The Lighting of Vehicles.
Page 82
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Notes with Regard to Present-day Methods of Illumination for Commercialmotor Vehicles.
It may be taken as a primary necessity, in regard to the design of the lighting facilities intended for use on motor vehicles, both of the pleasure-car and of the industrial kinds, that it must be of such a nature as to serve the dual purpose of enabling the driver to see far enough ahead for safety's sake, and to give other people warning of the presence of the vehicle on the road. Such lighting should clearly define both the position of the vehicle and its approximate size. The headlights, if such be used, should be powerful enough to light the road for a, considerable distance ahead. Modern headlamps of even moderate power are quite capable of illuminating a road clearly for 100 yards or more ahead, and even to cast shadows at a distance of a quarter of a mile : such lights are obviously of sufficient power for any type of commercial vehicle.
The Position of Lamps.
Lamps should invariably be placed as high as possible on the vehicle, in c -der that the road may be lighted well ahead, and so that the resultant beam will be projected on to the road at a considerable angle.. If the axis of the beam of light be nearly parallel to the surface of the road, it will invariably cast black shadows into every small hole on the road
surface. It is a matter of extreme difficulty for a driver to distinguish these small dips, under such conditions, from deep and dangerous potholes. A strip of road of. considerable width should be illuminated, especially whea the vehicle is being driven on a winding country road, and for this reason it is advisable to place the headlights, if there be more than one, as far apart as possible.
Paraffin as a Standby.
It is useful, even if acetylene or electric headlamps be employed, to use paraffin side lamps as standbys, and especially is this the case in view of the fact that they are cheaper to keep alight during long wayside waits than are acetylene, petrol vapour, or electric lamps. They, too, have the additional advantage that paraffin may be obtained in any village almost in any part of the world. The most important point to remember, in fixing paraffin side lamps, is that they psust be so mounted as to be quite clear of the dashboard, windscreen, or body, so that they are not affected by back currents of wind ; such lamps are found to keep alight in any wind, so long as the direction of the air current be not rapidly varied.
We do not, however, advise owners to place complete, reliance upon paraffin lamps as a Hole npeans of road illumination. They cannot, under hard working conditions, supply a sufficiently powerful or steady light to free all ordinary night driving from the element of worry, unless it be under exceptionally clear atmospheric conditions.
• The Two Chief Systems.
We may briefly include in the present notice an account of the principal features of the two chief types of vehiclelamp systems, viz., the acetylene and the electric. Acetylene lighting systems may be. carried into effect in four different ways : by combined lamps and generators ; by lamps which are fed from a single distinct generator ; by lamps which take their gas from a cylinder of dissolved acetylene ; and by lamps which are fed from a cylinder of compressed gas. The last mentioned method is not an economical possibility for employment Overseas. in view of the difficulty of obtaining the necessary charged cylinders in out-of-the-way districts. It has proved to be the sa-se, notably an Royal Mail vans in the home country, that a single headlight often is ample, and in this ‘14 and many other similar cases a self-contained head lamp and generator will, as a rule, prove safer and more economical than one with a separate generator. The liability to leakage of pipe joints is almost entirely removed. If a separate generator be employed, it is essential that the piping should be of the best, and that all metal joints should be properly made ; copper pipes should on no account be used. On many commercial vehicles, if in. or in. gas pipes are frequently employed with considerable success. It should be remembered that the longer the surface pipe, the cooler will be the gas when it reaches the burner. It is wet, hot gas which generally causes acetylene burners to become smoky.
The Cleanliness of Electricity.
In respect of cleanliness, the electric method of illumination is undoubtedly better than any other system, and it also lends itself to the employment of portable inspection lamps for use when making adjustments. As a rule, the principal electric systems comprise a dynamo, which can be driven from any convenient shaft on the gear, a battery of accumulatom, and a magnetic cut-out or controller, in addition, of course. to necessary switches, Wires, lamps, etc.
We may usefully refer our readers to a notice with regard to the well-known O.A.V. electric-lighting system, which appears under the individual paragraphs which follow in this section. In connection with electric lighting systems, it must be remembered that a battery is necessary, and that with but one or two exceptions in regard to the best known arrangements it has six cells, which are capable of supplying current direct to all lamps at one and the same time.
Costs of Lighting.
Taking the case of a fleet of taxicabs, os each of which there are two side lamps, one tail lamp, and a fourth one to light up the dial of the taximeter, such a set of lamps in black finish costs about 30s., and the charge for fuel, cleaning and repairs, including all material and labour, is, approximately, 46s. 8d. per annum per cab, or less than is. per week. If this charge be reduced to a mileage basis, the cost per set is approximately .045d. per mile. This is a figure which has been realized in actual experience. In regard to motorbus lighting, the latest type of machine is provided with seven or eight lamps, and .their maintenance, including repairs, carbide and other material and labour, for a big company, costs about 5s. per week, or .087d. per set per omnibus-mile, assuming that a motorbus runs 700 miles per week, the hours of lighting being taken as an average of both summer and winter conditions. From these two sets of costs it is found that the acetylene system is slightly more economical than the paraffin method, while the lighting power of the former is infinitely greater. One or two omnibus companies have tried electric lighting, but only in a small way. and so far there, is no really sound available data with regard to their costs for big mileage.
It is interesting to note that the increasing use of tar spray, at any rate on the roads of European countries, gives increased importance to the present subject. There is no longer, on many highways, the oldtime white ribbon of road between dark hedge borders, and the ability to distinguish dark objects thereon, at a fair distance, is largely decreased. The useful contrasts of road and obstruction have largely disappeared. A dead black object on a dead*blaok surface is, to all intents and purposes, invisible. The question of illumination of the roadway ahead of the vehicle, in country districts, is all important.