124 Mr. Fairbairn — Experiments on the Effects [Feb. 4, 



After the beam had thus sustained one million changes of load without 

 apparent alteration, the load was increased to 10,486 lbs., or f ths of the 

 breaking-weight, and the machinery again put in motion. "With this addi- 

 tional weight the deflections were increased, with a permanent set of '05 

 inch, from '23 to '35 inch, and after sustaining 5175 changes the beam broke 

 by tension at a short distance from the middle. It is satisfactory here to 

 observe that during the whole of the 1,005,175 changes none of the rivets 

 were loosened or broken. 



The beam broken in the preceding experiment was repaired by replacing 

 the broken angle-irons on each side, and putting a patch over the broken 

 plate equal in area to the plate itself. A weight of 3 tons was placed on 

 the beam thus repaired, equivalent to one-fourth of the breaking-weight, 

 and the experiments were continued as before. 



Experiment III. 



Date. 



Number of 

 changes 

 of Load. 



Deflection, 

 in inches. 



Permanent 

 set, in 

 inches. 



Remarks. 



i860. 



August 9 



August ti .. 

 August 13 .. 



August 13 ., 

 December i 



1861. 



March a 



May 4 



September 4 

 October 16.. 



158 



12,950 

 25,900 



25,900 

 768,100 



1,602,000 

 2,110,000 



2,7?'7.754 

 3,150,000 



o-i; 

 o-il 



o-i8 

 0*17 

 0-I7 

 0-17 



o 



O'OI 



O'OI 

 O'OI 

 O'OI 

 O'OI 



The load during these changes 

 was equivalent to 10,500 lbs., 

 or 4-6875 tons at the centre. 

 "With this weight the beam 

 took a large but unmea- 

 sured set. 



During these changes the load 

 in the beam was 8025 lbs., 

 or 3-58 tons. 



Load reduced to 2*96 tons, or 

 :^th the breaking-weight. 



At this point, the beam having sustained upwards of 3,000,000 changes 

 of load without any increase of the permanent set, it was assumed that it 

 might have continued to bear alternate changes to any extent with the 

 same tenacity of resistance as exhibited in the foregoing Table, It was 

 then determined to increase the load from one-fourth to one-third of the 

 breaking-weight ; and accordingly 4 tons were laid on, which; increased the 

 deflection to '20. 



