II KQCATIOXS FOR TIIK INI- FACTOR 55 



We can then write down the value of the induction 

 factor of a motor which, when geared to a main shaft with 

 velocity ratio r, will give a tractive effort of T pounds at 

 the centre of a driving wheel of diameter >> inches. /.' h.-in^r 

 the tension of the line, and If the resistance of the motor; 

 we have 



when ' the velocity of the centre of the driving 



wheel, expressed in miles per hour. 



have assumed that the whole resistance to motion 

 can be represented by a force <-f / jH.und.s acting at the 

 rim of th,- driving wheel. This resistance may for con- 

 venience be divided into frictional ami gravitational 

 resistance. The frictional resistance may be further 

 divided into friction of tin- motor and it- equipment, and 

 n of the shafts and axle* driven ly the motor. The 

 force exerted in overcoming tin- latter i- .-otnetimee called 

 the 'useful effort.' though strictly the effort is not more 

 useful than that exerted in overcoming the friction of the 

 gearing. 



In Kquntion _'l. /'include* all miistanctis to motion. 

 In the case of a locomotive the fractional remstance of tin- 

 axles of the carriages is represented by a force exerted at 

 the draw bar : we may also require a force at the draw Imi 

 to overcome a gravitational force du to an incline. Besides 

 these there will U- the frictional reMisUnce of the in 

 and their i-o,uipm<-nt-<. In a motor car there is strictly no 

 draw bar pull. lut there will U- its ,- ( jni\al. nt if the car in 

 ascending nn incli 



When n mot.. i i- .! ..f i-\ertinga 



