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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



121 



which was colJ-hammereil at one end, havinjj received 20+ blo-vs 

 on all sides frtini a 3j ton tilt hammer; 110 blows with a sledije 

 hammer were jjiven to nick this end all round which had been cold- 

 hammered, and it required only 5 blows from a 3j ton hammer to 

 break it; the other end which had not been cold-hammered, alter 

 receiving the same number of blows in nicking-, required 78 blows 

 under the 3j ton hammer to break it, thus proving the enormous 

 amount of deterioration of the strength of the iron caused by the 

 cold-hammering process. 



No. 9. A piece of round iron 2| inches diameter which had two 

 bearings turned (one at each end) l| inch diameter by 2i inches 

 long, was allowed to run at a considerable velocity for about an 

 hour, with one end oiled and the other dry, the dry end being 

 cooled with water repeatedly when it became hot; the iron was 

 then experimented upon in order to determine by the different 

 force requii-ed to break the end whicli had been injured by want of 

 lubrication, the relative strength of each bearing, but such was tlie 

 remarkably tough quality of this iron, that although it received 

 520 blows of a heavy sledge hammer in every possible way to break 

 it in one direction (without being nicked), no fracture could be 

 effected, but the iron seemed to be drawing out at the back of the 

 journal on end, as will be seen by tlie meeting. 



This last case is noticed in particular, as the following experi- 

 ment of a similar character with an old axle of larger dimensions, 

 shows in strong contrast the altered nature of similar iron from use 

 on a railway, owing to the jar or vibrating action it has suffered. 



In the 9tli experiment a piece of new iron intended for part of 

 an axle, although run dry and cooled with water, yet was so fibrous, 

 having received no jar, that it resisted all effort to break it. 



No. 10. Another experiment of a similar character was tried on 

 an old axle which had been a long time in use, of the same kind of 

 iron and manufacture as the bar in No. 9 experiment. This axle 

 with the wheels on was run in its own bearings in a lathe at a velocity 

 equal to 10 miles per hour for 5 hours; one journal was kept run- 

 ning dry, and when heated by the friction cooled with water, while 

 the other journal was kept well lubricated with oil. When taken 

 out, the journal which had been heated was broken with 12 blows 

 of a hammer 22 lb. in weight, while the lubricated journal required 

 91 blows with the same hammer to break it, in both cases without 

 being nicked; this appears satisfactorily to prove the injury to the 

 axle which results from the practice of throwing cold water on the 

 journal to cool it when it has become nearly red hot from want of 

 proper lubrication. 



In addition to various other experiments with the view of deter- 

 mining the change which is gradually going on in railway axles, and 

 Oilier iron liable to a jarring, vibrating motion, the writer would 

 refer the meeting to a few samples of broken axles sent to him 

 from various quarters, which, if proof were wanting, completely 

 substantiate, in his opinion, the certainty of the crystalline change. 



Before reading some of the communications received from other 

 gentlemen containing their experience on the subject, he would 

 first call attention to the two experiments which were tried in rela- 

 tion to the proportion and form of axle, in order to meet the objec- 

 tion raised at the I'ormer meeting, " that the slow pressure on the 

 flanches of the wheel to discover where the axles were most exposed 

 to the bending strain was not a faithful representation of what 

 takes places in practice." The axle was fixed upright, so that the 

 wheels were i)laced in such a position that the violent blow when 

 the wheels of the carriage jarred upon the rail was fairly repre- 

 sented by the blow caused by the descent of a weight of 17 cwt. 

 which «<«s allowed to fall upon the edge of the wheel at A, from 

 a height of 9,4 feet. It is most satisfactory to find that the curve 

 into which the axle was bent, is quite in accordance with the for- 

 mer results, which were obtained by slow pressure applied at the 

 same points, and establishes the rule of proportion of the axle 

 therein stated. See figs. 10 and 11, Plate IV. 



The following are some instances of tough fibrous wrought -iron 

 being rendered brittle and breaking off quite square with a close- 

 grained fracture from the effect of the concussion of very small 

 blows rapidly repeated for a long period; the blows being very 

 small in force compared to the strength of the iron. These speci- 

 mens are from the machines for making button shanks, in JMr. 

 Heaton's .Mills, Birmingham. The hammer in these machines is 

 about 2g lb. weight, and is lifted by a rod i|-inch square, which has 

 a pull upon it of about 12 lb. from the difference of leverage; the 

 hammer strikes 120 blows per minute, but the cam that drives it 

 acts only during one-fourth of its revolution, so that the velocity 

 of the hammer is equal to four times the number of blows, or 

 nearly 1000 changes of motion per minute. The lifting-rods always 

 break with a close-grained short fracture, although made of the 



toughest and most fibrous ircju that can be obtained, and they 

 sometimes last (uily a few months; the rods break near to the end, 

 which is fixed witli a coupling, and the deterioration of the iron 

 appears to be confined within a small portion, tlie iron remaining 

 quite tough and fibrous within an inch of the fracture, as shown by 

 the specimen, which has been bent doulde at that part. The ham- 

 mer is snatched suddenly by the lifling-rod, and is ])ulled against 

 a strong spring for the purpose of getting a quick recoil and a 

 sharp blow of the hannner, much quicker than it would fall by 

 gravity. 



