Is electric lighting and starting equipment justifiable on commercial cars? Many engineers consider it an unnecessary complication; others hold that with it economy as well as convenience is gained. A resume of the advantages and disadvantages may prove interesting especially since the Government specifications for the military trucks included this equipment.
Many mechanical problems must be considered in selecting electrical equipment for commercial cars. While these units have worked out satisfactorily for passenger vehicles that are equipped with pneumatic tires, it is a question whether they will endure the greatly aggravated vibration of motor trucks having solid tires, stiffer springs and are compelled to travel cobble-stones and rough roads. Such consideration as frequent troubles from inability to withstand the hard usage, are very important and may more than offset the advantages gained through the use of such equipment. It is true that some of these equipments have worked out very satisfactorily on commercial cars; however, they are generally designed to meet these more exacting conditions. They are sturdier and stronger built devices, while the battery must also be of such capacity as to permit frequent starting and must have some special mounting to resist vibration.
The arguments for and against electrical equipment, covered in the following, are the result of a general study of this subject and are not based on the opinions of makers of these units.
Four units generally comprise the complete electric system, the ignition system, the generator, the starting motor and the battery. Ignition systems were previously described and will not be considered in this article. The generating system consists of a generator or dynamo, its drive and mounting and also an output regulator and reverse current cutout. The starting system consists of an electric motor, its drive and mounting and a suitable switch for starting purposes. The link between the two systems is the storage battery which serves in effect as a reservoir for accumulating electricity.
The generators of different systems now in use vary in construction or type, some having a permanent and others an excited or wound field. Fundamentally, there are three types of generators in use - shunt wound, compound wound and differentially wound generators. The field itself may either carry simple or compound windings. The armature revolving between the poles of the field generates electric current, the output of which is governed by the output regulator. The method of generating electric current was described previously in the chapters of magnetos. The reverse current output prevents the flow of current through the generator from the battery.
The starting motor which takes the place of the ordinary hand crank is operated by current from the battery. This unit is similar but opposite to the generator in that instead of motion producing current, current flowing through the fields energizing them and causing the armature to rotate produces motion. Speaking loosely, electricity that has been pumped into the battery by the generator, runs out through the motor. If the motor is properly interconnected with the engine it can be made to turn the latter over until it starts.
A definite amount of work must be done to produce electricity, and that work is done by the generator. The electrical energy that the generator produces is stored in the battery for use when the generator itself cannot supply the current as when the engine is to be started.
The advantages on a commercial vehicle of electric lights and starter are as follows in their order of importance:
1. Greater economy due to saving gasoline and time when many stops are made by not keeping the engine running.
2. Increased life of the engine, as shutting it off at each stop, eliminates considerable needless wear.
3. Saving of time over hand starting increasing the actual working hours of the car and operator.
4. Better lighting and easier driving for night work and fewer accidents from the rear light going out.
5. Better finished appearance of cars for certain classes of work.
To these may be added the possibility of getting more for certain types of cars for special service, where the advertising value is considered.
The principal disadvantages in equipping commercial vehicles with these units are:
1. Additional first cost and added complications which the driver does not comprehend.
2. Increased maintenance cost and interest on additional investment.
3. Decrease in engine accessibility in making repairs, thus increasing the cost of these repairs.
4. Unreliability of certain parts, such as the storage battery and the possibility of these units being maintained far below their original efficiency.
5. The effect of vibration on units not originally designed for commercial car service.
6. Inability to keep the battery sufficiently charged owing to frequent starting and stopping.
7. Battery and other electrical troubles aggravated by the average commercial car driver not being familiar with the construction and care of the electrical system.
On trucks that have many stops to make such as house to house delivery, starters are no doubt desirable, considering the high cost of gasoline, as the operator will invariably allow his engine to run rather than crank it when making a stop of a few minutes. Stopping the engine will cut down the fuel bills.
But whether the starter will save time over cranking seems to be disputed. Various arguments are advanced covering the point of economy.
Any type of delivery car and even some of the large motor trucks make more stops during the day than the average touring car, and from the point of economy the commercial car would seem to have the greater need for a starter. Moreover, the starter is also a convenience and saves energy. Some imagine that the starter will start the engine when the driver cannot start it. This is not true unless the engine is too big to be spun by hand. The average truck engine can be spun easily by the average driver and if the gasoline mixture is getting to the cylinders and the spark is all right, it can be started as many times by man as bv a self-starter. A self-starter can do no more than man, but it does conserve his energy.
Some claim that the time saved with a starter even when stops are numerous is relatively small compared with the time the operator usually wastes in other directions. Cold weather must also be considered, which may average four months per year, when it is really advantageous to let the engine idle and prevent the radiator from freezing and to keep the mixture warm for a good start.
Stopping will increase the life of the engine, but in the absence of a starter with a bonus system to encourage economy, the driver would not let the engine run idle for long. Where, especially on the heavy vehicles, the drivers' union compels the owner to provide a helper on each car, there is still less excuse to keep the engine running.
Without question, electric lights are preferable to oil lamps, but it is for the owner to decide, especially whether they are worth their slightly greater cost if there is little operating at night. Accidents that may be traced to the lighting system will be reduced, if the lighting system is maintained at its original efficiency, which is doubtful on a commercial car.
Where appearance is a large factor, the additional first cost and maintenance are usually disregarded. Under certain conditions, especially on light deliveries, electric equipment adds considerable to the sales value. Conditions here approximate those of a touring car and there is no question of that feature in this case.