220 



Mr. H. Carrington on tlu 



Appendix by H. Carrington. 



Experiments were performed to determine the degree of 

 accuracy with which the buckling loads for cantilevers 

 loaded at one end, as calculated by the mathematical ex- 

 pression in (1) below, agreed with those obtained by 

 experiment. Five steel strips were used, each of which was 

 straight, free from dents, and accurately ground. 



The expression for the buckling load is 



P = 



4-012 VEttCK 

 I 2 



(1) 



where I is the length under test, EC the least flexural 

 rigidity, and Kn the torsional rigidity, so that in order to 

 calculate P it was first necessary to determine these 

 rigidities. 



The flexural rigidity of a strip was obtained by arranging 

 it as a cantilever and loading it with weights suspended 

 from the free end by a fine wire. The deflexions (S) of the 

 free end corresponding with increasing increments of load 

 were noted and plotted one against the other. The lines so 

 obtained are given in fig. 1, and the flexural rigidity (EC) is 



Fie. J. 



Deflection ( I division = Ol inch) 



WP 



w 



given in each case by the expression EC= -^ ^ , where 



do o 



is the slope of the line and I is the length under test. The 



thicknesses of the strips (see table below) were small 



compared with the lengths under test (10 in. and over) and 



the deflexions due to shear were accordingly negligible. 



In order to obtain the torsional rigidities the strips were 



