86 KANSAS ACADKMY OF SCIENCE. 



AN AUTOGRAPHIC RECORDING INSTRUMENT FOR 

 TENSION TESTS. 



By Geo. J. Hood, University of Kansas, Lawrence. 

 Bead (by title) before the Academy, at Topeka, December 31, 1904. 



^^HIS particular recording instrument, for tension tests of steel 

 -^ and iron, was designed and built by the author, for use with the 

 Tinius-Olsen testing- machine, in the testing laboratory of the Uni- 

 versity of Kansas. 



This testing-machine is of 100,000 pounds capacity, and is used for 

 tension, compression and transverse tests of the strength of various 

 materials. 



The autographic recording instrument is shown in the photographs, 

 plate VI and plate VII, in place, on a test piece. The instrument is 

 usually left on the test piece until the curve begins to fall. This sig- 

 nifies that the maximum strength of the test piece has been reached; 

 and the instrument is then removed, so that it may not be injured 

 when the test piece is broken. Plates VI and VII are similarly 

 lettered. 



The drum, D, which holds the cross-section paper upon which the 

 test is to be recorded, is revolved by the elongation of the test piece. 



The pens. Pi, P2, P3, and P4, move parallel to the axis of the drum, 

 and proportionally to the load on the piece which is being tested. 



The instrument is fastened to the test piece by the clamps, C ; the 

 distance between' the upper and lower clamp screws being eight 

 inches. 



The rack, R, is connected by a rod to the upper clamp. This rack 

 has sixteen teeth per inch, and meshes with a pinion of sixteen teeth. 

 This pinion is pinned to the same shaft with the gear Gi, of 254 teeth. 

 Gear Gi meshes with gear G2, of forty teeth. Gear G2 is pinned to 

 the shaft of the drum, D. The circumference of the drum is 7| inches. 



If the piece under test is elongated one inch, the relative movement 

 of the rack and pinion is one inch, and the pinion and the gear Gi 

 each make one revolution. At tlie same time the drum makes -4%4 

 revolutions, and the length of the cross-section paper passing under 

 the pens is -2/^* by 7^ inches, or 50.0006 inches, or, practically, 50 

 inches. Thus the elongation of the test piece is magnified fifty times. 



Each of the pens, P1-P4, is mounted on a short barrel, which slides 

 on the rod, A. Each barrel has a V projection, which reaches into 

 the threads of the lead screw, S. 



The lead screw, S, is connected by means of a flexible shaft, B, to 



