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ELECTRIC RAILWAY JOURNAL · Vol. 45, No. 13 · March 27, 1915 · pp 614-618.
The New York Municipal Car -- The Lighting
By W. G. Gove, Engineer of Car Equipment, New York Municipal Railway Corporation, and L. C. Porter, Edison Lamp Works, General Electric Company, Harrison, N. J. Abstract of a paper entitled "A Practical Study of Car Lighting Problems," read at a meeting of the New York Section of the Illuminating Engineering Society, March 11, 1915.
Many Lighting Combinations Were Tried in a Full-Size Template Car, Resulting in the Choice of Fifteen 56-Watt Bowl Frosted Tungsten Lamps along the Car Center Line, Besides Emergency Lamps.
Not the least of the advanced equipment of the New York Municipal car is its lighting. Many new problems had to be solved to meet satisfactorily the following desiderata: (1) Quantity of light; it is desirable to have an average intensity of not less than 3 foot-candles on a horizontal plane 42 in. above the floor, at 85 per cent normal voltage. (2) General effect and appearance of lighting system with lamps lighted or extinguished. (3) Lack of eyestrain for both seated and standing passengers, involving not only intensity and direction of light, but also glare and possible shadows thrown by standing passengers on the reading matter of seated passengers. (4) Efficiency. (5) Installation and maintenance expense. (6) Depreciation of equipment in service.
To study these problems tests were conducted in a full-sized model car. This car was 67 ft. 3 in. over all, 9 ft. 10 in. wide and 12 ft. 3 in. high. The interior dimensions were 65 ft. long and 9 ft. wide. The interior finish was white enameled headlining and walls down to the window sills. Below the sills the walls were painted gray. The floor was concrete and the seats were upholstered in yellow rattan.
Photometer tests were taken to supplement such data as observation of the general appearance, installation and maintenance cost figures, etc. The photometric measurements were not made to compare the efficiency of any particular types of illuminating devices or accessories thereto, though the average intensities obtained were used in securing the relative utilization efficiencies.
In making the photometer tests stations were chosen 2 ft. apart in a horizontal plane 42 in. above the car floor, over one-fourth of the floor area. The entire car, however, was equipped with lighting units. Five readings were taken at each station, on a portable photometer, recalibrated before each test. To make one reading comparable with any other, simultaneous voltage readings were taken, as constant voltage was found to be impracticable. Each photometer reading was corrected to normal voltage from the characteristic curves of the lamp and the five corrected readings averaged to obtain the station value. In obtaining the average intensity for the entire car, weight was given the stations in proportion to the area covered. The illumination values were also calculated for 85 per cent normal voltage. The same lamps, as far as practicable, were used in the various reflector equipments.
It was decided before the tests started that tungsten filament lamps would be used for illuminants, the question being what was the best method of applying the lamps. Three systems of illumination were tried out, namely, direct lighting, semi-indirect lighting and totally indirect lighting. To carry on the tests the interior construction of the car was altered when this was necessary.
Photographs of the interior of the car were taken with the lamps burning. The exposures were timed to exactly two minutes. These photographs have no bearing on the photometric readings, except to indicate in a comparative way the high and low lighting throughout the car.
The direct lighting tests made were as follows: No. 1. -- The lighting units consisted of a single row of fourteen 6-in. opal glass reflectors (Fig. 9) mounted along the center line of the ceiling and spaced as shown in Fig. 1. Ten reflectors were equipped with 56-watt clear bulb tungsten lamps and four with 10-watt clear bulb tungsten emergency lamps. The light distribution, Fig. 1, was good, though it had points of high intensity under the emergency lamps, due to the small lamp in the large reflector. No bare lamp filaments were visible along the normal line of vision. The efficiency of the system was high, installation costs -- on account of the single row of large units -- were low, and maintenance was good, the smooth surface of the reflectors facilitating rapid cleaning. The general appearance in the car was pleasing (Fig. 15) and the illumination good, averaging 5.7 foot-candles at normal and 3.2 at 85 per cent voltage, with an energy consumption of 1.03 watts per square foot. There were 5.54 effective lumens per watt and the effective utilization efficiency was 68.7 per cent. The utilization efficiency in an ordinary dark yellow car with similar equipment is about 30 per cent, showing the great advantage of the white enamel interior finish. No. 2. -- The second test. Fig. 2, was similar to the first, except that clear prismatic reflectors were used. The change of reflectors raised the average foot-candle intensity to 6.1 at normal and 3.4 at 85 per cent voltage. The effective lumens per watt were increased to 5.90 and the utilization efficiency to 73.2 per cent. Maintenance would be slightly higher, due to cleaning the prismatic glass. There was also a little more glare, though not an objectionable amount.
