98 



DUDLEY 



the rail to which the Stremmatograph was attached, the steam 

 having been shut off a few feet before reaching the instrument. 



The record of the molecular compression and elongation of 

 the metal due to the stresses in the base of the rail was very 

 smooth and distinctly delineated. 



For the unground tender wheels slight tremors in the rail 

 w^ere distinctly indicated, a fact previously noticed under switch- 

 ing locomotives with the same class of tender wheels running 

 over very light rails in the yard. 



The apparent mean stresses for the extreme fibres of five 

 inches in length of the base of the rail computed on a basis of 

 30,000,000 lbs. for the modulus of elasticity of the steel were as 

 follows. 



For a speed of 

 Two miles Ten miles 



per hour 



Compression in front of pony truck, 1 4 1 7 lbs 



Tension under pony truck, 7086 " 



Compression between pony wheel and front 



driver, 2129 



Tension under front driver, 10629 



Compression between front and middle driver 5433 



Tension under middle driver, 5905 



Compression between middle and rear driver, 4015 



Tension under rear driver, 93 7 6 



Compression between r^ar driver and first ten- 

 der wheel, 4015 



per hour 

 1653 lbs. 



7558 " 



4724 

 9448 

 8031 

 4960 



5673 

 9648 



i ( 



5473 



For the speed of ten miles per hour the locomotive was 

 working under steam and being accelerated as it passed over the 

 instrument modified the wheel pressures to some extent. 



The tremors from the tender wheels were very decided in this 

 run and were felt for the entire length of the rails. The fibre 

 stresses in tension are small for the loads upon the drivers even 

 for an 80-lb. rail, while those in compression are higher than 

 usual for the same weight of rail. The section is 5 ^ inches high 

 and the stiffest 80-lb. rail which has been rolled in this country. 



There is also another reason for the nearly balanced stresses. 

 The two ties between which the Stremmatograph was attached 



