STREMMA TOGRAPH. 103 



Tension. rear driver, 6,443 lbs. 



Compression between driver and tender tnick, 3^965 



Tension front tender wheel, 4>46o 



Compression between truck wheels, 1,487 



Tension rear tender wheel front truck 4j46o 



Compression between trucks 2,979 



Tension front wheel rear truck 4jI3o 



Compression between wheels, ij^S^ 



Tension rear wheel rear truck, 3,469 



The rail was the outside one on a 3 -degree curve ; stone bal- 

 last ; oak ties with tie plates — 24-inch centres. 



The marked reduction in the stresses on the 100- lb. rails is 

 very plainly seen. 



Testing the Stremmatograph February 14th, 1898; Grand 

 Central Yard at 48th Street, on lOO-lb. rail, special brick piers 

 capped with chilled iron supports 30 feet apart. Temperature 

 44 degrees Fahr. Fairbanks U. S. Standard weights. 



The modulus of elasticity taken at 30,000,000 lbs. which for 

 the temperature a number of tests have shown for the same rail 

 to be practically correct. 



The Stremmatograph was applied to the base of the rail, and 

 the deflection measured by a micrometer, securely attached to a 

 heavy bridge abutment by which the brick piers were purposely 

 located, and from the centre of the rail 500 lbs. of standard 

 U. S. weights were suspended and the deflection again meas- 

 ured. From the observed deflection the moment of inertia of 

 the rail was recalculated. The section for the test was origin- 

 ally slightly over-weight. The rail has undergone considerable 

 oxidation in two years, reducing the moment of inertia as origin- 

 ally rolled. 



For the 500-lb. load the stress in base of the rail computed, 

 2,747 lbs. 



On the Stremmatograph slide, the scriber point was set 

 and a short line ruled, the scriber point was not moved and a 

 second line ruled, but merely displaced by the elongation of 

 the metal, and then the slide slightly moved forward. The 

 slide was then measured under the filar micrometer with the 

 utmost precision and the observed stress computed 2,745 lbs. 