No. 3. -- In the third test five 94-watt clear tungsten filament lamps, equipped with clear prismatic reflectors, were located in a single row down the center line of the ceiling. Four 10-watt tungsten emergency lamps in clear prismatic reflectors were located between these. The resultant average intensity in the car body was good, but due to the relatively low hanging height and wide spacing of the units the distribution was very uneven (Fig. 3). The installation and maintenance of the system would be low, on account of the small number of large units to install and clean. The average foot-candles obtained were 5.0 at normal and 2.8 at 85 per cent voltage. The energy consumption was 0.87 watt per square foot; the effective lumens per watt were 5.75; and the effective utilization efficiency was 71.5 per cent.
No. 1.-- A very interesting method of lighting was used in the first semi-indirect lighting test. Twelve special 80-watt 95-volt turnip-shaped tungsten lamps, opal-dipped over the tip half, were installed down .the center line of the ceiling. Each lamp was suspended by an inverted white enameled cone, shown in Fig. 11. Three 10-watt tungsten emergency lamps were also used in small rosettes. The 80-watt lamps were connected six in series. All of the filament of the 80-watt lamps was located below the center of the bulb ; hence, none of it was in the line of vision. The opal on the lower half of the bulb served to protect the passengers' eyes from the glare of the bare filament and to reflect the light up to the ceiling. This system eliminated reflectors, special holders and other accessory equipment, thus lowering both installation and maintenance costs. The average intensity was 7.7 foot-candles at normal and 5.1 at 85 per cent voltage. The energy consumption was 1.69 watts per square foot, the effective lumens per watt 4.65 and the utilization efficiency 58.4 per cent.
No. 2. -- In the second semi-indirect lighting test a novel equipment was used (Fig. 10). Ten 56-watt clear tungsten lamps were located on the center line of the ceiling, supplemented by four 10-watt tungsten emergency lamps. At 6 in. below the ceiling, and extending the entire length of the car, was suspended a reflector consisting of a white enameled board 11 in. wide, convex on a 16-in. radius. The bowls of the 56-watt lamps extended through holes cut in this reflector. Under each hole was fastened a white glass dish to diffuse the glare of the bare filament. The plan was to utilize as much as possible of the direct light from the lamp, to illuminate the advertising signs ; the indirect light to give even distribution and the direct light to brighten up the under side of the reflectors. The light distribution was good, but the intensity low, averaging 3.9 foot-candles at normal and 2.2 at 85 per cent voltage. The watts per square foot were 1.03, effective lumens per watt 3.81, and the effective utilization efficiency was 47.2 per cent. The illumination was pleasant, but the appearance of the lighting equipment was rather crude, suggesting a watering trough down the center of the car. While both sides of the reflector and the ceiling were painted alike, the under side of the reflector appeared gray, due to the lower intensity of light on it. Another test with the interior finish silver gray instead of white lowered the efficiency about 10 per cent.
The next semi-indirect equipment tested consisted of ten 94-watt tungsten lamps equipped with five 13-in. glass bowls, mounted down the center line of the ceiling. There were two 94- watt lamps and one 10- watt emergency lamp in each bowl. The bowls were hinged to allow lowering for cleaning and lamp replacement. The bowls were suspended with their tops located 12 in. below the center of the ceiling. The illumination from this system was very uneven, being high directly under the units and low between them (Fig. 5). The average intensity was 5.7 and 3.2 foot-candles at normal and 85 per cent voltage respectively; watts per square foot 1.69, effective lumens per watt 3.36, and effective utilization efficiency 41.5 per cent.
To determine the effect of the shape of the ceiling on the light distribution, a special headlining consisting of a white enameled insert, having a 3-ft. span on an 18-in. radius, was inserted and the test repeated (Fig. 16). This raised the average foot-candles to 6.1 and 3.4 at normal and 85 per cent voltage respectively, effective lumens per watt to 3.62, and the utilization efficiency to 44.7 per cent.
The insert was then removed and the test repeated with a different spacing of the units. This resulted in a little improvement in distribution. The principal trouble was that the car headroom was not sufficient to allow the lighting units to be hung the proper distance below the ceiling.
The next equipment tested required special reflecting devices. Ten 56-watt clear tungsten lamps were located in a single line down the center of the ceiling, with five 10-watt all-frosted emergency lamps in rosettes between them. Each 56-watt lamp was equipped with a screen made from a circular piece of glass bent over a cylinder (Fig. 14). This gave a screen 11 in. long x 8 in. wide x 3 in. deep. When these screens were hung beneath the lamps with their open ends toward the side of the car, it was possible to see the lamp filaments from any part of the passenger car body; at the same time the direct light from a considerable portion of the lamp fell on the ceiling and reached the reading plane with but one reflection, making the system fairly efficient. The distribution lengthwise of the car was even, though the outboard seats received considerably less light than the center aisle of the car. The average intensity was 4.8 and 2.7 foot-candles at normal and 85 per cent voltage, the energy consumption 1.04 watts per square foot, effective lumens per watt 4.63, and effective utilization 57.6 per cent. The chief advantage of this equipment was the ease with which the reflectors could be cleaned.
