234 



RIEHLtf-GRAY AUTOGRAPHIC APPARATUS. 



position, along with the weighing lever of the testing 

 machine. The connection between the test specimen ana 

 the recording pencils is made through two sets of levers, 

 as will be seen in the illustration. Iwo pencils are used, 

 one of which is suspended from the long arm of the large 

 lever having a three-to-one velocity ratio, and thus magni- 

 fying the extension three times ; while the second pencil 



05 



3 6~9 12 



Total Load in Tons. 



A Swedish bar iron . 

 B Landore rivet steel. 

 C Cast steel. 



Fie. 111. Automatic Stress-strain Curves, drawn with the Kennedy- 

 Ashcroft Instrument. 



is hung from the third of a set of levers having a total 

 velocity ratio which can be set to 100, 200, 300, 400, or 

 500 to 1. The former of these pencils is used as in the 

 instrument last described for drawing the diagram cover- 

 ing the whole test. The second pencil, which has a 

 movement from 100 to 500 times the /stretch of the 

 specimen, is used within the elastic limit, or to a point 



