Dynamo electric lighting for motor cars

The design of motor car lighting apparatus begins with the choice of a satisfactory lamp equipment. This fixes the quantity of energy which the lighting system must supply at any time, and indicates the dynamo capacity to be provided. The dynamo must be geared to give its full output at the average speed reached when driving, with all lights on, in order that the battery reserve may be drawn upon only when the car is not in motion. When a battery auxiliary is used it must be connected to the dynamo when conditions are right for charging, and disconnected when the engine is at rest, to prevent discharge through the dynamo. Safety and convenience require that this action should be automatic, also that the output of the dynamo should be limited to a predetermined and safe maximum, regardless of dynamo speed. This leads to a discussion of methods devised to secure automatic control, and to the speed rating of the dynamo itself. This is limited on one hand by the weight, size and cost of slow-speed dynamos, and on the other, by consideration of wear on bearings, commutator and driving means of the high-speed type. Following this are notes on storage battery capacity, and wiring.