No. 1. -- The first totally indirect equipment tried consisted of eight special indirect fixtures, these being white porcelain enameled on steel, 15-1/2 in. in diameter and 5-1/2 in. deep. Each fixture contained three 36-watt tungsten lamps mounted vertically. The fixtures were hung in a single row down the center line of the ceiling, the tops of the reflectors being 13 in. below the ceiling. The spacing of the units is shown on Fig. 6. The resultant illumination was uniform and of fairly good in- tensity, averaging 5.1 and 3.2 foot-candles at normal and 85 per cent voltage, for an energy consumption of 1.47 watts per square foot. The effective lumens per watt were 3.43 and the effective utilization efficiency was 46.3 per cent. The chief drawback of these fixtures was their liability to catch and collect much dirt, thus materially reducing their efficiency; also to obtain good distribution it was necessary to hang them so low that they might be in the way of tall passengers.
No. 2. -- To get away from a low fixture in the center line of the car, the next equipment tested consisted of twenty 36-watt tungsten lamps in indirect reflectors. These were mounted in two rows of ten each on the sides of the car, just above the deck sill between the ventilators, as shown in Fig. 17. Five 10-watt frosted lamps in rosettes were mounted on the ceiling for emergency lights. The 36-watt lamps were mounted horizontally with their centers 7 ft. 4 in. above the floor. The spacing of the lighting units and the distribution therefrom is shown in Fig. 7. The resultant illumination was of low intensity, averaging 3.5 and 2.2 foot-candles at normal and 85 per cent voltage. The wattage consumption was 1.32 per square foot, effective lumens per watt were 2.67, and effective utilization efficiency 36.3 per cent. The main objection was keeping the reflectors clean.
No. 3. -- The last test was made on twelve 94-watt tungsten lamps in indirect reflectors and five 10-watt emergency lamps in rosettes, located down the center line of the ceiling. To get maximum headroom for these reflectors and still have them out of the way of passengers, special inverted cone-shaped containers for the reflectors were built into the stanchions along the center line of the car (Fig. 18). Unfortunately the construction of the car necessitated spacing the units rather far apart, so that uneven illumination resulted. In addition to the bowls, smaller inverted bowls were mounted on the horizontal grab rails, at points shown in Fig. 8. Each of these contained one 94-watt tungsten lamp, making a total of twelve 94-watt and five 10-watt lamps in the car. The average foot-candles were 8.5 and 4.7 at normal and 85 per cent voltage, watts per square foot 2.01, effective lumens per watt 4.21, and the utilization efficiency was 53.4 per cent. Much difficulty would be experienced in keeping this equipment clean.
General Effect and Appearance. -- The general effect and appearance of each system under test were judged by comparison with present methods of car lighting for similar service, namely, with the use of tungsten lamps but without reflectors. Under this item was also considered the effect of the distribution of light on the various parts of the car.
Lack of Eyestrain. -- The effect of the light on the eyes was particularly noted by a large number of observers.
Ease in Reading for Seated and Standing Passengers. -- Particular attention was given to the possible shadows thrown on reading matter of seated passengers by passengers standing in a crowded car. In some cases it was found that passengers could obtain proper light in any position; in others it was necessary for them to move in their seats, often to uncomfortable positions, to obtain proper light.
Efficiency of System. -- The efficiencies of the systems tested differed widely. In some cases this was largely due to the type of reflector used; in others to the position of the reflector, shape of the ceiling, etc. In several tests it was evident that improvement could be made by changes.
Maintenance. -- The question of maintenance was serious. Some of the most desirable arrangements of reflectors and lights were handicapped by the dust problem. With a large number of small units this difficulty increases.
Energy Consumption. -- To secure a reasonable operating cost, low energy consumption was one of the important factors. The indirect system of lighting required considerably more power than the direct, while the semi-indirect came between these two.
Depreciation. -- The relative loss of reflecting power, due to accumulation of dust on the various types of reflectors, also received consideration.
Emergency Lighting. -- It was decided that sufficient light would be obtained from the emergency lamps to permit clearly distinguishing people and various objects in the car with the main lamps extinguished.
A thorough study finally led to the adoption of a single line of fifteen 56-watt bowl-frosted tungsten lamps placed symmetrically down the center line of the ceiling, equipped with reflectors, as shown in Fig. 19, supplemented by six 10-watt all-frosted round-bulb tungsten emergency lamps. One big unit was placed on each end bulkhead of the car to bring up the illumination at these points. This system was chosen as the one containing the highest percentage of satisfactory illumination, low energy consumption, low maintenance and upkeep and pleasing appearance.
