How Railway Materials Are Tested.

weight of about 7 cwt . falling from a height of , say nineteen or twenty feet , increasing by two feet for each successive blow . In this way it must Avithstand a bend of nine inches , and a further bending back of nine inches ; the operation being continued until the axle has withstood more than six

thousand feet pounds . Another test for a 4 | inch steel axle is to place it upon bearings as above stated , and they must Avith stand a bend of more than 9 f inches under a 7 ewt . monkey falling from a height , of nearly fifteen feet . They must then alloAv

themselves to be bent straight back in the same manner , Avithout breaking , Wrought Iron . It is not advisable to restrict manufacturers by stating the proportions and classes of iron to be mixed , as they will in most cases be better able to

judge of the mixtures to be made in order to produce a specified result . Iron broken by a sudden strain presents a crystalline fracture . When broken by a gradually increasing strain , a fibrous fracture results . Whether the iron is fibrous or crystalline , its quality may to some extent be judged

by the fineness of its texture and the irregularity of its fracture . Messrs . Clarke , Reeves , & Co ., American bridge builders , specify that all bars subject to tensile strains may be tested to 20 , 000 lbs , ( nearly 9 tons ) per square inchand

, struck a smart blow with a hammer Avhile under tension , and if any show signs of imperfection they shall be rejected . This test is mentioned because in a competition the firm secured a contract against English firms .

Another test is—take a piece of iron 2 inches wide and - £ inch thick , and of sufficient length to have 7 inches under actual tension , the said piece having been cut out of a plate intended for use on the Avork , and the following tensile strains must be applied : —The plates of a similar

manufacture to be rejected if the extension of the piece tested is greater than | of an inch under 18 tons , ¦ £ of an inch under 21 tons , and £ an inch under 23 tons , and f of an inch under 24 tons , all bars and angleirons being required to bear a tensile strain of 25 tons before fracture .

Malleable Cast Iron , patented by Mr . Samuel Lucas , of Sheffield , in 1804 , has lately attracted some attention amongst engineers . It is easily stamped , drawn

and hammered without neating . It can . also be worked well under the hammer at a low heat , and at this stage hammering appears to improve the grain . It is now being used for tram-car wheels , cross heads , and connecting rod straps for engines , link

reversing and expansion gear , & c . Unlike wrought iron it is not liable to defective Avelds , and Avith ease complicated patterns and shapes can be produced at a reasonable cost . A superior kind of small soft casting is

made by the Nottingham Malleable Iron Co ., which , from being subject to a partial annealing , is very easily got up to a bright polish , the difference in cost being tallyrecouped by saving in labour and tools . When we consider that there are

upwards of 130 tons of rails and nearly 65 tens of cast iron chairs in one single mile of line , exclusive of sidings , it will at once show the importance of a strict supervision of the maintenance and renewal of

permanent way , therefore Ave next give—Rails . The usual modes of testing rails are — 1 . Static , or by a dead central Aveight . 2 . Dynamic , or test by impact . 3 . A combination of No . 1 and 2—firs by a central and afterwards by a falling load . 4 . Chemical or acid test .

5 . Test by rolling weight . To these might be added one of torsion of twisting . Taking the Static test and apjilying it to an iron rail 75 lbs . per yard , a length p laced upon bearings 3 feet 8 inches apart

should carry a hanging weight of 12 tons for five minutes , and only give a deflection of one . seA enth of an inch . The same kind of rail tested by impact should with the same bearings ( 3 feet 8 inches ) take blows from a tup 648 lbs . weight falling 7 feet

on the centre between points of support , and under this test the rail may bend , but not show any trace of destruction . Good steel rails Aveighing 80 lbs . per yard , placed upon bearings 3 feet apart , will stand a test of a 10 ewt . ball being

raised 10 feet and fall three times , and only g ive a deflection of 3 inches . The rails used on the Metropolitan Railway , when placed on bearings 5 feet asunder , will stand a pressure in the centre of upwards of 26 tons , and only deflect 9 inches .