ON THE RESISTANCE OF KOAD VEHICLES TO TRACTION. 



367 



the lurry-wheel 

 by the removal 

 3 feet 2 inches loug, 2| inches wide, and {',■ inch thick 



This series 

 macadam road, 

 wet in places ; 

 I'espectively. 



mentioned previously, but they were reduced in strength 

 of four plates, so tliat each spring consisted of two plates 



of experiments was conducted on a level stretch of 

 the surface of which was in fairly good condition, slightly 

 runs were made with loads of 315, 427, 539, and 651 lbs. 



Fig. 1. — Tractive-eSorfc Velocity Carves for 40" Iron Tj'ie on Selts. 



e 9 10 



* Vclboity — Jliles per lioul'. 



Fig. 2 shows tractive effort and velocity plotted for each of these 

 loads. It will be noticed that the ratio of tractive effort to load for 

 these curves is very nearly constant, and that the tractive effort increases 

 slightly with the velocity. Sutiicienfc results have not yet l^een obtained 

 to enable this Committee to state delinitely the law relating to tractive 

 effort and load, but the results of the experiments that have been made 

 agi'ee witli those obtained by such pioneers in this research as General 

 Morin, M. Dupuit, M. Michelin, and others. Assuming for the time that 

 the tractive effort is directly proportional to the load, a curve has been 