The emergency lamps were placed in rosettes, one being located on the side wall over each pair of doors. These lamps do not burn while there is power on the line, but the instant that fails they are automatically thrown onto a storage battery.
In the car as finally equipped the illumination averaged 5.94 foot-candles at normal and 3.85 at 85 per cent voltage, the energy consumption was 1.44 watts per square foot, effective lumens per watt 4.14, and the utilization efficiency 50.6 per cent. These data are not comparable with the other tests, due to the use of bowl frosted lamps (instead of clear), also a larger number and different arrangement of lighting units.
It was interesting to note that the low intensities of illumination, at stations 7 and 17, were opposite the entrance doors, which are dark green, in comparison to the white finish between doors. The curves were slightly high at stations 2, 3 and 4, due to the fact that the end lamps are located on the bulkheads considerably lower than the rest of the lamps in the car.
On the whole, the illumination is remarkably soft, even and pleasing. It is not possible to note any unevenness with the naked eye. The use of bowl-frosted lamps lowers the efficiency a little, but also eliminates, glare, even when one looks directly at the lamp.
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| NEW YORK MUNICIPAL CAR -- FIGS. 1, 2, AND 3 -- CHARTS SHOWING DISTRIBUTION OF LIGHT AND EFFECTIVE ILLUMINATION. Fig. 1 shows ten 56-watt, 120-volt tungsten filament lamps In glass reflectors, and four 10-watt, 115-volt tungsten emergency lamps with same reflector. Fig. 2 shows ten 56-watt, 120-volt tungsten lamps in prismatic reflectors and four 10-watt, 115-volt tungsten emergency lamps in prismatic reflectors. Fig. 3 shows five 94-watt, 120-volt tungsten lamps in prismatic reflectors and four 10-watt, 120-volt emergency lamps in prismatic reflectors. |
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| NEW YORK MUNICIPAL CAR -- FIGS. 4, 5 AND 6-- DISTRIBUTION OF LIGHT AND EFFECTIVE ILLUMINATION. Fig. 4 shows an installation of indirect reflectors set in coves, ten on each side of car, and five 10-watt frosted emergency lamps along center line of car, set in ceiling rosettes. Fig. 5 shows a semi-indirect installation of two 94-watt (horizontal) lamps and one 10-watt (vertical) lamp for each of five units. Fig. 6 shows an indirect installation comprising eight white enameled steel indirect reflectors with three 36-watt, 115-volt lamps per unit. |
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| [Left] NEW YORK MUNICIPAL CAR -- FIG. 7 -- CHART SHOWING DISTRIBUTION WITH COVE LIGHTING (SEE FIG. 17). [Right] NEW YORK MUNICIPAL CAR -- FIG. 8 -- CHART SHOWING DISTRIBUTION WITH LIGHTS ON GRAB RAILS (SEE FIG. 18) |
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| NEW YORK MUNICIPAL CAR -- FIGS. 9, 10 AND 11 -- ARRANGEMENTS AND TYPE OF LIGHTS. Fig. 9 shows 56-watt tungsten lamps in white glass reflectors. Fig. 10 shows 56-watt lamps with reflector board below ceiling. Fig. 11 shows SO-watt turnip-shaped lamps. |
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| NEW YORK MUNICIPAL CAR -- FIGS. 12, 13 AND 14 -- ARRANGEMENTS AND TYPE OF LIGHTS. Fig. 12 shows an indirect fixture with three 36-watt tungsten lamps (see Fig. 6). Fig. 13 shows semi-indirect lighting with two 94-watt and one 10-watt lamp per bowl. Fig. 14 shows tungsten lamps and special curved white glass screens. |
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| [Left] NEW YORK MUNICIPAL CAR -- FIG. 15 -- LIGHTING EFFECT OF INSTALLATION SHOWN IN FIGS. 1 AND 9. [Right] NEW YORK MUNICIPAL CAR -- FIG. 16 -- SEMI-INDIRECT LIGHTING WITH SPECIAL CEILING INSERTS. |
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| [Left] NEW YORK MUNICIPAL CAR -- FIG. 17 -- INDIRECT LIGHTING WITH REFLECTORS SET IN COVES, TEN ON EACH SIDE. [Right] NEW YORK MUNICIPAL CAR -- FIG. 18 -- INDIRECT LIGHTING FROM UNITS ON GRAB RAILS. |
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| NEW YORK MUNICIPAL CAR -- FIG. 19 -- LIGHTING ADOPTED. 56-watt bowl-frosted lamps in white glass reflectors, and 10-watt all-frosted emergency lamps. |
Sources: Electric Railway Journal, McGraw Hill Company, Digitized by Microsoft, Americana Collection, archive.org.
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