[Annals N. V. Acad. Sci., XI, No. 6, pp. 89 to 116, April 20, 1898.] 



THE USE OF THE DUDLEY '' STREMMATOGRAPH " 



IN DETERMINING STRESSES IN RAILS 



UNDER MOVING TRAINS. 



P. H. Dudley, C.E., Ph.D. 



(Read February 7, 1898.) 



[Plates X-XIII.] 



On former occasions I have presented to the Academy dia- 

 grams of railwa}- tracks showing the undulations of different 

 weights of rails under moving loads as taken by my Dynagraph 

 and Track Indicator car. 



Attention was directed to the marked reduction in the undu- 

 lations in the stiffer and heavier rails put into service in recent 

 years as a result of the earlier investigations. 



I also stated that with rails of a given stiffness, surfaced in 

 the track to their highest condition, the trackmen can only re- 

 duce the undulations to definite minimum limits for the wheel 

 loads ; therefore, all undulations under the moving wheel loads 

 of locomotives and cars with their increased dynamic effects due 

 to speed can not be entirely reduced. 



To carry the trains, the rails not only deflect under the wheel 

 loads, but the ties, ballast and road-bed are compressed until 

 the total resistance equals the load. Action and reaction 

 must be equal and before the latter is obtained for heavy loads 

 on light rails rapid destructive \vork is done upon the ties and 

 ballast, requiring frequent surfacing to keep the track up to its 

 proper standard. The destructive Avork on the ties and ballast 

 under stiffer and heavier rails is reduced as well as the neces- 

 sary labor to keep them in surface. 



The weight of the locomotives and cars can only be transmit- 

 ted to the road-bed through the wheel contacts on the rails, 

 which produces a general deflection of the rails under the wheel 



(89) 