Another specimen from the same machines is the lever for push- 

 ing oft' the work from the machine when stamped; the lever is 

 about ^-inch square, made of the toughest wrought-iron, it is 9 

 inches long, and falls back against a stop at one-third of its length 

 from the centre of motion at the bottom, being thrown back 

 sharply by a spring, the total strain upon the lever varying from 

 about lib. to about 12 lb., according to the accidental circum- 

 stances in the working of the machine. These levers all break off' 

 quite short and close-grained within an inch of the p irt that strikes 

 against the stop, but the iron continues quite fibrous and unchanged 

 to within an inch of the point of fracture, as shown in the speci- 

 men. They were driven at the same speed as menticuied above, 

 amounting to nearly the velocity of 1000 changes of motion per 

 minute; but they broke so freciuently, lasting sometimes only a few 

 weeks, that it was determined at last to reduce the speed of the 

 machines from 120 to about 100 blows per minute, and in conse- 

 quence of this reduction in speed the levers are much less fre- 

 quently broken, and last on the average about four times as luog 

 as before. 



Communication from Mr. John Kekwick: — 



"The Holmes, Rot/:er/iam, it/t December, 1S49. 



" I have l)een reading in the Mechanics' Magazine for last monch a 

 report of your ahN paper on railway axles, and 1 notice Mr. Robert Sie- 

 pliensiin said tliat Mr. McConnell had ex|)ressed a strung opinion that a 

 change tnok place from a ^fi»ou4' htruciure lo a crystalline one during the 

 time of its heinii in use, and it wuuld be satisfactory if an instance could 

 lie pointed out where this change had occurred owing to vibration or other 

 treatment, &c, &c. 



1 think I can furni=h an instance in proof of ynur opinion on this point : — 

 In one of our forges we are daily in the haljii of using a metal helve or 

 hammer weii^hing abuut -t tons, for the purpose of drawing large sizes of 

 steel, and tiie sliaft nf this helve is 17 inches by 9 inches. Folding great 

 inconvenience and danger from the breakage of cast iron helves, we were 

 induced tu try a wrought-'non one 16 inches by S inch's. After using this 

 for several months, the shaft broke in two about the middle, and the fracture 

 presented a crystalline appearance of 'short' cast-iron: we repaired the 

 shaft, and in the course of a few months it again broke about tlie same place, 

 and it again presented a similar granulated, cast-iron like, crystalline appear- 

 ance throunliout the face of the fracture. 1 attributed this change solely lo 

 the vibration and jar occasioned in the process of hammering steel, more 

 parlnularly cns<-steel." 



Communication from Mr. Benjamin Gibbons: — 



"Shut End House, near Dad ley, Ibth January, 1850. 



*' When the hea\y cast-iruu helves were used for drawing out bars, and 

 the art of chilling iron was little understood, tlie nose or that part of the 

 iron helve struck by the cam to lift it was protected by a wrought-iron plate 

 well fitted, and this was secured by a large pin countersunk into it, and 

 extended tbrnugb a hole cast through the nose of the helve, and screwed as 

 fast as possible on the upper side. The very best and most jibrous iron 

 (itscertained to he so hy previous breaking) was always selected, and yt 

 when the pin broke by the repealed shocks it had to sustain (about 90 ti-nes 

 per rainutf), it always broke with a large bright grain, H'i/;^o«^ ^//e lea-^i 

 trace of fibre. This was so regularly the ease that I never knew a pin la>t 

 for many months. 



Another instance was in a fly-wheel where wrought-iron arms were used 

 instead of cast iron, for the purpose of throwing the weight to the outer 

 circumference, and this wheel was applied to a forge-hammer engine. It 

 woiked well for a time till the arms got loose in the cast iron rim, and then 

 a violent shock was received every time the cam struck the lielve ; after soiiid 

 time, the arms began to break one after the other, and though the iron was 

 of the toughest description originally, it was found that any part broken was 

 of a bright crystalline grain. 



The pins of shears for culling down large cold bars sustain violent shocks ; 

 they perpetually break with the same bright grain, though made of t)ie 

 toughest iron. Also the iron arms of common carts always break wiin that 

 grain from the same apparent cause. 



1 have taken iron of this bright crystalline character which I had [jre- 

 viously known to he fibrous, and by drawing it down a little at a proper heut 

 have never failed to restore the fibrous texture of the iron." 



The practiciil suggestions derivable from the foregoing experi- 



