88 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[March, 



as good, if not }>etter tlian other forms, besides beino:, as bclievod, 

 less liable to theoretical objections than others, experiments were 

 made upon castinfrs with rectang^iilar and cir(-iilar sections. These 

 experiments are in Table II., and tlie results from the cruciform 

 section were in all the sound castings somewhat higher than those 

 from tl;e otlier sections. 



In Table I. the specific gravities of 17 kinds of iron are i^vcn; 

 they are obtained both from the thickest and the thinnest parts of 

 the castings torn asunder. 



Abstract No. II. — Collisions Atio Vibrations. 



I'over nf Beams of Cast-iron to sustain long-continued Impact. 



The effect of impact and vibration upon structures, was a lead- 

 ing object of inquiry with tlie Commission; and the first series of 

 experiments instituted upon this subject was, to determine the 

 power of beams to sustain impacts many times repeated. For tliis 

 purpose, 16 bars were cast, all from Blaenavon Iron, No. 2, and 

 five at least of the 16 were found to be sliglitly defective at some 

 place where tliey gave way. M'liether these small defects were 

 more numerous than would be found in practice, it would be diffi- 

 cult to determine. 



Six of the bars were each 15 feet long and 3 inches square, and 

 placed on supports 13 ft. 6 in. asunder; seven were each 10 feet 

 long and 2 inches square, and 9 feet between the supports; and 

 three were each 5 feet long, 1 inch square, and 4ij feet between the 

 supports. Of these bars, six were bent through ^rd of their ulti- 

 mate deflection at each blow, and five of them bore each 1000 

 blows without breaking; the sixth was broken at a flaw with 10S.5 

 blows. One large bar, bent by impact through y^ths of its ulti- 

 mate deflection, was broken at a defective place witli 13.50 l)lows. 



Of six bars bent by blows through half tlieir ultimate deflection, 

 five were broken with less than 4000 blows each; one with 29; one 

 with 127, &c. The only bar which bore the 4000 blows was one of 

 the smallest kind, or 1 inch square. 



Of three bars, one bent to i^ths, and two to |rds the ultimate 



deflection; all were broken; the two latter with 127 and 474 Wowg 

 respectively: the former required 3700 blows to break it. 



Of ten bars of Low Moor Iron No. 2, each 10 feet long and 2 

 inches square, placed on supports 9 feet asunder, and struck in the 

 middle with long-continued iin|)act, as before, four broke at de- 

 fective places, and two at sound ones. Tliree were subjected to 

 impacts, bending them through yrd of their ultimate deflections, 

 and bure the test without fracture; of three bent by blows through 

 half their ultimate deflection, two were broken; those bent through 

 |rds were all broken. 



On the w hole, it appears that no bar but one, and that a small 

 one, stood 4000 blows, each bending it through half its ultimate 

 deflection; but all the bars, when sound, stood that number of 

 blows, each bending them through ^rd their ultimate deflection. 

 It must, however, be borne in mind that a cast-iron bar will be 

 bent to ^rd of its ultimate deflection with less than ^rd of its 

 breaking weight laid on gradually; and jtth of the breaking weight 

 laid on at once, would produce the same efi'ect, if the weight of 

 the bar was very small compared with the weight laid on it. 

 Hence the prudence of always making beams capable of bearing 

 more than six times the greatest weight which will be laid upon 

 them. 

 Transverse Strength to resist long-cnntiiiued Impart from Bulls 



striking horizo.vtally against tlie middle of Burs, tlie Bulls acting 



as Pendulums with a radius (r) of 17 ft. 6 in. 



The bars were cast of three sizes — viz.: 15 feet long and 3 inches 

 square; 10 feet long and 2 inches square; and 5 feet long and 1 inch 

 square. A thin piece of lead, varying from 21b. to 4 lli. weight, 

 was generally attached to the side of the bar where struck, to pre- 

 vent injury to its surface by the impact. 



Sixteen Bars of Blaenaeon Iron No. 2. 



• The ultimate deflection was obtained from the Experiments on Transverse Pressure. 

 t B.iri, slightly defective. 



Ten Bars of Low Moor Iron, and one of a mixture of Wrought 

 and Cust Iron. 

 These bars were cast to be 10 feet long and 2 inches square; they 

 were placed on supports 9 feet asunder. The radius (r) of the 

 pendulum was 17-208 feet when the weight of the striking ball was 

 60,3 11).; and 18-208 feet when the weight of the striking ball was 

 151;Llb. 



1 Slightly rtefective on one sitle 



" Rrtther defei-tive on the convex side. 



3 Slight defect or discolou'-ation on the convex side, 



4 The bar broke about Hj inches from the centre, where there was a defect o i fie con- 

 vex side, i inch area. 



s ^Mixture of wrought and cast iron. 



