels nearly touching each other. The hollow 

 axles would certainly resist deflection better than solid ones of corresponding 

 weight. 



In answer to a question, Mr. Y'ork said that the iron was chiefly injured 

 by the amount of hammering which it received in forging. 



Mr. Taylor remarked, that the question of the amount of injury received 

 by iron in working, was discussed at the meeting of the British Association 

 in 1842, and the effects of vibration and electricity had also been treated of 

 by foreign engineers. It appeared to be generally admitted, that the great 

 source of mischief was the cold swageing, which the iron received, in order 

 to give the work a good appearance. In order to test this, Mr. Nasmyth 

 subjected two pieces of cable bolt iron to 160 blows between swages and 

 afterwards annealed one of the pieces for a few hours. The unannealed 

 piece broke with five or six blows of a hammer, showing a crystallized frac- 

 ture; while the annealed piece was bent double under a great number of 

 blows, and exhibited a fine fibrous texture. The fact of the fibre being re- 

 stored by annealing was well understood and practised by smiths, particu- 

 larly in chain-making. 



Mr. York could not entirely subscribe to the great benefit of annealing, 

 as he had found that after annealing one end of a hollow axle for 48 hours, 



it was broken off by 82 blows, while the other (unannealed) end of the same 

 axle resisted as far as 78 blows. 



In answer to a question from Alderman Thompson, Mr. York said that he 

 had found as much mischief arise from over-heating iron as from over-ham- 

 meriug it ; but the difference of the appearance of the fracture, indicated 

 immediately when iron had been burned. 



Mr. Taylor said that in Mr. Nasmyth's experiments, the over-heated iron 

 was almost as fragile as glass. 



Mr. Gravatt believed that vibration, whether caused by the smith in 

 working the iron, or by the use to which the bar was appropriated, was the 

 reason of its fracture, and it was certain that a constant change was going 

 on in all manufactured iron. At the Thames Tunnel the •' fleeting bars " 

 used as levers for turning the large screws for forcing forward the shield, 

 never lasted longer than three or four weeks, although they were very strong, 

 and were made from the best materials by careful smiths. They were only 

 used occasionally, and then without any concussion, having only the power 

 of eight men exerted upon them : yet they broke constantly, and the fracture 

 exhibited a bright crystallized appearauce. It was found at last, that in 

 order to give them duration they should be left rough, and not hammered 

 much in working. 



Mr. Newton observed that full 10 years since, Dr. Church had used hollow 

 axles for his experimental steam coach on common roads, being convinced of 

 their superiority. 



Mr. Fox was an advocate for the hollow axles, but he did not consider the 

 present experiments quite conclusive, as there were differences in the relative 

 dimensions of the axles experimented upon; he would suggest another 

 series of trials, upon a larger number of axles, as the subject was one 

 of great importance, not only to manufacturers but to the public, whose 

 safety in travelling depended upon the goodness of the axles under the car- 

 riages. He had used upwards of 5000 axles made by the Patent Axle Com- 

 pany, and bad made many experiments by breaking them ; the average re- 

 sult was equal to that quoted by Mr. York. He agreed in the danger arising 

 from over-heating iron, as also from over-hammering it, and for some time 

 past he had caused all the axles to be made six inches longer than was ne- 

 cessary, in order to cut three inches off each end, to try the quality and the 

 appearance of the fracture of the iron. 



The President remarked, that there could not exist a doubt as to the 

 greater strength of a hollow axle, as compared with a solid one, both con- 

 taining the same weight of material; the principal question to be considered 

 was, that of vibration, and its effect upon the cohesive strength of the 

 metal; whether the action upon the particles was more irregular in the solid 

 body and more distributed in the hollow one; he recommended this investi- 

 gation to some of the mathematicians who were present ; the result of their 

 inquiries might materially aid in the development of truth from the prac- 

 tical experiments. 



February 28. — The President in the Chair. 



" Description of the Roofs over Buckingham Palace, covered with Lord 

 Stanhope's composition." By Peter Hogg, Assoc. Inst. C. E. 



The mixture invented by Lord Stanhope, and used by the late Mr. Nash, 

 for covering the nearly flat fire-proof roofs of Buckingham Palace, is des- 

 cribed in the paper as being composed of Stockholm tar, dried chalk in 

 powder, and sifted sand, in the proportions of three gallons of tar, to two 

 bushels of chalk, and one bushel of sand, the whole being well boiled and 

 mixed together in an iron pot. It is laid on in a fluid state, in two separate 

 coats, each about three-eighths of an inch in thickness, squared slates being 

 imbedded in the upper coat, allowing the mixture to flush up between the 

 joints the whole thickness of the two coats, and the slates being about an 

 inch. The object in embedding the slates in the composition, is to prevent 

 its becoming softened by the heat of the sun, and sliding down to the lower 

 part of the roof, an inclination being given of only 1-} inch in 10 feet, which 

 is sufficient to carry off the water, when the work is carefully executed. One 

 gutter, or water-course, is made as near to the centre as possible, in order to 

 prevent any tendency to shrink from the walls, and also that the repairs, 

 when required, may be more readily effected. It is stated, that after a fall 

 of snow it is not necessary to throw it from the roof, but merely to open a 

 channel along the water-course, and that no overflowing has ever occurred ; 

 whereas, with metal roofs it is necessary to throw off the whole of the 

 snow on the first indication of a thaw. These roofs have been found 

 to prevent the spreading of fires, and it is stated, that on one occasion, 

 to test their uninflammability, Mr. Nash had a bonfire of tar barrels lighted 

 on the roof of Cowes castle. Another advantage is stated to be, the facility 

 of repair which the composition offers, as if a leak occurs, it can be seared 

 and rendered perfectly water-tight, by passing a hot iron over it ; and when 

 taken up, the mixture can be remelted and used again. The author proposes 

 to obviate the disadvantage of the present weight of these roofs, by buildiug 

 single brick walls at given distances, to carry slates, upon which the compo- 

 sition should be laid ; instead of filling the spandrils of the arches with solid 

 materials, as has been hitherto the custom. 



The reported failures of this species of covering at Mr. Nash's house in 

 Regent Street, and iu other places, are accounted for by the composition 

 having been used in one thin coat, laid upon an improper foundation of laths 

 and tiles. The durability of the roofs, which were carefully constructed 



