Challenger of Locomotive 141 



to utilise the overload capacity of the electric 

 portion without imposing overloads on the 

 engine, yet at the same time to make the 

 maximum use of the prime mover. 



It may be said at once that when compared 

 with the locomotive, the motor-coach prob- 

 lem is really the simpler of the two; thus 

 motor-coach services generally consist of 

 work upon a definite route, the load varying 

 only very slightly due largely to the weight of 

 passengers carried per trip. The difference 

 may be accentuated at times by the addition 

 or withdrawal of a trailer coach, but it is 

 always possible to provide in the electrical 

 equipment certain features which will 

 permit the power equipment to accom- 

 modate itself automatically to the required 

 service. 



The English Electrical Company have 

 had the whole question of Diesel-electric 

 traction under special notice. They have 

 adopted their own design of equipment for 

 motor coaches, and in it supply the traction 

 motors from a generator provided with two 

 fields. One field is excited at approximately 



