381 



SECTION 12. APPLIED MECHANICS. 



SOUTH GALLERY. GROUND FLOOR, ROOMS B. C. 



I. -PROPERTIES OF MATERIALS. 



1925. Chinese Steel Helmets (2). 



Rennet Woodcroft, F.R.S. 



1926. Chinese Cane Helmets (2). 



Bennet Woodcroft, F.R.S. 



1927. Cast-iron Test Bars. Specimens to illustrate the 

 forms and positions of fractures when exposed to a breaking load. 



W. J. Millar, C.E. 



The bars were of 36" span, 2" deep, and 1" broad. 



The load was applied at centre of bars. Straight fractures occurred when 

 bars broke at, or close to, centre of span ; curved fractures followed when 

 bars broke at points more or less removed from centre. 



1957b. Drawings of Hydraulic Apparatus for the study 

 of the extension, compression, and flexion of prismatic bars. 

 Constructed by Professor Wischnegradski. 



Laboratory of Mechanics, Technological Institute, St. 

 Petersburg. 



This apparatus consists of a hydraulic cylinder, the piston of which bears 

 a table supporting four iron columns, connected at the top by a strong 

 cast-iron cross piece, that has at the centre a conical opening, and below a 

 spherical excavation within which pivots a hemispherical cast-iron piece, 

 traversed by a powerful iron screw fixed by two nuts ; to this screw is 

 attached the upper end of the bar subjected to the experiment of extension ; 

 the lower end of the bar is fastened to the large lever placed at the base of 

 the apparatus and which pivots round an axle fixed in an immovable bearing. 

 This lever is connected with the upper lever, by means of two iron braces 

 suspended to one end of this lever ; at the other end are hung a scale board 

 for the weights used in calculating the tension effected. The ratio of the two 

 arms of the lower lever is 5, and that of the two arms of the upper lever is 

 20. So that each lever being perfectly balanced the tension of the bar is 

 exactly 100 times that of the weight on the scale board. By means of the 

 screw described above, and by inverting the intermediate iron pieces, it is 

 possible, with this apparatus, to experimentalise upon bars of any length 

 provided they do not exceed 10 feet English. 



